Newton'a law of gravity has three elements to it.

1/ The inverse square law

2/ A direct proportion between mass and gravity strength

3/ Every particle attracting every other particle.

The first two seem to pass scrutiny.

With the third can anyone point to empirical evidence of a smaller mass 'pulling' a larger mass. The tides and cavendish experiments don't do it from all the published imformation I've seen.

In the case of cavendish experiments only the small mass moves and with the high tide under the moon, all that is observed is a lesser gravitation towards the earth because of the interaction of earth and moon gravities. Which, of course isn't a gravitation towards the moon.

Any ideas?

Astronomers measure the "wobble" of stars being yanked around by planets too small to see directly.

One can also measure the deflection of the earth from it's orbit, by the moon's pull.

Newton'a law of gravity has three elements to it.

1/ The inverse square law

2/ A direct proportion between mass and gravity strength

3/ Every particle attracting every other particle.

The first two seem to pass scrutiny.

With the third can anyone point to empirical evidence of a smaller mass 'pulling' a larger mass. The tides and cavendish experiments don't do it from all the published imformation I've seen.

In the case of cavendish experiments only the small mass moves and with the high tide under the moon, all that is observed is a lesser gravitation towards the earth because of the interaction of earth and moon gravities. Which, of course isn't a gravitation towards the moon.

Any ideas?

The Earth and the Moon ?
Anyway, way would only larger objects pull smaller objects ?
If the Earth pulls on an apple does the mean nothing can pull on the Earth ?

look at the wobble of the sun as the planets orbit, especially pluto because its orbit is so ecliptical. If only a large pulls a small the sun would stay exactly sationary in relation to the rest of the solar system, if its not then something is causing it to wobble

The Earth and the Moon ?
Anyway, way would only larger objects pull smaller objects ?
If the Earth pulls on an apple does the mean nothing can pull on the Earth ?

The earth is not the biggest mass in the universe. So no.


Astronomers measure the "wobble" of stars being yanked around by planets too small to see directly.

One can also measure the deflection of the earth from it's orbit, by the moon's pull.

This seems to be in conflict with the high tide under the moon being the result only of an interaction of earth and moon gravities.

In mathematics, the moon's gravity doesn't reach the earth. It lessens the earth's gravity to cause a high tide. Doesn't actually pull the ocean. To theorize from there that the moon's 'pull' accounts for the earth criss cross of it's solar orbit is interesting but not to the point.

look at the wobble of the sun as the planets orbit, especially pluto because its orbit is so ecliptical. If only a large pulls a small the sun would stay exactly sationary in relation to the rest of the solar system, if its not then something is causing it to wobble


You are arguing against every particle 'pulling' every other particle when you pre-suppose that only solar system particles can affect the sun's position in space.

Has anybody set up a small mass in a lab and demonstrate that it 'pulls' a larger nearby mass?

The earth is not the biggest mass in the universe. So no.

It was a rhetoric question ;)

no im not, my theory works either way. If ANYTHING that has a mas smaller than the sun pulls it anyway then your theory is wrong.

your also forgeting that netonian science has been disproven, try relitivity.

Think about holding an apple in you hand. The apple pushes down on your hand with the same force that your hand pushes up on the apple, it's called equilibrium. In the same way the gravitational pull from the earth to the moon is the same as teh moon to the earth. The real issue is that there is no such thing as a gravitational force. See the thread on curved space lower down.

no im not, my theory works either way. If ANYTHING that has a mas smaller than the sun pulls it anyway then your theory is wrong.

I don't actually have a theory. Just inquiring to find out if anyone knows of a a large mass moving towards a smaller mass under laboratory conditions.

Think about holding an apple in you hand. The apple pushes down on your hand with the same force that your hand pushes up on the apple, it's called equilibrium. In the same way the gravitational pull from the earth to the moon is the same as teh moon to the earth. The real issue is that there is no such thing as a gravitational force. See the thread on curved space lower down.


You can measure the force of the apple on the hand. If you trace the opposite force to this force you find that it is the force down on the direct opposite side of the earth. (in your logic the ground supports the hand owner, the earth's mantle supports the ground and so on until you find that the equal and opposite vector to the one the apple exerts on the hand is the weight of the earth on the direct opposite side of the earth.)

With respect of your real issue, I am just after a link to an observation of a large mass moving towards a small mass.

We know that mathematical analysis of the high tide under the moon yields the high tide being a result of the earth and moon gravities interacting.

I.E. You subtract the moon's gravity at an ocean from the earth's gravity at an ocean and you are at the beginning of mathematical logic of why the ocean weighs less under the moon. The moon's gravity has lessened the earth's gravity under the moon.

This logic only deals with rates of acceleration through space. In no way does it indicate that every lunar particle is hooking up with every particle of the earth and 'pulling' said particles. Which is what the third element of Newton's law of gravity specifies happens.

If you read Newton's opening burst in Principia, where he says we must allow that every particle in the universe is attracting every other particle in the universe, the only smaller mass pulling a larger mass he cites is the moon pulling the earth (evidenced by a high tide in his critique).

Cavendish experiments do not show a large mass moving towards a large mass. Does anyone know of someone hanging a large mass next to a small mass and observing the large mass moving towards the small mass. Cheers

it would be almost impossable to do any meaningful experiment on the earth because the gravity of the earth would get in the way

however if you look at puto and her moon (sorry the name escapes me) they are both relitivly small and they orbit a common point rather than eachother. Now if you make the observations of the earth and OUR moon the center of orbit will be much closer to the core of the earth but not quite because the moon has mass to. If you calculate the center of orbit and compare the 2 as well as the relitive masses of both sets. If they are of a similar ration then you have proved it, if they are way off then they arnt

anything i missed in the calculations?
like volocity or distance?

I don't actually have a theory. Just inquiring to find out if anyone knows of a a large mass moving towards a smaller mass under laboratory conditions.

Well, of COURSE you won't find this in the lab. The large mass and small mass will fall towards a common center of mass. Likewise, in stable orbits, large masses and small masses orbit about the center of mass---for the earth-sun system, this center of mass is actually inside the sun (if i recall correctly) which is why the sun ``wobbles''.

In this sense, measuring the ``wobble'' of a more massive object confirms the Newtonian prediction.

In your apple-Earth system, the center of mass is pretty damned close to the center of the earth. You could do the calculation, but what you'd find is something like

\frac{M_{apple}}{M_{earth}}\times r

where r is the distance between the COM of the apple and the Earth. (If anyone can do the calculation outright, then please do! I am on my way to work.)

So yes---the Earth and the apple fall to the point \frac{M_{apple}}{M_{earth}}\times r.

Nice thread/

I have a theory going right now that forces between each other such as gravity is nothing but an electrostatic power. We haven't seen gravitational waves, which should vibrate the universe... neither have we seen a graviton...

It begs the question whether we have the idea right, and that Einstein might have followed an illusion.

plane:

With the third can anyone point to empirical evidence of a smaller mass 'pulling' a larger mass.

The moon pulling on the Earth is a good example. The Moon creates tides on Earth, and the Earth obviously pulls on the Moon because otherwise the Moon would not orbit the Earth.

This seems to be in conflict with the high tide under the moon being the result only of an interaction of earth and moon gravities.

In mathematics, the moon's gravity doesn't reach the earth. It lessens the earth's gravity to cause a high tide. Doesn't actually pull the ocean. To theorize from there that the moon's 'pull' accounts for the earth criss cross of it's solar orbit is interesting but not to the point.

Gravity is an inverse-square law. The gravity of a particular mass, like the moon, NEVER goes to zero, although it drops off with distance.

The moon doesn't "lessen" Earth's gravity. The Moon's own gravity combines with (technically, adds vectorially to) the Earth's gravity to create a net force on the oceans.

We know that mathematical analysis of the high tide under the moon yields the high tide being a result of the earth and moon gravities interacting.

I.E. You subtract the moon's gravity at an ocean from the earth's gravity at an ocean and you are at the beginning of mathematical logic of why the ocean weighs less under the moon. The moon's gravity has lessened the earth's gravity under the moon.

That explanation is ok, but in making it you're already presupposing that the Moon exerts a force on the ocean, which proves the point that the Moon attracts the Earth.

Oooh... wait a minute. Are you saying that the moon (a large mass) only attracts the oceans (a smaller mass), but not the entire Earth (which is larger than the moon)?

Are you saying that masses somehow "know" which one is bigger, and the bigger one then dominates? If so, think about this:

Suppose I have two 1-kilogram masses in space, side by side. Then, I add 1 gram to mass number 1. Mass number 1 is then bigger than mass 2, so by your argument, mass 2 is attracted by mass 1's gravity, but mass 1 doesn't attract mass 2 at all. On the other hand, if I added the 1 gram to mass 2 instead, the opposite would happen. Is that what you're claiming? In other words, what determines the entire attraction is not the 1000 grams of mass in each object we started with, but really the 1 gram that is added at the end? Does that not seem a little strange to you?

---

I should say that there are very good theoretical reasons why a small mass must attract a large mass.

First and foremost we have Newton's third law: for every action, there is an equal and opposite reaction. This says, in effect, that all forces involve an interaction between two objects. When object A exerts a force on object B, object B always exerts a force of equal magnitude but in the opposite direction on object A.

If this was not true, laws of physics such as the conservation of momentum in collisions simply would not hold, and yet thousands of experiments are taking place every day which verify the law of conservation of momentum.

Second, you can look at Newton's law of gravity itself.
F = \frac{GMm}{r^2}

This law does not make a distinction between M and m. Swap the positions of the two masses and the magnitude of the force is the same.

---

There are many astronomical examples where a smaller mass clearly pulls on a larger one. These include binary stars orbiting each other, the "wobbles" of stars due to planets pulling on them (mentioned earlier), even the motion of galaxies in our local group.

it would be almost impossable to do any meaningful experiment on the earth because the gravity of the earth would get in the way

This is a bit troubling when Cavendish experiments do measure the movement of the smaller mass.

however if you look at puto and her moon (sorry the name escapes me) they are both relitivly small and they orbit a common point rather than eachother. Now if you make the observations of the earth and OUR moon the center of orbit will be much closer to the core of the earth but not quite because the moon has mass to. If you calculate the center of orbit and compare the 2 as well as the relitive masses of both sets. If they are of a similar ration then you have proved it, if they are way off then they arnt

anything i missed in the calculations?
like volocity or distance?

The earth crisscrossing its solar orbit might give a first glance indication of the moon ‘pulling’ the earth. However the numbers don’t stack up. The sun’s gravity at the earth is much stronger than the moon’s.

When the moon is outside the earth’s orbit (further from the sun than the earth), how does the weaker moon gravity overcome the sun gravity.

And that’s before we get to the question of the earth spinning on two axes concurrently. For example get a car wheel. Put a rod through each of two stud holes. Then try and get the wheel to spin around both concurrently.


Well, of COURSE you won't find this in the lab. The large mass and small mass will fall towards a common center of mass.

Can you explain why they will fall to a common centre Ben. That’s the question. If you can show that it is more than a presumption on your part, I’ll be a happy little camper.


plane:



The moon pulling on the Earth is a good example. The Moon creates tides on Earth, and the Earth obviously pulls on the Moon because otherwise the Moon would not orbit the Earth.

You use an interesting word three in and further on as well. Can you explain the physics of a ‘pull’? A push is an exertion of one particle upon another. But just what is the description of the pull. The term appears constantly during gravity discussions but just what is it?. 'Creates' is a word with a bit of license to. How does the moon create tides on earth?



Gravity is an inverse-square law. The gravity of a particular mass, like the moon, NEVER goes to zero, although it drops off with distance.

The moon doesn't "lessen" Earth's gravity. The Moon's own gravity combines with (technically, adds vectorially to) the Earth's gravity to create a net force on the oceans.



That explanation is ok, but in making it you're already presupposing that the Moon exerts a force on the ocean, which proves the point that the Moon attracts the Earth.

Oooh... wait a minute. Are you saying that the moon (a large mass) only attracts the oceans (a smaller mass), but not the entire Earth (which is larger than the moon)?

Are you saying that masses somehow "know" which one is bigger, and the bigger one then dominates? If so, think about this:

Suppose I have two 1-kilogram masses in space, side by side. Then, I add 1 gram to mass number 1. Mass number 1 is then bigger than mass 2, so by your argument, mass 2 is attracted by mass 1's gravity, but mass 1 doesn't attract mass 2 at all. On the other hand, if I added the 1 gram to mass 2 instead, the opposite would happen. Is that what you're claiming? In other words, what determines the entire attraction is not the 1000 grams of mass in each object we started with, but really the 1 gram that is added at the end? Does that not seem a little strange to you?

---

I should say that there are very good theoretical reasons why a small mass must attract a large mass.

First and foremost we have Newton's third law: for every action, there is an equal and opposite reaction. This says, in effect, that all forces involve an interaction between two objects. When object A exerts a force on object B, object B always exerts a force of equal magnitude but in the opposite direction on object A.

If this was not true, laws of physics such as the conservation of momentum in collisions simply would not hold, and yet thousands of experiments are taking place every day which verify the law of conservation of momentum.

Second, you can look at Newton's law of gravity itself.
F = \frac{GMm}{r^2}

This law does not make a distinction between M and m. Swap the positions of the two masses and the magnitude of the force is the same.

---

There are many astronomical examples where a smaller mass clearly pulls on a larger one. These include binary stars orbiting each other, the "wobbles" of stars due to planets pulling on them (mentioned earlier), even the motion of galaxies in our local group.


Forgive me if you did not follow what I posted.

The earth’s rate of acceleration due to gravity at sea level and under the moon = 9.8 m/s/s. The moon’s gravity in the same vicinity = 0.0003 m/s/s (approx).

Resultant rate of acceleration at an ocean under the moon = 9.7997 m/s/s.

Which is a lesser weighting of an ocean towards the centre of the earth than what would be the case if the moon wasn’t present. Thus a high tide under the moon.

Presuming you are okey doke with that, it is just simple mathematical analysis of the situation so you should be, it is not mathematical evidence of the moon pulling the ocean or the earth. Thus is not evidence of a smaller mass ‘pulling’ a larger mass. It is just evidence of opposite directions of gravity interacting. There is no ‘pull’ whatsoever involved.

I do appreciate that you are putting a bit of faith in binary stars as proof of an apple attracting the earth but you can perhaps see that if the high tide under the moon is not evidence of apple attracting the earth, then perhaps binary stars and the like aren't either. Also happy to discuss your theoretical reasons if you want, but we probably should get the high tide under the moon out of the road first. It simply is not evidence of an apple attracting the earth.

Can you explain why they will fall to a common centre Ben. That’s the question. If you can show that it is more than a presumption on your part, I’ll be a happy little camper.

If by ``presumption'' you mean ``empirically measured fact'' then I don't need to explain it---it is what Newton predicted, it is measured in the lab. What's so difficult about this?

If by ``presumption'' you mean ``empirically measured fact'' then I don't need to explain it---it is what Newton predicted, it is measured in the lab. What's so difficult about this?


What lab are you referring? Cavendish experiments only have the small mass moving.

But, no I mean can you explain why two masses would fall towards a common centre. The nitty gritty reason.

plane:

What do you think about my thought experiment:

Suppose I have two 1-kilogram masses in space, side by side. Then, I add 1 gram to mass number 1. Mass number 1 is then bigger than mass 2, so by your argument, mass 2 is attracted by mass 1's gravity, but mass 1 doesn't attract mass 2 at all. On the other hand, if I added the 1 gram to mass 2 instead, the opposite would happen. Is that what you're claiming? In other words, what determines the entire attraction is not the 1000 grams of mass in each object we started with, but really the 1 gram that is added at the end? Does that not seem a little strange to you?

Plane: How would the larger mass know it was the larger one, and the smaller one know it was the smaller, so as to cancel or employ their "pull" appropriately ? Wouldn't they have to somehow have to gauge distance, etc, to make that decision ?

What happens if they are exactly the same mass ?

And I still don't know how the earth's wobble in orbit, in synchrony with the moon's obit, is explained without invoking some kind of "pull" by the moon.

The earth crisscrossing its solar orbit might give a first glance indication of the moon ‘pulling’ the earth. However the numbers don’t stack up. The sun’s gravity at the earth is much stronger than the moon’s.

When the moon is outside the earth’s orbit (further from the sun than the earth), how does the weaker moon gravity overcome the sun gravity.

The Earth is in orbit around the Sun. Without going a lot deeper into orbital mechanics, this can be simply described as a tug of war between the Earth's natural tendancy to fly off in a straight line and the Sun's gravity. For a circular orbit this tug of war is perfectly balanced and the Earth manitains a constant distance from the Sun. The moon simply upsets this balance. When it is outside of the Earth, its pull tips things very slighty in favor of the Earth traveling in a straight line and the Earth starts to drift slowly away from the Sun. When it is on the inside, it tips things in favor of the Sun and the Earth drifts slowly towards the Sun. This causes the Earth to weave in and out from the Sun.
The fact that the Sun's gravity on the Earth is so much stronger than the Moon's is not a factor as the Sun's gravity pull on the Earth is "all used up" just holding the Earth in orbit.

And that’s before we get to the question of the earth spinning on two axes concurrently. For example get a car wheel. Put a rod through each of two stud holes. Then try and get the wheel to spin around both concurrently.

False analogy, as you are trying to make the second axis located at a physical point of the wheel and this is not the case. Here's a more accurate analogy. Put one rod through the center hub hole. After the rod extends out the bottom bend it at a right angle. Then at a pont equal to the distance of one of the stud holes from the center of the wheel bend it at a right angel in the downward direction (away from the wheel). This gives you something that looks like a crank. The part of the rod sticking through the wheel is the "handle" of the crank and the part extending downward is its axis of rotation. The wheel can both spin on the handle and the crank can turn (carrying the axis of the turning wheel in a circle at the same time. The two motions are indendent of each other.






The earth’s rate of acceleration due to gravity at sea level and under the moon = 9.8 m/s/s. The moon’s gravity in the same vicinity = 0.0003 m/s/s (approx).

Resultant rate of acceleration at an ocean under the moon = 9.7997 m/s/s.

Which is a lesser weighting of an ocean towards the centre of the earth than what would be the case if the moon wasn’t present. Thus a high tide under the moon.

Presuming you are okey doke with that, it is just simple mathematical analysis of the situation so you should be, it is not mathematical evidence of the moon pulling the ocean or the earth. Thus is not evidence of a smaller mass ‘pulling’ a larger mass. It is just evidence of opposite directions of gravity interacting. There is no ‘pull’ whatsoever involved.



You do realise that the Moon produces two tidal bulges? There is a high tide bulge on the side directly under the Moon as well as one on the side opposite that of the Earth. This is why high tides are a roughly 12.5 hrs apart rather than roughly 25 hrs apart.

Your "lessening of opposite directions of gravity interacting" theory doesn't fit this fact, as on the opposite side of the Earth the gravities would work in the same direction, increasing the acceleration due to gravity, and causing a low tide rather than a high tide.

What does explain it is the differential pull of the Moon across the diameter of the Earth. The near side of the Earth feels a stronger pull from the Moon than the center of the Earth does and the far side even less than the Center. This difference creates a net pull that tends to stretch the oceans (and to a certain extent the Earth itself) along a line that joins the Earth and Moon, causing the two tidal bulges.

plane:

What do you think about my thought experiment:

Rather think it is avoiding the issue. To indulge you, underpinning what you are ‘thinking’, is the question of what happens when two masses are precisely equal if a small mass does not attract a large mass. Iceaura, you are on the same theme.

There can never be two masses that are precisely the same is the first point to make. But if they were precisely the same, neither would attract the other. That is on simple mathematical reasoning.

Suppose I have two 1-kilogram masses in space, side by side. Then, I add 1 gram to mass number 1. Mass number 1 is then bigger than mass 2, so by your argument, mass 2 is attracted by mass 1's gravity, but mass 1 doesn't attract mass 2 at all. On the other hand, if I added the 1 gram to mass 2 instead, the opposite would happen. Is that what you're claiming? In other words, what determines the entire attraction is not the 1000 grams of mass in each object we started with, but really the 1 gram that is added at the end? Does that not seem a little strange to you?

Why would it seem strange to me? I do invite you to address the rest of my original reply to you. Beginning with an explanation of the physics of a word you used. That is when you employ the term pull with respect of gravity, what do you mean in terms of physics.

Also

The earth’s rate of acceleration due to gravity at sea level and under the moon = 9.8 m/s/s. The moon’s gravity in the same vicinity = 0.0003 m/s/s (approx).

Resultant rate of acceleration at an ocean under the moon = 9.7997 m/s/s.

Which is a lesser weighting of an ocean towards the centre of the earth than what would be the case if the moon wasn’t present. Thus a high tide under the moon.

Presuming you are okey doke with that, it is just simple mathematical analysis of the situation so you should be, it is not mathematical evidence of the moon pulling the ocean or the earth. Thus is not evidence of a smaller mass ‘pulling’ a larger mass. It is just evidence of opposite directions of gravity interacting. There is no ‘pull’ whatsoever involved.

Not thought experiments, that is really where the issue of the thread is at.



The Earth is in orbit around the Sun. Without going a lot deeper into orbital mechanics, this can be simply described as a tug of war between the Earth's natural tendancy to fly off in a straight line and the Sun's gravity. For a circular orbit this tug of war is perfectly balanced and the Earth manitains a constant distance from the Sun. The moon simply upsets this balance. When it is outside of the Earth, its pull tips things very slighty in favor of the Earth traveling in a straight line and the Earth starts to drift slowly away from the Sun. When it is on the inside, it tips things in favor of the Sun and the Earth drifts slowly towards the Sun. This causes the Earth to weave in and out from the Sun.
The fact that the Sun's gravity on the Earth is so much stronger than the Moon's is not a factor as the Sun's gravity pull on the Earth is "all used up" just holding the Earth in orbit. .

‘All used up’. In the language of the age lol. Sorry about that. I know what you are trying to say but whatever way you try and spin it with words, when you add the sun and moon rates of acceleration together at the distance from the sun that the earth is, you get a resultant rate towards the sun. Look Newton has left us a pretty confusing lot. You want the earth to be falling towards the sun and the moon at the same time. Your trouble is no-one has ever observed anything falling both up and down simultaneously. The situation is the earth would be falling towards the sun at a lesser rate because of the moon, but not towards the moon at all, if you were on the right track.


False analogy, as you are trying to make the second axis located at a physical point of the wheel and this is not the case. Here's a more accurate analogy. Put one rod through the center hub hole. After the rod extends out the bottom bend it at a right angle. Then at a pont equal to the distance of one of the stud holes from the center of the wheel bend it at a right angel in the downward direction (away from the wheel). This gives you something that looks like a crank. The part of the rod sticking through the wheel is the "handle" of the crank and the part extending downward is its axis of rotation. The wheel can both spin on the handle and the crank can turn (carrying the axis of the turning wheel in a circle at the same time. The two motions are indendent of each other.

No. It’s a good analogy. You cheat with your second right angle. It comes back towards the wheel and through the wheel.

You do realise that the Moon produces two tidal bulges? There is a high tide bulge on the side directly under the Moon as well as one on the side opposite that of the Earth. This is why high tides are a roughly 12.5 hrs apart rather than roughly 25 hrs apart.

Your "lessening of opposite directions of gravity interacting" theory doesn't fit this fact, as on the opposite side of the Earth the gravities would work in the same direction, increasing the acceleration due to gravity, and causing a low tide rather than a high tide.

What does explain it is the differential pull of the Moon across the diameter of the Earth. The near side of the Earth feels a stronger pull from the Moon than the center of the Earth does and the far side even less than the Center. This difference creates a net pull that tends to stretch the oceans (and to a certain extent the Earth itself) along a line that joins the Earth and Moon, causing the two tidal bulges.

Well aware that there is like tides on direct opposite sides of the earth. My lessening of opposite directions gravity fits perfectly with there being a high lunar tide on the direct opposite side. The first issue, though, is the one on the moon side.

Like JR, you use the term ‘pull’. A push is an exertion of mass upon mass. Can you define the physics of a pull. All we really know about gravity is that it is an acceleration through space towards the centre of a mass. What is this pull you cite.

Iceaura, you are on the same theme. I had two other questions, different.

One is how you explain the wobble of the earth's solar orbit, in synchrony with the moon's orbit of the earth.

The other was how the smaller mass identified itself as such, and the larger one knew it was the one that should be pulling. Wouldn't therre have to be some kind of distance guage ?

plane:

When the moon is outside the earth’s orbit (further from the sun than the earth), how does the weaker moon gravity overcome the sun gravity.

It doesn't. Both the Moon and the Earth have a net force towards the Sun at all times. They share an orbit around the Sun.

And that’s before we get to the question of the earth spinning on two axes concurrently. For example get a car wheel. Put a rod through each of two stud holes. Then try and get the wheel to spin around both concurrently.

I don't understand what you're talking about here. The Earth only spins around one axis - the one through the poles.

You use an interesting word three in and further on as well. Can you explain the physics of a ‘pull’? A push is an exertion of one particle upon another. But just what is the description of the pull. The term appears constantly during gravity discussions but just what is it?

There are only four fundamental interactions in the universe: the strong and weak nuclear interactions, electromagnetism and gravity. All manifestations of force result from one of these interactions.

Gravity is a purely attractive interaction. Every mass in the universe attracts every other mass. In contrast, electrostatic forces, for example, can be either attractive or repulsive, depending on the electrical charges involved. But both gravity and electromagnetic forces are non-contact forces. In other words, things don't need to physically touch in order to feel these forces. This is an obvious truth.

The terms "push" and "pull" are not terms that always have well-defined meanings in physics. When they are used, simply apply your common sense and you ought to be able to convert them so that you know whether an attractive or repulsive interaction is being discussed. In the case of gravity, things are simple, because gravity is always attractive.

Hence, when somebody says "The moon's gravity pulls on the Earth", you can read that as "The Earth and Moon interact gravitationally, such that each attracts the other."

Does that make sense?

'Creates' is a word with a bit of license to. How does the moon create tides on earth?

Have you read the standard Newtonian explanation of the tides, involving centre-of-mass of the Earth-moon system, the mutual gravitational force and the centrifugal or centripetal force associated with their orbits around the centre-of-mass?

Forgive me if you did not follow what I posted.

The earth’s rate of acceleration due to gravity at sea level and under the moon = 9.8 m/s/s. The moon’s gravity in the same vicinity = 0.0003 m/s/s (approx).

Resultant rate of acceleration at an ocean under the moon = 9.7997 m/s/s.

Which is a lesser weighting of an ocean towards the centre of the earth than what would be the case if the moon wasn’t present. Thus a high tide under the moon.

Presuming you are okey doke with that, it is just simple mathematical analysis of the situation so you should be, it is not mathematical evidence of the moon pulling the ocean or the earth.

How do you account for the "lesser weighting of the an ocean towards the centre of the earth" then? What's causing the lesser weighting? Does it have anything to do with the moon?

I do appreciate that you are putting a bit of faith in binary stars as proof of an apple attracting the earth but you can perhaps see that if the high tide under the moon is not evidence of apple attracting the earth, then perhaps binary stars and the like aren't either. Also happy to discuss your theoretical reasons if you want, but we probably should get the high tide under the moon out of the road first. It simply is not evidence of an apple attracting the earth.

I'm not sure you understand what causes tides, so perhaps you picked a difficult example. In that case, it might be better to start with the basics of action-reaction force pairs and so on, as I touched on in my initial reply. Tides are complicated because they involve not only gravity but also the fact that the Earth and moon are orbiting a common centre of mass.

How do you account for the high tide on the side of the Earth opposite the moon, by the way?

Rather think it is avoiding the issue. To indulge you, underpinning what you are ‘thinking’, is the question of what happens when two masses are precisely equal if a small mass does not attract a large mass. Iceaura, you are on the same theme.

There can never be two masses that are precisely the same is the first point to make. But if they were precisely the same, neither would attract the other. That is on simple mathematical reasoning.

Standard physics says that if they were both exactly the same, then both would attract the other, just as they do when their masses are different. Can you give any reason why you expect gravity to suddenly switch off if two masses happen to become equal?

For example, suppose I have a 1 kg mass and a 1.1 kg mass. According to you, the 1 kg mass is attracted to the 1.1 kg mass, which presumably just sits still. Now, suppose a piece of dust lands on the 1 kg mass, making its mass 1.1 kg. Suddenly, there is no attraction at all? Now, another piece of dust lands on the same mass, making it 1.2 kg. Suddenly, it stays still and attracts the other mass, and gravity swaps direction?

Can you give any theoretical or observational reason why we ought to believe this?

Look Newton has left us a pretty confusing lot. You want the earth to be falling towards the sun and the moon at the same time. Your trouble is no-one has ever observed anything falling both up and down simultaneously. The situation is the earth would be falling towards the sun at a lesser rate because of the moon, but not towards the moon at all, if you were on the right track.

This is a matter of being careful with reference frames. If you view the situation from the Sun, both the Moon and Earth fall towards the Sun. But if you're on Earth then you're in an accelerating reference frame in which both the Earth and Moon are in free fall around the Sun and you must "subtract off" the Sun's gravitational effect to get the Moon's motion with respect to the Earth. I suspect you may find this difficult to follow. If so, please forgive me and hopefully we'll get there after a bit more discussion. This is why I think we need to start with the basics of force, rather than jump straight into tidal effects and the like.

May I ask how much physics you have studied formally? That way, I'll be better able to tailor my responses so as not to either confuse or patronise you.

james sorry if this is a stupid question. if there are only those 4 forces which is a true "push". ie if i walk up to you and push you over which one of the 4 forces am i exerting on you?

Largely electromagnetic.

Although this is somewhat of a trick question because you are not a fundamental object, despite what you think.

The answer can get as complex as you'd like, but basically the atoms in your hand form bonds that are not easily broken.

if there are only those 4 forces which is a true "push". ie if i walk up to you and push you over which one of the 4 forces am i exerting on you?
That push is an example of the normal force (the same thing that keeps you from sinking into the ground or from walking through walls). The normal force in turn is an example of the electromagnetic force. To be a bit too anthropogenic, the electrons in your body do not want in the same place as the electrons in my body. In fact, they cannot be in the same state per the Pauli exclusion principle. When electrons start getting close to violating this principle they exchange virtual photons to transfer momentum from one electron to the other.

interesting, always wondered what inertal colisions actually WERE

I had two other questions, different.

One is how you explain the wobble of the earth's solar orbit, in synchrony with the moon's orbit of the earth.

The other was how the smaller mass identified itself as such, and the larger one knew it was the one that should be pulling. Wouldn't therre have to be some kind of distance guage ?

You have wobble as proof of a smaller mass pulling a larger mass? When the physical relationship between mass and gravity is not understood there could easily be a different explanation.

Not a matter of the smaller mass identifying its self and yes, opposite directions of the inverse square law provide a distance gauge. At some point between adjacent masses the direction of fall alternates. From that point going towards the larger mass, there is no direction of fall towards the smaller mass. Thus it is mathematically impossible for a smaller mass to attract a larger mass. You can work that out for your self but, look, I am just after the accepted proof of apple attracting the earth. If you want to go with the wobble, I’ll mark that down.


plane:



It doesn't. Both the Moon and the Earth have a net force towards the Sun at all times. They share an orbit around the Sun.

If it doesn’t why does the earth move away from the sun and towards the moon. That does not appear to be a sensible answer to the problem.



I don't understand what you're talking about here. The Earth only spins around one axis - the one through the poles.

The earth and moon are supposed to be turning around a common centre of gravity, one that is located within the earth.





There are only four fundamental interactions in the universe: the strong and weak nuclear interactions, electromagnetism and gravity. All manifestations of force result from one of these interactions.

Gravity is a purely attractive interaction. Every mass in the universe attracts every other mass. In contrast, electrostatic forces, for example, can be either attractive or repulsive, depending on the electrical charges involved. But both gravity and electromagnetic forces are non-contact forces. In other words, things don't need to physically touch in order to feel these forces. This is an obvious truth.

The terms "push" and "pull" are not terms that always have well-defined meanings in physics. When they are used, simply apply your common sense and you ought to be able to convert them so that you know whether an attractive or repulsive interaction is being discussed. In the case of gravity, things are simple, because gravity is always attractive.

Hence, when somebody says "The moon's gravity pulls on the Earth", you can read that as "The Earth and Moon interact gravitationally, such that each attracts the other."

Does that make sense?

You used the term pull. You still haven’t explained what one is. Noting your shift in language, can you describe the physics of ‘attraction’. Or, perhaps more to the point, can you explain how mass causes an acceleration towards its centre..




How do you account for the "lesser weighting of the an ocean towards the centre of the earth" then? What's causing the lesser weighting? Does it have anything to do with the moon?

Of course it does. I have posted the arithmetic for you. Please go back to it if you are at all interested.



I'm not sure you understand what causes tides, so perhaps you picked a difficult example. In that case, it might be better to start with the basics of action-reaction force pairs and so on, as I touched on in my initial reply. Tides are complicated because they involve not only gravity but also the fact that the Earth and moon are orbiting a common centre of mass.

How do you account for the high tide on the side of the Earth opposite the moon, by the way?

In one breathe unsure that I understand the cause of the tides and next having the confidence to ask me how the high tide on the side of the earth away from the moon is caused. Interesting.

Newton’s third law is how I account for the second high tide but at this stage can’t you understand the difference between the earth’s gravity being slightly less under the moon because of the opposite direction of the moon’s gravity and water falling towards the moon. The difference isn’t even really subtle. If you can’t understand that, I’ll see about posting a diagram to explain it for you. Critical point. If you are genuinely interested in the tides, you won't pay it lip service.



Standard physics says that if they were both exactly the same, then both would attract the other, just as they do when their masses are different. Can you give any reason why you expect gravity to suddenly switch off if two masses happen to become equal?

Not suddenly switch off. Still be a direction of fall of each towards each but not beyond the point that is mid way between the two.

For example, suppose I have a 1 kg mass and a 1.1 kg mass. According to you, the 1 kg mass is attracted to the 1.1 kg mass, which presumably just sits still. Now, suppose a piece of dust lands on the 1 kg mass, making its mass 1.1 kg. Suddenly, there is no attraction at all? Now, another piece of dust lands on the same mass, making it 1.2 kg. Suddenly, it stays still and attracts the other mass, and gravity swaps direction?

Can you give any theoretical or observational reason why we ought to believe this?

Refer to the above answer. You are presuming gravity is an indefinite extension. That doesn’t stand up to mathematical scrutiny.



This is a matter of being careful with reference frames. If you view the situation from the Sun, both the Moon and Earth fall towards the Sun. But if you're on Earth then you're in an accelerating reference frame in which both the Earth and Moon are in free fall around the Sun and you must "subtract off" the Sun's gravitational effect to get the Moon's motion with respect to the Earth. I suspect you may find this difficult to follow. If so, please forgive me and hopefully we'll get there after a bit more discussion. This is why I think we need to start with the basics of force, rather than jump straight into tidal effects and the like.

May I ask how much physics you have studied formally? That way, I'll be better able to tailor my responses so as not to either confuse or patronise you.

Thanks for your rather somewhat impertinent thoughtfulness but as per my initial post in this thread, I am just after what you consider to be proof of an apple attracting the earth. What do you have marked down as proof. The post of mine you are responding to with the above was directed at the question of the earth’s crisscross of its solar orbit as the moon orbits the earth, not the physics of the moon’s orbit of the earth.

So what do you see as proof of a smaller mass attracting a larger mass. Mathematically the theory can be pulled to bits.

Ben the man, could I ask you why you haven’t provided information about what has been measured in a lab. As per post 16/17

Ben the man, could I ask you why you haven’t provided information about what has been measured in a lab. As per post 16/17

It doesn't matter what evidence I provide---you've already made your mind up about it.

This is, of course, how crackpots do science.

People have already tried to explain these things to you...there's little I can do to save you from your own ignorance.

it is measured in the lab.

Are you saying my mind is wrong because you can't explain what you mean here?

You actually misunderstand, anyway. Perhaps its my fault but I'm not really here to argue. Just trying to find reasons people believe an apple attracts the earth.

If you have knowledge of Cavendish type experiment where a large mass is observed to move towards a small mass in a lab, let nothing stop you from presenting it is the point. If your bluff, your bluff.

My mind at this stage says there is no evidence to consider that an apple attracts the earth.

And, if you want to get personal, the evidence would seem to be that your mind is made up in favour of the apple.

I don't need to explain it When I read that I will concede that I doubted whether or not you had serious evidence.

Anyway so far we have the earth's crisscross of it's solar path in tune with the moon's orbit of the earth as considered proof of a small mass attracting a large mass. And a mention of binary star systems,

Any other.

Ok.

You're right.

Maybe you should publish this result in a paper that is more prestigious than our lowly forum.

Thanks ben for acknowledging that I'm right. Here is a diagram for others.

http://www.fotothing.com/photos/065/0654fc95afac72948b816042231bc471.jpg?ts=1201813527

plane; if you imagine the sun, the moon, and the earth all attached to each other with strings, and all pulling on there strings it might help you to understand gravity.

Just because two people are pulling there strings attached to me from different sides doesn't mean i have to go both directions simultaneously, I merely go in the direction of the net force, same with gravity.

Ok now i can see your diagram I don't understand it, mind explaining?

plane:

Not a matter of the smaller mass identifying its self and yes, opposite directions of the inverse square law provide a distance gauge. At some point between adjacent masses the direction of fall alternates. From that point going towards the larger mass, there is no direction of fall towards the smaller mass. Thus it is mathematically impossible for a smaller mass to attract a larger mass.

This "direction of fall" you talk about is the direction a third object would fall, towards one or the other of the two gravitating objects. The assumption, of course, is that the third object is not massive enough to significantly perturb the system.

Where you go wrong is in jumping from the behaviour of a third body to conclusions about the original 2-body system.

It doesn't. Both the Moon and the Earth have a net force towards the Sun at all times. They share an orbit around the Sun.

If it doesn’t why does the earth move away from the sun and towards the moon.

It doesn't. The Earth is always falling towards the Sun.

I don't understand what you're talking about here. The Earth only spins around one axis - the one through the poles.

The earth and moon are supposed to be turning around a common centre of gravity, one that is located within the earth.

You're not being precise enough. There are actually three separate effects here. One is the intrinsic spin of the Earth around its axis; another is Earth's orbital motion about the centre of mass of the Earth-moon system; the third is the Earth's orbital motion around the Sun. These three motions are independent and have three different rotational axes.

You used the term pull. You still haven’t explained what one is.

I explained carefully to you that "pull" is just one way to denote an attractive force.

Noting your shift in language, can you describe the physics of ‘attraction’. Or, perhaps more to the point, can you explain how mass causes an acceleration towards its centre.

Nobody can explain why gravity is an attractive force. It just is. All observation confirms it. It's just an observed feature of our universe. You can imagine a universe where things fall up instead of down, but that's not our universe, obviously.

In one breathe unsure that I understand the cause of the tides and next having the confidence to ask me how the high tide on the side of the earth away from the moon is caused. Interesting.

I was trying to ascertain how much you understand about tides.

Newton’s third law is how I account for the second high tide...

I don't understand. Newton's third law concerns equal and opposite forces on different bodies. How does it explain the second high tide?

You are presuming gravity is an indefinite extension. That doesn’t stand up to mathematical scrutiny.

This is a basic error on your part.

All observational data supports the inference that gravity is an inverse-square force. It follows automatically that it has "indefinite extension".

Thanks for your rather somewhat impertinent thoughtfulness but as per my initial post in this thread, I am just after what you consider to be proof of an apple attracting the earth. What do you have marked down as proof.

My "proof" is:

1. Newton's third law states that for every force there is an equal and opposite force.
2. Therefore, when two bodies interact, if one exerts a force F on the other, the other exerts an equal force F on the first, but in the opposite direction.
3. Gravity is a force (in the Newtonian picture).
4. No known experiment with force has ever violated Newton's third law.
5. Therefore, if the Earth pulls on an apple, the apple must pull back on the Earth with an equal and opposite force.

That's really all the "proof" that is needed.

Of course, there's also a lot of direct evidence, such as the kind of astronomical evidence cited previously.

So what do you see as proof of a smaller mass attracting a larger mass. Mathematically the theory can be pulled to bits.

Show me.

Thanks ben for acknowledging that I'm right. Here is a diagram for others.

http://www.fotothing.com/photos/065/0654fc95afac72948b816042231bc471.jpg?ts=1201813527

This picture is true only for smaller masses present nearby the two bodies, assuming that the two bodies are motionless. It does not show at all what forces the two bodies themselves experience.

Think about this: The Earth is made of many atoms, and any atom is smaller than an apple. So the apple pulls the Earth.

Gravity is a purely attractive interaction.

Maybe it only seems so for us because we're so close to earth. Things that are further away, like the moon, might be repulsed by the earth. I have two magnets, a strong magnet and a weak magnet... when I try to put together north and north pole, they repel, but when i bring them closer, the north and north are attracted.

All objects are made of magnetic particles so for me it seems logical that all objects would be magnetic.

Yorda:

Maybe it only seems so for us because we're so close to earth. Things that are further away, like the moon, might be repulsed by the earth.

No. The moon's orbit is exactly what we would expect given purely attractive gravity.

I have two magnets, a strong magnet and a weak magnet... when I try to put together north and north pole, they repel, but when i bring them closer, the north and north are attracted.

Impossible. Two north magnetic poles always repel one another.

All objects are made of magnetic particles so for me it seems logical that all objects would be magnetic.

There are three types of magnetism, known as paramagnetism, diamagnetism and ferromagnetism. All objects are somewhat diamagnetic, but those effects don't show up in the ordinary course of events. The usual magnets you would be familiar with are ferromagnets, and only materials containing iron or a couple of other elements are ferromagnetic at all.

Moreover, magnetism and gravity are completely different forces. Magnetism relies on electrical charges interacting, whereas gravity is associated with mass. Gravitational attraction is not magnetic.

Think about this: The Earth is made of many atoms, and any atom is smaller than an apple. So the apple pulls the Earth. Indeed, Plane, your major problem is the assumption that both the apple and the earth are fundamental objects; they aren't.
Consider this (a reductio ad absurdem if you will).
1 Hydrogen atom is smaller than a planet, agreed? Therefore, by your theory, said planet pulls on the hydrogen atom, but the hydrogen has no pull on the planet.
This applies for every lone hydrogen atom.
Interstellar Nebula consist of lone hydrogen atoms.
Therefore, a planet pulls on a nebula, but a nebula does not pull on a planet.
But... observations show that nebula have significant gravitational influences on other interstellar bodies. How is this possible unless the smaller object does indeed pull on the larger object?

Alright, so now you say 'but the nebula is the bigger object!'
Now, a nebula is a region of space populated by a higher density of gases, when compared to other areas; (the density is still extremely small however,) usually hydrogen and helium, though some other elements, or molecules; but, ignoring the question this raises (at what density is gas then considered an object?) let's continue the argument.
So the nebula is the bigger object, the nebula pulls on the planet (as observed) and the planet does not pull on the nebula.
Newton’s first law states that unless the nebula is acted upon by an external force, it will stay in its current motion.
Thus, the nebula should be unaffected by our planet.
But this doesn’t happen! Instead as the planet approaches the nebula, a bit of it is pulled away towards our planet! Clearly, the planet is exerting a force on the nebula. It can't be the Weak or Strong at this distance, and the nebula isn't charged, so that leaves only gravity.

Questions that would need explaining if 'the apple doesn’t pull the earth'
How can you account for gravitational self forces? E.g. a star forms in this nebula because the gases own gravity pulls itself together, or a supernova collapses into a neutron star or black hole?
How dense does a gas, or any collection of matter, have to be before it is considered 'an object' What separates the apple as an object from the earth if it is within it's atmosphere, or better, a ball of lead sinking in the ocean, from the earth?

-Andrew

plane; if you imagine the sun, the moon, and the earth all attached to each other with strings, and all pulling on there strings it might help you to understand gravity.

Just because two people are pulling there strings attached to me from different sides doesn't mean i have to go both directions simultaneously, I merely go in the direction of the net force, same with gravity.

Ok now i can see your diagram I don't understand it, mind explaining?

Had a element of trouble with the diagram so it followed by about a quarter of an hour. Can understand that the first part of your post was made without the presence of the diagram.

The explanation of the diagram makes your string theory somewhat superfluous.

With that said, I can understand that no-one wants to debate a diagram that expressly says the third element of Newton’s law of gravity (every mass attracting every other mass) is wrong. That is why I just ask why people believe this to be true so as I can get a feel for why people believe what they do and get to the bottom of where everyone is at. Like no-one is born believing an apple attracts the earth. There has to be a moment in life when you decide it’s true, I’m just trying to find out what these moments are. I don’t think that is a rude thing to do. If people have beliefs, they should feel comfortable explaining the origin of their beliefs.

The diagram.

http://www.fotothing.com/photos/065/0654fc95afac72948b816042231bc471.jpg?ts=1201840939


Take the two masses two represent to adjacent celestial bodies. The earth and the moon if like but not necessarily. At all times and at all earth moon separations there is point along the axis between the earth and moon centres where the resultant rate of acceleration due gravity is zero.

Once you have found any resultant zero rate of acceleration you have disproved the universal aspect of Newton’s law of gravity. That’s the key point that no-one likes much.


Newton presumed that each gravity is an indefinite extension that is uninterrupted by any other gravity. As soon as you recognize that adjacent gravities must have a zero rate of acceleration between them, you are doing a mathematical analysis that undoes Newton’s premise of all gravities being infinite extensions. You then know he was wrong about an apple attracting the earth.

To make Newton right you have to manufacture an explanation of how a rate of acceleration due to gravity either physically or mathematically rebuilds its self beyond the zero point. Think such defies rational physical and mathematical logic but anyway some might like to try and explain how gravity does its rebuild from zero.

In the case of the larger field, you can mathematically see it exists on the other side of the smaller gravity field. Not marked on the diagram but on the other side there will be an equal and equal point. So you can see the larger mass exerts a force on the smaller gravity field, but not necessarily the smaller mass.

The reason the gravity field of the smaller mass is egg shaped is the decrease of the rate of acceleration due to the larger mass between the equal and opposite point and the equal and equal point.

Of course that isn’t the end of the explanation but you can see that your strings are at odds with the zero rate of acceleration due to gravity that is in between adjacent celestial bodies.

Reply to others later.

To make Newton right you have to manufacture an explanation of how a rate of acceleration due to gravity either physically or mathematically rebuilds its self beyond the zero point. Think such defies rational physical and mathematical logic but anyway some might like to try and explain how gravity does its rebuild from zero.
Simple; the forces of gravity never becomes 0, only the net force, and therefore acceleration. However, there is no mathmatical rule which states that because
z=x+y
and z=0, that x and y=0.
indeed, all that can be derived is that x=-y, or in terms of this application (z=net force x is gravity on apple byearth, y is gravity on apple by moon,) that there is a force of gravity of equal magnitude but in opposite direction also acting upon the object. The magnitude of either force of gravity is never 0, just as Newton predicted.
Your assumption that: if z=0, and z=x+y, x MUST = y MUST=0, is the source of mathmatical error.

-Andrew

There can never be two masses that are precisely the same is the first point to make. But if they were precisely the same, neither would attract the other. That is on simple mathematical reasoning.Not according to the textbook I used in 1st yr Physics.

Two bodies do attract each other with individual forces proportional to their individual masses.
It's called the Law of Universal Gravitation. It's known to act, for a given mass, with an attractive "pull", inversely proportional to the (square of the) distance of the other object. It takes two objects, or masses, for this to occur.

You can even write this in a mathematical formula. I can remember looking at this in high school...?
You're sure Kepler and Newton and everyone since (including me and the rest of "us"), all have the wrong idea with this?

Simple; the forces of gravity never becomes 0, only the net force, and therefore acceleration. However, there is no mathmatical rule which states that because
z=x+y
and z=0, that x and y=0.
indeed, all that can be derived is that x=-y, or in terms of this application (z=net force x is gravity on apple byearth, y is gravity on apple by moon,) that there is a force of gravity of equal magnitude but in opposite direction also acting upon the object. The magnitude of either force of gravity is never 0, just as Newton predicted.
Your assumption that: if z=0, and z=x+y, x MUST = y MUST=0, is the source of mathmatical error.

-Andrew


Your exactly right andbna. To a point anyway. X and Y are only theoretical values along the axis. One would exist if the other didn't

Here is a diagram of where they do exist.

http://www.fotothing.com/photos/6fa/6faba244d2dadc73fced465d6bba2f15.jpg?ts=1201849141

You get the picture. You have to think a bit and you will see it. Will reply to others later.

Plane,
It might have been pointed out, but if only the heavier mass attracts the lighter mass, how do you explain binary star systems and pulsars - where the stars rotate around each other?

Will reply to others later.

Come on. I showed your mistake and please don't run around saying this.

Side hint: Think about what happens exactly at the bodies on your picture.

plane:



This "direction of fall" you talk about is the direction a third object would fall, towards one or the other of the two gravitating objects. The assumption, of course, is that the third object is not massive enough to significantly perturb the system. .

Third object irrelevant. If zero objects are present direction of fall does not alter.


Where you go wrong is in jumping from the behaviour of a third body to conclusions about the original 2-body system.

Direction of fall is independent on falling body.



It doesn't. The Earth is always falling towards the Sun. .
Maybe having a misunderstanding about the issue at hand. Whatever, as the moon orbits the earth, the earths orbit of the sun is affected in such away that its distance from the sun increases. Look it up. If your result is different to this, post to that affect,
.


You're not being precise enough. There are actually three separate effects here. One is the intrinsic spin of the Earth around its axis; another is Earth's orbital motion about the centre of mass of the Earth-moon system; the third is the Earth's orbital motion around the Sun. These three motions are independent and have three different rotational axes. .

Your trouble is in explaining the second as being consistent with the first.



I explained carefully to you that "pull" is just one way to denote an attractive force. .

Not sure that your definition of carefully would match all others but what is an ‘attractive force’. A push is an exertion of matter upon matter. What is a pull in terms of matter?



Nobody can explain why gravity is an attractive force. It just is. All observation confirms it. It's just an observed feature of our universe. You can imagine a universe where things fall up instead of down, but that's not our universe, obviously. .

How do you know that nobody can explain it? Aren’t you saying you are god here?



I was trying to ascertain how much you understand about tides. .

Fair enough.



I don't understand. Newton's third law concerns equal and opposite forces on different bodies. How does it explain the second high tide?

Not really given to answering questions with questions, but how could Newton’s third law not explain equal and opposite high tides?




This is a basic error on your part.

Basic error on your part. What happens when opposite directions of ‘inverse square law’ meet. Indefinite extensions? Other than zero extensions are yours to explain.

All observational data supports the inference that gravity is an inverse-square force. It follows automatically that it has "indefinite extension".



My "proof" is:

1. Newton's third law states that for every force there is an equal and opposite force.
2. Therefore, when two bodies interact, if one exerts a force F on the other, the other exerts an equal force F on the first, but in the opposite direction.
3. Gravity is a force (in the Newtonian picture).
4. No known experiment with force has ever violated Newton's third law.
5. Therefore, if the Earth pulls on an apple, the apple must pull back on the Earth with an equal and opposite force.

That's really all the "proof" that is needed. .

Your problem is at three. Gravity is not a force. Gravity is known to cause an acceleration through space. This does not make gravity force. It makes it a cause of force. Incidentally, 3 to 5 is one hell of a jump.


Of course, there's also a lot of direct evidence, such as the kind of astronomical evidence cited previously.

How does the earth moon crisscross (which you seem to reject) and so called binary star systems prove an apple attracts the earth.



Show me.

Resultant zero gravity between adjacent objects pushes it aside.

Have a look at diagram in this thread.


This picture is true only for smaller masses present nearby the two bodies, assuming that the two bodies are motionless. It does not show at all what forces the two bodies themselves experience.

Think about this: The Earth is made of many atoms, and any atom is smaller than an apple. So the apple pulls the Earth.


Temur, this does not make sense. The question is whether or not the smallest mass could attract any other mass.

Not a matter of the smaller mass identifying its self The mass that is smaller has to know that somehow - otherwise how would it know when to stop attracting the other masses ?

Any mass is going to be sometimes smaller, sometimes bigger. How does it know which times are which ?

No. The moon's orbit is exactly what we would expect given purely attractive gravity.

if there was only pure attraction, the moon the whole universe would be stuck at one point. but if there is repulsion (http://en.wikipedia.org/wiki/Libration), it's easy to explain why planets rotate, have motion and specific distance (http://en.wikipedia.org/wiki/Titius-Bode_law) from the sun.

repulsion is an automatic consequence of attraction... when a river flows, i'm attracted to the way the river flows, and if i go upstream i'm repulsed. similarly, i think there is a magnetic river that flows through planets and everything.

Impossible. Two north magnetic poles always repel one another.

yes, but maybe it's because the strong magnet is smaller than the weak magnet, so the magnetic fields are a bit weird... or maybe they're bisexual? also, when i put together north and north the attraction is weaker than when i put together north and south.

if there was only pure attraction, the moon the whole universe would be stuck at one point. but if there is repulsion (http://en.wikipedia.org/wiki/Libration), it's easy to explain why planets rotate, have motion and specific distance (http://en.wikipedia.org/wiki/Titius-Bode_law) from the sun.

Yorda, did you read the introductory paragraph of the Wiki page to which you linked?
The Titius-Bode law (sometimes termed just Bode's law) is a hypothesis that the semi-major axes of planets in the solar system follow a simple rule. It was discredited with the discovery of Neptune in 1846.

Your first statement is incorrect. In Newtonian mechanics, gravity is a purely attractive force, and this purely attractive force coupled with Newton's laws of motion perfectly explains why things do not gather into one point. Do the math; the solution of the two body problem has been known for a long time. Things get a bit more difficult with general relativity, in which gravity is not a true force (it is a pseudo-force, like the Coriolis effect). This pseudo-force remains purely attractive, however.

Your exactly right andbna. To a point anyway. X and Y are only theoretical values along the axis. One would exist if the other didn't

Here is a diagram of where they do exist.
That is exactly what I mean.
But this in no way prooves that X or Y are 0 at any point; rather your diagram demonstrates that they do indeed still have non-zero values, and abide by Newtons predictions.
It shows there are instances when the net gravitational field strength, z, is 0, but that's perfectly in accordance with Newtons laws.

Your logical argument is that:
A and G affect P,
therefore A must affect G.
This is fallacioiuse however:

Imagine a tabletop RPG which sais "Roll 1 6sided die and 1 8 sided die and add them to find skill X"
your argument is then:
D6 and D8 affect X
therefore D6 affect D8.
Obviously the outcome of the 6 sided die has absolutly no influence on that of the 8 sided die.

Thus the moons gravity has no effect on the earths gravity, and vice-versa.

-Andrew

Yorda, did you read the introductory paragraph of the Wiki page to which you linked?

there is a reason the law doesn't work for neptune. http://ourworld.compuserve.com/homepages/dp5/pattern2.htm#p3

Not according to the textbook I used in 1st yr Physics.

Two bodies do attract each other with individual forces proportional to their individual masses.
It's called the Law of Universal Gravitation. It's known to act, for a given mass, with an attractive "pull", inversely proportional to the (square of the) distance of the other object. It takes two objects, or masses, for this to occur.

You can even write this in a mathematical formula. I can remember looking at this in high school...?
You're sure Kepler and Newton and everyone since (including me and the rest of "us"), all have the wrong idea with this?


Kepler had ideas of a central ‘force’ holding the planets in place but he did not go on about every particle in the universe attracting every other particle in the universe.

Two bodies do attract each other with individual forces proportional to their individual masses.

Can’t you see the contradiction in what you and Isaac say. You are emphatic about individual forces and then you move to both exerting the same force on each other.

Just doesn’t make rational sense. Isaac tried but do you think he really wanted to brainwash the world with something that doesn’t make sense? If he had his time over agian, doubt that he would do it again. How do the two forces suddenly become one?

The mass that is smaller has to know that somehow - otherwise how would it know when to stop attracting the other masses ?

Any mass is going to be sometimes smaller, sometimes bigger. How does it know which times are which ?

iceaura please look at the first diagram I posted. If your question is not answered there, let us know.

Plane,
It might have been pointed out, but if only the heavier mass attracts the lighter mass, how do you explain binary star systems and pulsars - where the stars rotate around each other?

Binary stars have been mentioned. If you looked at the earth moon system from said binary system, the earth moon system would appear to be the earth and moon rotate around each other.

That is exactly what I mean.
But this in no way prooves that X or Y are 0 at any point; rather your diagram demonstrates that they do indeed still have non-zero values, and abide by Newtons predictions.
It shows there are instances when the net gravitational field strength, z, is 0, but that's perfectly in accordance with Newtons laws.

Your logical argument is that:
A and G affect P,
therefore A must affect G.
This is fallacioiuse however:

Imagine a tabletop RPG which sais "Roll 1 6sided die and 1 8 sided die and add them to find skill X"
your argument is then:
D6 and D8 affect X
therefore D6 affect D8.
Obviously the outcome of the 6 sided die has absolutly no influence on that of the 8 sided die.

Thus the moons gravity has no effect on the earths gravity, and vice-versa.

-Andrew

Andrew Newton’s prediction is that A affects G. It is how he explains the high tide under the moon. Not sure how you can type your last line and acknowledge that the earth experiences a tidal system that is in a rhythm with the moon’s orbit of the earth. You are making up an argument to defeat your own argument as, incidentally, Newton did with himself.

I am only really after why people believe an apple attracts the earth but could you possible explain which of Newton’s laws predicts Z = zero as you state above?

Anyway we have the crisscross of the earth across its solar obit being in tune with the moon’s orbit of the earth, binary star systems and Newton’s third law as reasons that people believe an apple attracts the earth. And a few thought experiments. At first glance the most credible would be the crisscross but it has the problem of the sun’s gravity strength being stronger at the earth than the moon’s. Was initially disappointed in ben the man saying he had laboratory proof of the apple and then not being able to supply it but he did then acknowledge that I was right. Thanks. Will keep an eye out to see if any other reasons of belief turn up.

iceaura please look at the first diagram I posted. If your question is not answered there, let us know. No, it's not.

You are claiming that when two bodies are attracted to each other, only the larger is "pulling". The question is: how does either body know which one is larger ?

but he did then acknowledge that I was right. Thanks.

You're welcome.

I will also acknowledge that nothing you have said bears any resemblance to science, and that I made a mistake by not moving this thread in the first place.

Two bodies do attract each other with individual forces proportional to their individual masses. Can’t you see the contradiction in what you and Isaac say. What contradiction? Where is there a contradiction?:confused:You are emphatic about individual forces and then you move to both exerting the same force on each other.What do you mean "I move to both exerting the same force on each other"? What is this supposed to mean?? Each mass always exerts a force on another mass. The force is constant if the mass is constant.
They individually "exert" a force which is proportional to their individual mass.

For a two-body system. there is a centre/center of mass which lies outside of the CoM of either individual body. The Solar system has such a center, which is always outside the actual center of mass of the Sun.
With the planets, the center of mass changes, the Sun wobbles around this CoM constantly, because of the gravitational attraction (an individual attractive force from each individual mass).

Andrew Newton’s prediction is that A affects G.
Really? Please, site your source.
The high tide under the moon is caused because the net force acting upon the water has changed, not because the gravitational field strength of the earth has changed. That said, the tides are a complex process, and are thus a fairly poor example.

Not sure how you can type your last line and acknowledge that the earth experiences a tidal system that is in a rhythm with the moon’s orbit of the earth. Simple: I acknowlege Netwons second law of motion as well, and all works out.

could you possible explain which of Newton’s laws predicts Z = zero as you state above?
Certainly, though he doesnt have a single law, it is more of applying his laws to the scenario you created.

The net force is defined as the sum of all forces acting upon an object, which is how we get z=x+y, assuming we keep our system simple (only taking the gravitation of the two bodies into account.) From here, it is all mathmatics (using Newtons law of universal gravitation to find out values for x and y)
Z=0 if the location of our particle happens to resault in an x value of equal magnitude as the y value, but in an opposite direction.

So, let's model the apple between the earth and moon, using newtons equations.
The scenario to be modeled: earth and moon and apple are in a line, apple is some distance d, from earth and moon, determin acceleration, y, on apple at given distance d.
Assume the moon has distance 5 from earth.
Let d be the distance of the apple to earth, where 5<d<0.
Let y be the net acceleration of the apple towards earth. (Negative meaning towards moon, force is a vector, so a negativ simply denotes opposite direction.)

Using Newtons law of universal gravitation:
If we say Fearth=G*Earth*Apple/d^2
Let G*earth*apple=4
Fearth=4/d^2

Fmoon=G*moon*apple/(5-d)^2
where G*moon*apple=1 (moon's mass is roughly 1/4 of the earth's)
Fmoon=-1/(5-d)^2
(5-d) meaning, the distance of the moon to earth minus the distance of the apple to earth give us the distance of the apple to the moon, -1 because the moon is pulling the apple away from the earth.

Now, we know that Fnet equals the sum of all forces, so assume the two above are the only forces in the system:

Fnet=Fearth+Fmoon

Newtons second law states that Fnet=ma, where y=a, and the mass of apple is 1:
ma=Fearth+Fmoon
my=Fearth+Fmoon
y=(Fearth+Fmoon)/m
y=(Fearth+Fmoon)/1
y=Fearth+Fmoon
y=4/d^2 + -1/(5-d)^2

So we have 3 functions, the acceleration on the apple due to the earth, Fearth (okay thats the force but deviding by the 1 mass of apple keeps the function the same)
the acceleration on the apple due to the moon Fmoon, and the aceleration on the apple due to both, y.

Now punch those into a graphing calculator such as this one:
http://my.hrw.com/math06_07/nsmedia/tools/Graph_Calculator/graphCalc.html
And we see that, according to newton, the acceleration of the apple is indeed 0 at one point, because the function y intersects the d-axis (near 3.3)
We can also note that at that value of d, the forces due to the gravity of the earth and the moon have non-zero magnitudes, furthurmore they have equal magnitudes, and are opposite, fullfilling newtons first law; as they are balanced, and causing there to be no acceleration on the apple.

-Andrew

plane:

With that said, I can understand that no-one wants to debate a diagram that expressly says the third element of Newton’s law of gravity (every mass attracting every other mass) is wrong.

What are we doing now, if not debating?

Take the two masses two represent to adjacent celestial bodies. The earth and the moon if like but not necessarily. At all times and at all earth moon separations there is point along the axis between the earth and moon centres where the resultant rate of acceleration due gravity is zero.

Once you have found any resultant zero rate of acceleration you have disproved the universal aspect of Newton’s law of gravity. That’s the key point that no-one likes much.

You go wrong in the bolded sentence.

Gravitational forces obey what in mathematics is called the Principle of Superposition. This means that at a given point in space, the gravitational forces on any object are a simple vector sum of the individual gravitational forces from the surrounding objects.

Take two equally-massive objects, and place a test mass exactly half way between them. The test mass experiences no net gravitational force. Why? Not because gravity is not "universal", but simply because the two gravitational forces from the surrounding masses are equal in magnitude and opposite in direction at the position of the test mass.

Newton presumed that each gravity is an indefinite extension that is uninterrupted by any other gravity.

Not exactly. He presumed (and all the evidence says he was right) that individual gravitational forces add vectorially.

As soon as you recognize that adjacent gravities must have a zero rate of acceleration between them, you are doing a mathematical analysis that undoes Newton’s premise of all gravities being infinite extensions. You then know he was wrong about an apple attracting the earth.

You're laboring under a simple misapprehension.

I suggest you grab any introductory textbook on physics and read up on Newton's laws of motion. You'll probably only need to go as far as the first three chapters or so to understand your error.

------

In response to your comments on my previous post...

Maybe having a misunderstanding about the issue at hand. Whatever, as the moon orbits the earth, the earths orbit of the sun is affected in such away that its distance from the sun increases. Look it up. If your result is different to this, post to that affect.

No need. I agree with you. So what?

You're not being precise enough. There are actually three separate effects here. One is the intrinsic spin of the Earth around its axis; another is Earth's orbital motion about the centre of mass of the Earth-moon system; the third is the Earth's orbital motion around the Sun. These three motions are independent and have three different rotational axes.

Your trouble is in explaining the second as being consistent with the first.

The motions are independent. There's no inconsistency to explain.

I explained carefully to you that "pull" is just one way to denote an attractive force.

Not sure that your definition of carefully would match all others but what is an ‘attractive force’. A push is an exertion of matter upon matter. What is a pull in terms of matter?

A pull is an exertion of matter on matter too. There's no difference at the atomic level.

Nobody can explain why gravity is an attractive force. It just is. All observation confirms it. It's just an observed feature of our universe. You can imagine a universe where things fall up instead of down, but that's not our universe, obviously.

How do you know that nobody can explain it? Aren’t you saying you are god here?

Ok, let me carefully qualify my statement. I personally know of nobody who can explain why gravity is an attractive force.

Do you?

Not really given to answering questions with questions, but how could Newton’s third law not explain equal and opposite high tides?

Merely stating Newton's third law is not an explanation. You'll have to do better than that.

My "proof" is:

1. Newton's third law states that for every force there is an equal and opposite force.
2. Therefore, when two bodies interact, if one exerts a force F on the other, the other exerts an equal force F on the first, but in the opposite direction.
3. Gravity is a force (in the Newtonian picture).
4. No known experiment with force has ever violated Newton's third law.
5. Therefore, if the Earth pulls on an apple, the apple must pull back on the Earth with an equal and opposite force.

That's really all the "proof" that is needed.

Your problem is at three. Gravity is not a force. Gravity is known to cause an acceleration through space. This does not make gravity force. It makes it a cause of force. Incidentally, 3 to 5 is one hell of a jump.

Pick up any textbook and you will see that all physicists agree that gravity is a force. (Caveat: we're not dealing with the general relativistic description of gravity here. Walk before you run.)

Do you think all physicists are wrong?

pardon
what is the gr des of grav?

this boggles
how can something so basic be such a mystery?

pardon
is it a mystery?

You're welcome.

I will also acknowledge that nothing you have said bears any resemblance to science, and that I made a mistake by not moving this thread in the first place.


Ben thanks for moving into what is known as pseudoscience. Only complaint is it didn't have moved status on the other forum. Had a bit of trouble finding it. Thought it must have been censored for a start.

Anyway all replies received definitely have a pseudo element to them so this is a fitting spot.

I should state though, that there is nothing false about pursuing what others consider to be proof of an apple attracting the earth. That is a genuine thing to do.

On going though just what everybody seems to have in their heads, there is mildly reoccurring theme. A beleaguered cry of how would the smaller mass know it was the smaller mass and thus know not to not use its gravity.


You are claiming that when two bodies are attracted to each other, only the larger is "pulling". The question is: how does either body know which one is larger ?

For a start I don't use the term pulling. In between adjactent bodies, the direction of acceleration of gravity of each is always opposite.


http://www.fotothing.com/photos/065/0654fc95afac72948b816042231bc471.jpg?ts=1202089341

Mathematically there must always be a termination of gravity at some point between the adjacent bodies. It is not a matter of the smaller body somehow knowing it is smaller, beyond the termination point there is no direction of fall towards it. Pretty straight forward really. Surprised that you are having trouble seeing it. Possibly you are missing seeing that the direction of fall between adjacent bodies is always in opposite directions.



Really? Please, site your source.
The high tide under the moon is caused because the net force acting upon the water has changed, not because the gravitational field strength of the earth has changed. That said, the tides are a complex process, and are thus a fairly poor example.

You are like JR and have to explain how you know that gravity is a force. Not sure why you would say the gravitational field strength of the earth has not changed. Drop something under the moon. It falls at a slower rate to something dropped 6 hours further around the earth. The change is measurable. You are trying to say black isn't black for some reason or other.

Simple: I acknowlege Netwons second law of motion as well, and all works out.


Certainly, though he doesnt have a single law, it is more of applying his laws to the scenario you created.

The net force is defined as the sum of all forces acting upon an object, which is how we get z=x+y, assuming we keep our system simple (only taking the gravitation of the two bodies into account.) From here, it is all mathmatics (using Newtons law of universal gravitation to find out values for x and y)
Z=0 if the location of our particle happens to resault in an x value of equal magnitude as the y value, but in an opposite direction.

So, let's model the apple between the earth and moon, using newtons equations.
The scenario to be modeled: earth and moon and apple are in a line, apple is some distance d, from earth and moon, determin acceleration, y, on apple at given distance d.
Assume the moon has distance 5 from earth.
Let d be the distance of the apple to earth, where 5<d<0.
Let y be the net acceleration of the apple towards earth. (Negative meaning towards moon, force is a vector, so a negativ simply denotes opposite direction.)

Using Newtons law of universal gravitation:
If we say Fearth=G*Earth*Apple/d^2
Let G*earth*apple=4
Fearth=4/d^2

Fmoon=G*moon*apple/(5-d)^2
where G*moon*apple=1 (moon's mass is roughly 1/4 of the earth's)
Fmoon=-1/(5-d)^2
(5-d) meaning, the distance of the moon to earth minus the distance of the apple to earth give us the distance of the apple to the moon, -1 because the moon is pulling the apple away from the earth.

Now, we know that Fnet equals the sum of all forces, so assume the two above are the only forces in the system:

Fnet=Fearth+Fmoon

Newtons second law states that Fnet=ma, where y=a, and the mass of apple is 1:
ma=Fearth+Fmoon
my=Fearth+Fmoon
y=(Fearth+Fmoon)/m
y=(Fearth+Fmoon)/1
y=Fearth+Fmoon
y=4/d^2 + -1/(5-d)^2

So we have 3 functions, the acceleration on the apple due to the earth, Fearth (okay thats the force but deviding by the 1 mass of apple keeps the function the same)
the acceleration on the apple due to the moon Fmoon, and the aceleration on the apple due to both, y.

Now punch those into a graphing calculator such as this one:
http://my.hrw.com/math06_07/nsmedia/tools/Graph_Calculator/graphCalc.html
And we see that, according to newton, the acceleration of the apple is indeed 0 at one point, because the function y intersects the d-axis (near 3.3)
We can also note that at that value of d, the forces due to the gravity of the earth and the moon have non-zero magnitudes, furthurmore they have equal magnitudes, and are opposite, fullfilling newtons first law; as they are balanced, and causing there to be no acceleration on the apple.

-Andrew

That’s rubbish Andrew. You are presuming that the apple attracts the earth, rather like in Cavendish experiments where a universal constant is worked out when the large mass has not been observed to move and the small mass has taken no part in the calculation. Your trouble is you are seeing Z as a net force of zero. It is a resultant rate of acceleration of zero.




Pick up any textbook and you will see that all physicists agree that gravity is a force ?

Sorry JR but this does not make gravity a force. You seem to be saying gravity is a force because everyone says it’s a force. That is very much a psuedoscience answer.

We know

1/that gravity causes mass to accelerate

or that 2/ gravity causes mass to become weight when such acceleration is restricted by the presence of other mass

How and why do you jump to gravity is a force from there beyond doing it because everyone else does is yours to answer. Not mine.

plane:Do you think all physicists are wrong??

Anybody who believes that a small mass attracts a large mass has their case to prove.

http://www.fotothing.com/photos/065/0654fc95afac72948b816042231bc471.jpg?ts=1202089341

Can you really explain how there is an acceleration towards the smaller mass from the point indicated.

Please don’t waste your time replying if you don’t want to.

Only really after why everybody believes a small mass attracts a large mass. The asking of "how would the small mass know its the small mass" has been of some help.

Cheers.

plane:

You seem to be saying gravity is a force because everyone says it’s a force. That is very much a psuedoscience answer.

We know

1/that gravity causes mass to accelerate

or that 2/ gravity causes mass to become weight when such acceleration is restricted by the presence of other mass

You're arguing against yourself.

Take your point (1): gravity causes mass to accelerate. Newton's second law says what? Hmm... that's right. Here it is:

F = ma

On the right we have mass and acceleration. On the left, we have what causes that acceleration. What causes acceleration? Oh look! Force. And you know what? Nothing other than a force can cause a mass to accelerate. That's what we mean by "force". A force is something that causes an acceleration.

Therefore, we see by your own statement that gravity is a force.

I don't understand statement (2); it's not clear.

Please don’t waste your time replying if you don’t want to.

I'll be selective - just as you are selective in responding to my points. I notice that you won't engage with points you find inconvenient for your argument.

Do you have an open or closed mind about this?

What do you mean "I move to both exerting the same force on each other"? What is this supposed to mean??

A mass always exerts a force on another mass. The force is constant if the mass is constant.
They individually "exert" a force which is proportional to their individual mass.

What is the big problem with this, that 2 bodies will attract each other with force proportional to mass?
Why would this become zero at some point? There is a point between two bodies, that will see no net attraction because the forces are equal, or whatever third object is at such a point will not accelerate, or will have no weight in either gravitational field, it's said to be at an equilibrium point.
This isn't because the attraction from either mass on the third body between them is zero, it's just balanced, or algebraically zero--like when two cars collide head-on, their velocity becomes zero, but momentum doesn't.

You are like JR and have to explain how you know that gravity is a force... ...You seem to be saying gravity is a force because everyone says it’s a force. That is very much a psuedoscience answer.
Looks like James covered this well.

Not sure why you would say the gravitational field strength of the earth has not changed. Drop something under the moon. It falls at a slower rate to something dropped 6 hours further around the earth. The change is measurable. You are trying to say black isn't black for some reason or other.
It seems you completely ignored the fact that acceleration is dependant on the NET FORCE on an object, not the graviational field strength.
It only appears I'm saying black is not black is because you won't open your eyelids to look at the object.

You are presuming that the apple attracts the earth Well I wouldnt be testing Newtons theories by assuming the apple does anything else, now would I?

Your trouble is you are seeing Z as a net force of zero. It is a resultant rate of acceleration of zero.
Ok good, now do some critical thinking and you can derrive that:
F=ma
F=m*0
0m=0
F=0

Or in plain english: When the acceleration of an object is 0, the net force acting upon the object is 0.
My argument still stands... And so does my nebulous one a page back, would you care to address it's points?

-Andrew

plane:



You're arguing against yourself.

Take your point (1): gravity causes mass to accelerate. Newton's second law says what? Hmm... that's right. Here it is:

F = ma

On the right we have mass and acceleration. On the left, we have what causes that acceleration. What causes acceleration? Oh look! Force. And you know what? Nothing other than a force can cause a mass to accelerate. That's what we mean by "force". A force is something that causes an acceleration.

Therefore, we see by your own statement that gravity is a force.

I don't understand statement (2); it's not clear.



I'll be selective - just as you are selective in responding to my points. I notice that you won't engage with points you find inconvenient for your argument.

Do you have an open or closed mind about this?

No, my mind is very open. Would suggest that is what would lead someone to question whether an apple really does attract the earth.

Also I will engage in any point you want to that has to do with gravity. As long as you stick to it to an end point. This thread was started in an effort to find the considered proof of an apple attracting the earth. You tied your proof to gravity being a force. That is what I address.


Been able to see what you are saying.

Only force can cause acceleration thereforce gravity is a force. That is what you are saying.

What we know of gravity is that it is a mathematical construct in space. It is an inverse square law around mass.


Mathematical construct = force?

If gravity is a force, what is its equal and opposite when mass is not present at any point in the mathematical construct?

Yours to answer. Please don't make Newton's third law wrong.




Or in plain english: When the acceleration of an object is 0, the net force acting upon the object is 0.



Andrew, Z is not an object. It is a point in space. You've got get past seeing the necessity of a second object for gravity to exist.

Just think of a point in space 100,000 km from the earth. No mass is present. Is there gravity?

Then is there force? There is no m to give you a m.a so there is no force.

Thus ideas of gravity being a force are yours to substantiate. You can answer JR's equal and opposite question if you like.


I would really like proof along the lines of the large mass moving in a Cavendish experiment.

Intellectual arguments can hardly be expected to carry the day.

There will be a point (actually a surface) between the two bodies where the net force is zero. This does not mean the force acting on both bodies will be zero (If your reasoning is correct you would imply not only the force acting on the big body is zero, the force on the smaller body is zero too, so there would be no gravitational interaction at all). You imagine moving from the middle (zero force) surface to the bigger body slowly. Then the gravitational force would increase from zero to some (vector) value pointing to the bigger body. When you approach the bigger body, the force will tend to infinity. But if you are standing EXACTLY on the bigger body, the force will be directed towards the smaller body. That is because exactly at the bigger body (assuming the body is pointlike), the gravitational force from itself is ZERO. This may sound strange but you can make it precise by considering locally supported distribution of mass. Generally in nonstatic situations gravitational force of a body acted on itself becomes nonzero.

You've got get past seeing the necessity of a second object for gravity to exist. In order for there to be a force of gravity between two objects, there has to be 2 objects... a fairly obviouse fact.
That said, my proof works with or without an apple, devide one mass out of the equations and they still work (you will notice the functions do not change one bit, and what's more, an acceleration value is still given.)
This is because I measured the gravitational field strength at Z, which is the amount of acceleration any body will experiance at Z due to the gravitational effects. The net field strength is 0 at Z, however the strength of the earth an moon are still non-zero, all in accordance with Newton.
My argument stands.

What we know of gravity is that it is a mathematical construct in space. It is an inverse square law around mass. False, we know that gravity exists, that it a scientific fact, don't believe me? Then fly away. Can't? Well then a force MUST be preventing you, this force is gravity. Newton modled it in mathmatical terms, and the function describing happens to be an inverse square.

If gravity is a force, what is its equal and opposite when mass is not present at any point in the mathematical construct? When no second mass is present, there is no two objects presant for there to be a force between them, simple as that. The derived function when a second mass is not presant is the gravitational field strength which can predict the acceleration another mass would feel at a given point due to the first mass, you might have heard of the g constant? 9.8ms^-2 ? This is an approximation of the gravitational field stength of earth near it's surface.

Just think of a point in space 100,000 km from the earth. No mass is present. Is there gravity?

Then is there force? There is no m to give you a m.a so there is no force.[QUOTE]
I would have thought the lack of force as being unmentionably obviouse, however Newton predicts the force of gravity to occur between 2 object, so there is no problem with his model. He does however predict a gravitational field strength for a given point, which describes the acceleration a body in that position would undergo. Perhaps you have heard of g=9.8ms^-2 the gravitational field strength of the earth at an arbitrary point near the surface of the earth? Please also note that this field strength is for one body, the actual acceleration felt will be the net field strength, calculated by adding the field strength of all bodies (this net value can be 0, the actual field strength of a single body cannot be.)

[QUOTE]I would really like proof along the lines of the large mass moving in a Cavendish experiment.

Intellectual arguments can hardly be expected to carry the day. Well, since your ignoring the cosmological amount of cosmological evidence, I'm afraid that's not possible. You see, masses manageable by humans create forces which are simply too small; the error of any test would be many times that of the resault, or expected resaults, themselves. Of course, if you can provide an experiment in which to test, which would produce a percent error of usable amounts, by all means share your ideas.

-Andrew

plane:

Only force can cause acceleration thereforce gravity is a force. That is what you are saying.

What we know of gravity is that it is a mathematical construct in space. It is an inverse square law around mass.

Mathematical construct = force?

Now you're confusing the description of gravity with the physical reality of gravity. The physical reality of gravity is that when you drop an apple it falls to the ground (and the ground falls towards it, though that is much harder to see). The inverse square law quantifies how gravity changes with distance.

It is nonsense to say that gravity is "just a mathematical construct", if that is what you're claiming. It has real, observable, measurable effects.

If gravity is a force, what is its equal and opposite when mass is not present at any point in the mathematical construct?

I'm not sure what you're asking, but perhaps you're alluding to the gravitational field, as opposed to the gravitational force. Unlike the force, which is measurable, as a first approximation you can consider the field to be a pure mathematical construct. The gravitational field strength at a given point in space tells you what force would be experienced by a standard "test mass" if it were placed at that point. But the field is just a calculational convenience. It is the force that is real.

There is no Newton's Third Law for fields. Nothing in physics requires that every field has an equal and opposite field. Newton's third law only applies to force interactions between two objects. So, if you have only one object, Newton's third law is totally irrelevant.

Just think of a point in space 100,000 km from the earth. No mass is present. Is there gravity?

Observationally, there's no way to tell unless you put a mass at the point in space.

Theoretically, as a calculation convenience, we say that there is a gravitational field at the point in space, such that if you put a standard mass there it would feel a particular force.

Then is there force? There is no m to give you a m.a so there is no force.

Correct.

There will be a point (actually a surface) between the two bodies where the net force is zero. This does not mean the force acting on both bodies will be zero (If your reasoning is correct you would imply not only the force acting on the big body is zero, the force on the smaller body is zero too, .

No Temur. Go through the thread. Look at the second diagram. Small gravity field within the large gravity


In order for there to be a force of gravity between two objects, there has to be 2 objects... a fairly obviouse fact.

If objects cause gravity and gravity is a force, why does there have to be a second object present for gravity to be a force.


That said, my proof works with or without an apple, devide one mass out of the equations and they still work (you will notice the functions do not change one bit, and what's more, an acceleration value is still given.)
This is because I measured the gravitational field strength at Z, which is the amount of acceleration any body will experiance at Z due to the gravitational effects. The net field strength is 0 at Z, however the strength of the earth an moon are still non-zero, all in accordance with Newton.
My argument stands.

Your argument does not stand. Stating however proves nothing.

How do the earth and moon gravities cause a net acceleration of zero and still exist whilst they do it.?

Do they cause the net result in once instance, then go back to their otherwise values in the next instance then cause the net result again etc. How can a net result and the causes of a net result co-exist. Physically and mathematically impossible. Please don’t take it to personally but it makes you look very weak when you insert however the way you do with nothing to back it up.





False, we know that gravity exists, that it a scientific fact, don't believe me? Then fly away. Can't? Well then a force MUST be preventing you, this force is gravity. Newton modled it in mathmatical terms, and the function describing happens to be an inverse square.

You are obviously scraping the bottom of the barrel a bit with your must in capitals. If that is your best ‘argument’, you better give up. What prevents me from flying away is my weight. My weight is a product of my mass and the earth’s gravity strength.

When no second mass is present, there is no two objects presant for there to be a force between them, simple as that. The derived function when a second mass is not presant is the gravitational field strength which can predict the acceleration another mass would feel at a given point due to the first mass, you might have heard of the g constant? 9.8ms^-2 ? This is an approximation of the gravitational field stength of earth near it's surface. .


So you are saying that gravity is not a force unless there are two masses present.. Doesn’t fit with your other logic of mass causes gravity and gravity is a force. Your second logic says gravity is a force because of one mass, not because of two masses.



I would have thought the lack of force as being unmentionably obviouse, however Newton predicts the force of gravity to occur between 2 object, so there is no problem with his model. He does however predict a gravitational field strength for a given point, which describes the acceleration a body in that position would undergo. Perhaps you have heard of g=9.8ms^-2 the gravitational field strength of the earth at an arbitrary point near the surface of the earth? Please also note that this field strength is for one body, the actual acceleration felt will be the net field strength, calculated by adding the field strength of all bodies (this net value can be 0, the actual field strength of a single body cannot be.)

Well, since your ignoring the cosmological amount of cosmological evidence, I'm afraid that's not possible. You see, masses manageable by humans create forces which are simply too small; the error of any test would be many times that of the resault, or expected resaults, themselves. Of course, if you can provide an experiment in which to test, which would produce a percent error of usable amounts, by all means share your ideas.

-Andrew

Reading your Newton predicts force of gravity to occur between two bodies, he doesn’t really. He predicts every particle “attracts” every other particle. Then goofs off into a formula only involving two particles.

Not ignoring cosmological evidence. The criss cross of the earth across its solar path in tune with the moon’s orbit of the earth is noted. This is evidence of the earth and moon as a whole moving away from the sun. Not evidence of the moon attracting the earth.

plane:



Now you're confusing the description of gravity with the physical reality of gravity. The physical reality of gravity is that when you drop an apple it falls to the ground (and the ground falls towards it, though that is much harder to see). The inverse square law quantifies how gravity changes with distance.

It is nonsense to say that gravity is "just a mathematical construct", if that is what you're claiming. It has real, observable, measurable effects. .



Confusing nothing. The mathematical construct has a real observable effect. Acceleration. Acceleration that decreases as an inverse square of distance moved away from the mass the construct is around. You have confessed to not knowing has mass causes gravity so probably wouldn’t hurt you to get a little deeper into this area if you have anything of a genuine interest in gravity.

Your notion seems to be that the potential for acceleration is not there unless a second mass is present. You aren't in the dark ages are you? Very much you seem like a pseudo scientist.


I'm not sure what you're asking, but perhaps you're alluding to the gravitational field, as opposed to the gravitational force. Unlike the force, which is measurable, as a first approximation you can consider the field to be a pure mathematical construct. The gravitational field strength at a given point in space tells you what force would be experienced by a standard "test mass" if it were placed at that point. But the field is just a calculational convenience. It is the force that is real. .

Refer to previous answer.

There is no Newton's Third Law for fields. Nothing in physics requires that every field has an equal and opposite field. Newton's third law only applies to force interactions between two objects. So, if you have only one object, Newton's third law is totally irrelevant. .

Your are supposed to be addressing what is the equal and opposite force to gravity if gravity is a force, as you claim it to be.

As an incidental, if gravity strength is proportional to quantity and if an apple did attract the earth, why would you multiply the apples quantity by the earth’s quantity to find a composite force.

If the apple and the earth did produce a composite force, would you not add their quantities if quantity and gravity strength are directly proportional.


So the question to answer for today is

If mass causes gravity and gravity is a force, where is the equal and opposite force to the force that mass is causing?

Hit the keyboards. Give it your best shot. Almost bet that no answer of sense will be forthcoming.

I already said what is wrong with your point and you ignore it so I have no interest in coming back here again.

If objects cause gravity and gravity is a force, why does there have to be a second object present for gravity to be a force. All forces are interactions between 2 objects, always.
How do the earth and moon gravities cause a net acceleration of zero and still exist whilst they do it.? The exact nature of 'how' is irrelevant, the issue is that it does, and there is no law or logic which dictates that they cease to exist.
An analogy: A man is place on The Rack, one rope binds his arms and pulls up, the other to his legs pulling down. The man himself does not move, the net force on him is 0, however, he still feels the forces of each rope pulling in opposite directions; if the forces ceased to exist, the torture device would have been ineffective, however they do not.
As it turns out, gravity can cause a similar fictional force; the Tidal force. The apple, or whatever object, if placed at Z, would experience a force. One side attracted toward the moon, the other toward earth. While not significant at this scale, replace moon and earth with a binary neutron star system, and the tidal force at Z could be fatal.

How do the earth and moon gravities cause a net acceleration of zero and still exist whilst they do it.? Once again, the 'how' is unimportant, your under the impression that there is a law which states that if 2 vectors add to 0, they must not exist. I have heard of no such thing.

Do they cause the net result in once instance, then go back to their otherwise values in the next instance then cause the net result again etc. What do you mean by 'instance' ?

How can a net result and the causes of a net result co-exist. There's nothing which prooves they cannot, and by all observations, they do. This is a question of philosophy, not science, to which I can ask "How can anything exist?"
Physically and mathematically impossible. Proof?

What prevents me from flying away is my weight. My weight is a product of my mass and the earth’s gravity strength. ‘Gravity strength’ is not a defined term in physics. However weight is clearly defined as being proportional to mass and the gravitational field strength at a given location, obviously on earth, this is earth’s gravitational field strength, thus it is earth’s force of gravity acting upon you which prevents you from flying away.
So you are saying that gravity is not a force unless there are two masses present.. Doesn’t fit with your other logic of mass causes gravity and gravity is a force. Your second logic says gravity is a force because of one mass, not because of two masses. Straw man argument. I stated that the force of gravity only exists as an interaction between two masses. This applies to all forces, for example electromagnetic.

Reading your Newton predicts force of gravity to occur between two bodies, he doesn’t really. He predicts every particle “attracts” every other particle. Seriously? If there wasn't another particle to attract, and therefore another mass, then there would be no gravity, now would there?
Then goofs off into a formula only involving two particles.
Perhaps because 2 particles is the simplest problem to which his theory can be applied to, from which, the interaction between multiple particles can be computed?

As an incidental, if gravity strength is proportional to quantity and if an apple did attract the earth, why would you multiply the apples quantity by the earth’s quantity to find a composite force.

If the apple and the earth did produce a composite force, would you not add their quantities if quantity and gravity strength are directly proportional. Because if x and y are proportional to z, then z=xy, that is what the word 'proportional' signifies when used in a mathematical context.

Your are supposed to be addressing what is the equal and opposite force to gravity if gravity is a force, as you claim it to be.
If mass causes gravity and gravity is a force, where is the equal and opposite force to the force that mass is causing?

Hit the keyboards. Give it your best shot. Almost bet that no answer of sense will be forthcoming. "The earth pulls on the apple (Fg earth on apple) and the apple pulls back on the earth (with equal and opposite strength, Fg apple on earth, is the reaction force.)"
Perhaps you expect the reaction force to be of a different nature than the action force? It is rather, always of the same nature.


...it makes you look very weak when you insert however the way you do with nothing to back it up.
You are obviously scraping the bottom of the barrel a bit with your must in capitals.
If that is your best ‘argument’, you better give up.
You have confessed to not knowing has mass causes gravity so probably wouldn’t hurt you to get a little deeper into this area if you have anything of a genuine interest in gravity.
You aren't in the dark ages are you? Very much you seem like a pseudo scientist.
Arguments ad hominem.

-Andrew

plane:

If we're not going to have an honest conversation, then you're wasting my time. You're going to need to start addressing all the points I make, and not ignoring the ones that are inconvenient for you.

Your notion seems to be that the potential for acceleration is not there unless a second mass is present. You aren't in the dark ages are you? Very much you seem like a pseudo scientist.

This is the kind of dishonesty I'm talking about. You slip in the word "potential", but you must realise that there is a difference between an actual acceleration and a "potential for acceleration". In fact, I tried to carefully educate you on the difference between force and field in my previous post, but you conveniently ignore what you learned there in making the above statement. This suggests to me either that you're stupid and really can't understand explanations, or that you're dishonest and want to stick your fingers in your ears and pretend not to hear things you don't like the sound of.

Making accusations that I am a pseudoscientist makes you look even more on the fringe than how you started. The only things I have told you are what standard physics, accepted by all professionals in the field, says.

As an incidental, if gravity strength is proportional to quantity and if an apple did attract the earth, why would you multiply the apples quantity by the earth’s quantity to find a composite force.

It's a simple matter of logical deduction. Take two masses, 1 kg and 1 kg. Measure the gravitational force exerted by one on the other at a given distance. Now, replace one of them by a mass twice as large, 2 kg. Measure the force again. It is twice as large. So, we conclude that the force depends on the product of the masses. It cannot, for example, depend on the sum of the masses.

If the apple and the earth did produce a composite force, would you not add their quantities if quantity and gravity strength are directly proportional.

No. In my example, if we added the masses, then in the second case there would be a total of 3 kg, as opposed to an initial 2 kg total, so we'd expect an increase in the force by a factor of 3/2. Instead, we observe a doubling of the force.

So, your hypothesis is easily disproved.

If mass causes gravity and gravity is a force, where is the equal and opposite force to the force that mass is causing?

If mass A exerts a gravitational force on mass B (remember, two masses are required, since all forces are interactions), then B exerts a force of equal magnitude on A, in the opposite direction. This is Newton's third law.

Hit the books. Give it your best shot. Who knows? Maybe even you will be able to learn the basic laws of motion if you try.

Andrew don’t know how you type this. No point going around in circles with the rest of it but this

Seriously? If there wasn't another particle to attract, and therefore another mass, then there would be no gravity, now would there.

You jest. You are saying if only mass existed in the universe, that mass would have no gravity?

Because if x and y are proportional to z, then z=xy, that is what the word 'proportional' signifies when used in a mathematical context.

X and y and not proportional to z. Mass is proportional to gravity strength. Not mass x mass is proportional to gravity strength.

plane:





This is the kind of dishonesty I'm talking about. You slip in the word "potential", but you must realise that there is a difference between an actual acceleration and a "potential for acceleration". In fact, I tried to carefully educate you on the difference between force and field in my previous post, but you conveniently ignore what you learned there in making the above statement. This suggests to me either that you're stupid and really can't understand explanations, or that you're dishonest and want to stick your fingers in your ears and pretend not to hear things you don't like the sound of..

You just don’t get my point. I guess that is my fault. To a certain extent anyway. By potential I mean that a rate of acceleration exists in space whether or not an object is present and all I am doing, anyway, is trying to follow your logic. You say gravity is a force. And this is proof of an apple attracts the earth.

My "proof" is:

1. Newton's third law states that for every force there is an equal and opposite force.
2. Therefore, when two bodies interact, if one exerts a force F on the other, the other exerts an equal force F on the first, but in the opposite direction.
3. Gravity is a force (in the Newtonian picture).
4. No known experiment with force has ever violated Newton's third law.
5. Therefore, if the Earth pulls on an apple, the apple must pull back on the Earth with an equal and opposite force.

And then you posted that gravity is a force because physics say so. I pointed out what we know about gravity with respect of 3 but perhaps we better go back to2. Your proof I suppose is fundamentally dependent on the ‘if’ in 2.

http://www.fotothing.com/photos/0d2/0d2e0f48151cd2c567639d2bd3f4e1c9.jpg?ts=1202286576

You presume the red arrow is a force. How is it applied to the apple?




Making accusations that I am a pseudoscientist makes you look even more on the fringe than how you started. The only things I have told you are what standard physics, accepted by all professionals in the field, says.

I have told you before, everyone accepting that something is right doesn’t make it right. Professional scholars once accepted that the earth is the centre of the universe. If you think your a genuine scientists, nothing I post should change that.







It's a simple matter of logical deduction. Take two masses, 1 kg and 1 kg. Measure the gravitational force exerted by one on the other at a given distance. Now, replace one of them by a mass twice as large, 2 kg. Measure the force again. It is twice as large. So, we conclude that the force depends on the product of the masses. It cannot, for example, depend on the sum of the masses.



No. In my example, if we added the masses, then in the second case there would be a total of 3 kg, as opposed to an initial 2 kg total, so we'd expect an increase in the force by a factor of 3/2. Instead, we observe a doubling of the force.

So, your hypothesis is easily disproved.

Really. Didn't even think I put a hypothesis up. Just asked a question.

Your conclusion aside all you do is state that mass is proportional to a rate of acceleration due to gravity..

What I mean is this.

We have two masses. One 2 kg and the other 5kg. They are separated by a certain distance. F = G x 5 x 2/ d x d. So we have 7 kgs producing a gravitational force that equals 10.

Now we rearrange the masses and take 1kg from the larger mass and attach it the smaller. In a Cavendish type situation if you like. We don’t alter d.

Now we have F = G x 4 x 3/d x d. So now, according to the Cambridge scholar of yesterday year, we have 7 kgs of mass producing a graviational force that equals 12.

And yet gravity strength is proportional to quantity.

How does the gravitational force increase from 10 to 12 after some of one mass is transferred to the other?

To me that is an important consideration to be addressed before I hitch my wagon to an apple ‘attracting’ the earth in accordance with Newton’s law of gravity.

Of course you will come up with a glib answer to make this consideration irrelevant.

Incidentally, have pointed out in this thread that the small masses are always cancelled out during the calculation of G in Cavendish experiments. And that the experiments only confirm a relationship between the quantity of the large mass and its gravity strength.

Sorry for wasting your time but anyone with a questioning mind can only exercise doubt about an apple attracting the earth.

plane:

You just don’t get my point. I guess that is my fault. To a certain extent anyway. By potential I mean that a rate of acceleration exists in space whether or not an object is present...

To measure a "rate of acceleration" you need something to be accelerating.

But maybe you're just talking about the field again, without being specific. Do you understand the distinction between force and field?

My "proof" is:

1. Newton's third law states that for every force there is an equal and opposite force.
2. Therefore, when two bodies interact, if one exerts a force F on the other, the other exerts an equal force F on the first, but in the opposite direction.
3. Gravity is a force (in the Newtonian picture).
4. No known experiment with force has ever violated Newton's third law.
5. Therefore, if the Earth pulls on an apple, the apple must pull back on the Earth with an equal and opposite force.

And then you posted that gravity is a force because physics say so.

The term "force" is defined to anything that causes an object to accelerate. If you agree that gravity causes objects to accelerate, then gravity is a force.

If you wish to redefine the word "force", please tell me what your own idiosyncratic definition is. All I've told you is how physicists define it. If your definition is different, then we're talking at cross purposes and the discussion will go nowhere. We need to agree on what "force" is, before we can even being to discuss gravity in any meaningful way.

You presume the red arrow is a force. How is it applied to the apple?

It's action at a distance. Quite clearly, gravitational forces do not require direct contact between objects.

I have told you before, everyone accepting that something is right doesn’t make it right. Professional scholars once accepted that the earth is the centre of the universe. If you think your a genuine scientists, nothing I post should change that.

Don't worry about me. I'm quite content in what I believe about myself, I assure you.

What I mean is this.

We have two masses. One 2 kg and the other 5kg. They are separated by a certain distance. F = G x 5 x 2/ d x d. So we have 7 kgs producing a gravitational force that equals 10.

Now we rearrange the masses and take 1kg from the larger mass and attach it the smaller. In a Cavendish type situation if you like. We don’t alter d.

Now we have F = G x 4 x 3/d x d. So now, according to the Cambridge scholar of yesterday year, we have 7 kgs of mass producing a graviational force that equals 12.

And yet gravity strength is proportional to quantity.

This may help us make some progress.

Probably, your misconception lies in the last sentence quoted here. You assume, for reasons that are unclear, that "gravity strength is proportional to quantity", by which I assume you mean that the force between two objects is proportional to the total mass of the two objects combined.

There's a problem. The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects. To make this clearer, let's consider the acceleration of one of the two objects instead of the force. Take object M to be the one creating the force (for example, M is the Earth), and object m to be the one experiencing the force. Now, according to Newton's second law, the acceleration of m is:

a = F/m

And, the force on m is

F = GMm/r^2.

Therefore, the acceleration of m is:

a = GM/r^2.

Notice that the acceleration of m is determined by its distance from M and the magnitude of M only. The mass of m itself does not enter the equation.

Now, look again at your example. Let's take M=5 kg and m=2 kg, as in your first situation. The acceleration of the 2 kg mass towards the 5 kg mass is then

a = G(5)/r^2

In your second situation, you have M=4 kg and m=3 kg. The acceleration of m is now:

a = G(4)/r^2

It's less than before. But that makes sense, because there's now less mass "pulling" it. Whereas before a mass of 5 kg was attracting it gravitationally, now there's only a mass of 4 kg attracting it. Hence, less acceleration.

While we're at it, consider the acceleration of the larger mass in the two situations. Before the mass change, the acceleration of the 5 kg mass towards the 2 kg mass is

A = G(2)/r^2

Afterwards, it is

A = G(3)/r^2

So, the acceleration of the larger mass towards the smaller one increased, while the acceleration of the smaller mass decreased, as we would expect.

The important thing to take away from this is that the acceleration of one object is determined only by the mass of the other.

But...

How does the gravitational force increase from 10 to 12 after some of one mass is transferred to the other?

It increases because the effect of mass is multiplicative, not additive. There's really little else that can be said about this. It's an experimentally confirmed fact about how gravity works. Sure, you may be able to imagine a world in which gravity didn't work like that, but it's just not our world. Like it or not, you have to live with it. We can't dictate to nature how she works.

plane:



To measure a "rate of acceleration" you need something to be accelerating.


Not really. You can use the inverse square law to calculate what a rate of acceleration in space would be.





The term "force" is defined to anything that causes an object to accelerate. If you agree that gravity causes objects to accelerate, then gravity is a force.



If you wish to redefine the word "force", please tell me what your own idiosyncratic definition is. All I've told you is how physicists define it. If your definition is different, then we're talking at cross purposes and the discussion will go nowhere. We need to agree on what "force" is, before we can even being to discuss gravity in any meaningful way.

Well I have posted my definition several times if you have been following. Force is the exertion of matter upon matter.



It's action at a distance. Quite clearly, gravitational forces do not require direct contact between objects.

How is an action at a distance applied? Do you know?






There's a problem. The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects. To make this clearer, let's consider the acceleration of one of the two objects instead of the force. Take object M to be the one creating the force (for example, M is the Earth), and object m to be the one experiencing the force. Now, according to Newton's second law, the acceleration of m is:

Not sure why you can’t see it. Newton’s law of gravity specifically says that both masses create the force.


Every particle in the universe attracts every other particle in the universe with a force that is proportional to the product of their masses etc.

The force is proportional to the product of their masses.

You multiply the masses together to find the force. That’s the what the law states.

When you go setting mg equal to G.M.m/d x d (mg = G.M.m/d x d) on the left hand side you have the force m experiences courtesy of the large Mass.

On the right hand side you have a force that supposedly is a force that M and m jointly create (once again the product of their masses).




a = F/m

And, the force on m is

F = GMm/r^2.

This what you have to answer,JR

How does m cause the force on its self? You might notice you have the small mass in your second equation.

Therefore, the acceleration of m is:

a = GM/r^2.

Which is just the inverse square law and an expression of the gravity strength of a body (M in this case) being proportional to its quantity. Refer you to the forst post in this thread.

You can see that you are saying the small mass is causing a force on its self can’t you?

Not much point going through the rest of your post unless you can see that. I have put it in bold back up the page a bit for you but everything I posted about 5 kg and 2 kg and 3 kg and 4 kg masses is consistent with
Every particle in the universe attracts every other particle in the universe with a force that is proportional to the product of their masses

Your reply was at odds with it. Somehow I feel sorry for you.

For good measure




This law does not make a distinction between M and m. Swap the positions of the two masses and the magnitude of the force is the same.



Take object M to be the one creating the force (for example, M is the Earth), and object m to be the one experiencing the force.

JR the first is what you posted in post 14. The second is what you posted in post 71.

Initially you say M and m are necessary to F. Swap the positions of M and m and the magnitude of the force is still the same. Can only mean both masses create the force.

Later you move to one of the masses being the force creator. If what you post in post 71 is true

Take object M to be the one creating the force

gravity can hardly be said to be proven to be universal by you.

If you have the intellectual integrity you seem to pride your self in, you can see you have work to do to get your self sensible.



And you can see that I am well within my rights to call you a pseudo scientists if you vacillate between M and m causing the force and M only causing the force. Any 15 year old would be uncertain of just where you are at from what you are posting. Is it M or is it M and m. Cheers.

plane:

You can use the inverse square law to calculate what a rate of acceleration in space would be.

Yes. That value is called the gravitational field magnitude, as I explained earlier.

Well I have posted my definition several times if you have been following. Force is the exertion of matter upon matter.

That's so vague as to be unusable as a definition.

How is an action at a distance applied? Do you know?

Well, yes, I do, but it isn't relevant to the present conversation. I'm not about to launch into a discussion of quantum field theories here. You're still back at the stage of wondering what a force is.

Not sure why you can’t see it. Newton’s law of gravity specifically says that both masses create the force.

No, it doesn't. But we're splitting hairs here.

What Newton's law of gravity says is that the force experienced by one mass due to the presence of another depends on the product of the two masses. It does not talk about which mass "creates" the force at all.

We can have a semantic argument about this if you like, but it is peripheral to the issue.

If we go back to Newton's third law, it says that every action (force) has an equal an opposite reaction (force). But it says NOTHING about which force is the "action" and which is the "reaction". Both forces are, in fact, on an even footing. One force doesn't "cause" the other. Both result from an interaction.

When you go setting mg equal to G.M.m/d x d (mg = G.M.m/d x d) on the left hand side you have the force m experiences courtesy of the large Mass.

That's what I said.

How does m cause the force on its self?

This is a meaningless semantic question again. M and m interact gravitationally, such that each experiences a force of the same magnitude. Take away either one of the two masses and the other experiences no force. So, both masses are required for a force to exist on either of them.

You cannot say that only one of the masses "causes" the force. The force only exists when there are two masses.

Not much point going through the rest of your post unless you can see that. I have put it in bold back up the page a bit for you but everything I posted about 5 kg and 2 kg and 3 kg and 4 kg masses is consistent with

Every particle in the universe attracts every other particle in the universe with a force that is proportional to the product of their masses

No. Your conjecture is consistent with

"Every particle in the universe attracts every other particle in the universe with a force that is proportional to the sum of their masses"

This is false. This is where you went wrong.

Initially you say M and m are necessary to F. Swap the positions of M and m and the magnitude of the force is still the same. Can only mean both masses create the force.

Later you move to one of the masses being the force creator.

I will be more careful with my use of language in future posts. Clearly, you are easily confused.

It seems like the original problem is getting 'cloudy,' especialy since the majority of these rescent posts are semantic based, or misunderstandings.
To restate one proof of "the apple pulling the earth:"

1.The apple's momentum is increasing in the direction of the earth.

2. The law of conservation of momentum states that the momentum of a system must stay constant, unless acted upon by an outside force. This has never been falsified (http://en.wikipedia.org/wiki/Falsifiability) to my knowlege.

3. There is no outside force of the apple-earth system.

4. Thus, in the apple-earth system, in order for the apple to gain momentum in the direction of the earth, the earth must gain an equal, though opposite amount of momentum.

Gravity, nor forces, need not even enter the picture.
Simple as that.

-Andrew

http://www.fotothing.com/photos/ce8/ce8d83379a7283250bc7bc77efb9e12f.jpg?ts=1202623398


JR is this what you see when you see 'universal' gravitation? Cheers

plane:

I see no problem with that.

If you don't like the force explanation, by the way, then andbna's explanation is another good alternative (although actually conservation of momentum is equivalent in content to Newton's third law, which brings us back to forces by a roundabout route).

There are many different ways to see that the apple must attract the Earth, or else it would violate numerous well-tested physical laws that are not restricted to applications involving gravity.

If you think the apple does not attract the Earth, then really you need to refute Newton's third law.

If you think the apple does not attract the Earth, then really you need to refute Newton's third law.

No, not refute Newton’s third law at all. Something I would never want to do. It more or less explains existence. However Newton’s third law might be subject to a wrong application with respect of Newton’s law of gravity. We’ll see.

So next I presume you are saying that Newton developed his law of gravity through his second law.

On the left side of the diagram 4 is the quantity of mass in question and 10/d x d is a measure of the acceleration due to gravity that the 4 mass is subject to.

A mass of 10 would produce a certain rate of acceleration at the distance of the surface from it s centre.

Then the rate of acceleration towards the centre of the 10 mass at the 4 mass would be found by 10/d x d



Do you have any trouble with that?

Cheers.

http://www.fotothing.com/photos/e5b/e5b63c3c33a955d00fd73e9317165741.jpg?ts=1202716763

plane:

That's approximately correct, except where you put the k. (Actually, it's usually written G.)

The acceleration of gravity at distance d from the 10 kg mass is

a = \frac{G(10)}{d^2}

The force on the 4 kg mass is then

F = ma = (4)a

where a is as above.

If you want to find the force on the 10 kg mass, just swap the 4 and the 10 in the above equations.

plane:


The acceleration of gravity at distance d from the 10 kg mass is





Having a hard drive problem, can't put a diagram up but wouldn't mind knowing what someone believes acceleration of gravity

plane:

That's approximately correct, except where you put the k. (Actually, it's usually written G.)

The acceleration of gravity at distance d from the 10 kg mass is

a = \frac{G(10)}{d^2}

The force on the 4 kg mass is then

F = ma = (4)a

where a is as above.

If you want to find the force on the 10 kg mass, just swap the 4 and the 10 in the above equations.

1/ What is the acceleration of gravity? (acceleration due to gravity?) That reads as if gravity its self is accelerating.

2/ How does the magnitude of a force applied to a mass involve the mass its self.

The force on the 4 kg mass is then

F = ma = (4)a



Makes no sense. Take the apple on the ground or hanging from a branch. You should be able to see that Newton has taken the mass of the apple, multiplied the mass by the rate of acceleration caused by the earth's gravity and then said this is the force the apple applies to the ground or the branch.

When you use F = ma = (4)a all you are finding is the weight of the 4 mass if it isn't moving towards the 10 mass.

That is sort of where your juxtaposed conclusion that gravity is a force because anything that causes acceleration is a force breaks down.

When mass is not moving towards a centre of gravity, it is not accelerating.

I am in the process of getting a new computer and haven't the software on this one to do a diagram to show precisely what I am getting at, but will do so within a week or so if all goes well with the delivery.

However, you should be able to see that here you are saying the force of gravity applied to mass is dependent on the quantity of the mass subject to the gravity in accordance with Newton's second law.

In other places you say the force is dependent on the force this mass places on another mass in accordance with Newton's third law.

Which is it?

a = \frac{G(10)}{d^2}

This says that mass provides an acceleration towards its self at a certain rate at a certain distance from its self.

There is no second mass involved. Says nothing more than gravity is a rate of acceleration towards mass. Also does not say that gravity is a force.

Says that gravity exists whether or not a second mass is present. And that is what my whole treatment of gravity is based upon. (yet I am the pseudo scientist;))

where a is as above.

So now every particle in the universe attracts every other particle in the universe with a force that is proportional to the mass of the particle being attracted.

Sounds rather like nothing less or more that Newton's second law when you recognize a = \frac{G(10)}{d^2} as a tool for measuring potential rate of change of momentum.

Newton has probably become besotted by the way Galileo's shift from Aristotle ( F = mv to F = ma) mirrored when he set up things in a way I have done with the 4 and 10 mass diagrams.

From there has apparently forgotten that saying k.m.a = G.M.m/d x d is saying k.m.a = k.m.a


Obviously he has had an excited moment but more to the point, he has missed considering what happens when the opposite directions
a = \frac{G(10)}{d^2} and
a = \frac{G(4)}{d^2} meet before respectively they reach the 4 and the 10 mass.





Cheers.

Newton'a law of gravity has three elements to it.

1/ The inverse square law

2/ A direct proportion between mass and gravity strength

3/ Every particle attracting every other particle.



All that from one falling fucking apple...fucking hell, I should have paid attention to physics at school!

plane:

1/ What is the acceleration of gravity? (acceleration due to gravity?) That reads as if gravity its self is accelerating.

I already carefully explained this to you in a previous post.

When we say "acceleration due to gravity" at a particular point in space, we are saying that if a mass is placed at that point it will accelerate at that rate. It's just short-hand.

Do you understand the distinction between force and field?

2/ How does the magnitude of a force applied to a mass involve the mass its self.

I already explained that to you.

Makes no sense. Take the apple on the ground or hanging from a branch. You should be able to see that Newton has taken the mass of the apple, multiplied the mass by the rate of acceleration caused by the earth's gravity and then said this is the force the apple applies to the ground or the branch.

Well, technically, in that case Newton would be first calculating the force on the apple. Then, using Newton's third law, he would deduce that the apple exerts an equal and opposite force on the Earth.

When you use F = ma = (4)a all you are finding is the weight of the 4 mass if it isn't moving towards the 10 mass.

It doesn't matter whether it is moving towards the 10 mass or not. It's weight is the same.

When mass is not moving towards a centre of gravity, it is not accelerating.

Correct. And in that case it must have at least two forces on it - its weight (due to gravity) and some other force preventing it from falling.

However, you should be able to see that here you are saying the force of gravity applied to mass is dependent on the quantity of the mass subject to the gravity in accordance with Newton's second law.

Technically, this is in accordance with Newton's law of gravity, and not a direct application of Newton's second law. Newton's law of gravity is an independent empirical deduction, compared to Newton's second law.

In other places you say the force is dependent on the force this mass places on another mass in accordance with Newton's third law.

Which is it?

Both. Newton's second law and Newton's third law are independent of one another. One cannot be derived from the other.

This says that mass provides an acceleration towards its self at a certain rate at a certain distance from its self.

There is no second mass involved. Says nothing more than gravity is a rate of acceleration towards mass. Also does not say that gravity is a force.

Do you understand the difference between force and field?

So now every particle in the universe attracts every other particle in the universe with a force that is proportional to the mass of the particle being attracted.

Correct. That is an empirical fact.

Newton has probably become besotted by the way Galileo's shift from Aristotle ( F = mv to F = ma) mirrored when he set up things in a way I have done with the 4 and 10 mass diagrams.

It is another empirical fact that F=mv is incorrect. You don't even need to look at gravity to disprove F=mv.

From there has apparently forgotten that saying k.m.a = G.M.m/d x d is saying k.m.a = k.m.a

You seem to think that Newton's law of gravity and Newton's second law of motion are two ways of saying the same thing. They are not. They are independent statements about different things.

Obviously he has had an excited moment but more to the point, he has missed considering what happens when the opposite directions
a = \frac{G(10)}{d^2} and
a = \frac{G(4)}{d^2} meet before respectively they reach the 4 and the 10 mass.

Correct. Are you aware of the principle of superposition of forces?

plane:



I already carefully explained this to you in a previous post.

When we say "acceleration due to gravity" at a particular point in space, we are saying that if a mass is placed at that point it will accelerate at that rate. It's just short-hand.

Do you understand the distinction between force and field?

So try again.

You introduced the phrase “acceleration of gravity”. I inquired as to whether or not you meant “acceleration due to gravity”.

Your reply is not in keeping with the inquiry.







I already explained that to you.

Didn’t. This was your answer.

This is a meaningless semantic question again. M and m interact gravitationally, such that each experiences a force of the same magnitude. Take away either one of the two masses and the other experiences no force. So, both masses are required for a force to exist on either of them.

You cannot say that only one of the masses "causes" the force. The force only exists when there are two masses.

As you can see this is not consistent with The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects. To make this clearer, let's consider the acceleration of one of the two objects instead of the force. Take object M to be the one creating the force (for example, M is the Earth), and object m to be the one experiencing the force

Take M to be the one creating the force/ you cannot say only one of the masses causes the force. At that point I elected to introduce the 10 - 4 diagram to try and get to the bottom of what you actually believe. As already explained, am without ability to do diagrams at the moment but as you can well see you lack coherency from page to page of this thread.




It doesn't matter whether it is moving towards the 10 mass or not. It's weight is the same.

Think you mean its mass is the same. A free falling body is weightless.





Technically, this is in accordance with Newton's law of gravity, and not a direct application of Newton's second law. Newton's law of gravity is an independent empirical deduction, compared to Newton's second law.


This is where you completely lose me. Go back to the diagram in post 78 and your reply in post 79. Your answer says nothing but Newton’s law of gravity was deduced from Newton’s second law. You are all over the shop. There is nothing clear and consistent coming through.


Do you understand the difference between force and field?

The point I have consistently made is the field causes a mass within the field to either have a momentum change or become a weight (force) directed towards the centre of the field.

So now every particle in the universe attracts every other particle in the universe with a force that is proportional to the mass of the particle being attracted.


Correct. That is an empirical fact.

You’re doing it again. You are saying the force applied to m is dependent on the magnitude of m.

Like saying the force a bat applies to a ball is dependent on the mass of the ball.

A bigger ball (in terms of mass) will require a greater force relative to a smaller ball to be accelerated at the same rate.

But basically, get a bigger faster bat, more force applied to any sized ball.



It is another empirical fact that F=mv is incorrect. You don't even need to look at gravity to disprove F=mv.

Irrelevant answer to the point made.








Correct. Are you aware of the principle of superposition of forces?

Thanks for agreeing that Newton didn't investigate what happens where opposite directions of a field meet. Such is irrelevant to the super position of forces.

Cheers.

I haven't bothered to read the entire thread but the gist of it is plane denying that the Moon attracts the Earth but only vice versa, rather than the mainstream view which is they attract one another.

How then does plane explain the effect the Moon has on the Earth. We see the tides and it's been measured by laser ranging that the surface of the Earth's crust actually rises and falls about 30cm each day (as well as the tides) due to the Moons effect.

The Earth and the Moon orbit a common centre of mass (which is just below the Earth's surface if I remember correctly), not the Moon orbiting the dead centre of the Earth. This is a measured fact by satellites.

This essentially just the Earth/Moon version of the stellar wobble seen in distant stars with huge planets going around them.

PS I love how plane was totally oblivious to Ben's sarcastic "You're right". :lol:

plane:

You seem to be playing dumb, by homing in on what you apparently think are inconsistencies in the statements I have made, while at the same time ignoring the information that has been patiently given to you.

Still, as I said, I will try to explain things more carefully to you, since you seem to have trouble grasping things (whether this be innocent ignorance on your part or a wilful attempt at obfuscation).

You introduced the phrase “acceleration of gravity”. I inquired as to whether or not you meant “acceleration due to gravity”.

The wording is unimportant. We talked about meaningless semantics previously.

This is a meaningless semantic question again. M and m interact gravitationally, such that each experiences a force of the same magnitude. Take away either one of the two masses and the other experiences no force. So, both masses are required for a force to exist on either of them.

You cannot say that only one of the masses "causes" the force. The force only exists when there are two masses.

As you can see this is not consistent with

The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects. To make this clearer, let's consider the acceleration of one of the two objects instead of the force. Take object M to be the one creating the force (for example, M is the Earth), and object m to be the one experiencing the force

Take M to be the one creating the force/ you cannot say only one of the masses causes the force. At that point I elected to introduce the 10 - 4 diagram to try and get to the bottom of what you actually believe. As already explained, am without ability to do diagrams at the moment but as you can well see you lack coherency from page to page of this thread.

Your problem here comes back to Newton's third law again.

Newton's third law implies that ALL forces arise from interactions between two objects. Each object exerts a force of the same magnitude on the other, but the forces are oppositely directed. This is as true for a baseball hitting a bat as it is for an apple attracting the Earth gravitationally. This was the gist of my first quoted statement, above.

My second statement involves Newton's law of gravity. It allows us to calculate the magnitude of the gravitational force on either of two objects (mass M and mass m). The direction of that force will be opposite for each of the objects, but the magnitude is the same for both - a fact that is in total agreement with Newton's third law.

My statement that the law of gravity gives the force on one object has to do with the interpretation of that law, including the directional information. It also has to do with the definition of the term "force" itself. I was trying to make clear to you that a force, by definition, only ever acts on one object. When we talk about "a force", we always mean a force that is "caused" by one object and acts on another. So, for example, I can talk about the "force on an apple due to the Earth" or the "force on the Earth due to the apple". In this example, there are two forces. One acts on the apple, one acts on the Earth. As it happens, the two forces have the same magnitude in this case, but opposite directions. In technical terms, they form what is known as an action-reaction pair of forces, in the terminology of Newton's third law.

So, when I wrote this:

Take object M to be the one creating the force (for example, M is the Earth), and object m to be the one experiencing the force

I was merely indicating to you that I wished to select out mass m as the object being acted upon and mass M as the object causing the action. Why? Because I wished to look at the acceleration of mass m, and to determine that I needed to look at the force on mass m only. There is, of course, an equal and opposite force on mass M due to mass m, but for the purpose of my discussion at the time, I did not wish to consider that.

I hope this clears up your misunderstanding of this simple issue. I really can't be much clearer.

Think you mean its mass is the same. A free falling body is weightless.

That depends on how you define "weight". For clarity, let me tell you how I define it. I define the weight of an object to be the gravitational force exerted on it. Using this definition, a free-falling object is not weightless.

There is, however, no universally agreed definition of "weight". Some physicists prefer to define weight as what a scale would measure. I prefer to call that "apparent weight". For an object in free fall, a scale will read zero, and so the object has no apparent weight. But it still has weight, according to my definition.

I hope this also clears up any confusion you have on this point. Having explained how I am using the word "weight", we will now be on the same page.

This is where you completely lose me. Go back to the diagram in post 78 and your reply in post 79. Your answer says nothing but Newton’s law of gravity was deduced from Newton’s second law. You are all over the shop. There is nothing clear and consistent coming through.

Newton's second law contains nothing about the inverse-square nature of Newton's law of gravity. This alone ought to make it clear to you that the law of gravity cannot be deduced from Newton's second law. On the other hand, Newton's method of arriving at the law of gravity involved a process both of induction from observation and deduction using his other knowledge of the laws of motion. Perhaps this confused you.

You’re doing it again. You are saying the force applied to m is dependent on the magnitude of m.

That is true for gravitational forces, according to Newton's law of gravitation. Just look at the equation if you're in any doubt.

Like saying the force a bat applies to a ball is dependent on the mass of the ball.

A bigger ball (in terms of mass) will require a greater force relative to a smaller ball to be accelerated at the same rate.

But basically, get a bigger faster bat, more force applied to any sized ball.

You're mixing all kinds of concepts here.

When a bat hits a ball, then according to Newton's third law, both the bat and the ball experience forces of equal magnitude and opposite directions. The bat exerts a force on the ball; the ball exerts a force on the bat. If you do not believe that the ball exerts a force on the bat, you need to explain why you can feel the ball hitting the bat, though the handle.

If the force exerted by the bat on the ball is F, then the acceleration of the ball is

a = F/m

where m is the mass of the ball. So, what you said about the effect of the mass of the ball is correct. Bigger m requires more F for the same acceleration.

You may well be able to apply more force if you get a more massive bat, or swing it faster. I am puzzled as to how you think this is relevant to gravity.

Thanks for agreeing that Newton didn't investigate what happens where opposite directions of a field meet. Such is irrelevant to the super position of forces.

Ok. If it's irrelevant, I won't worry about addressing it.

I haven't bothered to read the entire thread but the gist of it is plane denying that the Moon attracts the Earth but only vice versa, rather than the mainstream view which is they attract one another.

How then does plane explain the effect the Moon has on the Earth. We see the tides and it's been measured by laser ranging that the surface of the Earth's crust actually rises and falls about 30cm each day (as well as the tides) due to the Moons effect.

The Earth and the Moon orbit a common centre of mass (which is just below the Earth's surface if I remember correctly), not the Moon orbiting the dead centre of the Earth. This is a measured fact by satellites.

This essentially just the Earth/Moon version of the stellar wobble seen in distant stars with huge planets going around them.

PS I love how plane was totally oblivious to Ben's sarcastic "You're right". :lol:

Alphanumeric this diagram from post 42 explains the high tide on the moon side of the earth.

http://www.fotothing.com/photos/6fa/6faba244d2dadc73fced465d6bba2f15.jpg?ts=1201849141

X, Y and Z are equidistant from the earth. X and Y have fields strengths directed towards the centre of the earth.

Z does not.

Thus the field strength beneath Z all the way to the centre of the earth is less than beneath X or Y at the same distance from the centre of the earth.

Thus a high tide beneath Z and low tides beneath X and Y.

Any trouble following that I will explain further. Interesting though you have to come to pseudo science to get science.

The wobble you mention is the centre of the earth moving across its solar path as the moon orbits the earth. Both the earth and the moon move away from the sun or towards the sun in unison. Thus it is not evidence of the moon 'pulling' the earth.

PS I love how plane was totally oblivious to Ben's sarcastic "You're right". :lol:

All it says is that there is a twisted juvenile peer group within so called science, one that I have no wish to belong to.






JR, your reply does not cover your contradictions. I am questioning whether or not a small mass attracts a large mass.

Stating what the laws says does not prove the law. And you simply do not address why or how m (or M) is able to play a role in causing a force upon its self. As in F = G.M.m/ d x d.

You don't address it and I don't think you have the wherewithal to address it. Or so far you haven't shown that you are going to be able to.

F = G.M.m/ d x d

Once again how can a mass be a factor of the magnitude of a force applied to it. You never seem to have an answer. And yet you say you have 'proof' of the formula.



However, I do agree with you when you say our problem lies with Newton's third law.

I have no evidence as to whether or not it is Newton's original work. I once inquired on this forum as to whether or not it was and nobody knew.

As his first and second laws are always accepted as coming from the continent, I find it probable that the third law came down through the ages to Newton.




Newton's third law states that for every force there is an equal and opposite force.



It is a law of cause and effect. You use it so as an effect can cause a cause and vica versa.

If you want to believe that the law is other than cause and effect, I'm not going to stop you. But while you use it outside the realm of cause and effect, you are not honoring the law.

That is where the base mistake in your proof is. Unless, of course, you can prove that Newton's third law isn't a law of cause and effect.

If we go back to Newton's third law, it says that every action (force) has an equal an opposite reaction (force). But it says NOTHING about which force is the "action" and which is the "reaction". Both forces are, in fact, on an even footing. One force doesn't "cause" the other. Both result from an interaction.

In this mess is where your problem lies.

Newton's third law says the action is the action and the reaction is the reaction.

It does not say they are interchangeable or one can be the other. That is pure invention on your part.

Action causes reaction. One before the other.

Hit a wall. That is the action.

What the wall experiences is the reaction.

When you invoke Newton's third law in a way that has action and reaction indistinguishable, you aren't invoking Newton's law.


Thus your 'proof' does not stand as you use Newton's third law in way that action and reaction are indistinguishable.

Bad luck and cheers to all.

plane:

X, Y and Z are equidistant from the earth.

From your diagram, it looks like X and Z are equidistant from the Earth, and Y is further away...

Stating what the laws says does not prove the law.

You're right; it doesn't. The evidence for Newton's law of gravity is that it accurately predicts the motions of stars, planets, apples, galaxies - anything subject to gravity in fact. No law of physics exists in a vacuum. We always need to check laws against the real world. Newton's law of gravity passes every test with flying colours.

And you simply do not address why or how m (or M) is able to play a role in causing a force upon its self. As in F = G.M.m/ d x d.

On the contrary, I have already justified to you why the product of the two masses appears in the force law. Please review my previous posts.

However, I do agree with you when you say our problem lies with Newton's third law.

I have no evidence as to whether or not it is Newton's original work. I once inquired on this forum as to whether or not it was and nobody knew.

As his first and second laws are always accepted as coming from the continent, I find it probable that the third law came down through the ages to Newton.

Newton's third law was Newton's idea. It did not "come down through the ages" to Newton. But it doesn't matter, for the purposes of the current discussion.

If we go back to Newton's third law, it says that every action (force) has an equal an opposite reaction (force). But it says NOTHING about which force is the "action" and which is the "reaction". Both forces are, in fact, on an even footing. One force doesn't "cause" the other. Both result from an interaction.

In this mess is where your problem lies.

Newton's third law says the action is the action and the reaction is the reaction.

It does not say they are interchangeable or one can be the other. That is pure invention on your part.

Action causes reaction. One before the other.

Hit a wall. That is the action.

What the wall experiences is the reaction.

When you invoke Newton's third law in a way that has action and reaction indistinguishable, you aren't invoking Newton's law.

Hit a wall with what? Your body? Let's take that as an example.

What made you decide that your body provided the "action"? Was it the fact that the wall was stationary and you were moving?

If you were standing still and a wall fell over on you, would the wall then be the "action", according to you, or is the only "action" the act of a conscious human being?

Newton's third law says that when a wall hits you, the wall exerts a force on you and you exert an equal and opposite force on the wall. Call yourself the action and the wall the reaction, or call the wall the action and you the reaction; it doesn't matter either way.

You say "action causes reaction", above. You need to explain how. Whenever the wall exerts a force on you, you simultaneously exert a force on the wall. Your force does not appear before the wall's force; it appears at the same time. So it cannot be said to "cause" the wall's force.

Understand yet?

plane:



From your diagram, it looks like X and Z are equidistant from the Earth, and Y is further away...

Sorry, Alphanumeric. JR has pointed out a re pasted without due care problem. The diagram was not specifically made for your question and I replied to you without looking closely at the diagram.

http://www.fotothing.com/photos/6fa/6faba244d2dadc73fced465d6bba2f15.jpg?ts=1201849141

X and Z are equidistant from the earth. The X points have field strengths directed towards the centre of the earth.

Z does not.

Thus the field strength beneath Z all the way to the centre of the earth is less than beneath the X points at the same distance from the centre of the earth.

Thus a high tide beneath Z and low tides beneath the X points.

Sorry Alpha. Thanks JR.

You're right; it doesn't. The evidence for Newton's law of gravity is that it accurately predicts the motions of stars, planets, apples, galaxies - anything subject to gravity in fact. No law of physics exists in a vacuum. We always need to check laws against the real world. Newton's law of gravity passes every test with flying colours.

Poetic license is still your tool. Get specific about Newton's law gravity demonstrating that a small mass attracts a large mass. Issue at hand. Refer to first post. The inverse square law or a direct proportion between mass and gravity strength is not held to question.





On the contrary, I have already justified to you why the product of the two masses appears in the force law. Please review my previous posts.

The justification?

You cannot say that only one of the masses "causes" the force. The force only exists when there are two masses.

It moves to newton's third law if it is and it doesn't appear that you have addressed your cause and effect issue.








Newton's third law was Newton's idea. It did not "come down through the ages" to Newton. But it doesn't matter, for the purposes of the current discussion.

Can you provide evidence that it was? Won't accuse you of unbacked up statement yet. Really like to see it if you have evidence.



Hit a wall with what? Your body? Let's take that as an example.

What made you decide that your body provided the "action"? Was it the fact that the wall was stationary and you were moving?

If you were standing still and a wall fell over on you, would the wall then be the "action", according to you, or is the only "action" the act of a conscious human being?

Newton's third law says that when a wall hits you, the wall exerts a force on you and you exert an equal and opposite force on the wall. Call yourself the action and the wall the reaction, or call the wall the action and you the reaction; it doesn't matter either way.

You say "action causes reaction", above. You need to explain how. Whenever the wall exerts a force on you, you simultaneously exert a force on the wall. Your force does not appear before the wall's force; it appears at the same time. So it cannot be said to "cause" the wall's force.

Understand yet?

Understand yet? I understand that the person hits the wall before the wall reacts to the force applied by the person. That makes the person the cause of the action and the wall the entity experiencing the reaction.

Of course if the wall fell on me it would be action and I would experience the reaction.

The action precedes the reaction.

You may think it is a deft intellectual manipulation to have the wall fall on a person, but it completely and I mean completely fails to make action and reaction indistinguishable. Would have to suspect that you knew it in your "heart" when you proposed it to. You actually seem above that sort of pathetic trickery.

Keep trying if you like but in terms of physics if it very easy to distinguish between a person hitting a wall and a wall falling on a person. (honestly if you can't see it wait till next week and I'll do you a helping diagram)

Thanks again for the diagram pick up but still yours to show that Newton's third law is not a cause and effect law.

Your proof of his law of gravity hinges on your ability to do so.

Cheers and all the best.

plane:

X and Z are equidistant from the earth. The X points have field strengths directed towards the centre of the earth.

That's still wrong.

At the points X, the gravitational field vector does not point directly towards the Earth. It points off to one side, in the direction of the moon. It would only point directly towards the centre of the Earth if the moon didn't exist.

Poetic license is still your tool. Get specific about Newton's law gravity demonstrating that a small mass attracts a large mass. Issue at hand. Refer to first post. The inverse square law or a direct proportion between mass and gravity strength is not held to question.

Ok. So you don't question that gravity is an inverse-square law and that it depends on the mass of at least one of two objects. Right?

Next you need to understand is Newton's third law, and you'll understand why the gravitational force must be proportional to the product of the two masses. Finally, to understand the field at a distance from either of the masses, as at points X, Y and Z in your diagram, you need to understand the principle of superposition of forces.

Have you heard of superposition? And is Newton's third law starting to make sense to you, or do you dispute it? I'm just trying to gauge where you're at.

I have justified to you why the product of the two masses appears in the force law.

The justification?

Justification for why Newton's law of gravity says that the gravitational force is proportional to the product of the two masses.

1. You admit that the gravitational force F on mass m depends is directly proportional to the "other" mass, M, and inversely proportional to the square of the distance between the two masses.
2. By Newton's third law, if mass M produces a force F on m, then mass m must produce an equal and opposite force on mass M.
3. Hence, we conclude that the force on mass M is also directly proportional to the mass of M. (This follows from steps 1 and 2.)
4. Since the force on mass M is directly proportional to M (from step 3), and also directly proportional to mass m (from step 1, with M and m swapped), then the force is proportional to both M and m - i.e. proportional to their product.

Newton's third law was Newton's idea. It did not "come down through the ages" to Newton. But it doesn't matter, for the purposes of the current discussion.

Can you provide evidence that it was? Won't accuse you of unbacked up statement yet. Really like to see it if you have evidence.

Sure. See Newton's Principia, where Newton's third law of motion was first published. There is no prior publication containing Newton's third law.

If you believe that Newton unjustly claimed priority, you need to produce a publication from earlier than 1687 that predates Newton's publication of the third law. Otherwise, the assumption has to be that the 1687 publication by Newton was the first.

Understand yet? I understand that the person hits the wall before the wall reacts to the force applied by the person. That makes the person the cause of the action and the wall the entity experiencing the reaction.

You made a mistake. The wall does not react to the person after the person hits it. It reacts at the same time that the person hits it. I explained this fact to you earlier.

The action precedes the reaction.

No. They are simultaneous.

Until you correct this misconception of yours, you can't hope to understand Newton's third law.

Keep trying if you like but in terms of physics if it very easy to distinguish between a person hitting a wall and a wall falling on a person.

No, it isn't. There's no way to distinguish, just by analysing the forces acting on the person and/or on the wall.

I repeat my previous argument for why the apple pulls on the Earth:

1. Newton's third law states that for every force there is an equal and opposite force.
2. Therefore, when two bodies interact, if one exerts a force F on the other, the other exerts an equal force F on the first, but in the opposite direction.
3. Gravity is a force (in the Newtonian picture).
4. No known experiment with force has ever violated Newton's third law.
5. Therefore, if the Earth pulls on an apple, the apple must pull back on the Earth with an equal and opposite force.

That's really all the "proof" that is needed.

This thread looks an awful lot like real science.

This thread looks an awful lot like real science.
There is science here, but it is one-sided and it is not on the side of the original poster. The original post is not scientific, period. James R has been very patient and has indeed used an awful lot of real science to debunk the non-scientific concepts presented in the original post.

What is going on here? Mod wars? This thread does not being in the science section. The thread violates at least two items from the Physics&Math Alternate Theories policy:
3. Posters who are critiquing accepted physical or mathematical ideas should clearly point out what is wrong with those ideas, providing clear examples showing where the accepted theories are or may be incorrect. Preferably, such examples should be testable, backed by evidence of some kind or (in the case of mathematical criticisms) accompanied by proof.

4. Posters putting forward alternative theories should clearly explain the basic ideas of their theory, how their theory differs from conventional theories, and how their theory is likely to improve on accepted theories. Explanations should be backed by evidence. Theories should be testable and falsifiable. In short, alternative theories must be classifiable as science rather than pseudoscience.

D H:

I see this thread more as asking a question than as a critique of Newton's law of gravity. plane hasn't put forward any alternative theory either, as far as I can tell. plane wants to know how we know that an apple attracts the Earth, just as the Earth attracts an apple. I've explained it to him.

I hope that this thread may help any other person who has trouble understanding Newton's third law, in particular.

That's still wrong.

At the points X, the gravitational field vector does not point directly towards the Earth. It points off to one side, in the direction of the moon. It would only point directly towards the centre of the Earth if the moon didn't exist.

No it’s not. Look at the extent of the moon’s (smaller masses) gravity on the diagram.

http://www.fotothing.com/photos/6fa/6faba244d2dadc73fced465d6bba2f15.jpg?ts=1201849141

The egg shape is the extent of a direction of fall towards the moon. I know what you are trying to say. Your problem is you can’t substantiate a direction of fall towards the moon beyond the egg shape.

Ok. So you don't question that gravity is an inverse-square law and that it depends on the mass of at least one of two objects. Right?

Well, if you read the original post.

Newton'a law of gravity has three elements to it.

1/ The inverse square law

2/ A direct proportion between mass and gravity strength

3/ Every particle attracting every other particle.

The first two seem to pass scrutiny.

With the third can anyone point to empirical evidence of a smaller mass 'pulling' a larger mass. The tides and cavendish experiments don't do it from all the published imformation I've seen.

In the case of cavendish experiments only the small mass moves and with the high tide under the moon, all that is observed is a lesser gravitation towards the earth because of the interaction of earth and moon gravities. Which, of course isn't a gravitation towards the moon.


Next you need to understand is Newton's third law, and you'll understand why the gravitational force must be proportional to the product of the two masses.

To every action there is an equal and opposite reaction = multiply masses together. JR you are grasping at a straw. You are trying to force an opinion, not explain anything in a rational way.

Finally, to understand the field at a distance from either of the masses, as at points X, Y and Z in your diagram, you need to understand the principle of superposition of forces.

Have you heard of superposition?



Go back to the diagram. It is of field strengths. Force does not come into it.


And is Newton's third law starting to make sense to you, or do you dispute it? I'm just trying to gauge where you're at.

No, not refute Newton’s third law at all. Something I would never want to do. It more or less explains existence. However Newton’s third law might be subject to a wrong application with respect of Newton’s law of gravity. We’ll see.

1. You admit that the gravitational force F on mass m depends is directly proportional to the "other" mass, M, and inversely proportional to the square of the distance between the two masses.

Do not ‘admit’ this. You may recall that I have explained to you that there is no evidence that gravity is a force. Told you that the evidence is gravity either causes mass to accelerate or causes mass to become forceful (weight).

From there you are getting ahead of your self with Newton’s third law. Very much you have a mathematical approach to Newton's third law. You are not looking at as a physicists should.

Sure. See Newton's Principia, where Newton's third law of motion was first published. There is no prior publication containing Newton's third law.

If you believe that Newton unjustly claimed priority, you need to produce a publication from earlier than 1687 that predates Newton's publication of the third law. Otherwise, the assumption has to be that the 1687 publication by Newton was the first.

That’s not evidence. I mean a moment of deduction like an apple falling. It may have been his original deduction. Or given that the first two laws were not his original work, it could have come from intellectual circles of the day. Not published else where means nothing, particularly as publishing wasn’t push button as it is today.

If it’s Newton’s original work, what caused him to make the deduction?



I guess your wish to argue Newton’s law of gravity sensible is disallowing you from seeing what you are really saying. To apply Newton’s third law as you do to Newton’s law of gravity, the reaction has to be simultaneous.

So you try and bluster forth that action and reaction occur simultaneously.

Take a collision about to occur. How can a force in the opposite direction to the direction of motion of the faster moving body begin until after the collision occurs? That is just so basic.

http://www.fotothing.com/photos/ac0/ac0e6046e5fba58768c133c0bcc83ad2.jpg?ts=1203627667


You are trying to say the reaction occurs faster than the speed of light.

There is science here, but it is one-sided and it is not on the side of the original poster. The original post is not scientific, period. James R has been very patient and has indeed used an awful lot of real science to debunk the non-scientific concepts presented in the original post.

DH, care to elaborate on how the original post is not scientific. Just stating that something is unscientific does not make it unscientific.

Incidentally, JR is not being ‘patient’. He claims to have intellectual proof that an apple attracts the earth. And he is trying to substantiate that claim. At the moment he is hoping to being able to intellectually explain that a reaction to an action happens faster than the speed of light.

This first diagram in this post is intellectual proof that an apple does not attract the earth.

So I am just trying to get to the bottom of how and why everybody has got this wrong belief about an apple attracting the earth. Made some progress on that front. If everyone is believing a reaction occurs simultaneously with a reaction, it is fairly black and white as to where everyone is going wrong.


I hope that this thread may help any other person who has trouble understanding Newton's third law, in particular.

It won't if they start to rationalize that a reaction can occur faster than the speed of light. It will work counter to your hope if that occurs.

No it’s not. Look at the extent of the moon’s (smaller masses) gravity on the diagram.
Stop with the silly diagram. Physical theories are mathematical explanations of how we observe the universe is, not how we want it to be.

Observation piled upon observation have shown that gravity makes masses attract other masses. That the Earth attracts the Moon and that the Moon attracts the Earth are observable facts.

DH, care to elaborate on how the original post is not scientific. Just stating that something is unscientific does not make it unscientific.

There is nothing scientific in that post, or in any of your posts. You do not offer any alternative theories. You do not propose new experiments that would falsify extant theories of gravity while validating yours. You do not point out any experiments that falsify the concept that all particles are attracted to all other particles gravitationally. All you do is claim a dislike for this concept. Science is about determining how the world is. How the world "should" be is the domain of religion, politics, and philosophy.

That objects attract one another is an observable scientific fact. We don't know exactly why this is so, or even the exact nature of the attraction. Newton proposed one scheme based on observations (not wishes). Einstein proposed another scheme based on more refined observations (not refined wishes). Except in the case of large, concentrated masses or very rapidly moving objects, general relativity simplifies to Newtonian gravity.

I really should avoid this part of sciforums because I have no clue what's being discussed. o-o

Take a collision about to occur.OK, there are two cars headed straight towards a point (of collision) from opposite directions - let's make it from due north and due south towards this point.
How can a force in the opposite direction to the direction of motion of the faster moving body begin until after the collision occurs?It can't. There is no "force" in either direction after the collision. But during the collision there is.

"That is just so basic."

Try another example - an apple hanging on a tree. The apple is nice & ripe looking - maybe it will "fall off" the tree soon? Try to think of simultaneous actions and forces, instead of "before" and "after".
Examine (if possible) the "forces" acting on the apple: one (gravity) is "pulling" the apple downwards towards the ground; the other - opposing "force" is keeping the apple stuck to the tree - this is due to the cells (made of strong protein materials like lignin and also cellulose polymers).

There's a layer of cells at the "tree" end of the stem (the thing connecting the apple and responsible for the opposing force), that changes slowly - the abscission layer. Cells in the abscission layer die off slowly and release the hold (continuous connection) that the apple + stem has. Eventually, the layer becomes discontinuous, or sufficiently disconnected so that gravity "forces" the apple to disconnect altogether from the tree - it falls to the ground.
The "cause" is gravity, and the gradual changes (death and discontinuity) in the layer of cells in the stem. Two things -two opposite "forces".

Gravity is apparent as a force when two (or more) masses are present in "space".
The forces are present (simultaneously) from both (or each) mass, and exert a "pull" or attraction on the other (or each other) mass.
Gravity is not apparent from just one mass - but there is no way to "measure" gravity without using another mass - right?

plane:

At the points X, the gravitational field vector does not point directly towards the Earth. It points off to one side, in the direction of the moon. It would only point directly towards the centre of the Earth if the moon didn't exist.

No it’s not. Look at the extent of the moon’s (smaller masses) gravity on the diagram.

The egg shape is the extent of a direction of fall towards the moon. I know what you are trying to say. Your problem is you can’t substantiate a direction of fall towards the moon beyond the egg shape.

You yourself have agreed that gravity is an inverse-square law. Therefore, the Moon's gravity extends to infinity, and not just within your "egg shape".

Your diagram is clearly incorrect. The moon's gravity does not suddenly stop at the boundary of your egg. Nor does the Earth's gravity stop at point Z on your diagram. If it did, the moon would not be in orbit around the Earth, because it would be out of Earth's "egg".

Moreover, it is an experimentally observable fact that a body placed at point X in your diagram will NOT accelerate straight towards the centre of the Earth. The reason is that the moon's gravity also pulls on it, just as the Earth's does.

Go back to the diagram. It is of field strengths. Force does not come into it.

Do you know what force and field are? You sound like you have no idea.

You may recall that I have explained to you that there is no evidence that gravity is a force. Told you that the evidence is gravity either causes mass to accelerate or causes mass to become forceful (weight).

Please review my previous posts where I walked you through the implications of Newton's second law, relating force and acceleration.

If it’s Newton’s original work, what caused him to make the deduction?

Try reading the Principia. You might find what you're looking for in there.

So you try and bluster forth that action and reaction occur simultaneously.

Take a collision about to occur. How can a force in the opposite direction to the direction of motion of the faster moving body begin until after the collision occurs? That is just so basic.

It is indeed basic. There's no point in my repeating myself, so I'm not going to. You need to make an effort to learn this stuff yourself. And for that, you need to want to learn.

You are trying to say the reaction occurs faster than the speed of light.

Force does not have a "speed". Your idea makes no sense at all. Moreover, this is a straw man, since I made no such statement.

Incidentally, JR is not being ‘patient’. He claims to have intellectual proof that an apple attracts the earth.

I have a presented clear, step-by-step justification, twice now. Both times, you have ignored it.

I'm beginning to regard you as a troll. I can't see that further discourse with you is likely to be fruitful.

So I am just trying to get to the bottom of how and why everybody has got this wrong belief about an apple attracting the earth.

Has it occurred to you that, just possibly, it may be that everybody else in the world is right and you are wrong?

plane---

Did you ever explain why the wobble in a star is NOT caused by the gravitational influence of an orbiting body?

http://www.fotothing.com/photos/6a1/6a1ef3cf84e5d43e1d266d31a41cfa6a.jpg?ts=1203938476

http://www.fotothing.com/photos/3ad/3ad8f654ef94c1e382be5548baf080f5.jpg?ts=1203938568

The point of raising the issue is, according to Newton’s third law, directly opposite the above arrow the weight of the earth should be a construct of 9.799 m/s/s. Not 9.8 m/s/s. It is being suggested to the learned that the explanation of the high tide on the opposite side of the earth is an equal and opposite reaction to the one induced on the other side by the moon.

This could be important to science.

I have misplaced my copy of Principia but if you read Newton’s introduction to universal gravitation where he declares that we must allow that all bodies whatsoever are endowed with a principal of mutual gravitation, the only small mass he cites as ‘attracting’ a larger mass is the moon to the earth through the tides.

If he has mathematically mistaken a lesser gravitation towards the earth for a gravitation towards the moon, you can see there is a chink in the ogic about a smaller mass attracting a larger mass.

In Cavendish experiments, the large mass is not observed to move.


It can't. There is no "force" in either direction after the collision. But during the collision there is.

During does not equal simultaneous. During equals a series of cause and effect actions and reactions. JR has the problem of making action and reaction simultaneous and not cause and effect. That does not help him.

Force does not have a "speed".

Force travels through matter. Apply a force to one side of anything. It is not instantaneously felt on the other side. E.G. (vivid) Pushing passengers on a train in Japan.

During does not equal simultaneous.
During a collision, there are forces acting simultaneously, so it does equal simultaneous.
During equals a series of cause and effect actions and reactions.So, when two cars, or other masses collide, it's a series of actions? I thought a collision was a single action.
What do you think "during" means? You know there is no "moment" of collision that can be recorded or otherwise seen, right?
JR has the problem of making action and reaction simultaneous and not cause and effect. That does not help him.But isn't it you that has the problem with cause and effect?
You keep saying that one "precedes" the other. How do you "know" this is the case?
Can't a cause and an effect be simultaneous? I thought that's what Newton (and my Physics teacher) was talking about, did I get this wrong? There's a cause, then the effect comes "later on"?
Why is there a delay? Have you managed to determine the length of this cause-effect delay interval? Is it constant or does it depend on something else?

plane:

It is being suggested to the learned that the explanation of the high tide on the opposite side of the earth is an equal and opposite reaction to the one induced on the other side by the moon.

Impossible, because forces in an action-reaction pair, according to Newton's third law, always act on different objects.

I have misplaced my copy of Principia but if you read Newton’s introduction to universal gravitation where he declares that we must allow that all bodies whatsoever are endowed with a principal of mutual gravitation, the only small mass he cites as ‘attracting’ a larger mass is the moon to the earth through the tides.

Now you just need to catch up on all the other things that have happened in physics in the past 330 years or so.

In Cavendish experiments, the large mass is not observed to move.

Well, it's fixed in place, after all...

Force travels through matter.

Rubbish. Force does not travel anywhere.

I repeat: you need to get yourself an introductory textbook on physics. Find out what a force actually is. Learn what Newton's laws say.

Apply a force to one side of anything. It is not instantaneously felt on the other side. E.G. (vivid) Pushing passengers on a train in Japan.

You're confused because here you're not talking about one force, or one point-like object. Rather, you're talking about many forces and many objects, all at once.

The reason a passenger on the far side of the train does not feel the push on the near side instantaneously is because the push on the near side creates a pressure wave that has to propagate through several other passengers, and that takes time.

You're mixing up the movement of a pressure wave with the idea of force. The two things are not the same. Force has no speed. Force does not move.

The point of raising the issue is, according to Newton’s third law, directly opposite the above arrow the weight of the earth should be a construct of 9.799 m/s/s. Not 9.8 m/s/s. It is being suggested to the learned that the explanation of the high tide on the opposite side of the earth is an equal and opposite reaction to the one induced on the other side by the moon.
Plane,

Tidal effects are proportional to 1/r3, not 1/r2. This is important to science ...

This could be important to science.
... but what you wrote is not important to science. What you wrote is a red herring.

Force travels through matter. Apply a force to one side of anything. It is not instantaneously felt on the other side.
One of the cornerstones that distinguishes science from mere naval gazing is that scientific theories must agree with observations. We have amassed an incredible amount of data regarding the motion of the bodies in the solar system. The observed data agree with the central axiom shared by Newton's law of gravity and general relativity: to wit, all masses attract all other masses.

There are some flaws in Newton's law of gravity. One of them is that Newton's formulation assumes gravity propagates at an infinite speed. You are assuming this flaw (mostly a minor flaw regarding bodies in our solar system) falsifies everything in Newton's formulation. General relativity addresses this flaw. General relativity also explains why the assumption of infinite propagation speed is a very, very good one. The assumption only fails when coupled with very high speeds and long observation times-- e.g., the orbit of Mercury.

I was a bit leery in bringing GR to fore because you do not have an adequate understanding of the basics (Newtonian gravity). Jumping into advanced physics when you haven't even mastered the basics is usually not a good thing to do. The reason I brought GR into play is because you have raised the issue of infinite propagation speed more than once. Note well: All masses, small or large, attract all other masses in general relativity.

D H:

Realise that plane's issues are not primarily with gravity. That's one reason I have tried to avoid GR.

plane's issue is more fundamental: he doesn't understand Newton's laws of motion. He doesn't really know what a force is, and Newton's third law is a complete mystery to him.

James,
I realize that. Plane has raised the issue of infinite propagation speed multiple times. I decided to address the issue up-front.

Plane,
The infinite propagation speed in Newtonian gravity is a minor issue in comparison to what is going on in this thread. Before you even start to come to grips with advanced physics you need to have a solid handle on the basics. Newton's third law is one of those basics, and so is Newton's law of gravitation.

No has addressed the mathematical point made in post 100 about whether or not a lesser gravitation towards the earth is a gravitation towards the moon.


All replies that don't address that issue are off target.


Can address the staggering obfuscation if wanted but this is a pre Newton issue.

Newton assumed that a lesser gravitation towards the earth is a gravitation towards the moon.



http://www.fotothing.com/photos/6a1/6a1ef3cf84e5d43e1d266d31a41cfa6a.jpg

http://www.fotothing.com/photos/693/693f5d356064478c29a7f6573dd58b6d.jpg?ts=1204113585


Well, if it is rational, beyond me to see how.

Can anyone really explain why Newton mathematically saw a lesser gravitation towards the earth as a gravitation towards the moon.

If the big mass in Cavendish experiments are fixed, they are fixed. Get around to checking that out when time permits.

The "lesser" gravitation is a term in the same formula that describes the (same) mutual attraction between a two-body system (like a kind of coupled oscillator), it's never equal to zero. The oscillator is "free moving", sort of, except it's also coupled to the Sun.

But if you treat the Earth-Luna system as a term in the formula for the Solar coupling, that has a solution, a result, too.
The Sun isn't fixed, as such, but it's orbiting (coupled to) the galactic centre.

BTW that must mean tides are raised on the surface of the Sun by the Earth-Luna system. Very small tides, but still tidal.

No has addressed the mathematical point made in post 100 about whether or not a lesser gravitation towards the earth is a gravitation towards the moon.
Yes, I did.
Tidal effects are proportional to 1/r3, not 1/r2.

So, what is the perceived difference in gravitation acceleration on someone standing on the Earth due to a full moon versus a new moon? The Earth, along with the person on the Earth is accelerating toward the Moon. The difference in the acceleration toward the Moon between the point on the Earth closes to the Moon and the center of the Earth is


\Delta a(a_m-Re, a_m) =
GM_{moon}\left(\frac 1 {(a_m-R_e)^2} - \frac 1 {a_m^{\;2}}\right)


Since a_m \gg R_e,


\Delta a(a_m-Re, a_m) \approx
2\frac {GM_{moon}}{a_m^{\;3}}R_e


Doubling this to get the difference between full moon and new moon,


\Delta a(a_m-Re, a_m+R_e) \approx
4\frac {GM_{moon}}{a_m^{\;3}}R_e


Or about 2.2 nanometers/second squared.

During a collision, there are forces acting simultaneously, so it does equal simultaneous.



So, when two cars, or other masses collide, it's a series of actions? I thought a collision was a single action.

I am probably wrong. Newton’s third law should be worded “To every action there is an equal and opposite action” ,though.


Impossible, because forces in an action-reaction pair, according to Newton's third law, always act on different objects.

Well there is forces directly opposite on either side of the earth. One side of the centre of the earth is one object, the other the other object. Not sure what you are getting at.

Well, it's fixed in place, after all...

Not clear that it is. The large dumbell is mechanically moved towards the small dumbbell. The two dumbbells are on the same axis. Whatever, without the large mass "gravitating" towards the small mass, not proof of apple attracting the earth. And as, explained setting mg =k. M.m/d x d, is only setting Newton’s second law equal to its self.




Rubbish. Force does not travel anywhere.
You're confused because here you're not talking about one force, or one point-like object. Rather, you're talking about many forces and many objects, all at once.

The reason a passenger on the far side of the train does not feel the push on the near side instantaneously is because the push on the near side creates a pressure wave that has to propagate through several other passengers, and that takes time.

You're mixing up the movement of a pressure wave with the idea of force. The two things are not the same. Force has no speed. Force does not move.

Fair enough.

Plane,

Tidal effects are proportional to 1/r3, not 1/r2. This is important to science ...

Think the 1/r3 is used to get around the sun having a greater rate of acceleration at the earth than the moon at the earth using 1/r2.

.. but what you wrote is not important to science. What you wrote is a red herring.

Why? How do you know that a lesser weight upon the earth is a weight directed at the moon.

If it is simple a lesser weight directed towards the moon because of the interactions of earth and moon gravities in the space between the earth and the moon, it is a significant deduction, one that culminates is a more rational understanding of why there are like tides on opposite sides of the earth and much, much more. Gives a plausible insight into the rotation rates of the planets.

the interactions of earth and moon gravities in the space between
Try to think of the gravitational interaction as a coupling.

It's like a big spring that keeps the Earth and Moon connected, there's a mutual connection, not two separate connections. The spring has "settled" and doesn't "spring" much, but it does still extend and contract a bit. It's had a few billion years to relax into the present state.

P.S. The 1/r^3 relation is to do with spheres, not distance from the surface, like gravity which is 1/r^2. Have another look at the math.

Try to think of the gravitational interaction as a coupling.

It's like a big spring that keeps the Earth and Moon connected, there's a mutual connection, not two separate connections. The spring has "settled" and doesn't "spring" much, but it does still extend and contract a bit. It's had a few billion years to relax into the present state.

Coupling does not make sense when directions of descent are opposed.

A big spring implies a physical connection. That yours to explain what is in your mind but I think you should be able to see that I do not see two connections.

The proof of the smaller mass falling towards the larger mass is yet to appear in this thread.

http://www.fotothing.com/photos/728/72877a2bc1306b429ab9ea13df1233be.jpg?ts=1204542245

Fundamental question.

With respect of this thread, the conviction that a large mass does not fall towards a small mass has grown.

Also the likelihood that Newton's third law is not his own has increased.

Thanks for leading the horse to the water on that Vkothii. All my back of the head thinking on force was that it is spontaneous. However had always assumed it was cause and effect from the way the law is framed in school books. You are a good teacher. Made me really think about what I believed.

Cheers

What do you mean "I move to both exerting the same force on each other"? What is this supposed to mean??

A mass always exerts a force on another mass. The force is constant if the mass is constant.
They individually "exert" a force which is proportional to their individual mass.



Every particle in the universe "exerts" a force that is directly proportional to the product of their masses ans inversely proportional to the square of the their separation.

The famed law states different to what you post, Frud11.

The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects.

Look deeper. The formula says M and m apply equal forces to each other.

JR contradicts your line Frud.

It's a bit sad this. Anyone who argues in favour of Newton's law of gravity on pure logic uses their intelligence badly is probably the best way to put it.

Newton entered an illogical phase when he proposed that unlike masses exert equal force upon each other. It was a nonsense to come up with.

So sad. Newtonian physics hides the tides and the most probable explanation of why all the planets rotate at the rates they do amongst much else.

Good bye and good luck. Newton's law of gravity is wrong. Any evidence that you believe demonstrates an apple pulling the earth, be scientific and look for other explanation.

Every particle in the universe "exerts" a force that is directly proportional to the product of their masses ans inversely proportional to the square of the their separation.You've done it again. You've gone from "particle", to "their masses"; you've gone from one thing to more than one thing without drawing a breath.
How do you do that?

My alter-ego said:
"A mass always exerts a force on another mass." - Note, here it's one mass, and another mass.

" The force is constant if the mass is constant." - This means: if the mass is not constant, the force will change.

"They individually "exert" a force [on each other] which is proportional to their individual mass." - actually the force is exerted [between] both, and it's proportional to the product/sum of the masses, or it's a ratio of the product.

Yep, that last bit as it stood, was misleading, because neither body "exerts" a force, the force exists because there are two bodies.

P.S. you may not have realised that overturning Newton's theories will require that you explain Einstein's theories in a different way? You will also need to overturn 300 years of scientific thinking?

Go for it (God loves a trier, dude).

It's a bit sad this. Anyone who argues in favour of Newton's law of gravity on pure logic uses their intelligence badly is probably the best way to put it.

Newton entered an illogical phase when he proposed that unlike masses exert equal force upon each other. It was a nonsense to come up with.

Since it is tied up in the very way that he defined the term "force", it is perfectly logical. If you have an alternative system that defines force differently, perhaps now would be a good time to outline your vision for us.

So sad. Newtonian physics hides the tides and the most probable explanation of why all the planets rotate at the rates they do amongst much else.

And I suppose you have a better explanation?

*yawn*

There is no need for proof.

The apple does indeed pull on the Earth........except that pull is so insignificant it does not matter.

Duffers.


The question is how can the earth exert as much force on the sun as what the sun exerts upon the earth.

That is what happens according to Newton's guess at gravity. If you haven't the brains to answer, don't worry, it doesn't make you a lesser person.


Goodbye and good luck.

http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/NewtonsLawOfUniversalGravitation.svg/300px-NewtonsLawOfUniversalGravitation.svg.png

They have different masses children.

(JR, you have a lead in to a far superior explanation within this thread. Look back a few posts, you oaf. A lesser gravitation towards the earth, etc )

Duffers.


The question is how can the earth exert as much force on the sun as what the sun exerts upon the earth.

That is what happens according to Newton's guess at gravity. If you haven't the brains to answer, don't worry, it doesn't make you a lesser person.


Goodbye and good luck.

http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/NewtonsLawOfUniversalGravitation.svg/300px-NewtonsLawOfUniversalGravitation.svg.png

They have different masses children.

(JR, you have a lead in to a far superior explanation within this thread. Look back a few posts, you oaf. A lesser gravitation towards the earth, etc )

It does not matter that they have different masses, as the force takes into account both masses.

They have different masses children.That's why there is a force seen between them.
Why they accelerate towards each other.

What would there be if there was just one mass? Then say you divide this mass in two parts and move them apart?
Do you have the brains to try answering either question?

It does not matter that they have different masses, as the force takes into account both masses.

Is this a genuine response?

The question is how can F1 = F2 if the masses are different.

(Mass proportional to gravity is not consistent with F1 = F2.)

That's why there is a force seen between them.
Why they accelerate towards each other.

What would there be if there was just one mass? Then say you divide this mass in two parts and move them apart?
Do you have the brains to try answering either question?

Avoided replying to you last night. You work out why. I stated Newton's law of gravity as it stands. Your defence of Newton's law of gravity was an attack on what I stated.

Moderators of a genuine physics forum would have picked you up on it.

The question, this forum being genuine or otherwise, still is how can the earth exert as much force on the sun as what the sun does upon the earth.

To answer your questions. If there was just one mass, there would be just one mass.


If you split them, inverse square law vector analysis says the smaller one will fall towards the larger one.

Why those with an education can't answer how the earth exerts as much force on the sun as the sun does on the earth is, well, mildly intriguing. I know no-one can but it is still intriguing finding out that scholars become dumb when the question is posed.

Check out binary stars. They are proof that the smaller mass can pull the larger mass.
If it wasn't so, the smaller star would orbit the larger one.
That however does not happen. And what does happen is they orbit the centre of mass of the pair.
They would only do this if the smaller star attracts the larger star.

Here's my two second psuedofilled section.

I think gravity is grosely misunderstood, and even worse, it's seen to be quantuized.

To answer your questions. If there was just one mass, there would be just one mass.Re-stating the question doesn't furnish an answer, Mr "I'm a clever scholar".
If you split them, inverse square law vector analysis says the smaller one will fall towards the larger one. So, before you split them, what about this inverse square, and acceleration?

how can the earth exert as much force on the sun as what the sun does upon the earth.This question has been answered many times, here in this thread, and in lots of others. And in a lot of books; a lot of people understand how.

But you don't; perhaps you don't have the brains?
How many times does someone have to tell you it's a SINGLE FORCE.
Yes, that's right. There is only ONE force between two bodies.
I can write that out again for you, if you didn't understand it the first 27 times...?

Hello plane, et al.

The pseudo force we call "gravity" is the result of "time gradients". All mass, no matter how small or large, generates/causes a reduction in the rate of time at its location in space. Time gradients appear to fall of at 1/r^2. Time gradients, from mass, are additive. All particles will experience a continuous force towards an area/point of "slowest time rate".

The "time gradients" of the Earth and Moon, as a system, are added together and form points of "slowest time rate". One point is within the Earth and another point is within the Moon. The point within the Earth is offset towards the Moon so there is a net force affecting the Earth towards the Moon. The offset within the Moon is towards the Earth so there is a net force affecting the Moon towards the Earth.

The other part of the orbital equation is another pseudo force we call "centrifugal force" which has its own affect on "time rates".

:)

Perhaps plane can overturn Newton's laws and gravity simultaneously?
We will all thank him for pointing out that for over 300 years, the moon has not been gravitationally bound to our planet by gravity. Gravity is an illusion, obviously: if there are two bodies, there are two forces to explain, so Newton's single force is wrong - the moon shouldn't be where it is.

We all eagerly await plane's next publication, in which he explains how the moon is where it should be after all. We can't explain why because Newton was wrong - this guy is so utterly brilliant, no-one can even look at his working or understand it.

The question is how can F1 = F2 if the masses are different.

Well, Newton's law says they are equal, for one.

The question, this forum being genuine or otherwise, still is how can the earth exert as much force on the sun as what the sun does upon the earth.

The force is due to an interaction between the Sun and the Earth. The Earth doesn't generate the force on its own. Also, see Newton's third law, which I so patiently explained to you earlier.

Well, Newton's law says they are equal, for one.

The question is how not who. You do get some junk posters on this forum.


You assume, for reasons that are unclear, that "gravity strength is proportional to quantity", by which I assume you mean that the force between two objects is proportional to the total mass of the two objects combined.

Gravity strength is proportional to mass. If you are on the sun you fall faster than what you do on Mercury. Your assumption is hard to follow.


The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects.


The force is due to an interaction between the Sun and the Earth. The Earth doesn't generate the force on its own. Also, see Newton's third law, which I so patiently explained to you earlier.

James R is a living part of Newton's contradiction. Many are.

For James R, not shared one day, due to an interaction a few months later. This is not physics on James R's part. It's language.

Appreciate those saying that a binary star system proves an apple attracting the earth. Why I stated look more deeply a few posts back. If you were on a said binary star, the earth moon system would look like a binary system. Don't forget that Tyco Brahe was drawn to astronomy by an accurate prediction of a lunar eclipse. Yet Tyco and the predictors believed the earth is in the centre of all things. The way things appear may not be the way they are. Good bye, good luck and good living.

The way things appear may not be the way they are. Good byeYou mean, we aren't going to see any more of your incomprehension, stubborn refusal to accept that you're just wrong, and continual re-posting of the same boring questions, over and over, the same tired answers, that you then ignore altogether, and ask the same tired questions again...?

You're blind to logic, I would say. You have some sort of logical dyslexia. I'd go and seek help.

P.S. You see, if this has all got this far, and you still have the same question as when you started all those posts ago, do you think your stubborn attitude and wilful blindness to reality have helped you along at all? Now that you so obviously understand as little as you did when you started, I mean?

P.S. You see, if this has all got this far, and you still have the same question as when you started all those posts ago

The question is the same area as asking for the proof of an apple attracting the earth but it isn't that question, old son.

I don't think you even know what Newton's gravity guess. It is "Every particle in the universe attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of their distance apart"

I stated the first part of it and you said I was committing an error in going from particles to masses. All I did was state Newton's guess as it appears in school books. From that I have trouble taking you seriously.

Anyway the question is not seeking the considered proof. It is seeking how anyone can reconcile unlike particles exerting a like force on each other.

No-one has offered any semblance of a mechanical explanation as to how this can be so.

James R said earlier in the thread that the F in F = G.M.m/d x d is to be treated as the magnitude of force on one object.

More recently he has said the F in F = G.M.m/d x d comes about from an interaction of M and m.

James R is unlikely to be able to clarify his contradiction and that is where we are at.

So you can see I am pretty much showing that Newton's gravity has contradiction within it's structure in these more recent postings. Earlier I was seeking the considered proof of an apple attracting the earth. If it can be seen to structurally unsound, apple proof seeking becomes redundant. I did start a new thread about this but a not so wise moderator closed it.

Hope that helps you but I really have trouble taking you seriously.

I am pretty much showing that Newton's gravity has contradiction within it's structureWell, old son, I'd say you're totally alone there. But you don't actually want any explanations or help, do you?

You're here to try, and try again (and if there is no response, or not the one you expect, you try again, don't you?), to tell everyone that Newton's Law of Universal Gravitation has a big gaping hole in it, right?

The thing with that theory is: you are the only person here who can see this problem, unfortunately I can't see it (I must be suffering from some strange blindness).

So, youre all on your own. You have your entire brain to yourself.
Who knows, you may work out the problem as you see it, one day. But as I say, you are the only one who can see this problem you appear to be complaining over and over again about. No-one else seems to be able to see it either.

Maybe you have some kind of super-vision, or your genes are different. But because no-one can help you with this problem (because none of us can see what you keep saying you can see), you will have to figure it out all by yourself, I'm afraid.

P.S. This means I personally will not respond to any more of your posts from this point - I'll just assume you are talking out loud, or trying to declare something so you can examine your own ideas more closely. You're obviously better off without all us ignoramuses anyway.

plane:

The formula F=GMm/r^2 gives the magnitude of the force on one object (either M or m), and not some kind of "shared" force that applies to both objects.

...

The force is due to an interaction between the Sun and the Earth. The Earth doesn't generate the force on its own.

For James R, not shared one day, due to an interaction a few months later.

...

James R said earlier in the thread that the F in F = G.M.m/d x d is to be treated as the magnitude of force on one object.

More recently he has said the F in F = G.M.m/d x d comes about from an interaction of M and m.

James R is unlikely to be able to clarify his contradiction and that is where we are at.

There is no contradiction between my two statements:

1. The force of gravity involves an interaction between at least two objects.
2. Newton's law of gravity gives the magnitude of the force on either one of the two objects involved (since each experiences a force of equal magnitude).

Why do you think there is a contradiction?

A force (any force) only acts on one object at a time, by definition of what we mean by "force". In a gravitational interaction, a Newton's third law action-reaction pair of forces is involved. For example, when the sun and earth interact gravitationally, the earth experiences an attractive force towards the sun, and the sun experiences an attractive force of equal magnitude towards the earth. To repeat myself again: one force acts on the Sun; the other acts on the Earth. Two objects - two forces. One interaction.

What is it about this that confuses you so much?

James R: There are not two forces, there's one force and one lot of inertia to react to it.
The force (any inertial force, as in Newtonian) appears because of another equivalent inertial mass or reaction (as a force or opposition to the applied force).

One force, two things.

Newtons formula for gravitational "charge" is expressed as A mass and a derived mass. You need one to see the other. You get two results by running the algorithm twice; you iterate the formula for EACH body in the interaction - gets really tricky after [more than] two of them are around.

It's definitely two forces I'm afraid. A simple reason is that Force diagrams will always apply at least two directional arrows. One for Weight the other for Normal Reaction

I'm sure this is probably what James R was referring to.

You aren't seeing this are you?
There are only two forces because that's how we draw them - one at at time is how we do that.
They do it one at a time too, but together (at the same time).
Do you want that put another way...?

You aren't seeing this are you?
There are only two forces because that's how we draw them - one at at time is how we do that.
They do it one at a time too, but together (at the same time).
Do you want that put another way...?

Are you trying to refer to Lagrangian Mechanics?

"you want that put another way..."

The computer here is two masses that are "gravitationally bound" right?

The two forces in James R's post and your weight and reaction, are the things our computer maps back onto the real one.

Layman's version: if you stretch an elastic band or string, then both ends will pull on your hands - each hand sees a "pull" toward the centre of the length of elastic: is it two forces from one interaction, or a single force (pull) from one rubber band? As long as you're clear about the parallel side of it, then each hand simultaneously experiences what we call a force, and we can describe each separately which of course is just a convention.

plane:





There is no contradiction between my two statements:

1. The force of gravity involves an interaction between at least two objects.
2. Newton's law of gravity gives the magnitude of the force on either one of the two objects involved (since each experiences a force of equal magnitude).

Why do you think there is a contradiction?

A force (any force) only acts on one object at a time, by definition of what we mean by "force". In a gravitational interaction, a Newton's third law action-reaction pair of forces is involved. For example, when the sun and earth interact gravitationally, the earth experiences an attractive force towards the sun, and the sun experiences an attractive force of equal magnitude towards the earth. To repeat myself again: one force acts on the Sun; the other acts on the Earth. Two objects - two forces. One interaction.

What is it about this that confuses you so much?

Hardly worth you replying JR. I am satisified an apple does not attract the earth. And satisfied that I know how Newton made his mistake.

You are saying without hesitation in this post that the sun and earth apply equal force to each other.

If Newton's guess at gravity is ever to exposed as the guess that it is, physicists are going to have to be put in a position where a multitude of everyday people doubt what they are saying. That may never happen but if what you are saying is couched in terms of a 500 horse power bulldozer and a 200 horse power bulldozer pushing on each other, you never know, the penny might drop.

You/Newton are saying that each bulldozer applies the same force to each other. Somehow they link up so as each applies 1000 horspower to the other.

In effect Newton's law of gravity is espousing a principle that goes down this line.

If it is pointed out to everyday people that this is the principle that Newton's law of gravity espouses, then everyday people would look to physicists for an explanation as to how unlike opposed forces sources link up to generate equal and opposite like forces that is the product of the two force sources.

I don't think you can explain mechanically how M and m join together to produce one force that is the product of the two masses. We have been through it already and you haven't been able to.

This is a diagram of where I think Newton's guess has sprung from.

http://www.fotothing.com/photos/bd2/bd2102368212281ddcd19bfea9612dfe.jpg?ts=1218067852

He has said each of unlike forces is subject to the new world of Galileo. (F = k.m.a)

Next he has placed in m/D x D and M/D x D for A and a respectively.

http://www.fotothing.com/photos/bb0/bb0ab9a63e786d1a0dd12463392d91a1.jpg?ts=1218069115

And have presto he has believed that he has had a universal law of gravity.

His base problem was the presumption that the small m could subject the large M to Newton's second law.

As I said I am satisfied that is how it has come to be. Just a bit sad that it hides a far more rationale explanation of the high tide on the side of the earth away from the moon.

That as it maybe, I know I am not going to get sense out of anyone who believes in a rote like way that earth applies the same force to the sun as what the sun does to the earth.

Sure you have better things to do than reply. Goodbye and good luck.

Is there an echo in here?

Just, for a sec there...

P.S. Scientists gave up trying to explain things mechanically some time ago. Mechanistic theories keep bumping into the sort of difficulties that a certain iterative poster seems to have (right here).
The problem with it is you cannot just consider forces, you have to look at the whole thing; the whole thing does it simultaneously - we can't do that when we analyse it, except at the end of a series of determinations; someone here seems to be unable to see past this.

Could you name these scientists? perhaps state an exact number with a reference to collaborate your findings?

The reason I ask this Vkothii is because there are certain people that choose to either misinterpret things for fun, or perhaps have their own agenda for mis-interpretation and when they do so in regards to science they are creating what is known as "Junk Science". This is where they blatantly lie, manipulate results and otherwise attempt to undermine Science in general.

Now I'm not saying you are doing this, but there are similarities to it that I thought should be pointed out.

Might have to go back a century or so, first.

plane:

Hardly worth you replying JR. I am satisified an apple does not attract the earth.

Good luck to you, then. You're out of touch with 99.999% of the scientific community, but maybe you'll convince somebody, somewhere.

You are saying without hesitation in this post that the sun and earth apply equal force to each other.

It's implicit in what we mean by the term "force". It's a definitional fact. Arguing it is, frankly, quite silly. To do so effectively, you really need to rework the whole notion of "force" - something you have so far made no attempt to do.

You/Newton are saying that each bulldozer applies the same force to each other. Somehow they link up so as each applies 1000 horspower to the other.

Bear in mind that power is not the same as force. In fact, if a large truck pushes on a small car, or vice versa, the force that each exerts on the other are always equal and opposite, in accordance with Newton's third law of motion. Your failure to properly understand that law is the source of all your problems with Newtonian gravity, as well. I advised you when you first brought the subject up to go away and learn Newton's laws from scratch. I can only repeat my advice.

As I said I am satisfied that is how it has come to be. Just a bit sad that it hides a far more rationale explanation of the high tide on the side of the earth away from the moon.

What far more rational explanation? Didn't we cover the faults in your explanation earlier?

You are saying without hesitation in this post that the sun and earth apply equal force to each other.Yes. It's measured. The Sun isn't set at the centre of the solar system, it orbits the barycentre of the solar system, which is the 'centre of mass' of all the planets and the Sun (as well as moons etc) added together and averaged over their interactions.

As I said to you before, we observe massive planets in distant solar systems not by seeing them but by seeing their influence on their stars. A planet 10 times the mass of Jupiter as close to the Sun as Mercury will affect the Sun a lot, enough to be seen light years away by technology we have at the moment. If there wasn't this mutual back reaction, we'd not see all the planets we do.

Then there's other systems which are gravitational and involve close-ish masses. The Moon, compared to the Earth, is very large. It's the second largest moon/planet ratio in the solar system (I'll get to the first in a moment) and so the Earth doesn't just have the Moon going around it, both of them orbit a point which is their 'centre of force', their barycentre. The Moon isn't large enough to make the centre of their mutual orbits to be above the Earth's surface.

However, the Jupiter/Sun system is! The Sun actually orbits a point above it's surface!! And the system with the largest moon/planet ratio is Pluto and Charon. They are very close is size and orbit about a point somewhere between the two of them.

See http://en.wikipedia.org/wiki/Center_of_mass#Barycenter_in_astronomy and the animations just below it.

So we have demonstrated proof that you're wrong.

Just wait for the echo...

Just wait for the echo...

Scientists gave up trying to explain things mechanically some time ago

Scientists should never give up on that chore. Not scientists if they do.

plane:







It's implicit in what we mean by the term "force". It's a definitional fact. Arguing it is, frankly, quite silly. To do so effectively, you really need to rework the whole notion of "force" - something you have so far made no attempt to do.




It's non implicit in quantity of mass being directly proportional to the rate of acceleration towards mass, James R. The greater the mass, the greater the rate of acceleration towards it. The moon 1/6 the gravity of the earth etc.


Your definition of force (anything that causes acceleration) lacks scientific substance.

That defines what force does. It doesn't define what force is. My definition is far better. It defines what force is.

Will try and teach you. Your idea of unequal masses causing equal forces is what you are trying to explain. Will try and help you.

Question.

Does the apple's gravity cause the earth to accelerate towards the apple faster than what earth's gravity causes the apple to accelerate towards the earth? Or vica versa?



Your answer, correct me if I am wrong, is the apple accelerates the faster because it has less mass.

That defines what force does. It doesn't define what force is. My definition is far better. It defines what force is.
So, we are finally going to learn after all this time (Galileo, Kepler, Newton, the Renaissance thing) what a force is, as well as what a force does; an independent (possibly using some brand new math) description of forces, distinct from those things - material bodies that we can't explain the existence of either - that forces are seen (by our eyes) acting upon somehow or other?

Fascinating, really, I'm all eyes.

plane:

The greater the mass, the greater the rate of acceleration towards it.

Your definition of force (anything that causes acceleration) lacks scientific substance.

You're contradicting yourself. In the first quote here, you rely on Newton's definition of force to say that force is proportional to acceleration and mass (i.e. Newton's 2nd law). In the second quote, you claim you don't believe in Newton's definition of force.

So, which is it? Are Newton's laws of motion true or false? Time to decide.

Does the apple's gravity cause the earth to accelerate towards the apple faster than what earth's gravity causes the apple to accelerate towards the earth? Or vica versa?

The acceleration of the Earth towards the apple is less than the acceleration of the apple towards the Earth. That follows from Newton's second law and the fact that the force on the apple is equal to the force on the Earth (the point that you dispute).

What do you think the answer to your question is? And why?

Your answer, correct me if I am wrong, is the apple accelerates the faster because it has less mass.

Yes. a = F/m. Given the same F, the larger mass accelerates at a slower rate.

Do you believe in Newton's second law? Yes or no?

I thought we settled this. The apple does pull on the Earth;....all matter has gravity. However the gravity of the apple is insignifcant in comparison with that of the Earth.

I thought we settled this. The apple does pull on the Earth;....all matter has gravity. However the gravity of the apple is insignifcant in comparison with that of the Earth.

The gravity is the same if we only consider the apple and the Earth.
The acceleration of the Earth is insignificant.

The gravity is the same if we only consider the apple and the Earth.It's the same if you only consider the apple, too.
It's the same for both, F_{apple} = F_{earth}

At least, it is if you sit in an orchard and watch apples and earths accelerate toward each other.

So, we are finally going to learn after all this time (Galileo, Kepler, Newton, the Renaissance thing) what a force is,


I would say force is the exertion of matter upon matter.

plane:

You're contradicting yourself. In the first quote here, you rely on Newton's definition of force to say that force is proportional to acceleration and mass (i.e. Newton's 2nd law). In the second quote, you claim you don't believe in Newton's definition of force.

So, which is it? Are Newton's laws of motion true or false? Time to decide.

Time for who? I would say my decisions are made. Not sure that you have actually made decisions about Newton's work.

On your inquiry as to my position, some right, some absurd, and some not what they purport to be. (Newton’s third law should read to every force there is a like and opposite force, law of gravity absurd, first law of motion Newton’s second law under the condition of zero unbalanced force.)

You are saying if one element of Newton’s laws are right, all elements are. Doesn’t necessarily follow.

In the first quote I am relying in the earth having a greater rate of acceleration towards it because it has the greater mass (http://www-library.desy.de/preparch/physics/9902/9902044.html). Newton’s second law is not in the picture. Drop the apple on the moon. It accelerates at a rate proportional to what? The moon’s mass. Force is not introduced. Acceleration is proportional to mass. That is all we have.

Look closely at my first quote and understand your mistaken reading on what I post. I make no mention of force. You read what I write and you bring force into it. If we are debating, as you say we are earlier in the thread, your standard of debating does not amount to much. If you want to say what someone says is wrong, deal with what they say.




The acceleration of the Earth towards the apple is less than the acceleration of the apple towards the Earth. That follows from Newton's second law and the fact that the force on the apple is equal to the force on the Earth (the point that you dispute).

More explanation. You are hiding your brain in the betwixt of Newton's work. A few posts back I said not worth your time replying. And I meant it. You haven't been able to answer how an the lesser mass of an apple applies the same force to the earth as what the earth does to the apple. The truth is you don't know and we both know that you don't, so why bother replying? I will try and teach you as per last post, I guess, if you do.

What do you think the answer to your question is? And why?

The apple accelerates towards the earth. The earth does not accelerate towards the apple.



Yes. a = F/m. Given the same F, the larger mass accelerates at a slower rate.

Around the circle we go. How the same F if the earth has more mass than an apple? You will never answer.

Do you believe in Newton's second law? Yes or no?

Ja. You? Has this link got it wrong. If Newton said gravity is proportional to mass and also that unlike masses apply an equal force to each other, he contradicted himself. No big deal, I guess, but he did.

Isaac Newton said that gravity is proportional to mass, (http://www-library.desy.de/preparch/physics/9902/9902044.html)

The apple accelerates towards the earth. The earth does not accelerate towards the apple.

How do you explain, planetary wobble then? Or binary star systems etc.

Ja. You? Has this link got it wrong. If Newton said gravity is proportional to mass and also that unlike masses apply an equal force to each other, he contradicted himself. No big deal, I guess, but he did.

Where is the contradiction?

plane:

What is it about Newton's law of gravity that you can't grasp? It involves two masses. Look:

F=\frac{Gm_1 m_2}{r^2}

In other words, the gravitational force acting on mass 1 is equal to the gravitational force acting on mass 2, and the magnitude of the force depends on the magnitudes of both masses.

You seem to think that gravitational force depends only on the mass of the larger object. But Newton's law of gravity plainly contradicts you, and you are offering no alternative formula.

I would say my decisions are made. Not sure that you have actually made decisions about Newton's work.

You're babbling at random. Try to make sense, please.

On your inquiry as to my position, some right, some absurd, and some not what they purport to be. (Newton’s third law should read to every force there is a like and opposite force, law of gravity absurd, first law of motion Newton’s second law under the condition of zero unbalanced force.)

What on earth does this mean? It reads like nonsense.

You are saying if one element of Newton’s laws are right, all elements are. Doesn’t necessarily follow.

Er... no, I'm not saying that. Conceivably, Newton's law of gravity could be wrong, while his laws of motion are correct. As for the laws of motion themselves, the third law is automatically correct, seeing as it is tied up to how the term "force" is defined. For Newton III to be wrong, we'd need a new definition of "force". As for Newton I and II, both are well established and supported by literally millions of experiments and observations.

You haven't been able to answer how an the lesser mass of an apple applies the same force to the earth as what the earth does to the apple. The truth is you don't know and we both know that you don't, so why bother replying?

I've explained it to you at least 3 times now. Gravitational attraction between two objects is an interaction. Take another look at the equation above. The force magnitude depends on the masses of both objects taking part in the interaction, not on the mass of just one of them.

You have no alternative to offer, or any coherent objection.

The apple accelerates towards the earth. The earth does not accelerate towards the apple.

But it is an observed fact that both masses accelerate in a gravitational interaction, not just one, contrary to your claim.

If Newton said gravity is proportional to mass and also that unlike masses apply an equal force to each other, he contradicted himself. No big deal, I guess, but he did.

Your imprecision with language makes it not worth replying to this, since I'd have to guess what your meaning is here. Want to try again?

Isaac Newton said that gravity is proportional to mass,

"gravity" is an effect. It is not proportional to anything. Are you referring to gravitational force, gravitational acceleration, or what? Be specific, and try to be clear.

What is a "force"? I bet that plane dude doesn't really know; although it looks a lot like he said he does back there, the definition has yet to appear.

Then there's the question of what a force does, distinct from what it is. No answer yet.

Why not just tell us, since no-one else appears to have worked it out?
(And Newton thought he knew, obviously that guy was nowhere near as intelligent).

Can plane describe why I feel both hands being pulled together, if I hold either end of an elastic string and stretch it outwards?

Why doesn't just one hand feel a pull?
Or if I tie one end to a nail in a wall, and pull the elastic with both hands. Does the wall feel a pull, or just my hands? Or should I only use one hand, to be consistent?

How do you explain, planetary wobble then? Or binary star systems etc.



Where is the contradiction?

If the concept of a small mass pulling a large mass is flawed, the explanation to phenomea believed to be explained by it will lie else where.

The contradiction.

1/ The greater the mass, the greater the rate of acceleration towards mass.

2/ Newton's gravity says the product of unlike masses produce a like force.

In 1/ a falling object is subject to a force proportional to the mass that is falling towards.

In 2/ A falling object is subject to a force that is proportional to the product of its mass and the mass it is falling towards.

Think I have some diagrams a few posts back explaining how Newton went wrong.

What is it about Newton's law of gravity that you can't grasp? It involves two masses. Look:



In other words, the gravitational force acting on mass 1 is equal to the gravitational force acting on mass 2, and the magnitude of the force depends on the magnitudes of both masses.

You seem to think that gravitational force depends only on the mass of the larger object. But Newton's law of gravity plainly contradicts you, and you are offering no alternative formula.

Why would I offer an alternative formula? Would I not just point out the problems with the errant formula. As I have done.

James R I have reached the stage in life where I recognize that you can’t reason with people who believe that a small mass pulls a large mass as much as a large mass pulls a small mass. So my heart isn't really in this.

But do you understand you explain nothing?

On what you post here, 1/ How is the gravitational force acting on mass 1 equal to the gravitational force acting on mass 2?

Stating it doesn’t explain it.

Then 2/ How do mass 1 and 2 physically link up to produce these two forces? If that is what you believe happens.

Your prerogative but you never even begin to answer these questions


You're babbling at random. Try to make sense, please.

Bit subtle for you. I was implying that you have learnt by rote without understanding what you are learning. Went over your somewhat brainwashed head I guess.



What on earth does this mean? It reads like nonsense.

It means Newton’s first law of motion is not a law of motion, Newton’s third law is not presented correctly and Newton’s law of gravity is absurd. I mean, a particle in your near vicinity pulling the whole universe towards it. If someone came on a science forum with that theory, the pseudo science section is where it would belong for a very long time.

Er... no, I'm not saying that. Conceivably, Newton's law of gravity could be wrong, while his laws of motion are correct. As for the laws of motion themselves, the third law is automatically correct, seeing as it is tied up to how the term "force" is defined. For Newton III to be wrong, we'd need a new definition of "force". As for Newton I and II, both are well established and supported by literally millions of experiments and observations.

Newton’s second law passes muster.

I've explained it to you at least 3 times now. Gravitational attraction between two objects is an interaction. Take another look at the equation above. The force magnitude depends on the masses of both objects taking part in the interaction, not on the mass of just one of them.

Pardon me but would you not need to elaborate on what you physically mean be interaction to have credibility in your explanation. Honestly, if you know what you are on about, you should be able to do better than italics to explain things.

You have no alternative to offer, or any coherent objection.

I do have a perfect alternative explanation about the tides to offer. And my objections seem more than coherent to me. Be specific about which one you find incoherent.

But it is an observed fact that both masses accelerate in a gravitational interaction, not just one, contrary to your claim.

What observation are you referring to? We will go through it if you want.

Your imprecision with language makes it not worth replying to this, since I'd have to guess what your meaning is here. Want to try again?

Language precise actually. Read again. Newton said 1/ gravity is proportional to mass and 2/ unlike masses (your m1 and m2) apply equal forces to each other. I have done a bit in this thread to explain it, if you can’t get it, not sure what else I can do. If you have a closed mind, you have a closed mind.

If you only want to pay lip service (or typing service if that is the equivalent on the internet), why bother replying?

"gravity" is an effect. It is not proportional to anything. Are you referring to gravitational force, gravitational acceleration, or what? Be specific, and try to be clear.

Referring to the link provided (underlined if you go back to the post in question). James R, you aren’t really up to serious debate. Three or more questions here you are shy on answering. You can either answer them or you can't.

The contradiction.

1/ The greater the mass, the greater the rate of acceleration towards mass.

2/ Newton's gravity says the product of unlike masses produce a like force.

In 1/ a falling object is subject to a force proportional to the mass that is falling towards.

In 2/ A falling object is subject to a force that is proportional to the product of its mass and the mass it is falling towards.

Think I have some diagrams a few posts back explaining how Newton went wrong.

Stick F=Ma into Newton's law of gravitation and you will see there is no contradiction.

I have watched this for a very long time. I wish the 'so-called' professionals of physics would explain this properly.

The M and m, hold the same value, but not intensity of the gravitational force. But, there is an equal force, but not intensity, acting on both objects. So if there is a magnitude of 10,000 units, whereas, an apple may have 0.003 % of that value, that value according to relativity is reduced from 10,000, so that the value spoken of in the latter, has a value of intensity stronger than that of the apple, so that the apple does not alter the earth in any dramatic way.

It's the same as the train phenom in relativity. Suppose a train was moving 5 miles per hour, and aboard the train where Jack and James, and they wanted to play a game of catch with a ball. Imagine Jack stood at one end of the cart and James stood at the other end.

Now, Jack throws the ball to James at six miles per hour, and James throws it back, at the same speed. Aboard the train nothing looks wrong. The ball is thrown back and forth at the same speed. For those stationed on the platform watching the game, it is a little different. When Jack throws the ball to James, the ball is observed to move faster with a speed of eleven miles per hour. When James throws the ball it moves considerably slower, only one mile per hour.

Why does the ball move at different speeds? - Well, one needs to take into consideration the velocity of the train, including the direction the ball is thrown. If Jack throws the ball, the speed of the ball works with the train, so the speed of the train must be added with the speed of the ball. If James throws it, The speed of the train must be deducted from the speed of the ball, because the throw is going against the momentum of the train. If the ball was a photon (fastest particle of light), things change. The photon will be seen to be traveling at the same speed according to the observers on the platform and the observers aboard the train, no matter how fast it was moving!

plane:

The contradiction.

1/ The greater the mass, the greater the rate of acceleration towards mass.

Maybe this is part of your problem, since it is wrong. The acceleration of object A falling towards object B is NOT determined by the mass of object B. Acceleration of object A depends on the force on object A and the mass of object A.

To summarise for you: the acceleration of object A depends on the mass of object A, not object B.

Why would I offer an alternative formula?

You should offer some evidence against Newton's law, if that is what you're disputing. So far, you haven't provided anything that backs up your claims. Physics is a quantitative science. It makes numerical predictions of things like accelerations, not just qualitative hand-waving nonsense.

James R I have reached the stage in life where I recognize that you can’t reason with people who believe that a small mass pulls a large mass as much as a large mass pulls a small mass. So my heart isn't really in this.

Ok. You can leave sciforums now, then. Bye.

On what you post here, 1/ How is the gravitational force acting on mass 1 equal to the gravitational force acting on mass 2?

Stating it doesn’t explain it.

I think it would be a complete waste of my time to attempt to explain the concept of a field to you, or virtual particle exchange, or any other conceptualisation of how gravitation works. You haven't even managed to learn Newton's laws of motion yet, so how can you hope to understand anything more complicated, without any kind of grounding in the basics?

Bit subtle for you. I was implying that you have learnt by rote without understanding what you are learning. Went over your somewhat brainwashed head I guess.

Meh. Whatever. You're hardly in a position to judge my learning.

It means Newton’s first law of motion is not a law of motion, Newton’s third law is not presented correctly and Newton’s law of gravity is absurd.

Explain yourself - if you can - or this is just another collection of empty nonsense.

Why is Newton's 1st law not a law of motion? What is it, then?
How should Newton's 3rd law be presented "correctly"? (You haven't given any sign of understanding it, based on your posts above, so you're not in a position to judge whether it is presented correctly or not, as far as I can tell.)
And what would be a correct numerical law of gravity, if Newton's law is wrong?

Put up or shut up.

Newton’s second law passes muster.

Well then. You should be aware that the m in Newton's second law refers to the mass of the accelerating object, and not the mass of the object it is accelerating towards. Agreed?

Pardon me but would you not need to elaborate on what you physically mean be interaction to have credibility in your explanation. Honestly, if you know what you are on about, you should be able to do better than italics to explain things.

All forces are interactions. By "interaction", I mean that one object causes another object to do something. I push you - you move backwards. My push was a force acting on you, and what occurred was an interaction between the two of us. As I push you, I also feel some resistance to my push - that's the equal force pushing back on me, in accordance with Newton's 3rd law of motion (which you believe is somehow "incorrectly presented", though you can't explain how or why).

I do have a perfect alternative explanation about the tides to offer.

I believe I debunked that earlier in the thread. Please review my previous posts.

But it is an observed fact that both masses accelerate in a gravitational interaction, not just one, contrary to your claim.

What observation are you referring to? We will go through it if you want.

Take, for example, any binary star system with two stars of approximately equal mass. They are observed to orbit around their common centre-of-mass position. What is NOT observed is one star (the slightly more massive one) sitting still in space while the other one (the less massive one) orbits around the centre of the first star.

We can go through it if you want.

Language precise actually. Read again. Newton said 1/ gravity is proportional to mass

What do you mean when you write "1/gravity"? Is this an obscure reference to force, or what?

What's so hard about understanding that two bodies accelerating toward each other's centre, each see an equivalent FORCE, because it's one interaction - the force is distributed by the masses of each body?

So they accelerate accordingly - their acceleration is distributed as the mass (of each body)?

A spring has a constant, gravitation has a constant; the analogy fits. One spring or constant pull on two objects connected to the ends.
Why is this such a problem?

Why does Newton use the same formula, essentially for both mechanics/dynamics fields, which is how he understood them?

Stick F=Ma into Newton's law of gravitation and you will see there is no contradiction.

Rubbish.

mg = kM/d x d

Means the mass of the body causing the falling is proportional to the rate of acceleration of the body doing the falling.


Maybe this is part of your problem, since it is wrong. The acceleration of object A falling towards object B is NOT determined by the mass of object B. Acceleration of object A depends on the force on object A and the mass of object A.



No. You are the wrong one.

Whether it be an egg or an elephant, the acceleration rate towards the earth is the same. The earth's mass determines the rate of acceleration towards the earth.

Understand that and I will go through the rest of your nonsense.

mg = kM/d x d

Means the mass of the body causing the falling is proportional to the rate of acceleration of the body doing the falling.No, you mean mg = \frac{GMm}{r^{2}}, which simplifies down to g = \frac{GM}{r^{2}}, so the acceleration, for any object, is proportional to the mass of the object creating the gravitational field.

Why did you ignore my last post plane? I commented that the things I'd talked about were observed : http://en.wikipedia.org/wiki/Center_of_mass#Barycenter_in_astronomy

We do see the Sun be affected by the gravitational effects of the planets. It orbits about a point above it's surface, the barycentre of the solar system. Pluto and it's moons also orbit a position above the surface of Pluto.

The back reaction of the smaller object on the larger one is seen. We see binary pulsars orbiting their barycentre, not the smaller one going around the larger one. As the ratio of the masses gets larger and larger, the back reaction gets smaller and smaller, because while the forces each experiences are the same, the resultant acceleration of the larger due to the smaller gets less and less.

The forces must be the same or else there would be an overall spontaneous resultant force on them, which would mean the total mass of the two objects is accelerating, all on it's own! But if they are experiencing equal and opposite forces then there is no resultant force on the system overall and so things like momentum conservation are obeyed.

If you are correct in your claims, why do we have such an excellent and experimentally verified grasp of mechanics?

plane:

No. You are the wrong one.

Whether it be an egg or an elephant, the acceleration rate towards the earth is the same. The earth's mass determines the rate of acceleration towards the earth.

Understand that and I will go through the rest of your nonsense.

I understand, but read what I wrote again.

Let me explain it step by step to make it easier for you to understand. First, the acceleration of an object of mass m subject to any force F is:

a = F/m

From this, we see that the acceleration is determined by (a) the magnitude of the force applied to the object, and (b) the mass of the object itself. This is called Newton's second law of motion.

Now, Newton's law of gravity says that the force on mass m due to some other mass M at distance r away from m is:

F =\frac{GMm}{r^2}

where G is a fundamental constant of nature. This is the force that acts on mass m (and also on mass M).

Strangely, you seem to agree with this law, all of a sudden, because you implicitly rely on it in your previous post. Yet, all the time in this thread you have been trying to dispute it. I think you're confused, but I hope this post helps you sort yourself out.

Now, if F is the force that acts on mass m, then the acceleration of mass m is:

a = F/m = \frac{GM}{r^2}

Interestingly, the mass m cancels out, so that the acceleration of mass m is determined by its distance from mass M and the mass of M itself. This is something specific to gravitation, whereas before I was making a more general point about force.

Now, the important thing to notice is that Newton's law of gravity doesn't specify that M must be a greater mass than m. In other words, the above argument is valid regardless of whether m or M is the greater mass.

This invalidates your silly argument that if m is greater than M it won't accelerate at all towards M.

Since you appear to agree that both Newton's law of gravity and Newton's second law are correct, I will now be interested to see if you still want to try to refute the above analysis. Certainly, you'll look like a fool if you now go on to refute a fact you just relied on a moment ago to make your argument.

Well?

No, you mean mg = \frac{GMm}{r^{2}}, which simplifies down to g = \frac{GM}{r^{2}}, so the acceleration, for any object, is proportional to the mass of the object creating the gravitational field.

Why did you ignore my last post plane? I commented that the things I'd talked about were observed : http://en.wikipedia.org/wiki/Center_of_mass#Barycenter_in_astronomy

We do see the Sun be affected by the gravitational effects of the planets. It orbits about a point above it's surface, the barycentre of the solar system. Pluto and it's moons also orbit a position above the surface of Pluto.

The back reaction of the smaller object on the larger one is seen. We see binary pulsars orbiting their barycentre, not the smaller one going around the larger one. As the ratio of the masses gets larger and larger, the back reaction gets smaller and smaller, because while the forces each experiences are the same, the resultant acceleration of the larger due to the smaller gets less and less.

The forces must be the same or else there would be an overall spontaneous resultant force on them, which would mean the total mass of the two objects is accelerating, all on it's own! But if they are experiencing equal and opposite forces then there is no resultant force on the system overall and so things like momentum conservation are obeyed.

If you are correct in your claims, why do we have such an excellent and experimentally verified grasp of mechanics?

No what I meant was if you set k.m.a = k.M/m/d x d you get a = k.M/d x d or, when you accept the inverse square law and repeated Cavendish experiments give you the same answer for k, you get knowledge that there is direct proportion between magnitude of gravity of a body and its mass.

After I posted I went to bed and remembered I hadn’t cancelled out one of the small masses but couldn’t be bothered correcting it. Was inebriated at the time.

The point is when the small masses take no part in the proportion, there is no legitimate reason to say they have.

I have not ignored your posts. I have said that if Newton’s law of gravity is structurally flawed, you have to look for other explanations of what it is currently believed to explain. I have also mentioned Tyco Brahe being drawn to astronomy by a precise prediction of when an eclipse of the sun would occur. At the time the sun was believed to be in orbit of the earth. Things are always going on in the universe, misapprehensions about reasons why all things are going on can easily occur.

Hope that helps. If you go back to post 136, you will see an explanation of how Newton derived his law of gravity out of F = k.m.a. To subsequently set k.m.a equal to k.m.a proves nothing except, as explained a direct proportion between mass and magnitude of gravity when you introduce different ways of measuring a.



James R, this reply to alphanumeric is relevant to you and pretty much covers where you are at.

From this, we see that the acceleration is determined by (a) the magnitude of the force applied to the object, and (b) the mass of the object itself. This is called Newton's second law of motion.

This just says that there is a problem with labeling gravity as a force. We know that all masses fall at the same rate. The mass of a falling object is not relevant to its rate of fall. Your (b) does not apply to a falling object. So that puts a question mark against the veracity of your (a).

With respect of gravity, it’s back to the drawing board for you. You are talking about a gravity logic that is proven to be counter to observation. All things subject to the same gravity fall at the same rate.

Best that you also go to post 136 and see that Newton has most plausibly derived his law of gravity from Galileo (F = k.m.a.) He knew the earth was subjecting the apple to that formula. Presumed the apple was subjecting the earth. Then introduced a = k.M/d x d and A = k.m/d x d and was left with twice with F = k.M.m/ d x d

But you can see, can't you, that various masses falling at the same rate tells you that it is incorrect to simply say that gravity is a force directed at mass? If you can't see that, not much I can really do for you.



First time for a while that I have come to this forum sober. You proud of me? More importantly do you understand that you are not giving due respect to unlike masses falling at a like rate.

Give that proper respect and you will see that your arguments about the mass of a falling body somehow being involved in its own rate of fall are just convoluted nonsese invented to try and make an original mistake correct.

But you can see, can't you, that various masses falling at the same rate tells you that it is incorrect to simply say that gravity is a force directed at mass? If you can't see that, not much I can really do for you.
Because different masses (that are much smaller than the mass of the earth) fall at the same rate, or accelerate as if the same force is applied, then there's a constant force due to the earth that will accelerate all bodies at the same rate (including the moon, asteroids, satellites we launch into orbit).

Actually anything that is a material body and so has mass, will accelerate towards the centre of mass of the earth, right?
But these bodies will only move along a path (that ends at the centre of the earth) if there's nothing in the way, right?
If the surface of either body is in the way, neither body will have a motion, but will be "at rest", wrt the centres of either, right?

Just trying to get some agreement here on what the subject might be, right? Not trying to "do anything for anyone" (considering I have said I won't be responding directly), just trying to make sense.
Right.

the mass of a falling body somehow being involved in its own rate of fall are just convoluted nonsese invented to try and make an original mistake correct.The mass of a body is the mass of a body.
If it isn't falling, does it have any mass? Can someone who can't see what an equation is (they seem to be incapable of figuring that one side is either equal, or alternatively equivalent to the other side depending on a few things like the units used in the equation, say), construct a logical answer, as to why a body on the surface of a planet (like their human body that stands still occasionally), has no mass, no acceleration, or doesn't feel a force since it isn't moving...?

Well, I wonder what the answer might be, right?

plane:

Since you haven't addressed the argument I put to you, there's no point in further discussion.

If a bottle of whiskey contains 750 grams of fluid, does drinking it increase the mass of the drinker? Do they then have a greater acceleration towards the centre of a local large concentration of mass?

If they drink two bottles, does the earth keep spinning?

Perhaps plane is investigating the possibility, and will let everyone know the answer in due course (when he's feeling better).

plane:

Since you haven't addressed the argument I put to you, there's no point in further discussion.



Your argument

From this, we see that the acceleration is determined by (a) the magnitude of the force applied to the object, and (b) the mass of the object itself. This is called Newton's second law of motion.

The address

This just says that there is a problem with labeling gravity as a force. We know that all masses fall at the same rate. The mass of a falling object is not relevant to its rate of fall. Your (b) does not apply to a falling object. So that puts a question mark against the veracity of your (a).

If you and haven't the intellectual guts to enter an avenue of thought where you could end up wrong and prefer to cheap out with a false accusation, not my worry.

Much of science is the art of searching for your mistakes. I have quite succinctly pointed your mistake out here. Makes me the scientist for both of us I guess.

Cheers.

Hello plane,

I am not sure why you are not satisfied with all of the logical reponses provided so far. So, please allow me to try a less logical approach.

Next time you go to the produce section of your local grocery store, place an apple on a scale and measure it's weight. After converting the unit of weight to Newtons, that value represents the force (F) due to the acceleration of gravity (g), and the mass of the apple (m) in kilograms.

F=mg

Where g=9.8 meters per second squared (m/s/s).

Notice the apple's mass is considered here, but the mass of the earth is not considered directly. It is indirectly factored in to the given value of g. Likewise, the the distance to the center of gravity of the earth is also already factored into g.

To prove that the apple does in fact pull the earth, we can repeat the above "scale experiment" only in-reverse. Instead of weighing the apple on planet earth, we can weigh the earth on "planet apple".

Turn the scale upside down so that the earth is sitting on the measuring platform of the scale. You will have to reset the scale to zero to correct for the weight of the scale's internal mechanisms. Now place "planet apple" on the bottom surface of the scale (where the earth used to be) and take a measurement of the earth's weight on planet apple.

As before, convert this value to Newtons, and then using the new formula:

F=Ma

Where (F) is the force due to the acceleration of gravity (a), and the mass of the earth (M).

Unlike the first equation where the acceleration on earth was known, we do not know the acceleration on planet apple. Fortunately, we have a measured value for F, and we can look up M in an astronomy book to find that it is approximately 5.97x10^24 kilograms, so we can calculate the value of a.

Now you should be able to visualize that planet apple does have a tiny gravitational field that pulls the huge mass of the earth to its surface. If you wave your hand around planet apple, you will not be able to feel its gravity because it is so small. But rest assured that it is there, or else the earth would have floated right off of the measuring platform! :p

Now place "planet apple" on the bottom surface of the scale (where the earth used to be) and take a measurement of the earth's weight on planet apple.

How do you know the earth places weight on the apple? Turning a set of scales upside down does not reverse what is measuring what.

That's hopeless, Neddy.

Just as hint, gravity is not a force. Gravity may be caused by force and may cause force, but gravity its self is simply an acceleration through space towards a centre of mass.

Your job is to have a penny drop.

Give you a hand. Mass places a force upon space in a direction away from mass.

The acceleration is through space in the opposite direction.

Explained gravity for you Neddy. Your lucky day. Sleep well.

Just as hint, gravity is not a force. Gravity may be caused by force and may cause force, but gravity its self is simply an acceleration through space towards a centre of mass.

This is so imprecise as to be useless.

Is there any difference between gravity and the acceleration of a car along a road, using your definition? (Because both are accelerations through space towards a centre of mass of some kind.)

How do you know the earth places weight on the apple? Turning a set of scales upside down does not reverse what is measuring what.

That's hopeless, Neddy.

Well, I warned you that I was going to present a "less logical approach". I was hoping it might appeal to the rebel in you.

So, are you claiming that, if two masses are touching, except for a set of scales between them, the only valid way to interpret the weight measurement is to say that the large mass is attracting the small mass, and not the other way round?

Just as hint, gravity is not a force. Gravity may be caused by force and may cause force, but gravity its self is simply an acceleration through space towards a centre of mass.

Yes, it can be considered to be a constant acceleration at one elevation, for example, at sea level on earth it is 9.8 m/s/s.

I went to the grocery store and weighed an apple. It was appropriately about 1 Newton. So on "planet apple", the acceleration would be about 1/5.97x10^24 m/s/s. Quite a bit less than the 9.8 m/s/s of earth, but certainly not zero. Otherwise it would be immune to gravity and permanently weightless. Wouldn't you agree?

Your job is to have a penny drop.

Give you a hand. Mass places a force upon space in a direction away from mass.

The acceleration is through space in the opposite direction.

Explained gravity for you Neddy. Your lucky day. Sleep well.

Thanks, but I'm afraid that your explanation is still unclear. Why are you claiming that the acceleration goes in the oppsite direction to the force?

So, are you claiming that, if two masses are touching, except for a set of scales between them, the only valid way to interpret the weight measurement is to say that the large mass is attracting the small mass, and not the other way round?

No. Not attracting but that is beside what you are trying to say.

The only valid interpretation is to say that the one that makes the scales accelerate (register) is accelerating towards the one that doesn't cause the scales to accelerate.

Thanks, but I'm afraid that your explanation is still unclear. Why are you claiming that the acceleration goes in the oppsite direction to the force?

Still your lucky day. This diagram explains gravity better than words

http://www.fotothing.com/photos/e45/e45aa53e9546e9b0e05ebe9045f54bd0.jpg?ts=1219839124

Didn't have to be a genius to work it out, either. Just an interest in the topic.

If you are going to say it's an errant diagram for some reason or other, hope you are able to put forward something about how the quantity of the earth does actually cause the earth to have what we refer to as gravity.

This is so imprecise as to be useless.

Is there any difference between gravity and the acceleration of a car along a road, using your definition? (Because both are accelerations through space towards a centre of mass of some kind.)

Just as a life tip James, you seem to be a chip on the shoulder poster. If you had of taken the entire post in context, you would have seen that the key point being made was the force is in the opposite direction.

I have taken the time to appreciate that your argument is that gravity is a force. If you are going to bother with posting, why not take the time to see just what the poster you are replying to is saying. Otherwise, why bother? You really owe me a poster to poster apology by now. Doesn't matter though. I'm just a happy chappy.

No. Not attracting but that is beside what you are trying to say.

The only valid interpretation is to say that the one that makes the scales accelerate (register) is accelerating towards the one that doesn't cause the scales to accelerate.



Still your lucky day. This diagram explains gravity better than words

http://www.fotothing.com/photos/e45/e45aa53e9546e9b0e05ebe9045f54bd0.jpg?ts=1219839124

Didn't have to be a genius to work it out, either. Just an interest in the topic.

If you are going to say it's an errant diagram for some reason or other, hope you are able to put forward something about how the quantity of the earth does actually cause the earth to have what we refer to as gravity.



Just as a life tip James, you seem to be a chip on the shoulder poster. If you had of taken the entire post in context, you would have seen that the key point being made was the force is in the opposite direction.

I have taken the time to appreciate that your argument is that gravity is a force. If you are going to bother with posting, why not take the time to see just what the poster you are replying to is saying. Otherwise, why bother? You really owe me a poster to poster apology by now. Doesn't matter though. I'm just a happy chappy.

Why wouldn't the earth fall down the apple's space gradient then?

plane:

You still haven't replied to my argument in post #161.

I assume you have no adequate response.

Enough said.

Does that diagram really say "space is forced into space around the earth"...?
That's real meaningful right there. How do you force space?

Why wouldn't the earth fall down the apple's space gradient then?

The earth is not in the apple's space gradient. The apple’s space gradient is terminated where the earth and apple space gradients otherwise would be equal and opposite in magnitude.

plane:

You still haven't replied to my argument in post #161.

I assume you have no adequate response.

Enough said.

Enough by you I guess. This was posted.

Whether it be an egg or an elephant, the acceleration rate towards the earth is the same. The earth's mass determines the rate of acceleration towards the earth.

And you posted in your post 161

Strangely, you seem to agree with this law, all of a sudden, because you implicitly rely on it in your previous post.

You explain that. I could not fathom it. It was completely non-sequitur.

You may have been reading what I posted to steve 100 which was

g = k.m/d xd (I had an uncancelled out m in the post which has subsequently been explained (was drunk)) but it still doesn't explain why anyone would suddenly say that I posted Newton's law of gravity makes sense.

I will go through it for poor you.

Cavendish experiments.

m.g is set equal to k.m.M/d x d

The small masses are cancelled out.

g = k.M/d x d

Taking the inverse square law as a given, all that says is that there is a proportion between the mass that the acceleration is towards (M) and the mass of M.

In no way does an acceptance of g = k.M/d x d equal an acceptance of a small mass 'attracting' a large mass. The small mass takes no part in the equation.

I still advise you to go back to post 136 I think it is so as you can get a bit of a drift on how Newton came up with his law. At this stage you don't seem to have a clue as to where he got it from.

Incidentally, you are a very weak debater. Your enough said does not in any way challenge my diagram. Even less so when if we went back through the thread we could find a post where you state that no one knows how mass causes gravity. Or something to that effect. If you were for real, you would do better than your "enough said" when you first come across an idea of how mass causes gravity. You just don't seem fair dinkum to me. If you are I apologize but you come across as a waste of time. A few brains in your head but not using them for the good of the earth.

Does that diagram really say "space is forced into space around the earth"...?
That's real meaningful right there. How do you force space?

Archimedes principle is the way I have it. In part anyway. The presumption is space is a spontaneously existing particle.

This is probably proveable through the solar system. Not sure that I will ever acheive as much though.

plane:

Cavendish experiments.

Maybe you ought to look those up.

g = k.M/d x d

Taking the inverse square law as a given, all that says is that there is a proportion between the mass that the acceleration is towards (M) and the mass of M.

Yes, and nothing in the equation says whether M is bigger or smaller than m.

A point I made earlier, and one you still haven't addressed.

In no way does an acceptance of g = k.M/d x d equal an acceptance of a small mass 'attracting' a large mass. The small mass takes no part in the equation.

Just to repeat, nothing in the equation says that M is a "big" mass and m is a "small" mass. M could be the small mass and m the big mass.

I still advise you to go back to post 136 I think it is so as you can get a bit of a drift on how Newton came up with his law. At this stage you don't seem to have a clue as to where he got it from.

Meh. Whatever. What matters is not where it came from, but whether it is correct.

Incidentally, you are a very weak debater. Your enough said does not in any way challenge my diagram.

Your diagram shows nothing useful. There's no need to challenge it.

Even less so when if we went back through the thread we could find a post where you state that no one knows how mass causes gravity.

Correct. And that includes you.

You just don't seem fair dinkum to me. If you are I apologize but you come across as a waste of time. A few brains in your head but not using them for the good of the earth.

Personal insults won't save your poor argument.

plane:







Yes, and nothing in the equation says whether M is bigger or smaller than m.

A point I made earlier, and one you still haven't addressed.



Just to repeat, nothing in the equation says that M is a "big" mass and m is a "small" mass. M could be the small mass and m the big mass.

In Cavendish experiments, the small mass is always the one cancelled. Was just explaining to you all Cavendish experiments can be taken to mean.





Meh. Whatever. What matters is not where it came from, but whether it is correct.

So you agree that Newton's law of gravity was derived from Newton's second law. That means when the "law" is set equal to Newton's second law (with a different way of measuring acceleration), nothing of much consequence can be said.

We have m.a (newton's law of gravity where a = M/d x d) = m.a (Newton's second law where a is measured under laboaratory conditions).

What grand conclusion can you draw from that monsieur.







Your diagram shows nothing useful. There's no need to challenge it.

If it is right, it might be the most useful diagram to hit the planet for a long time. Not sure why you say an understanding of the relationship between mass and acceleration towards mass is not useful. Each to their own I guess.



Correct. And that includes you.

Wonder why I label you a waste of time do you? I am putting forward why I think a smaller mass falls towards a large mass, you say it is wrong without offering a reason why it is wrong. I am proving that you are a waste of time if nothing else.



Personal insults won't save your poor argument.

From this thread, in particular your reaction to the last diagram I posted, a very sound conclusion is you don't use your brains for the good of the earth. That is hardly a personal insult. Just an observation that can be backed up with facts.

If you want to post on, advise rigourlessly dealing 1/ with the smaller mass always being the one cancelled out in Cavendish experiments and 2/ the full implications of Newton's law of gravity being derived from Newton's second law. Cheers

plane:

In Cavendish experiments, the small mass is always the one cancelled. Was just explaining to you all Cavendish experiments can be taken to mean.

Cavendish did the sensible thing and kept the larger masses stationary and the smaller masses accelerating in his experiments? Why? Because the larger masses will accelerate more slowly for the same force (a=F/m), and the accelerations involved are very small.

So you agree that Newton's law of gravity was derived from Newton's second law.

No. Newton's law of gravity is an independent law of nature. It cannot be derived from Newton's second law of motion. On the other hand, the reasoning process that led to Newton's law of gravity used the second law as a sensible rationale. And the law of gravity is compatible with the second law of motion, as it must be.

Not sure why you say an understanding of the relationship between mass and acceleration towards mass is not useful.

I don't say that. Please do not put words in my mouth. The fact is, we have a very good understanding of the relationship between mass and acceleration. It's called Newton's second law of motion.

I am putting forward why I think a smaller mass falls towards a large mass, you say it is wrong without offering a reason why it is wrong.

I explained very clearly in my very first reply to you why you are wrong. The fact that you haven't understood my explanation after a further 20 or so posts of further explanation is your problem, not mine.

I guess some people are uneducatable by choice.

plane:



Cavendish did the sensible thing and kept the larger masses stationary and the smaller masses accelerating in his experiments? Why? Because the larger masses will accelerate more slowly for the same force (a=F/m), and the accelerations involved are very small.


Amusing. So this proves the larger mass accelerates towards the smaller mass. Perhaps at a later point of time you will start using your brain.



No. Newton's law of gravity is an independent law of nature. It cannot be derived from Newton's second law of motion. On the other hand, the reasoning process that led to Newton's law of gravity used the second law as a sensible rationale. And the law of gravity is compatible with the second law of motion, as it must be.

How was it derived then? You either know or you don't. Willing to put plenty of good money on you not having a clue on how Newton derived F = k.M.m/d x d

Sure bet.



I don't say that. Please do not put words in my mouth. The fact is, we have a very good understanding of the relationship between mass and acceleration. It's called Newton's second law of motion.

Almost feel sorry for you, as if I am playing with you. How does mass (the mass of the earth for example) cause an acceleration towards its self is what we are discussing. Newton's second law explains a relationship between an applied force, acceleration and mass. It does not explain how mass causes gravity, whether gravity be a force applied at a distance (you) or an acceleration through space (fundamental approach to gravity).



I explained very clearly in my very first reply to you why you are wrong. The fact that you haven't understood my explanation after a further 20 or so posts of further explanation is your problem, not mine.

Your first post did not deal with mass exerting force on space. Why post stuff that doesn't make sense. Mass exerting a force on space was not introduced until the black diagram a few posts back.

I guess some people are uneducatable by choice.

It's your choice. A truck can be driven through Newton's law of gravity. If you want to go to your grave believing education equals an apple pulling a planet, your choice. A coffin is a coffin is a coffin but your death when it happens will be the death a dishonest human being.

plane:

Cavendish did the sensible thing and kept the larger masses stationary and the smaller masses accelerating in his experiments? Why? Because the larger masses will accelerate more slowly for the same force (a=F/m), and the accelerations involved are very small.

Amusing. So this proves the larger mass accelerates towards the smaller mass.

No. This is the answer to your question as to why Cavendish allowed the small masses to move and not the large ones. You asked, so I provided the answer.

No. Newton's law of gravity is an independent law of nature. It cannot be derived from Newton's second law of motion. On the other hand, the reasoning process that led to Newton's law of gravity used the second law as a sensible rationale. And the law of gravity is compatible with the second law of motion, as it must be.

How was it derived then? You either know or you don't. Willing to put plenty of good money on you not having a clue on how Newton derived F = k.M.m/d x d

Sure bet.

I explained Newton's reasoning earlier in the thread for you.

Have you already forgotten?

You know, this discussion will require some effort from you. I can't do your thinking for you, you know. All I can do is to answer your questions and hope you apply your brain at some point.

Try to keep up.

Almost feel sorry for you, as if I am playing with you.

I think I'm already tiring of your game. If you really have no desire to learn from an expert, then further discussion is probably a waste of my valuable time. I have plenty of students who want to learn from me.

How does mass (the mass of the earth for example) cause an acceleration towards its self is what we are discussing. Newton's second law explains a relationship between an applied force, acceleration and mass. It does not explain how mass causes gravity, whether gravity be a force applied at a distance (you) or an acceleration through space (fundamental approach to gravity).

Correct. Newton's second law provides no "mechanism" for gravity. It is a phenomenological law, later empirically tested and confirmed. Later, it was shown to be an approximation to the more accurate theory of general relativity.

Tell me: what's your explanation of why large masses cause gravity, while smaller ones do not?

Also, please explain the following thought experiment for me:

1. I take two masses. One mass is 1 kg. The other is 0.9 kg. I observe that if I hold the 1 kg mass in place, the 0.9 kg mass is attracted to it. Agree?
2. Now, I take a lump of plasticine and stick it on the 0.9 kg mass, taking the total mass to 1.1 kg. According to you, the 1 kg mass no longer attracts the 0.9+0.2 kg mass. Correct?

What I want to know is: how does the 1 kg mass "know" to stop attracting the 0.9 kg mass?

Presumably you will say that the 1.1 kg mass will suddenly start to attract the 1 kg mass now, as well. How does the 1.1 kg mass "know" to swap over and start attracting when the plasticine is stuck onto it?

It's your choice. A truck can be driven through Newton's law of gravity. If you want to go to your grave believing education equals an apple pulling a planet, your choice. A coffin is a coffin is a coffin but your death when it happens will be the death a dishonest human being.

Are you accusing me of dishonesty? Why? Where have I lied about what I believe?

You are accused of fooling around with the truth. It is not done lightly as you seem to be intelligent enough to see into your own nonsense.

To wit, the inverse square law provides relative information. Information relative and unique to individual mass. That can be demonstrated with arithmetic. We all know that without posting the sums.

Newton decided it linked up masses without further explanation.



Should point out that in no way have you explained how or why Newton arrived at his law in this thread.

You did not take us to an articulation by Newton as to why or how he came up with his formula.

Lastly, if it universally appears, by experiments and astronomical observations, that all bodies about the earth gravitate towards the earth, and that in proportion to the quantity of matter which they severally contain, that the moon likewise, according to the quantity of its matter, gravitates towards the earth; that, on the other hand, our sea gravitates towards the moon; and all the planets mutually one towards another; and the comets in like manner towards the sun; we must, in consequence of this rule, universally allow that all bodies whatsoever are endowed with a principle of mutual gravitation.

That is what Newton gave us in Principia.

There is no mention in Principia of a deduction of unlike masses exerting a like 'pull' upon each other.

End of thread I think. Appreciate the mentions of binary stars and the like but if no-one can explain how the inverse square law connects up masses, we all know the laws a dud.

“That one body may act upon another at a distance through a vacuum without the mediation of anything else , by and through which their action maybe conveyed from one to another , is to me so great an absurdity that , I believe , no man who has in philosophic matters a competent facility of thinking could ever fall into it.”

By his own admission, Newton was flummoxed by gravity. Dead horses can only be flogged so much.

Tell me: what's your explanation of why large masses cause gravity, while smaller ones do not?

Never said smaller ones do not.

Presumably you will say that the 1.1 kg mass will suddenly start to attract the 1 kg mass now, as well. How does the 1.1 kg mass "know" to swap over and start attracting when the plasticine is stuck onto it?

The 1.1kg mass was a 1kg mass. Think you are befuddling your self.

But through the arithmetic of opposing directions of the inverse square law is your answer.

Well, this is a bit of a first; someone has overturned Newton's law of gravitation.

But they haven't provided an alternative, and they haven't explained how the equations are wrong.
Or why scientists still use his equations to launch things into space. Strange, you think they might have noticed the big problem by now.

Alternatively, this is just a persistent illusion, a confused and drunken wander down a garden path that doesn't go anywhere useful.
After 10 pages and 182 posts, no-one except the thread opener understands a word of it.

Newton was wrong, we just have to accept it and accept that there aren't any alternatives, or there aren't any on offer, just a lot of rambling.

I wonder if this person can see that they haven't really said anything yet?

From the first post:
can anyone point to empirical evidence of a smaller mass 'pulling' a larger mass. The tides and cavendish experiments don't do it from all the published imformation I've seen.We see that the problem is, in fact, an inability to understand experimental evidence. Which is complicated by an inability to accept the possibility that one has not grasped certain fundamentals. And a certain level of stubborn pride in one's ability to 'see the truth', and accept no other explanations.

I think it's called being 'pig-headed'.

plane:

Since you failed to actually address anything I wrote, I won't bother continuing discussion with you.

Bye!

plane:

Since you failed to actually address anything I wrote, I won't bother continuing discussion with you.

Bye!

That's highly acceptable James R. You are not honest enough to discuss gravity with.

I think it's called being 'pig-headed'.

Not pig headed at all. I have acted in good faith with all posters. Not sure if that can be said the other way. I suppose the other side of that is other posters haven't the wherewithal to handle being wrong.

Anyway, Newton's law of gravity is clearly wrong. (http://riachella.com/newtonerror/Newton%27s-Folly-Demonstrated.php)

There's a web page that explains it for you. It's very to the point and quite irrefutable. The basic problem is the inverse square law constant is not constant. It's proportional to quantity.



Those who check into this forum seem to be prejudiced in favour of Newton's law of gravity. Do not expect that prejudice to be cast aside anytime soon.

Anyway, been honest with anyone who has posted in this thread.

Well, I might go and get slowly pissed somewhere.

Well, I might go and get slowly pissed somewhere.

It's interesting, isn't it. Can understand your reaction. All the best with coming to grips with the constant as the hangover settles down.

wow, First off this is elementary physics. A force of one object hitting another object will be reflected to the other object. That old toy with four balls on strings where when you pull one back and let go the one on the far end shoots up and vice versa.

ALSO there is no Newton's law. It is Newton's theory. There is no such thing as scientific fact. Anything can (main wordis "can" not "will") be disproven.

If you need more info look up the post entitled scientific fact vs. scientific theory.

That old toy with four balls on strings where when you pull one back and let go the one on the far end shoots up and vice versa.
Newton's cradle
ALSO there is no Newton's law. It is Newton's theory. There is no such thing as scientific fact. Anything can (main wordis "can" not "will") be disproven.
Because we don't make the rules, so we can only have a best guess. Unlike in mathematics where we make the rules.

there arent rules in mathmatics they are also theory's. there is pretty much nothing physical out there (and by physical i mean anything that is not from our imagination) that is a fact. As my physics teacher siad "If i cant prove you rdad is your dad, how can i prove quantum physics?" lolz.

there arent rules in mathmatics they are also theory's. there is pretty much nothing physical out there (and by physical i mean anything that is not from our imagination) that is a fact. As my physics teacher siad "If i cant prove you rdad is your dad, how can i prove quantum physics?" lolz.

Yes there are rules in mathematics.

Do you think someone discovered mathematics and then people started testing theories on it until we found the ones that fit best?