Why Gravitons?

[losfomot]

So what exactly is gravity? If Transdecimal was taking the analogy too literally, then is it right to assume gravity is an all-permeating aether as Descartes suggested? For example, imagine a pond. That pond is the universe and the water molecules are gravitons. Is this correct? Someone please explain.

 

 

I am going to second this call for an explanation.

 

Transdecimal's original question, coupled with Rekkr's question above seem unanswered.

 

I am led to believe that gravity (according to relativity) is the warping of space, by mass, just as a bowling ball placed on a rubber sheet warps the sheet so that a marble rolling by will get caught in the dip and orbit the bowling ball. If this is truly what is causing the 'force' we call gravity, then there is no need for a force particle, in fact they should not exist at all. To go a step further, it would seem to me, the confirmed discovery of the graviton should completely disprove relativity.

 

It does not make sense that relativity could be right AND there are such things as gravitons.

 

Unless, like Rekkr suggests, space is made of an aether of gravitons.

 

So, to quote Rekkr "Someone please explain."

[5614]

I am led to believe that gravity (according to relativity) is the warping of space, by mass, just as a bowling ball placed on a rubber sheet warps the sheet so that a marble rolling by will get caught in the dip and orbit the bowling ball. If this is truly what is causing the 'force' we call gravity, then there is no need for a force particle, in fact they should not exist at all. To go a step further, it would seem to me, the confirmed discovery of the graviton should completely disprove relativity.

Why so?

 

Did the discovery of the photon mean that classical 'light = wave' theories were wrong? No.

 

The ball/sheet analogy is just a way to picture it... but imagine the ball pushing on the sheet, that is the force... but what is that force? What causes it to push? How does the force get from the ball to the sheet? (ok, there's physical contact, but how about the moon orbitting us?) It needs to travel - how can it do that? Gravitons.

 

Relativity talks about the effects of gravity, not how it travels. A map tells you how to get from A to B, it doesn't mention whether to use a car or lorry.

[losfomot]

Why so?

 

Did the discovery of the photon mean that classical 'light = wave' theories were wrong? No.

 

But gravity is not a 'wave' theory' date=' that's my point.

 

I'm not saying that gravity waves cannot exist, Im sure that a dense vibrating mass, or a tight binary system, or some massive event like a supernova could all make 'gravitational waves' But that does not make relativity a wave theory of gravity.

 

Water can come in some pretty huge waves too. Heck, you can make waves in a tub full of marbles... marble waves.... ha

 

I bet you the wave function of a marble is pretty damn small.

 

The ball/sheet analogy is just a way to picture it... but imagine the ball pushing on the sheet, that is the force... but what is that force? What causes it to push? How does the force get from the ball to the sheet? (ok, there's physical contact, but how about the moon orbitting us?) It needs to travel - how can it do that? Gravitons.

 

If the ball/sheet analogy is just a way of picturing it and the real reason the moon is orbiting us is gravitons, then there is no warping of space at all. To me, this is what your saying. Warped space does not exist, gravitons are what tethers the moon to us.

 

Do you see what I mean? It can be one or the other, but not both. We are not dealing with a wave/particle argument, we are dealing with a warping of space/particle argument.

 

I understand that the smaller things are, the stronger the wave function. And I find the fact that light, or even electrons and other small particles, exhibit characteristics of both a wave and a particle... I find that fact amazing. I find the double slit experiments fascinating, and if someone tried to tell me that is how things worked without showing me experimental evidence, I would not believe it. So maybe you are right... maybe.

 

It just seems not a satisfactory explanation to just point at wave/partical duality and say 'Oh, I guess you don't believe in that either?' (that's not meant to be a direct quote) Yes I believe in that, but only because there is experimental evidence to back it up.

 

Back to the ball and sheet analogy, you said there is physical contact, and that is what causes the sheet to contort, but move two inches away from the bowling ball and the sheet is still contorted. There is no physical contact at this point, and yet a marble will still change direction if rolled over this area. THAT is how the moon is orbiting us (I thought.)

 

The Earth has physical contact with Space (if such a thing is fathomable) Space is stretched, to a lesser and lesser degree the farther you get from the massive object, just like the ball and sheet.

 

 

Relativity talks about the effects of gravity, not how it travels. A map tells you how to get from A to B, it doesn't mention whether to use a car or lorry.

 

Relativity talks about more than just the effects of gravity, it talks about the mechanism (warped space).

 

Gravity does not need to travel. In the rest frame of the sun, for example:

 

The mass of the sun has warped the space around it and the planets move accordingly, the warp is permanent as long as the mass of the sun remains the same.

 

Anyways, you are probably right, and I am probably wrong, I just wish I could understand how both ideas could be right, when they seem like two completely seperate mechanisms of gravity.

[5614]

Remember that gravitons have not been proved. You're asking me how it could be possible for gravitons to exist taking relativity into account, I'm not saying I'm right, I'm not saying gravitons exist, I'm saying they could and trying to explain why.

 

In the rest frame of the sun space is warped around it. But why? What causes that? If gravity is not a wave and there is no carrier particle, then what causes the space to be warped? Just because of the mass? But how can just a mass effect space in that way if there is no interaction? If there is an interaction, what form is that interaction in?

 

Surely if mass made a particle which made gravity it'd be logical, it's a way for an object to interact, its a reason that gravity is strong with more mass.

 

If gravity is just a word referring to an ether, something which is everywhere, why would it be stronger in some areas? Gravity relys on a mass. In a massless universe there is no gravity. So how does mass cause gravity? It must 'make' it somehow.

 

At first you see light all around you and you just think it's there, then you learn about light waves, then about photons.

 

At first you see yourself being pulled towards the Earth, then you learn about gravity, then about...........

 

Me being pulled to the chair I'm sitting on is an action, but what really is causing that interaction between me and the chair?

You say gravity, I say what is gravity?

You say warped space, I say what makes that space warped, space being warped is an action, what causes the interaction? What actually makes gravity what it is?

 

Remember that gravitons have not been proved. You're asking me how it could[/i'] be possible for gravitons to exist taking relativity into account, I'm not saying I'm right, I'm not saying gravitons exist, I'm saying they could and trying to explain why.

Do you see what I'm trying to get at?

[Daecon]

If gravity is just a word referring to an ether, something which is everywhere, why would it be stronger in some areas? Gravity relys on a mass. In a massless universe there is no gravity. So how does mass cause gravity? It must 'make' it somehow.

 

Perhaps it's like mass having a 'pressure' that pulls against space/time... matter interacting directly with the dimensions that the mass is in.

 

Does that help any?

[5614]

Perhaps it's like mass having a 'pressure' that pulls against space/time... matter interacting directly[/i'] with the dimensions that the mass is in.

 

Mass does act with the dimension it is in, we can see the effect or the action through an apple falling, but HOW does the mass interact with the dimesion?

 

Do you see what I am getting at?

[Daecon]

I think so. There must be some way of explaining it better than "it just does".

 

(What other scientific questions have the answer "it just does"?)

[5614]

GRAVITONS

 

 

I can't think of any other questions like that, although there may be.

[BlackHole]

GR says that no physical experiment can distinguish between a gravitational field and uniform acceleration. They are equivalent. Therefore it's reasonable to assume that if all motion stopped, there would be no gravity.

 

So could it be that hypothetical inertons, not gravitons are the cause of gravity?

 

In fact there is no reason to suggest there is a discrete particle for gravitation, except maybe for mass. So there must be a field, not a particle. The CMBR could be that field.

[losfomot]

In fact there is no reason to suggest there is a discrete particle for gravitation, except maybe for mass.

 

Which is exactly what I'm saying.

 

Remember that gravitons have not been proved. You're asking me how it could[/i'] be possible for gravitons to exist taking relativity into account, I'm not saying I'm right, I'm not saying gravitons exist, I'm saying they could and trying to explain why.

 

I have to disagree with you there. I think you are saying they exist. Your entire argument for gravitons is just the opposite question: How could space be warped without gravitons? see:

 

In the rest frame of the sun space is warped around it. But why? What causes that? If gravity is not a wave and there is no carrier particle' date=' then what causes the space to be warped? Just because of the mass? But [u']how[/u] can just a mass effect space in that way if there is no interaction? If there is an interaction, what form is that interaction in?

 

Surely if mass made a particle which made gravity it'd be logical, it's a way for an object to interact, its a reason that gravity is strong with more mass.

 

Me being pulled to the chair I'm sitting on is an action' date=' but [u']what[/u] really is causing that interaction between me and the chair?

You say gravity, I say what is gravity?

You say warped space, I say what makes that space warped, space being warped is an action, what causes the interaction? What actually makes gravity what it is?

 

GRAVITONS

 

 

You can't put forward an argument that says gravitons MUST exist (which is what you're saying) and then say

 

Remember that gravitons have not been proved. You're asking me how it could[/i'] be possible for gravitons to exist taking relativity into account' date=' I'm not saying I'm right, I'm not saying gravitons exist, I'm saying they could and trying to explain why.[/quote']

 

If you were truly saying that they are not necessary, but they could exist, then your argument that they must exist falls apart.

 

You are trying to explain to me how they could exist by asking me to explain how space can be warped without them.

 

Do you see what I'm saying?

[losfomot]

In the rest frame of the sun space is warped around it. But why? What causes that? If gravity is not a wave and there is no carrier particle, then what causes the space to be warped? Just because of the mass? But how[/u'] can just a mass effect space in that way if there is no interaction? If there is an interaction, what form is that interaction in?

 

I think the main question is 'What is space?' (or spacetime)

 

For relativity to talk about space being stretched, warped, curved, whatever... it must by a physically connected whole, just like the sheet of rubber. A ball on a sheet of rubber stretches the rubber, not just at the point of contact, but beyond. There is no force particle necessary to jump back and forth between the ball and the rubber to tell the rubber how to form itself at every single point of it's warp because the rubber can tell itself. It's all connected.

 

So is space. It is a physical thing that we can feel (gravity) but not actually touch or see (yet). In a way, we can even see it (gravitational lensing). It must be a physical thing which is physically connected, or all talk of warped, curved, and expanding space is absolute nonsense (or, at least, a misnomer).

 

And a physically connected space with a geometry that can be warped, does not need a force particle to tell it how to warp. If you push on a section of space, all connecting sections of space will be pushed as well, only to a lesser and lesser degree as distance increases from the original push.

 

Now you are left with HOW a section of space might be pushed, or stretched, or warped, or curved.

 

Mass.

 

How/Why does mass warp space? Perhaps it displaces space. However, that seems unlikely since an atom is mostly comprised of space itself, so it would take an awful lot of mass to displace any significant amount of space that we might notice any 'gravitational effects'.... wait a minute... it

does take an awful lot of mass... that could explain why gravity is so weak. Average mass is so anti-dense (I can't think of the opposite of dense at the moment) that it takes an enormous amount of it to significantly displace (or warp) space.

 

Well, it's a possibility.

 

Anyway, the alternative view is that space is nothing. It's just a void that happens to have some stuff in it and happens to be getting bigger and bigger. In this case you do require a force particle to explain gravity, but to say that gravity is the result of warped space in this view would be wrong. You can't warp nothing. You can't stretch it either. I don't think nothing can curve.

 

So here we have a universe in which force particles (we'll call them gravitons) are responsible for the 'force' called gravity. Warped space has nothing to do with it.

 

And that is what I see... one or the other... both doesn't make sense.

 

Do you see what I mean?

[5614]

http://en.wikipedia.org/wiki/Graviton

Gravitons are postulated simply because quantum theory has been so successful in other fields. For instance' date=' the electromagnetic interaction can be very well explained by the application of quantization to photons, a science known as quantum electrodynamics. In this case photons are being continually created and destroyed by all charged particles, and the interactions between these photons produce the familiar effects of electricity and magnetism.

 

Given the widespread success of quantum theory in describing the vast majority of basic forces in the universe, it seemed only natural that the same methods would work well on gravity as well. Many attempts finally led to introduction of a so-far unseen graviton, which would work in a fashion somewhat similar to the photon. It was hoped that this would quickly lead to a quantum gravity theory, although the mathematics became convoluted and no internally consistent theory has yet emerged.[/quote']

 

You are trying to explain to me how they could exist by asking me to explain how space can be warped without them.

What I'm trying to do is make you realise the logic in their being a force carrier for gravity.

 

And I do see what you are trying to say, I know that I am arguing for the existence of a particle which has not yet been proved!

 

So here we have a universe in which force particles (we'll call them gravitons) are responsible for the 'force' called gravity. Warped space has nothing to do with it.

Unless gravity is a force. Graivtons are the force carrier. The force acts against space-time and the force curves space-time. Thus we have gravitons curving space time.

[losfomot]

Unless gravity is a force. Graivtons are the force carrier. The force acts against space-time and the force curves space-time. Thus we have gravitons curving space time.

 

And now, just like that, I can understand how gravitons and relativity might exist together.

 

So, it may not be the mass itself that tells space how to curve, but rather a by-product of mass, a particle that mass produces, called the graviton.

 

It's amazing how something worded just right can bring forth enlightenment, thank you.

 

Of course, gravitons must come with some heavy baggage, so to speak. For one thing they must be continually emitted in ridiculous, near infinite number. And they must have energy to curve spacetime... if mass emits them in amounts that can alter the geometry of space, that energy must be substantial. Where does it come from? Is the Earth constantly losing mass at a rate equal to the energy needed to curve spacetime the way it does?

 

And if the graviton is a particle, does the gravity, it itself produces, affect it? (I'm sure that I've seen this question in another thread, so I'm not asking for an answer, Im just giving examples of the numerous problems that must be associated with a force carrying particle for gravity).

 

I kinda like my idea of mass displacing space better.

 

[J.C.MacSwell]

And now' date=' just like that, I can understand how gravitons and relativity might exist together.

 

So, it may not be the mass itself that tells space how to curve, but rather a by-product of mass, a particle that mass produces, called the graviton.

 

It's amazing how something worded just right can bring forth enlightenment, thank you.

 

Of course, gravitons must come with some heavy baggage, so to speak. For one thing they must be continually emitted in ridiculous, near infinite number. And they must have energy to curve spacetime... if mass emits them in amounts that can alter the geometry of space, that energy must be substantial. [b']Where does it come from? Is the Earth constantly losing mass at a rate equal to the energy needed to curve spacetime the way it does?

[/b]

And if the graviton is a particle, does the gravity, it itself produces, affect it? (I'm sure that I've seen this question in another thread, so I'm not asking for an answer, Im just giving examples of the numerous problems that must be associated with a force carrying particle for gravity).

 

I kinda like my idea of mass displacing space better.

 

 

I think it could recirculate, so no energy or mass loss?

[Severian]

And they must have energy to curve spacetime... if mass emits them in amounts that can alter the geometry of space' date=' that energy must be substantial. Where does it come from? Is the Earth constantly losing mass at a rate equal to the energy needed to curve spacetime the way it does?

[/quote']

 

Gravity is a two way bussiness. The Earth attracts you, but you attract the Earth. Each graviton the Earth sends to you transfers momentum (and energy) to you, and each graviton you send back transfers momentum back to it. There is no overall energy or momentum loss.

 

And if the graviton is a particle, does the gravity, it itself produces, affect it?

 

Yes. Since the graviton has energy, it exerts gravity itself. This is not the same as quantum electrodynamics, where the photon is neutral and doesn't feel the electromagnetic force. (But the gluon of QCD is colored, and feels the strong force.)

[elas]

CPL.Luke

yeah read some of the stuff done by one Allen Guth specifically relating to his work on false vaccuums

 

Can you give a specific reference please? I happen to think that vacuum force is all that is needed to explain everything (see- http://elasticity2.tripod.com/ )

[losfomot]

Gravity is a two way bussiness. The Earth attracts you, but you attract the Earth. Each graviton the Earth sends to you transfers momentum (and energy) to you, and each graviton you send back transfers momentum back to it. There is no overall energy or momentum loss.

 

But now we've eliminated curved space again. If gravity is just a particle that is exchanged between masses, then there is no need to talk about mass warping space and relativity is nullified. See this was my problem right from the start. How can relativity be right about mass changing the geometry of space and still there is such a thing as a graviton.

 

The only way they can both be right is if gravitons are constantly altering the geometry of space, but your description of gravitons doesn't show that at all. You're saying that gravitons only interact with other massive bodies.

 

Since the graviton has energy, it exerts gravity itself. This is not the same as quantum electrodynamics, where the photon is neutral and doesn't feel the electromagnetic force. (But the gluon of QCD is colored, and feels the strong force.)

 

See, if each graviton has energy and that energy had to come from somewhere then:

 

A- The Earth is constantly losing mass/energy

 

B- The Earth only emits gravitons toward another massive body which, in turn, emits gravitons back to the Earth.

 

or C- The Earth does not emit gravitons, but rather has a constant field of gravitons around it that interacts with any mass entering the field. (I'm not sure if this option even allows for gravitons as particles)

 

The only one of these choices that could include relativity is A.

B and C are self sustaining, the concept of warped space doesn't exist with them.

 

Sorry, I'm not trying to be a pain, I'm just trying to understand.

[Severian]

But now we've eliminated curved space again. If gravity is just a particle that is exchanged between masses' date=' then there is no need to talk about mass warping space and relativity is nullified. See this was my problem right from the start. How can relativity be right about mass changing the geometry of space and still there is such a thing as a graviton.

 

The only way they can both be right is if gravitons are constantly altering the geometry of space, but your description of gravitons doesn't show that at all. You're saying that gravitons only interact with other massive bodies.

[/quote']

 

The gravitons are ripples in space time. The particle wave duality from ordinary QM is just as valid here and the particle like graviton can be thought of as a gravitational wave. So the gravitons are altering the geometry of space. It is the same thing.

 

And I didn't say that the gravitons only interact with massive bodies. They interact with anything which has a stress-energy tensor, so basically anything with energy.

 

See, if each graviton has energy and that energy had to come from somewhere then:

 

A- The Earth is constantly losing mass/energy

 

B- The Earth only emits gravitons toward another massive body which, in turn, emits gravitons back to the Earth.

 

or C- The Earth does not emit gravitons, but rather has a constant field of gravitons around it that interacts with any mass entering the field. (I'm not sure if this option even allows for gravitons as particles)

 

The only one of these choices that could include relativity is A.

B and C are self sustaining, the concept of warped space doesn't exist with them.

 

I think you may be getting confused between the distinction of GR and Quantum gravity. In GR, there is no graviton since it is a clasical field theory (just as in classical electromagnetism there is no photon - only light waves). One has to quantize the theory to get particles and quantum gravity then has a graviton (and lots of problems!).

 

For classical GR, choice C would be correct (if you remove the word graviton) so that the Earth has a constant gravitational field around it. This is analagous to the electric field round a point charge in classical electromagnetism.

 

In QG choice B is correct if you modify it to be any body with energy (not just mass). In fact this analagous to Quantum Electrodynamics where photons are exchanged between charged bodies. In the covariant formulation of QED you can't even define which way the photon travels, ie. did it leave charge A and travel to charge B or the other way round (since photons are their own anti-particle).

[losfomot]

I think you may be getting confused between the distinction of GR and Quantum gravity. In GR' date=' there is no graviton since it is a clasical field theory (just as in classical electromagnetism there is no photon - only light waves). One has to quantize the theory to get particles and quantum gravity then has a graviton (and lots of problems!).

 

For classical GR, choice C would be correct (if you remove the word graviton) so that the Earth has a constant gravitational field around it. This is analagous to the electric field round a point charge in classical electromagnetism.

 

In QG choice B is correct if you modify it to be any body with energy (not just mass). In fact this analagous to Quantum Electrodynamics where photons are exchanged between charged bodies. In the covariant formulation of QED you can't even define which way the photon travels, ie. did it leave charge A and travel to charge B or the other way round (since photons are their own anti-particle).[/quote']

 

So, basically, you're saying (correct me if I'm wrong, of course) that the two (GR and QG (ie. the graviton)) do not work together, but rather are two completely seperate theories that cannot be (or, at least, have yet to be) unified.

 

But you are also saying that they could both be correct...

 

It's like we're living in 2 seperate universes simultaneously, each with their own laws of physics... It doesn't make a lot of sense.

 

Do most physicists agree that there probably is a graviton, despite the problems that come with it, and despite the fact that it has not been found yet?

[5614]

No. He was saying that gravitons do not exist in GR just as photons do not exist in classical physics.

 

Just as classical physics is right about light waves, it's right about gravitational waves.

 

And QM adds with the quantisation of the wave into photons or gravitons

 

It's like QM just adds details with quantisation of the wave...

 

The graviton is a pretty popular idea among physicists.

[Severian]

Actually we know that GR is wrong. That is, it does not correctly describe gravity at very small distances since it is a classical theory, not a quantum one. However, it is still a very good description of gravity at macroscopic distances so we should not throw it away.

 

We also know that our current theories of QG are wrong since they are either incomplete or have bad properties (like infinities cropping up all over the place).

 

So we don't really understand gravity very well yet. However, it is pretty certain that the correct theory of gravity will contain a graviton which mediates the force (so your case B). But this final theory has to look like GR at large distance scales: so if we screw up our eyes it should look like case C. The fact that it can look like both at once is a consequnce of particle-wave duality.

[5614]

One of the disads of teaching myself most of the stuff I know is that I miss out little things that I don't always hear about... when does GR fail?

 

[i mean, a bunch of classical stuff fails on a quantum scale, but the specific example in this case is???]

[Severian]

Well, it fails on a theoretical level. By the time we get down to a size where quantum effects are noticable, gravity is so weak that we can't do any experiments on it (yet). But the classical viewpoint of GR is incompatible with the rest of physics - for example, in classical GR one can know the position and momentum of a particle at the same time, which is inconsistant with QM.

[geistkiesel]

But gravity isn't really a wave though, is it...?

Transdecimal,

Gravity is the least understood of the forces, or so the claim. Now gravity wave actrivity has been observed, thiough the theories abound.

 

An arguement can be constructed that all the forces are misunderstood as they in fact are, but the confession of ignorance only extends openly to gravity. I have been toying with the concept that gravity is nothng more (which is in fact A LOT) than the manifest operation of the conservation iof angular momentum of the solar system, with possible peripheral forces resulting from all curved stellar motion external to the solar system-- all motion of stellar objects, stars, galaxies, clusters, etc is in curved trajectories, though locally the trajectories are often, more than otherwise, indistinguishable from straight-line motion. This implies that 'gravity forces' [conservation of angular momentum, COAM forces] is strictly a local effect, measurably.

 

The distances between even the closest stellar body external to the solar system is some star approximately 7 light years away has not been seen to affect the solar system motion i.e. the motion of the planets are insulated from external gravity activity, or "universal conservation of angular momentum constraints", unless someone knows something I don't, re gravitational dynamics. There are indeed a plethora of gravity theorues and current continuous gravity experiments to consider.

 

Interestingly enough the sun contains more than 1000x the mass of all the planets and satellite mass of the solar system combined, yet the sun contributes a mere 1-2 percent of the total angular momentum of the solar system.

 

Gravity aside, the forces observed in the maintenance of the conservation of angular momentum, easily enough verified, has not been given serious consideration as far as my cursory review of the subject has led me to believe. Methinks thee is a significant ;nionlocdal; thread tot he story. By nonlocal, I do not mean "disgtanr mass effects' as I did above using the word "local effect". I mean nonlocal forces in the context of quantum descriptions of the small world.

 

Of course gyroscopic motion has been studied in depth, but even here, there seems to be an unsatisfactory model, in terms of completeness, as the literature has an inherent insecurity thread regarding the dynamics of the forces involved. A lot of "whys" are unanswered and are filled in with mathematical contrivances that sweep the unknown aspects of guroscopic activity, GA, into oblivion with the claim of that gyroscopic forces are known to a certainty, i.e. the claim of completeness of the model.

 

Geistkiesel

[Severian]

Now gravity wave actrivity has been observed' date=' thiough the theories abound.

[/quote']

 

No they haven't. This is what advanced experiments such as LIGO are trying to do.