Why is it that bending space makes you move towards the earth?

I can see why it intuitivly works, since bending something will make a ball go where it is bent. However that the ball goes there depends on gravity.

Gravity doesn't depend on gravity the same way, so how can gravity be accomplished by simply bending the space a object takes up?

Does space become "thinner" so that it is in a "lower state" and thus releasing those gravitons, is that the understanding of it?

Also, these gravitons (this doesn't depend on the former question) how come a object will move closer to a bigger one, just because it got the information that space had bent??? Explanation is needed!

We could as well compare it to electricity where a less massive body would have the need, and thus the more massive would feel a drag towards the less massive. Or is it that it is "space" that moves, so that where massive objects have taken up space, there are less space, and there are more space in less massive bodies, so that the lesser space will have the need to go to more space?

Oh, and black holes has MUCH more space, every space wants to go there :)

Is it wrong to believe that there is no such thing as a graviton?

Is it wrong to believe that there is no such thing as a graviton?I don't think so, it's not wrong to think that there is either, however, I just don't see the need for it. After all, the real state of affairs we don't know, 'it could be wrong for me to say it is right, it could be right to say that it is wrong' and vice versa.

That's also why it is in questions, I don't claim to know, I want to examine the inconsistances in a deal that is safe.

Why is it that bending space makes you move towards the earth?

I can see why it intuitivly works, since bending something will make a ball go where it is bent. However that the ball goes there depends on gravity.

Gravity doesn't depend on gravity the same way, so how can gravity be accomplished by simply bending the space a object takes up?

Does space become "thinner" so that it is in a "lower state" and thus releasing those gravitons, is that the understanding of it?

Also, these gravitons (this doesn't depend on the former question) how come a object will move closer to a bigger one, just because it got the information that space had bent??? Explanation is needed!

We could as well compare it to electricity where a less massive body would have the need, and thus the more massive would feel a drag towards the less massive. Or is it that it is "space" that moves, so that where massive objects have taken up space, there are less space, and there are more space in less massive bodies, so that the lesser space will have the need to go to more space?

Oh, and black holes has MUCH more space, every space wants to go there :)


Actually weird. Why would space be so different from mass,liquids and gases. Liquids and gases equalize out everywhere until it reaches a point of balance (temperature, pressure, and area). In liquids it will transfer heat from a high energy molecule to lower energy molecules. and gases will expand until it covers it's area. It's always more going into the lesser value until equalization happens.

So why is space the exact opposite? Why would less space go into more space? Wouldn't it be the other way around The more space you have the more likely it wants to equalize with the less space.

But wait doesn't it already do this? You pressurize a canister and the air want to get out. You put a deep vacuum on a canister and the air on the outside wants to get in.

Yes the black hole would have to have less space. The black hole would have to be connected to something that as a space that is of less value of ours.

Yes the black hole would have to have less space. The black hole would have to be connected to something that as a space that is of less value of ours.Actually since, the massive objects are taking up so much space (being dragged in by the space that wants to be there) there are less space.

Sorry if I confused you.

If we look at it this way, the space that an object occupies is less than a space that has no object occupying it. The space is nearly vanished by all the particles taking it's place.

The area is in a lower space-state :)

(Keep in mind that this is only an idea)

The space cannot collapse on itself because of all the particles that is there.

This is a constant tension of course, it's in a constant lower-state (like a vaccuum contained in a bulb).

The more mass, the more vaccuum (if we use that analogy) meaning that it is in a lower state.

Matter may be a "gap" in space? Why not, since it takes up space?

I think it is hard to think of "space" as "nothing"...

Actually weird. Why would space be so different from mass,liquids and gases. Liquids and gases equalize out everywhere until it reaches a point of balance (temperature, pressure, and area). In liquids it will transfer heat from a high energy molecule to lower energy molecules. and gases will expand until it covers it's area. It's always more going into the lesser value until equalization happens.

So why is space the exact opposite? Why would less space go into more space? Wouldn't it be the other way around The more space you have the more likely it wants to equalize with the less space.

But wait doesn't it already do this? You pressurize a canister and the air want to get out. You put a deep vacuum on a canister and the air on the outside wants to get in.Well, I don't know, this little thought experiment became more complicated than I had counted on. The main thing is that matter takes up space, and in space perspective (without the matter) this would equal less space, meaning it would be more space in space perspective, but there isn't much ground that there even is such a perspective, or that it would be like space to space, that is why it became complicated, too much unknowns.

Cyperium:

Why is it that bending space makes you move towards the earth?

I can see why it intuitivly works, since bending something will make a ball go where it is bent. However that the ball goes there depends on gravity.

Gravity doesn't depend on gravity the same way, so how can gravity be accomplished by simply bending the space a object takes up?

Most people think of the "ball on a trampoline" analogy to imagine how the bend of space works. As you say, the main problem with the analogy is that gravity is a required force "external" to the analogy, whereas the bending of space actually is gravity.

The thing that is often forgotten in these discussions is that the bending is not just a bending of space, but a bending of space-time. Since the curvature of spacetime is fundamentally a four dimensional phenomenon, it is quite hard to picture.

In a nutshell, the reason a rock falls to the ground when you drop it is because it naturally follows the closest thing to a "straight line" that exists in its local spacetime vicinity, and that happens to be a path that takes it to the ground.

Also, these gravitons (this doesn't depend on the former question) how come a object will move closer to a bigger one, just because it got the information that space had bent??? Explanation is needed!

In a sense, all the small object needs to "know" is the curvature of spacetime in its immediate vicinity. Then, in the absence of any forces, it will follow a "straight-line" path through spacetime. The role of the large object is to create the larger curvature of spacetime around itself, in which the small object sits.

The picture is slightly complicated by the fact that the small object also curves spacetime around itself...

Well, I don't know, this little thought experiment became more complicated than I had counted on. The main thing is that matter takes up space, and in space perspective (without the matter) this would equal less space, meaning it would be more space in space perspective, but there isn't much ground that there even is such a perspective, or that it would be like space to space, that is why it became complicated, too much unknowns.

No I get what your saying, The space is of lower value because it has a lower value.Deeper vacuum maybe? It could even have a colder temperature or even experience time differently in that sector of space.

Black holes are created by super nova's right. Super nova's are huge and has enough force to blow away all the mass in the surrounding space and have the space be Absolute Vacuum or very very close to it. The space in this area is void of just about everything. The space outside has greater energy value and the law of equalization comes into play and equalization begins.

Like sticking your finger in water. While your finger is in the water the water is pushed back but when you take your finger out the water rushes back to the space where you finger was.

Hello all

You could look at gravity as force exerted by a time gradient.

Motion is the second derivative of acceleration.

Tidal forces (the rate of change of gravity) which is the rate of change of time or a time gradient is the second derivative gravity

:)

No I get what your saying, The space is of lower value because it has a lower value.Deeper vacuum maybe? It could even have a colder temperature or even experience time differently in that sector of space.

Black holes are created by super nova's right. Super nova's are huge and has enough force to blow away all the mass in the surrounding space and have the space be Absolute Vacuum or very very close to it. The space in this area is void of just about everything. The space outside has greater energy value and the law of equalization comes into play and equalization begins.

Like sticking your finger in water. While your finger is in the water the water is pushed back but when you take your finger out the water rushes back to the space where you finger was.What if the laws of space just ignores the planet and see only the hole in space, then space would be constantly rushing in where there is less space (more nothing), since the hole is never filled...more space (less nothing) would consequently become less space (or more nothing), what would that mean to energy? Well, it would become "more nothing" which tells us that energy should be released in some way, when less nothing becomes more nothing.

Now, "nothing" itself doesn't exist, non-existance would be the lowest level ever, infinitly small, so we can imagine that even black holes doesn't come near the real "nothing", well perhaps if the gravity is infinite. But in the terms of our earth, the matter contained in it and the distribution of it are far from achieving a "real nothing" state of space even the atoms themselves have alot of space in and of itself, and there is space between the atoms and there is probably space between the parts of electrons etc. too.

So the fill of the hole is not that dramatic and consequently not the release of energy.

Cyperium:



Most people think of the "ball on a trampoline" analogy to imagine how the bend of space works. As you say, the main problem with the analogy is that gravity is a required force "external" to the analogy, whereas the bending of space actually is gravity.

The thing that is often forgotten in these discussions is that the bending is not just a bending of space, but a bending of space-time. Since the curvature of spacetime is fundamentally a four dimensional phenomenon, it is quite hard to picture.

In a nutshell, the reason a rock falls to the ground when you drop it is because it naturally follows the closest thing to a "straight line" that exists in its local spacetime vicinity, and that happens to be a path that takes it to the ground.Ok, I see, but what makes it move? Somehow kinetic energy must be added to it. Is that through the graviton? As soon as something is added with kinetic energy it will allways follow a straight line, there is no such thing as a non-straight line, I see that, so even if space is curved it will be like a straight line to it.

So, could it be that kinetic energy is because that the object that is allready on the move constantly is added with kinetic energy because the straight line is allways curved into a lower level for it (thus gaining kinetic energy)? Could there be a higher level in space, so that the movement would increasingly be slower (as kinetic energy would be substracted in order to move the object to a higher level)?

I can see now how relative to the object there must allways be a straight line, and that energy is added or substracted accordingly.

In a sense, all the small object needs to "know" is the curvature of spacetime in its immediate vicinity. Then, in the absence of any forces, it will follow a "straight-line" path through spacetime. The role of the large object is to create the larger curvature of spacetime around itself, in which the small object sits.Why would it need to know this, why would it be in the form of information, but not only the actual curvature? If gravitons are released how can we be sure that they spread the information instead of just being a consequence of the object following a straight line into a lower curvature?


Oh, and it's not that complicated that the object has a curvature itself, as it isn't affected by it (it is allways at the center of it's own curvature, and won't be affected by it, it's the zero point so to say).

What if the laws of space just ignores the planet and see only the hole in space, then space would be constantly rushing in where there is less space (more nothing), since the hole is never filled...more space (less nothing) would consequently become less space (or more nothing), what would that mean to energy? Well, it would become "more nothing" which tells us that energy should be released in some way, when less nothing becomes more nothing.

Now, "nothing" itself doesn't exist, non-existance would be the lowest level ever, infinitly small, so we can imagine that even black holes doesn't come near the real "nothing", well perhaps if the gravity is infinite. But in the terms of our earth, the matter contained in it and the distribution of it are far from achieving a "real nothing" state of space even the atoms themselves have alot of space in and of itself, and there is space between the atoms and there is probably space between the parts of electrons etc. too.

So the fill of the hole is not that dramatic and consequently not the release of energy.
Outer Space isn't nothing. It's in a vacuum but that doesnt mean it's nothing. In between spaces in outer space are particles. Very few particles but particles non-the less. And yes your right there is space between mass. So I imagine the space between the mass experiences time differently then the space outside the mass. Because mass and space has become one and the space outside of the mass cannot be the same as the space on the inside. There becomes a difference in space/time.

Take for example germs multiply into the billions in little time. It took us a couple thousand years. How many times does the earth go around the sun in a orbit in a lifetime. Average around 76 times or 76 years. Seems slow doesn't it? How many times does an electron orbit around the nucleus of an atom? I don't know the exact answer but compared to our sun and planets it's a big difference.

Cyperium:

Ok, I see, but what makes it move? Somehow kinetic energy must be added to it.

The first thing to remember is that no force is necessary for something to keep moving at constant speed in a straight line. A spacecraft in space will travel forever at constant speed with no energy required. That's Newton's first law of motion.

But you might object that things seem to accelerate under gravity, which requires a force and an input of energy. From a relativistic point of view, though, objects in free fall do not accelerate - a "free fall" reference frame is the relativistic equivalent of one of Newton's constant-velocity frames of reference. In fact, that's the entire content of Einstein's famous equivalence principle. So, viewed from any freefall frame of reference, falling objects do not accelerate, and so do not gain any kinetic energy.

The "problem" with this is that we, standing on the Earth's surface, are NOT in a freefall reference frame. Therefore, an object falling to Earth, from our usual point of view, does seem to accelerate and thus to gain kinetic energy. But it only does so because of our "choice" of reference frame, which is non-inertial (not freefall).

Is that through the graviton? As soon as something is added with kinetic energy it will allways follow a straight line, there is no such thing as a non-straight line, I see that, so even if space is curved it will be like a straight line to it.

Objects only follow "straight lines" in spacetime if they are in free fall. They can and do follow other paths if "forces" other than gravity act on them. A rocket firing its engines in space does never follows a straight line in spacetime.

Why would it need to know this, why would it be in the form of information, but not only the actual curvature? If gravitons are released how can we be sure that they spread the information instead of just being a consequence of the object following a straight line into a lower curvature?

The theory of gravitons and the theory of curved spacetime are not compatible at our current state of knowledge. Einstein's theory of relativity does not involve gravitons. Gravitons would be the "carrier" particles of a quantum theory of gravity - a theory that doesn't yet exist.

So, be careful of mixing up concepts. Relativity, as it stands, is not a quantum theory - it is fundamentally classical.

James R,
But you might object that things seem to accelerate under gravity, which requires a force and an input of energy. From a relativistic point of view, though, objects in free fall do not accelerate - a "free fall" reference frame is the relativistic equivalent of one of Newton's constant-velocity frames of reference. In fact, that's the entire content of Einstein's famous equivalence principle. So, viewed from any freefall frame of reference, falling objects do not accelerate, and so do not gain any kinetic energy.
There is a problem with your explaination, James R. You left out the stipulation that 'free fall' frames do not accelerate relative to other 'free fall' frames in the same gravitational potential. They do accelerate relative to all other frames of reference. In addition, even then freely falling frames can accelerate toward each other if there is a tidal force affecting their motions. And free fall frames are not constant velocity frames, except relative to other free fall frames in the same gravitational potential. Relative to all other reference frames, free fall frames are changing velocity frames. Correct?

Cyperium:



The first thing to remember is that no force is necessary for something to keep moving at constant speed in a straight line. A spacecraft in space will travel forever at constant speed with no energy required. That's Newton's first law of motion.Yes, I know that.

So in the objects perspective it doesn't move. The only disruption would be acceleration or deceleration, which deals with energy.


If there is a sudden stop, say like 10000 km/h to 0 km/h in a nanosecond, to make it extreme, there would be released an gigantic burst of energy, since all the kinetic energy would have to go somewhere, right? So even if no kinetic energy is released or otherwise changed in constant speed, you can argue that the energy is THERE nonetheless and must have GOT there. See?





But you might object that things seem to accelerate under gravity, which requires a force and an input of energy. From a relativistic point of view, though, objects in free fall do not accelerate - a "free fall" reference frame is the relativistic equivalent of one of Newton's constant-velocity frames of reference.I take it that it seems to accelerate because of the curvature in space? But why does it really hold so much energy when it crashes?


In fact, that's the entire content of Einstein's famous equivalence principle. So, viewed from any freefall frame of reference, falling objects do not accelerate, and so do not gain any kinetic energy.Ok, so you say that the object does not require energy for it's motion because it isn't actually changing movement. If you drop a camera at point zero, and another camera at a point 2 seconds later, then the second camera will indeed register the first to be accelerating, since it is at another point of view. There we have a freefall reference which does seem view a acceleration from another freefall, maybe you were too general there? Or perhaps I'm not THAT good at referenceframes..?


The "problem" with this is that we, standing on the Earth's surface, are NOT in a freefall reference frame. Therefore, an object falling to Earth, from our usual point of view, does seem to accelerate and thus to gain kinetic energy. But it only does so because of our "choice" of reference frame, which is non-inertial (not freefall).In the reference of the object, earth seems to accelerate into it, even though earth is standing still.

Still they come closer to eachother, and eventually crashes, not too different from a car crash, still alot of energy seemingly coming from nowhere...uhm other than the speed itself, which would imply that the object has indeed been loaded with kinetic energy somehow.

Objects only follow "straight lines" in spacetime if they are in free fall. They can and do follow other paths if "forces" other than gravity act on them. A rocket firing its engines in space does never follows a straight line in spacetime.Actually they can never actually follow anything other than a straight line, and doing so would only begin another straight line, which is why centrifugal effect works (cause it NEVER follows the circular motion, but ONLY wants to go straight, and only DOES go straight from it's own point of view, as it is the only direction of speed that it can have).



The theory of gravitons and the theory of curved spacetime are not compatible at our current state of knowledge. Einstein's theory of relativity does not involve gravitons. Gravitons would be the "carrier" particles of a quantum theory of gravity - a theory that doesn't yet exist.

So, be careful of mixing up concepts. Relativity, as it stands, is not a quantum theory - it is fundamentally classical.Still there is only one concept in discussion, which is gravity, and if those gravitons does come up and was because of space-time bending the path into a lower energy level for the particles, then we would be happy if we DID mix up the concept of quantum gravity and general relativity gravity.

Cyperium:



The first thing to remember is that no force is necessary for something to keep moving at constant speed in a straight line. A spacecraft in space will travel forever at constant speed with no energy required. That's Newton's first law of motion.

But you might object that things seem to accelerate under gravity, which requires a force and an input of energy. From a relativistic point of view, though, objects in free fall do not accelerate - a "free fall" reference frame is the relativistic equivalent of one of Newton's constant-velocity frames of reference. In fact, that's the entire content of Einstein's famous equivalence principle. So, viewed from any freefall frame of reference, falling objects do not accelerate, and so do not gain any kinetic energy.Again quoting this, because I came up with something new.

You say that something with speed in space travels at a straight line, ok, and it seems to accelerate because that line is bent, ok, but in actuality it does not accelerate, for the object itself it is still at the same speed, now this would mean that if you stopped the object so that it didn't have speed, it would rest in space as it has no original motion for it to seem accelerating.

So the image is either false or we could achieve levitation this way.

Hmm...we won't achieve levitation would we...perhaps we need to slow it down slowely at a rate reversed to the speed of the seemed acceleration. This would according to your image achieve levitation.

...or actually we would only arrive at it's original speed, and stop the imaginary acceleration.

But what is the speed of anything anyway?

If there is a sudden stop, say like 10000 km/h to 0 km/h in a nanosecond, to make it extreme, there would be released an gigantic burst of energy, since all the kinetic energy would have to go somewhere, right?
From a different point of view, the object has gone from 0km/h to 10000km/h in a nanosecond. In that frame of reference, a crapload of other energy has suddenly disappeared, to be turned into kinetic energy.
Interesting!

I've been led to believe that something called the Stress-energy-momentum pseudotensor (http://en.wikipedia.org/wiki/Stress-energy-momentum_pseudotensor) is useful for modelling how energy is conserved in GR, but I have no understanding of it.


I found this interesting and relevant page in the UseNet Physics FAQ (http://www.math.ucr.edu/home/baez/physics/index.html): Is Energy Conserved in General Relativity? (http://www.math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html)