Proof of the apple 'pulling' the earth?

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?

 

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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.

 

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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 ?

 

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

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.

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?

 

It was a rhetoric question

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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.

 

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.

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?

 

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.

 

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

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.

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.

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?

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.

 

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: 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 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.

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.

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.