# Talk:Graviton

The experimental section needs revision. As an experimentalist in the field I will be happy to do this. Many new aspects for detecting the graviton have been proposed and many are extremely promising. Also, Id like to elaborate on the theory, which is extremely interesting and complex. This article as yet has no discussion of connections or requirements with the standard model, or extraspatial dimensionalities. Objections? Requests? Suggestions? Lagrangian

I find what looks like three different questions, so I'm giving three separate replies.

From a historical viewpoint it is quite intruiging, whether the graviton exists as elementary particle or not. 150 years ago physicists were searching for the calory. In the end the calory was not a particle but a property. [G.K.]

More like 250 years ago. They had no framework. The "calorie" was just an idea.
In contrast, gravitons have not been postulated to explain something presently incomprehensible, but are a seemingly inevitable consequence of two of our best theories of physics, GR and QM. Their biggest role in physics is to tell theorists whether or not their equations have a chance of talking about quantum gravity. These equations will normally be far more interesting than mere gravitons, and maybe someday one of them will be testable.--192.35.35.34 20:05, 16 Feb 2005 (UTC)

Why must gravitons be for attractive gravity? Gravity is, in fact, noticeably repulsive at extragalactic scales. (Think about universal expansion! and inflation.) How else could the universe counter an unsaturated force from a pseudosingularity? lysdexia 07:10, 16 Oct 2004 (UTC)

Who says that's "gravity"? Inflation results from GR mixed with GUT symmetry breaking.

Let's think about it. If you're going to have a process of coherence, you've got to start out some matter and a stasis of forces. Then you propose a condition of unbalance due to an intruding force gradient from an external source. In the case of gravitational attraction that would be a mass concentration. But it doesn't seem logical in a gravitationaly attractive system not to start out with the simplest possible system; which would be an initially diffuse system of matter, with potential energy but no kinetic energy, and let the accumulation and kinetic energy and cohesion process be sequential to that. WFPMWFPM (talk)WFPMWFPM (talk) 21:06, 28 September 2008 (UTC) 21:03, 28 September 2008 (UTC)But today with the "Big Bang" and present universal gravitational attraction or Space-Time curvature theories it would appear than the whole thing started from nothing and will disappear into nothing, contrary to Lucretious. WFPMWFPM (talk) 21:16, 28 September 2008 (UTC)

As it is, the "attraction" in question, when talking about quantizing gravity, is what gravity does "matter to matter". In other words, the people studying quantum gravity are studying this situation, and here is where they expect to find gravitons. The fun with GR, of course, is that space-time bending and warping is an added bonus. Quantization and the graviton concept does not touch these issues, although many people would like to find a way to do so.--192.35.35.34 20:05, 16 Feb 2005 (UTC)

The following is not a question concerning the article itself, but asking if the graviton itself has a function, while the below train of thought is correct:

How could a grivaton be able to transport the information if there is gravity (or not) through a black holes rim (schwarzschild radius) in order to make the singularity have gravitation, while it has to speed up the information faster than light to do this.

-nerdi (de.wp.org) 9.12.2004 Thank you in advance

Are we not in consensus that gravitons, should they exist, would be massless, and therefore not subject to gravity themselves? even photons have some mass, hence their attraction to singularities and "black holes", but gravitons not having a mass themselves would mean that they can travel freely out of a singularity. In addition, if they had no mass, then wouldn't a graviton, according to E=MC^2, be to travel faster than the speed of light? if they are less massive than a photon then can't they can travel faster with the same "energy"?

Butler-10/4/06

I disagree, on the basis that first comes matter and then the interacting force related to the matter. And if gravitons are massless, how are you going to accumulate any matter? WFPMWFPM (talk) 21:37, 28 September 2008 (UTC)This is one of the prime differences of concepts between Mathematics and Physics. In Mathematics there is no problem with having an infinite subdivision of an entity, But in Science and Physics entities always reduce to some discrete value. WFPMWFPM (talk) 21:54, 28 September 2008 (UTC) WFPMWFPM (talk) 21:57, 28 September 2008 (UTC)

I am not sure but if they didn't have a mass wouldn't that mean the speed in E=MV^2 would go to infinity or in other words be instantaneous thought out the universe? Virtual circuit 05:23, 9 January 2007 (UTC)

The short answer is that the treatment of force by exchange of virtual particles is really a heuristic for certain complicated mathematical calculations, whose validity as a calculation is unknown in regards to gravity. In other words, "no comment".
So perhaps the real question is how can physicists even think to be looking for quantum gravity with a theory that has gravitons escaping from a black hole all time, whence nothing (or essentially nothing) is supposed to escape? The answer is that virtual particles do not have most of the properties of real particles. In particular, they are not bound by the speed of light. So the Schwarzschild radius, defined as where the escape velocity is c, only restricts real particles.
In fact, an elementary argument says QFT + SR requires antimatter to exist, as follows: if two particles exchange a virtual particle that happens to be going faster than light, there must be a frame of reference that thinks the particle exchange happened in the reverse order. The virtual particle in this second frame has all the properties of the antiparticle to the virtual particle in the original frame.
Again, this is just a heuristic reading of certain mathematical calculations. There is no "information" involved, and SR is not violated. Note that this goes back to the birth of QFT in the thirties. In other words, it's a non-issue for black holes because it's a non-issue in general.--192.35.35.34 20:05, 16 Feb 2005 (UTC)

This entry needs more mathematical discussion. Showing how linearized gravity can be quantized would be nice.

Dark energy implies anti-gravity. Which makes sense why univerese expands like it does. Since it is 70% of Universe acording to wiki article and so little is known about them, it's futile to simply ignore a posible relationship. -- Cat chi? 15:42, 20 Mar 2005 (UTC)

No. Dark energy is a negative pressure. No antigravity. In fact, there can't be antigravity unless GR is seriously wrong. --Pjacobi 16:53, 2005 Mar 20 (UTC)
Antigravity in GR works just like antigravity in Newtonian gravity. It requires a negative stress-energy tensor. We see no negative mass particles around us. Negative mass particles would have behaviors at odds with physical reality. From a certain perspective negative pressure makes antigravity. It is a negative stress-energy contribution and is repulsive like a negative mass would be. The perspective depends on if you place the contribution on the right or left hand side of the equation. Your statement is valid though. (CHF 04:59, 28 October 2005 (UTC))
agree i once had a stone with a negative mass, but at one day when i opened the box to show it outdoors it went straight up in the sky, it was probapply the last stone of it's kind on earth.

Could this not raise questions about Antigravitons, though?

I believe not because gravity is not supposed to be a specific interaction. In fact there is no evidence for a gravitational force. -- Orionix 08:21, 11 Apr 2005 (UTC)

Ok, but if we think with scope about Newtonian physics, particularly Newton's third ("Whenever one body exerts force upon a second body, the second body exerts an equal and opposite force upon the first body.") the supposed force in this example is cultivated by 'gravity' and the opposing is the 'NRF'. Due to the nature of the topic (to theorize that such a particle as a graviton could exist), could you not also be led to believe that the cancellation of the two forces (gravity and NRF) are both diametric opposites? --- I apologize about the poor wording and how ill thought-through my theory is. Also for using a basic principle with outdated physics. Please feel free to correct, coment and criticise.

First of all, there are no antigravitons. Gravitons, like photons, must be their own anti-particle. This is true of any neutrally charged fundamental particle. However, it's not true of composite particles -- e.g., neutrons have an antiparticle, because they're not fundamental (they're made of quarks).
Second, I can't understand what Orionix means by "there is no evidence for a gravitational force." I just knocked a book off my desk and it fell to the floor -- is this not evidence of a gravitational force?
It depends on what you mean by gravitational force. If you mean some static attraction between the book and the Earth mediated by gravitons (left in physics as a Newtonian prejudice) then of course it doesn't exist. The gravitational force turned out to be an inertial force generated by the book itself. It is generated since in curved spacetime the internal energy of the book (it's gravitational energy) depends on distance x: ${\displaystyle F=-d(mc^{2})/dx=-2mcdc/dx=gm}$ since in curved spacetime ${\displaystyle dc/dx=-g/(2c)}$. Jim 20:37, 20 November 2006 (UTC)

Third, with regard to equal and opposite forces: Both forces are gravity. The Earth exerts a gravitational pull on the moon, pulling it towards the Earth. The moon likewise exerts the same force on the Earth, but in the opposite direction (towards the moon, not towards the Earth). -- Tim314 19:46, 10 July 2006 (UTC)
This is an example of this "Newtonian prejudice". The Moon acts only on the space(time) around it and the Earth feels only changes in the spacetime to which it reacts with movement along different path than it would take if there were no Moon. It simulates the existence of "gravitational attractive force" between the Earth and the Moon however not perfectly and that's why Einstein was able to figure out that this force is only apparent. There is no evidence for existence of such an attractive force and there is plenty that it doesn't exist. Even Newton didn't believe that it exists. As a real scientist he didn't mix supernatural ("spooky action at distance", as Einstein put it) with science. It turned out that Newton was right. So the "Newtonian prejudice" wasn't even that of Newton's himself. It's the prejudice of those who still believe in ghosts, which makes the majority of Earth population however not including neither Newton nor Enstein from whom we might learn what's real (Einstein's theory) and what's magic (Newton's theory, just math which works like magic but only approximately). Jim 08:32, 21 November 2006 (UTC)

Wouldn't gravitons be considered a boson or even a gauge boson? Or would this break the symmetry?

(1) Yes. (2) What symmetry? (CHF 13:24, 27 October 2005 (UTC))
A beautiful example of applied magic (a.k.a. applied math). To make the point visible even better I propose to split graviton into three more types of bosons:
to be sure which of those distinctive forces we really have in mind. Of course all of them spin 2 particles. Jim 09:01, 21 November 2006 (UTC)

## Fridge magnet comparison

Is the "an ordinary refrigerator magnet can generate enough force to lift a mass against the force of gravity generated by the entire planet" comparison valid? After all, the magnet isn't 6900km away. If the Earth's mass was concentrated in a 5cm sphere, I suspect its gravity would easily overwhelm a small magnet!

Furthermore, it doesn't show what is claimed - that gravity is the weakest force. A simple experiment will demonstrate this. The magnet also is not visibly affected by the weak or strong magnetic forces, yet taking the magnet slightly off the fridge causes it to fall to the earth. I could therefore hypothesize that the strength of the forces is magnetic, gravitational, everything else in order. The problem is that the experiment assumes the reader is familiar with other forces and their specific limitations. Any reader this knowledgable will already be aware that a 5g magnet can produce more than 5g-force. (Another counter argument is that galaxies are held together with gravity, not magnetism, so gravity is stronger)
A better experiment would be to try and measure gravity itself, perhaps by hanging lead weights and trying to measure the attraction to another weight. The difficulty in doing this compared to measuring the force produce by electrostatic repulsion is far more compelling. njh 01:06, 3 January 2006 (UTC)
I agree with the criticisms of the fridge magnet comparison. I've replaced it with an explanation of why gravity is dominant at large scales, despite being the weakest force (as far as individual particles are concerned). -- Tim314 20:07, 10 July 2006 (UTC)

## The strength

more should be discussed about why the graviton is not as strong as the other three forces should be addressed. Maybe Lisa Randall's proposal and others should be presented there.

It's already in there: "An interesting feature of gravitons in string theory is that, as closed strings without endpoints, they would not be bound to branes and could move freely between them; this "leakage" of gravitons from our brane into higher-dimensional space could explain why gravity is such a weak force" -- Xerxes 16:33, 14 December 2005 (UTC)

## Inter-brane communication

Does gravity leaking into other branes make it possible to communicate with other universes? Is a gravi-SETI in the works? -- id

-First the scientific community will require some evidence-based verification that branes - and other universes (for that matter) - actually exist. -Then we would need to devise some way of working out how to tell if communication had been succesful -then we would have to work out how intelligence could behave in this mysterious other universe -then we would have to look back on all these events, and decide wether or not all those billions of UN tax dollars/euros/whatevers had been worth it, and we would probably be forced to conclude that no, they had not been worth half as much as spending the same amount on real, tangible, human beings.

Not only that, but you Just Got Served by a teenager who hasn't even left high school yet. I recommend that you read newscientist, or even BBC Focus, just to stop coming up with such poo!

--the guy who just served you. Sorry.

He only asked if it was possible or in the works, he didn't say it was or should be in the works. And doing all of those things you mentioned to find out how feasible it is would be considered in the works in my book. Scientific discussion should be a joint effort at finding the best answers, not a competition to have the best answer and go around beating people over the head with it. It's a cooperative effort not a zero sum game. — Preceding unsigned comment added by Padraic54 (talkcontribs) 22:42, 3 November 2011 (UTC)

## Historical background needed

Article needs dates with small history background. Specifically:

1. who coined the term?
2. who framed the concept?
3. important theoretical contributors?
4. dates?
5. major developments?

If you know any such factoids, then please contribute them with sources.--Sadi Carnot 15:22, 27 February 2006 (UTC)

The term it self, Graviton, comes from Quantum Physics or quanta, (quantum theory of gravity.)quantization of all known forces, particles, etc..--David Sanchez

Other 3 types of bosons of the same spin 2:
The terms were coined, framed, theortically contributed to by Jim a few years ago (exact date unknown). The only known major development is a request from wikipedia folks to place theoretical considerations on talk pages rather than correcting article pages, which I'm just doing. Jim 09:25, 21 November 2006 (UTC)

## Gravitons transmit curvature

Item: In general relativity, a quadrupole moment is needed to generate gravitational waves. For example, a rotatating star will not generate gravitational waves, but a spinning bar (or co-rotating stars) will. Now as a spinning bar or co-rotataing stars do their thing, they are twisting the shape of spacetime in the neighboring spacetime (and to an ever-lessing extent beyond themselves). So what gravitational waves and therefore the gravitons they must harbor are transmitting is not gravitation but instead changes in gravitation.

I am quite frustrated that I cannot find a reference that directly makes this point. Without a good reference, I am not comfortable with placing this insight into this article, even though Gunnar Nordström abandonned his gravitational theory in favor of general relativity due to the lack of any way to transmit curvature change information to other parts of spacetime. --EMS | Talk 16:58, 23 March 2006 (UTC)

That's not necessarily true. For example, Coulomb's Law can be derived from considering the exchange of photons, so photons are not just connected with electromagnetic waves. I'm still somewhat of a novice at QFT, so I can't give complete details. Apparently Newton's law can be derived in a similar way from the exchange of gravitons. That's actually what I was looking for when I came here...
Shambolic Entity 23:50, 8 October 2006 (UTC)
I read a book that discussed precisely this some time ago, but now I can't remember the name in order to track it down... Sorry! --Grey Knight

## is a graviton required?

I'm not a physicist altough i watch and read science with great intrest. I remember one science expiriment in which it was proven that: 2 ship in water side by side. / or 2 mirrors side by side overtime without putting an extra force on them attract eachother, and it had al to do with wave functions (water waves for the ships, or light waves between the mirrors). The effect was almost nihil. now imagine particles as waves, quantum mechanics as a universe of waves. Then have u huge collections of such waves for example a plannet, i wonder i the same effect would work and could be like gravitation.

i'm sorry to have forgotten that first science expiriment perhaps a physican can put some light on this.

You're thinking of the Casimir effect. It has nothing to do with gravity, being entirely due to quantum mechanics. Its fall-off with increasing distance is much steeper than gravity; it is not proportional to mass; it is a strong function of geometry; and it has various other features that are nothing like gravity. -- Xerxes 21:16, 13 April 2006 (UTC)

## Graviton: building blocks

Gravitons are repulsive to each other but are attractive to other particles. More to the point they what all other matter goes through. When the universe first came into being after time split off from gravity then started to spin into a closed loop taking away from its mass to become a complete particle with a spin two. Being a spin two particle it since did not need forces to attract itself to other gavitons and repulsed each other but attracting other particles with higher vibration (mass), but lower spin (continuity) there by they were(and still are) open and have more influence(forces) over each other. When gravitons started repulsing one another that made the universe expand carrying with them random masses of matter and energy, a process called inflation. One may observe when many gravitons group together around gallaxies by x-ray hallos that surround them. The gravitons are more dense near the gallaxy(which would mean they may do infact have a mass themselves and/or are attracted and attacted by lower spin matter/energy). They do no stop between gallaxies but fill the 'void' throughout the universe. Photons are spin one and may be 'channeled' through a simular particle to the graviton the graviscar. About 74% of matter of the universe does not interact with present day methods of detecting it but it keeps the universe expanding at a higher and higher rate. About 22% of energy is seemingly unedectable. Which leaves 4% of detectable matter and energy including photons, and neutrinos which have a small almost neglegable mass.Zombiebhp 05:22, 31 May 2006

This material is original research. Please do not add it to the article. -- Xerxes 14:46, 31 May 2006 (UTC)
No it's not; it's just incoherent babble. Shambolic Entity 06:54, 11 October 2006 (UTC)
No it's not; it's just a contemporary physics (which should be called rather applied magic, but for some reason it is called physics so let's stick to the official terminology). Jim 09:50, 21 November 2006 (UTC)

## Strength

Many people are surprised to learn that gravity is the weakest force. A simple experiment will demonstrate this, however: an ordinary refrigerator magnet can generate enough force to lift a mass, such as a paper clip, against the force of gravity generated by the entire planet Earth.
I think that's a hazy analogy... gravity, all by itself, can accelerate something the size and mass of a battleship to 20 mph in just one second. I don't think we have any technology that could do that. Maybe "weak" isn't the right term. -Rolypolyman 15:21, 6 June 2006 (UTC)

Gravity is indeed exceedingly weak. A technical description in terms of the gravitational coupling constant or quark-quark cross sections would probably not be more illuminating than the description given though. -- Xerxes 15:50, 6 June 2006 (UTC)
I do think Rolypolyman has a point, though. While gravity can be overcome rather easily, perhaps a better word is in order, or an expansion on the example. A battleship has more mass, so needs a larger magnet to overcome the Earth's pull. --69.237.113.185 21:46, 7 July 2006 (UTC)
See comments above under the heading "fridge magnet comparison". Gravity is extremely weak at the level of individual particles, but is often the dominant force acting on large scale objects. I've added a brief explanation of this to the article (in place of the more confusing comment on magnets). -- Tim314 22:22, 10 July 2006 (UTC)
I don't understand how you can say electromagnetism is stronger than gravity. The gravitational constant is 6.6742e-11 m^3 s^-2 kg^-1. the electrostatic constant is 8.988e^9 kg m^3 C^-2 s^-2. This would make the gravitational constant to electrostatic constant ratio 7.4257e-21 C^2 kg^-2. If that's more than one, gravity is stronger; if it's less then one, electromagnetism is stronger. How much is a coulomb squared divided by a kilogram squared? If you use Planck units, the two forces are equal. — Daniel 01:21, 24 September 2006 (UTC)
There is no gravitational attractive force in the universe so the issue as a physical problem is moot. However to compare gravitational "ineraction" with electrical repulsion people compare the interactions of two electrons: (fictitious) "gravitational Newtonian force" and Coulomb repulsion and so the first one is many orders of magnitude smaller. Jim 10:03, 21 November 2006 (UTC)

Gravity was compared to a magnet. They said that magnetism is so much stronger because it can pick up a nail and overcome gravity. But gravity from the earth is coming from so far away, it's coming from within the earth. Let's take the nail and put it one foot or one mile above the earth, then take the magnet and put it one foot or one mile above the nail. Now tell me which one would win out! Just moving the magnet a foot away will make it useless, but moving the nail miles above the earth will make little difference. AntiLiberal2 20:36, 7 January 2007 (UTC)

## Neutrality?

Does this article seem biased at all, to anyone? The first section is definitely a harsh representation of a theory which has been neither proven nor disproven.

69.237.113.185 21:42, 7 July 2006 (UTC) (Alex)

At the very least, the opening section is a bit misleading. It points out that General Relativity (the theory of gravity) is background independent, whereas the Standard Model (the theory of all other forces) isn't. However, it gives the impression that this means gravity can't be treated like the other forces. Really, it means that GR and the SM are incompatible -- there needs to be some underlying "quantum gravity" theory that reconciles the two. Some proposed quantum gravity theories are background independent, and some aren't. We won't know whether gravity is "like the other forces" until we know which quantum gravity theory is correct.
The point about GR and the SM being incompatible is made further down the article, but not in a way that makes it clear that this addresses the issue of background independence raised above. I'm working on adding a brief section elaborating on these issues. --Tim314 16:38, 12 July 2006 (UTC)
OK, I've added a section called "Is gravity like the other forces?" addressing the role of gravity in the background independence of GR, and the fact that an underlying theory of quantum gravity may or may not share this background independence.
I also changed "success of the Standard Model" to "great success of the Standard Model" in the opening section. A layperson may not know much about the Standard Model. If it's being presented as the main reason for believing in gravitons, I felt it was necessary to make clear why physicists could find this reason compelling. To quote its own article: "To date, almost all experimental tests of the three forces described by the Standard Model have agreed with its predictions." --Tim314 17:20, 12 July 2006 (UTC)

## Problems with the graviton

There are a couple of problems I see with this section. First, this sentence:

"Many believe the graviton does not exist, at least in the simplistic manner in which it is envisioned. Superficially speaking, quantum gravity using the gauge interaction of a spin-2 field (graviton) fails to work like the photon and other gauge bosons do"

This is just making the point that gravity is nonrenormalizable (made at least twice above). But the people who believe gravitons exist (e.g., string theorists) generally don't believe they exist in this simplistic manner. The quoted comment isn't a criticism of gravitons in current quantum gravity theories, it's a criticism of gravitons as they were first proposed.

Also, much of the rest of the section seems to be talking about gravitational waves, which are something a bit different than gravitons. Perhaps someone more knowledgeable of General Relativity than I am could clarify these remarks, if they're relevant. --Tim314 17:32, 12 July 2006 (UTC)

I see you haven't gotten a response, and the section seems odd to me as well, though I'm not a physicist. Plus, it's unreferenced. I'll delete it. --Allen 23:13, 25 July 2006 (UTC)
I agree with the deletion. The section seemed very out of place with the rest of the article, and I think I've figured out why. It looks like those lines were taken from a version of the article on gravitational radiation, in which gravitons were briefly mentioned in regard to the analogy between gravitational waves and electromagnetic waves. But the rest of this article doesn't discuss the relation between gravitaional waves and EM waves. It presents the motivation for the introduction of the graviton as coming from the analogy between gravitational force and the other forces. So saying (essentially) "gravitational waves aren't like EM waves", as if that's a criticism of the graviton, doesn't make sense in this context.
In other words, the section seemed to be criticizing a different reason for believing in gravitons than the one given in this actual article. -- Tim314 17:07, 31 July 2006 (UTC)

## Realatively speaking

To me, I don't understand why there is such a strong correlation between mass and gravity in relativity and not in the standard model. We've never seen a higgs boson or a graviton. To myself it makes much more sense to propose a bound state of a higgs boson and a graviton to make up for experimental problems. Please, someone with experiance in this feild tell me if I'm on a good track or if I'm out in Left feild. -MJH

The main difference between the higgs and the graviton is that the former might exist but the latter can't. The simple reason is that gravitational force is not a fundamental force between particles but purely inertial force related to one particle only, to its mass (as inertia is). So if "graviton" is pure fantasy it may have any properties one wants it to have (e.g. it might be a string) and it should be mentioned in the article on graviton. In my opinion. I would also introduce other spin 2 bosons of this type like inertion, centrifugon, and Coriolison that mediate other types of gravitational forces. Why to limit our fantasis to only one particle? Jim 10:30, 21 November 2006 (UTC)
I think that you are in left field. The Higgs boson as hypothesized is too heavy to be observed using today's colliders. The graviton is something else. As there is evidence for gravitational radiation existing, it follows under quantum mechanics that it must be composed of gravitons. Do note that gravitons are as capable of existing in a bound state as a photon is, and photons cannot be bound. --EMS | Talk 21:26, 21 November 2006 (UTC)
Why, knowing for sure that gravitation is not a fundamental force, do you compare gravitons to photons and not to phonons? Consequently, why don't you specify phonons (bosons as well) as carrying fundamental force? To be true to yourself you should agree also to inertion, centrifugon, and Coriolison as the same type of bosons as graviton since they carry exactly the same type of force. Jim 06:40, 22 November 2006 (UTC)
Gravitons, photons, and phonons are all massless, quantized carriers of information.
• Gravitons are spin-2 particles which carry information about changes in spacetime curvature (so they communicate changes in gravitation instead of gravitation itself), photons
• Photons are spin-1 particles which carry information about the electromagnetic field.
• Phonons are spin-0 particles which carry information about changes in stesses and pressures in materials.
Beyond that appropriate bosons do transmit the strong and weak nuclear forces. Also, I thank you for pointing out the practical joke in messenger particle. I will fix that. --EMS | Talk 16:21, 22 November 2006 (UTC)
Sorry if the joke caused any problems.
But knowing that gravitons carry information and not any fundamental force, shouldn't they be classified similarly as phonons rather than as carriers of a non existing fundamental force? It might have prevented a lot of confusion since many astrophysicists ignore general relativity just because they think that it will be abolished as soon as the graviton is discovered and "fundamental gravitational attraction" established again as a fundamental force of nature. Something that even Newton didn't believe in. So maybe it's healhtier to make the joke permanent to promote Einstein's discovery? What we are doing here is ignoring for nearly a century a theory that is confirmed by all experiments up to date and predicted discoveries made 90 years after its discovery and contrary to all expectations of experts (eg. "accelerating expansion of the universe" while expets predicted collapsing one, and "anomalous" acceleration of Pioneers while exerts still scratch their heads, and a few not yet published in scientific journals, like eg. local quasars). Jim 21:45, 22 November 2006 (UTC)
I cannot at all see the geometric interpretation of spacetime being overthrown. Perhaps general relativity will be replaced by something else (which hopefully will be my own theory), but I cannot see the foundation that Einstein laid down being disrupted.
As for your made-up graviton categories: That was a piece of vandalism IMO. You need to keep things as accurate and informative as possible here. Gravitons are the constituints of gravitational waves. As Moon goes around the Earth for instance, how it tugs on the other planets changes. Those changes are represented by a twisting in the fabric of spacetime, and those twisings propogate outwards as gravitational waves. The analogy to phonons is fairly accurate, since they transmit information on changess in pressure. So gravitons relate to gravitation, but they are transmitters of changes and not of the effect itself. The new result is that photons are a quantum of gravitation, or at least of changes in gravitation. --EMS | Talk 22:41, 22 November 2006 (UTC)
Photons are a quantum of gravitation?
IMO keeping gravitons as mediators of one of the fundamental forces is neither informative nor accurate. IMO it is awfully cofusing especially to astrophysicists, and so keeping graviton as mediator of one of fundamental forces is vandalism performed on science. But I guess we have to leave it this way.
What is your theory? Is it described somewhere on the net and if so, could you supply a link? Jim 06:57, 23 November 2006 (UTC)
Unfortunately I don't have my own theory to share. Einstein's is enough for me. I'm just in a process of convincing the experts that this theory predicts much more than they think and that they goofed assuming Riemannian metric and that energy can be created permanently from nothing. Jim 10:45, 23 November 2006 (UTC)

## Is gravity like other forces?

I'm concerned about the statement that the standard model is not "background independent." You can certainly formulate the SM in a straightforward way on any spacetime that you like, using standard techniques. I suspect that this statement just spilled over somehow from a critique of string theory -- which is not background independent (as presently understood) since the perturbative series is defined explicitly through fluctuations about Minkowski space. The paragraph then goes on to make a worrying comment that general relativity and the standard model are incompatible. As a classical theory (which is what GR is) there are no problems that aren't already present in flat spacetime. As a quantum theory, perhaps; but GR isn't quantum. Wesino 10:52, 28 November 2006 (UTC)

Why do you think that GR isn't a quantum theory? What do you think prevents the transmission of energy from one particle to another in quanta? Jim 09:30, 11 March 2007 (UTC)
General relativity, as originally proposed by Einstein, is completely classical. While many have tried to quantize it, and many believe or hope it can be quantized, no one has been successful. And if someone was successful, they would have obtained "quantized GR" or something similar.
Think of the distinction between electrodynamics, which is completely classical, and QED, which is a quantum theory.
However, the main point of my original comment is that the standard model is completely background independent. There's nothing stopping you from formulating it on any background that you like. Reference -- Birrell and Davies, Quantum Fields in Curved Space, Cambridge University Press. Thus one of the claims in the final section of the article is false. I was hoping the original author (or someone who agrees) could explain what they meant.
I do agree that gravity has significant differences from other forces, but background independence (or lacking it) isn't one. Wesino 09:19, 15 April 2007 (UTC)

## How gravitons mediate centrifugal force?

Since centrifugal force is the same kind of force as gravitational force (except for being repulsive in general) then could anybody explain how gravitons madiate this force? What is the mechanism of exchanging gravitons, and between what particles, while something is spinning? Jim 16:07, 13 December 2006 (UTC)

For over three months nobody could answer such a basic question? How a graviton is going to be recognized when found if no one seems to know its properties? Jim 09:13, 11 March 2007 (UTC)
Um. "Centrifugal force" is not a force, but only a pseudo-force. It appears only to an observer who is not in an inertial system. As a pseudo-force, it is not mediated by anything. --Stephan Schulz 09:28, 15 April 2007 (UTC)
Maybe it was already detected but not recognized; can it be that the detected form at around 2.587 GeV in the particle spectrum, at the Japanese H-quantum experiments (1970's), may be a (heavier) graviton form?
"Another key point which needs consideration is the question of how a quantum
theory of gravitation which implies a graviton form as a unit of gravitational action can
account for weak gravitation forces that still depend upon G but arise from mass or its
energy equivalent that is much smaller than the graviton mass. The answer to this is found
by recognizing that gravitons, being leptons, can exist in charge pairs and can exchange
energy as between themselves and another associated particle form. On a steady
gravitational basis the taon form dominates the action according to the charge continuum
volume displaced but on a transient basis minor fluctuations in volume of a heavier
graviton form cater for the balance.
How then do those gravitons feature in the spectrum of particle physics? Research
shows that they mainly comprise the taon - the mystery lepton particle that sits alongside
the muon and the electron in the bottom line of the standard quark picture of the particle
grid. As to that heavier graviton form it is somewhat elusive but has been detected at
around 2.587 GeV in the particle spectrum and is best referred to as the ‘Japanese H-
quantum’ [2]. It exists in anti-particle pairs alongside two anti-particle taon pairs, meaning
that there is one such heavy graviton for every two taon-gravitons."
by H. Aspden [1], 2005; see also [2] (section "Introducing the Graviton"), 2003 [my bold]
Some related references (provided in the author's writings)
Particle Data Group, Physics Letters, 170B, 1986 > specifies a ‘(2585) bump’ at 2586 +/- 45 MeV;
Nanjo and Takana, Suppl. Prog. Theor. Phys., 54, 120, 1973 > identifies a mass energy between 2.4 and 2.6 GeV;
H. Aspden, The Theory of Gravitation, 1966 > theorizes a g-graviton form having a mass of some 5063 electron units (equation 5.19, pp. 76-79), 2.587 GeV.
Well, WP:OR or not, at least someone tries to openly explain it. Cheers.
For some reason I noticed text claiming that I added an unsigned comment just above -- but I didn't! So I removed the text. It seems to have appeared during an edit by someone else, here's the diff output. I wonder why this happened? Wesino 13:18, 15 April 2007 (UTC)

### Relating the Graviton, the Supergraviton cluster and the fundamental particles

Yet linked to the above explanation, I found also the following brief passage that seems to present a very interesting and deep insight; although it was written 10 years ago, it perhaps may still bring some new light into the Graviton issue:

"In spite of the resources deployed by high energy particle physicists, they still do not understand why Nature creates mesons such as the mu-meson, otherwise known as the heavy electron or muon. Nor do they recognize that elusive ghost, the signature of the graviton, which occurs at 2.587 GeV. This compares with the electron rest-mass energy of 0.000511 GeV, the muon rest-mass energy of 0.106 GeV or the proton rest-mass energy of 0.938 GeV.
However, in 1964, the aether theory I had then worked on for ten years revealed the secrets of the mu-meson and, shortly thereafter, in 1965, the 2.587 GeV graviton emerged. It was then a simple matter to evaluate theoretically the precise value of G, the constant of gravitation, expressed in terms of the electron charge-mass ratio and based on energy perturbations of that graviton form.
At pp. 81-82 of the 1966 edition of my book 'The Theory of Gravitation' I show how three well-known mesons were all unstable spin-off products of a decay involving the 2.587 GeV graviton. I also show, from pure theory based on my interpretation of the structured form of the dynamic aether, how its 5063 ratio of mass to that of the electron emerged from the theoretical analysis. By 1969, when I published 'Physics without Einstein' I was able to point to the relevance of the discovery, as later reported by Krisch et al [Physical Review Letters, 16, 709 (1966)], of the 'largest elementary particle to be discovered'. They write: "We believe that this is firm evidence for the existence of a nucleon resonance with mass 3,245 +/- 10 MeV ... It seems remarkable that such a massive particle should be so stable." This nucleon resonance occurred when protons were fed into a high energy environment in which pi-mesons (pions) were being produced. I immediately saw this as a particle resonance in which that graviton ghost had combined with the proton to shed pions and leave the transient signature as the energy quantum discovered by Krisch et al. Here was proton decay brought about by that graviton ghost! Note that 2.587 GeV plus 0.938 GeV less 0.279 GeV, the rest-mass of two pions, leaves 3.246 GeV.
Those were the days when particle physicists were probing the scope for creating exotic particles in the energy region we associate with the mass regime of protons, deuterons, and tritons, but nowadays they have gone to the very high energy region where they seek to decipher Nature by discovering particle resonances at mass values akin to those of atoms seated at the middle of the periodic table. This is the region where the supergraviton develops in response to the need for a more effective dynamic balance in that quantum jitter condition of the aether.
My onward research into that territory led me to discover that, if the gravitational balance were to be a joint effort shared by a group of ghost particles, where the mass and charge displacement properties were pooled, then the ratio of these quantitities which preserved the G-value would demand a unique supergraviton form as well as a super-heavy electron form (identified as the tau-particle or taon). The supergraviton is the cluster of such a group, but a degenerate form involving the mutual annihilation of a particle pair from this cluster leaves a residual neutral particle resonance in the region of 91-92 GeV, evidently the so-called neutral Z-boson which preoccupies much of the attention of theoretical particle physicists at this time.
The scientific paper disclosing this theory was published in Speculations in Science and Technology, 12, 179-186 (1989). The paper is entitled: 'The Supergraviton and its Technological Connection'. The supergraviton cluster has a rest-mass of 95.18 GeV, corresponding to 102.18 atomic mass units."
by H. Aspden [3], 1997 [my bold]

Thank you for your attention. Regards. —The preceding unsigned comment was added by 213.58.99.45 (talk) 00:48, 31 March 2007 (UTC).

P.S.: Available data, 2006, from Particle Data Group (website):

Graviton, Z boson (errata), Leptons

P.S.2: Meanwhile, also i found a paper stating "Experimental observation of lepton pairs of invariant mass around 95 GeV/c2 at the CERN SPS collider":

Physics Letters B, Volume 126, Issue 5, p. 398-410, 1983

Any thoughts? Cheers.

## Detecting a Graviton

The statement: "Since gravity is very weak, there is little hope of detecting single gravitons experimentally in the foreseeable future" is a little misleading I think.

Gravitons could be detected in a particle accelerator. If string theory is correct, we could witness the effects a graviton has on nearby objects and then see those effects stop when the graviton travels into another dimension. The best chance for this happening would be at the new LHC at CERN. Here is an article describing how it could be done: [4] (PDF File)

Gravitons could be detected in the near future. —The preceding unsigned comment was added by DavidKelly999 (talkcontribs) 03:06, 27 January 2007 (UTC).

Their existence could be proven unnecessary in the near future, and that is what I would put my money on. Whoever is putting the ungodly amount of money into finding this imaginary particle has been greatly mislead. --Neptunerover (talk) 08:34, 14 December 2009 (UTC)

I take that back. After further consideration, I realize there must be a graviton. --Neptunerover (talk) 00:20, 24 December 2009 (UTC)

## Edits concerning massive graviton

User 84.158.XXX.XX added the following text to the first paragraph:

[Braneworlds, conformal fields and the gravitons], J. Phys. A: Math. Theor. 40 (2007) 6991–6997, publ. June 2007, handling a 5D space to show graviton perturbations and their mass eigenvalues and wavefunctions from a Sturm–Liouville problem demanding besides a massless graviton (localized on the positive tension branes) an infinite discrete set of increasingly massive gravitons. They get masses in steps according to a frequency, similar to massless photons getting a Planck mass (m = h ${\displaystyle \nu \ }$/c²). De Matos and Tajmar found within a superconductor experiment that they had to set the graviton mass to be 10-54 kilograms (Physica C, vol 432, p 167).

I removed this for the following reasons:

1. It's usually the case in theories that consider the possibility of extra dimensions of space, that particles have an infinite tower of heavier "friends". This is not something that is special for gravitons, but occurs with all the other particles as well. See, for example, here. Of course it doesn't make any sense to mention this possibility in articles of all elementary particles (graviton, photon, electron, quark, neutrino, etc.) These ideas belong to the article on Kaluza-Klein theory or another article on extra dimensions. Note also that in all cases there is an exactly massless graviton, and the extra particles are in addition to that.

2. The statement "They get masses in steps according to a frequency..." is wrong. The mass formula given in your reference is something completely different. 3. As for the article by De Matos and Tajmar, it deals with properties of a superconductor. The authors themselves present their explanation as just a hypothetical possibility, and it doesn't seem like that work is notable enough to be described in Wikipedia: very small number of citations (and note that most of the citations belong to the same authors themselves). In any case, if one insists to include this story, this shouldn't be done in the first paragraph of the article, and more details should be given, otherwise it's just misleading.

Yevgeny Kats 20:09, 1 July 2007 (UTC)

### REMINDER GRAVITONS+PHOTONS HAVE A NON-ZERO MASS

Only a zero rest mass and by Einstein predicted non-zero relativistic mass:

• ESA = Europen Space Agency are certainly no stupids if they have to calculate satelites' way in space and have learnt from Pioneer anomaly in
• [[5]]: "1. Introduction: It is well known that the mass of the photon and graviton in vacuum must be nonzero. The first limit is given by Heisenberg’s uncertainty principle1 and the second by the measurement of the cosmological constant in our universe2-4."
• Some singular American physicians problem seems to be to consider only the so called zero rest mass but not the by Einstein predicted non-zero relativistic mass of photons, gravitons etc.
• E.g.: In nearly all German texts (to gravitons related) photons are calculated with only it's relativistic mass,
• ### even in the section "Masse" in related article photons (GERMAN WIKI "PHOTONEN"):
  There is found even that there cannot exist any real photon with a zero-mass (and why).


wfc-k 84.158.208.115 22:52, 17 July 2007 (UTC) Graviton wave length = h/lorentz factor*m(rest mass= zero)*group velocity(since it has no rest mass its phase velocity = zero) = infinity, meters. A graviton is every where at once, and yet is focused or localised at a given point in time and space, its focus has to move about or else how would it pass on gravitational pressure =Intensity*velocity = GMm/r^4? Since electrons are scattered in proportion to the riciprocal of wave length to the forth power, is gravity due to graviton scattering? --79.68.253.176 11:41, 16 November 2007 (UTC)

This makes no sense. Gravitational radiation has a finite wavelength. —Keenan Pepper 01:21, 17 November 2007 (UTC)
The anonymous person who posted the question about gravitron scattering deserves a pleasant, non-judgmental response, in my opinion. Sincerely, GeorgeLouis (talk) 22:03, 18 November 2007 (UTC)
So... are you saying that it makes sense, or are you saying that it doesn't make sense, but you don't want me to say so, to avoid hurting someone's feelings? —Keenan Pepper 20:12, 19 November 2007 (UTC)

## Why spin 2?

Can somebody explain why should gravitons have spin 2, and not spin 1 like photons which mediate EM interaction, which is similar to gravitation? What is the difference between EM interaction and gravitation that would make their force carriers have different spin?

Article states that graviton must have a spin of 2 (because gravity is a second-rank tensor field). What does this mean, and which experimentally observed aspects of gravitation shows that gravity is a second-rank tensor field?

And wikilinking the "tensor field" doesn't help at all because tensor field article doesn't say anything about n-th rank tensor fields (there is currently no mention of word "rank" in the tensor field article), or about their force carriers.

Somebody shoud fix this and clarify why should gravitons have spin 2. Thanks. --83.131.17.173 13:42, 27 October 2007 (UTC)

The electromagnetic field is a vector field with the vector in question being the electromagnetic four-potential (which combines the electric potential and the magnetic vector potential). The gravitational field is a symmetric tensor field with the tensor in question being the metric tensor. "Tensor" unqualified tends to mean a rank-2 tensor, much like "space" unqualified tends to mean 3-dimensional space. One consequence of gravitation's being a tensor field is that there's no gravitational dipole radiation (only quadrupole and higher). This is important because the earth would long since have fallen into the sun otherwise. The fact that there's only one kind of gravitational charge, and that like charges attract rather than repelling, also follows from its being a tensor field (though I don't really understand why). Rank-N tensor fields are always associated with field bosons of spin N, but again I don't understand why. Of course, I shouldn't be saying any of this here; I should be adding it to the articles, but I'm not sure where to put it (and I'm not exactly an expert on the subject anyway). -- BenRG 16:26, 28 October 2007 (UTC)
This may not help answer your important questions, or add much to the above response, but tensor rank information can be found here. However, the 'Importance and Applications' section further down on that page gives some more insight about tensor rank and what it means. Very loosely speaking, the electromagnetic four-potential is a vector (or one-form) field (a rank 1 tensor thingy - only 1 index) whereas the gravitational potential is described by the metric tensor, a rank 2 tensor field (2 indices - basically a matrix). Hope this clarifies the situation somewhat.

## How can gravitons get out of black hole?

As black hole gravitationally affects outer objects, gravitons must be coming out of it. But how can they? Photons with zero mass (same as gravitons) can't get out of it. What is the difference between gravitons and photons in this case? --Acepectif (talk) 08:01, 23 April 2008 (UTC)

I don't know the answer to this question, but I do know something that might make you less confused (or more confused, I dunno). If a black hole is electrically charged, opposite charges will be attracted to it and like charges repelled. What particle carries this electric force? It must be the photon, but photons can't get out of the black hole... The reason has to do with this: Real photons aren't particles of the electric or magnetic fields. They are particles of quantized electromagnetic radiation, which involves electric and magnetic fields oscillating together. Static electric and magnetic forces aren't carried by real photons, but by "virtual" photons which aren't subject to the same laws of energy conservation and so on (they're allowed to be "off shell"). It's the same way with gravitons (or rather it would be if we actually had a quantum theory of gravity). A graviton is a particle of quantized gravitational radiation. Static gravitational fields are not carried by real gravitons, but virtual ones. I assume that if you had a source of gravitational radiation inside a black hole, the radiation couldn't be observed outside, but I don't really know because I'm way out of my depth here... —Keenan Pepper 21:03, 23 April 2008 (UTC)
Photons are not electrically charged. (And they are not particles; they are quanta.) And no, gravitons do not exist. If they do, what is their speed? No, you're not outside of your depth, your instincts are right. And there is no such thing as a "virtual" quantum; all quanta are perceived or not. If it act like a quantum, it's a quantum.--Mr. Shawn H. Corey (talk) 01:14, 5 June 2008 (UTC)
There's a good discussion of this issue at How does the gravity get out of the black hole? from the Usenet Physics FAQ. Basically the idea is that in quantum field theory, forces are mediated by "virtual" particles rather than physically observed ones--see the virtual particles FAQ--and virtual gravitons, if they exist, could escape black holes in just the same way that virtual photons are imagined to escape from charged black holes and be responsible for the electromagnetic force they exert on outside objects. Measurable non-virtual gravitons would only be associated with gravitational waves (gravitons basically just represent the idea that gravitational waves would have quantized energy levels), just as non-virtual photons are associated with electromagnetic waves (electromagnetic waves are only emitted when charged objects accelerate, so you can have a situation where a non-accelerating charged object is exerting an electromagnetic force on other objects yet is not emitting any electromagnetic waves). Hypnosifl (talk) 17:35, 15 June 2008 (UTC)
You know what? In all my years in physics (which really isn't that big a number), I've rarely seen a question of such quality asked. Kudos (y). I'd give you the good question barnstar if it existed. 17:41, 15 June 2008 (UTC)

## Why do most theoretics want to find a place for the graviton in their theories at all cost?

It is not necessary that it exists at all. As it is not necessary that the gravitation should work in similar way as the other fundamental forces. For example the General Relativity gives a completely different way of thinking about the gravity (that is an curvature of the space-time), and there it is not a "force" or "interraction" in the sence the other fundamental interactions are in the quantum mechanics. Why on earth is everyone trying to fit the gravitation in the template of the 3 QM forces? This seems to me a completely arbitrary idea. And it has the problem that is is not easely combined with the General Relativity way of thinking. And the General Relativity has proven itself through numberless empirical evidences and experiments that is well worthy and capable of describing it's part of the physics. Whereas all attempts to artificially device theories that describes the so wanted graviton consistently fail. I don't count the string theories as successful as of now because they have yet to prove that they are actually capable of anything besides predicting a spin-2 graviton.

I dont think a prejustice is any good for the science (the assumption that graviton should exist a priori)

It is remarkable how they are willing to accept the big prices that the string theories impose in terms of overwhelming complexity, introducing of such radical things as more spatial dimensions (which is extremely brutal IMO) and so on, and all of this just because these theories allows them to... have a spin-2 graviton. Whoa!

 —Preceding unsigned comment added by 213.240.234.31 (talk) 19:11, 22 July 2008 (UTC)

Gravitation isn't as different from the other forces as you think. All of the forces of the Standard Model are gauge forces, meaning that they all arise (or can be seen as arising) as a side effect of a distortion in the background. They're not really forces in the same way that gravitation is not really a force. The difference is that the Standard Model forces come from a distortion of internal degrees of freedom (with the symmetries U(1)×SU(2)×SU(3)) rather than spacetime dimensions. You can think of the internal degrees of freedom as little curled-up dimensions, an idea which goes back at least to Kaluza-Klein theory. From this gauge mechanism you get a force "field" which can undulate, and in quantum mechanics undulations are quantized. One quantum of undulation in a gauge field is called a gauge boson. So force-carrying bosons are not assumed but predicted by the Standard Model.
People have tried to construct theories in which gravitation is classical and everything else is quantum, but I don't think anyone has even managed to make a logically coherent theory of this type, much less one that's predictive. The current lack of interest in doing this reflects the fact that no one has any new ideas in that direction. Also it's considered implausible that gravitation alone is classical, because it is so similar to the other forces. Once you accept that gravitation is quantum and that there are undulations in the spacetime metric (i.e. gravitational waves) it's practically inevitable that the undulations will be quantized, and those quanta get the name "graviton".
How this relates to the graviton in string theory I have no clue. -- BenRG (talk) 13:04, 11 August 2008 (UTC)
------------
This sounds reasonable, but I still can not see a really compelling reason to think that gravity should be any similar tho the other fundamental forces. I don't see why the space-time perturbations should be quantized as the ones in the little internal degrees of freedom that cause the other forces. I don't say this can not be the case. I just wonder why everyone seems so sure this is the case. They take it as a postulate.
You said "Also it's considered implausible that gravitation alone is classical, because it is so similar to the other forces.". From the history we know our lesson that the way the things look (and our intuition) could be very deceptive. For example the first scientists to conceive the notion of electrons imagined them as some tiny charged balls, very similar to a macroscopic ball except for their very tiny size. And naturally they tried to apply the already known macro-world mechanical laws to describe the electron's behavior. But they had no idea how far they were from the truth :) I just want to illustrate that in very general terms when we consistently fail to build a good theory based on our intuition, maybe we should ask ourselves if there isn't something wrong with our intuition after all. The assumption that the gravitation should be quantized is purely derived from our intuition, there is no empirical evidence for this as of now (is there?) and so far this assumption seems to lead us nowhere (in therms of building a consistent theory). —Preceding unsigned comment added by 213.240.234.31 (talk) 16:18, 3 October 2008 (UTC)
I also have a problem understanding this. You say "Gravitation isn't as different from the other forces as you think" yet from my (admitedly popular-science based)reading, gravity in relativity isn't considered a force at all, merely the result of space-time curvature - which had been experimentally proven. So where is the need to force (pun unintentional) it into being a force, in order to explain a particle that hasn't been found anyway?88.105.55.43 (talk) 13:14, 22 January 2009 (UTC)TheDixieFlatline

## non-massless photon

There is also a possibility that photons are not completely massless. What is normally called the "speed of light" is actually the "speed of massless particles". [6]

Then again there is also the possibility of tachyons, wormholes, free utlrafilters, and airlines which don't lose luggage, but unless their existence would have some bearing on gravitons, I suggest we spare our dear readers these speculations; they can go to other articles to find them - in this case I think having an explanation at speed of light will be enough. --192.75.48.150 (talk) 15:32, 29 July 2008 (UTC)

## QUESTION : Could gravitons be tachyons?

At some point there are many similars charactheristics of both particules in which i find interesting.

1- They are both massless 2- They are both hypothetycal 3- They are both related to strings theory 4- Gravitational energy tends to be weak, so much its hard to be detected, but has unlimited range; tachyons tends to have infinite speed at low or zero energy. Being not a physicist i can hardly explain the correlation but thats somehow why i ask the question ;). —Preceding unsigned comment added by 96.20.61.73 (talk) 09:57, 11 August 2008 (UTC)

1. Gravitons are massless but tachyons aren't: they have "imaginary mass" or negative mass-squared. 2. That's a pretty weak connection; life on Mars is hypothetical too. 3. They show up in string theory but also in many other places. 4. Gravitational waves are known to propagate at the speed of light. -- BenRG (talk) 12:25, 11 August 2008 (UTC)

I've wondered about this too actually, there are other similarities as well. Also, how can we know gravitational waves propogate at the speed of light if we have yet to observe them? —Preceding unsigned comment added by 69.91.148.179 (talk) 18:27, 14 January 2011 (UTC)

If gravitons exist, they are massless, because gravity has infinite range. Massless particles travel at the speed of light. In addition, general relativity predicts that gravitational effects move at the speed of light (eg, if the Sun blew up suddenly, the Earth would continue orbiting it for another eight minutes, etc). — Preceding unsigned comment added by 92.27.55.215 (talk) 12:28, 2 May 2012 (UTC)

## "required to conform to Newton's law of gravitation"

I just choked on my cereal reading this in the introduction -- "In the classical limit, both approaches give identical results, which are required to conform to Newton's law of gravitation."

Newtons law of gravitation is testably false! That is the only reason general relativity was needed in the first place. Suggest deletion of the last sentence.KoreanApple (talk) 10:49, 25 May 2009 (UTC)

Newton's law of gravitation is testably false, but only in situations with large masses or high speeds, i.e. far from the classical limit. The phrase in the classical limit means that the following statement is not exactly true, but the limit of its error is zero as both the gravitational potential and all speeds involved go to zero. In this limit, general relativity reduces to Newton's law, and the sentence in question says that the simple graviton-mediated interaction also reduces to Newton's law, which is perfectly true. —Keenan Pepper 04:24, 26 May 2009 (UTC)
Oh, in which case my problem is probably just one of terminology. I thought the classical limit of a quantum theory just meant ${\displaystyle \hbar \to 0}$, I didn't think/realise it implied the non-relativistic limit as well, but I guess I could be wrong ^^.KoreanApple (talk) 05:20, 27 May 2009 (UTC)

${\displaystyle \hbar \to 0}$ ???????? The (reduced) Planck Constant is... well it's a CONSTANT, not a function, it cannot go to zero. The CLASSICAL LIMIT holds when quantum effects become irrelevant or at low fields and speeds.

Also: Newtonian Mechanics is NOT "FALSE": it's an approximarion at certian limits (yes it's different than just being 'false'). False would mean it would be completely wrong which is not. Actually some parts of newtonian mechanics to carry over to GR and QM.

In any case ANY theory must give the 'Classical Limit' in the end! If there is a discrapancy between the theory and the observations where 'classical mechanics' apply, that the theory is wrong. — Preceding unsigned comment added by 131.175.12.86 (talk) 13:40, 24 June 2013 (UTC)

From the article:

"If it exists, the graviton must be massless..."

"For example, if gravitational waves were observed to propagate slower than c (the speed of light in a vacuum), that would imply that the graviton has mass." 02:20, 11 September 2009 (UTC)

I don't know if I'm right, but the second statement can't be correct.Just check if I am-- if at all gravitons have mass, they'll be attracted by other gravitons, and so black holes can't send out any gravitons. And there'll be no gravity near black holes. But this isn't the case. I'm not sure if gravity will act on graviton itself, but that must happen if it has some mass.

As my previous contribution was deleted by an editor, I'll try again here. An alternate view of the graviton is that it is NOT massless, but rather has most of the mass of the universe. In that view, the graviton is a tachyon, moving faster than light at all times, and containing 40% of the mass of the photon, and most of the mass of the charged particles. If it has a large imaginary rest mass, it will exactly obey Planck's law: its wavelength would vary inversely with its energy, and it would have a constant frequency. This follows from the Lorentz equation: 1/gamma = √(1-(V/c)^2) which for tachyons becomes iV/c as the velocity is large. If the rest mass is around Planck's mass, it would have a frequency around 10^42 vibrations per second. It would orbit the universe in the same time it orbits within an electron. The leptons and quarks, having charge, would also have proto-photons in orbit, trapping the graviton within the overall structure. The graviton can escape black holes not because it lacks mass, but because it causes it. —Preceding unsigned comment added by DenverRedhead (talkcontribs) 07:24, 2 December 2009 (UTC)

If electrons could generate and absorbs Photons, what practical could generate and absorbs Gravitons? E:Y,?:G (talk) 20:03, 2 September 2010 (UTC)E:Y,?:G (talk) 20:29, 2 September 2010 (UTC)

## Gravihuh?

This Graviton stuff is such crap.--Neptunerover (talk) 00:04, 14 December 2009 (UTC)

How about if we put something in the article about how the search for the graviton is in fact the search for a point particle of zero dimension. Such a thing, whether it numbers one or two or infinity, cannot be found because it has no dimension because it is nothing. Nothing plus nothing gets nothing, which is exactly equal to infinity nothing, so there is nothing to find! --Neptunerover (talk) 09:29, 14 December 2009 (UTC)

Actually, that's it! "Graviton" is a good name for it, too (defined as the infinite point of zero dimension). There can be only one, no matter how many there are, because they are all it: The Graviton. That fits! And here I've been so vehemently against the very suggestion that a particle was needed to transmit the gravitational force, while at the same time theorizing on the Infinite Nothing Number(.0000000...1). It's so peculiar, that feeling of "Eureka!" at the same time as that of "well duh!" --Neptunerover (talk) 10:10, 14 December 2009 (UTC)

Forgot to take your pills today? --Michael C. Price talk 12:09, 14 December 2009 (UTC)
The foundations of science understandably wish not to be rocked. The box, which contains so many thoughts, resents thoughts who freely roam outside, without the narrow box to contain them. This is understandable since thoughts inside of a box try very hard to see the box they are contained in, although they cannot see it because they are inside of it, which causes thoughts inside the box to try all the more hard to see the box from the inside, but no matter how hard they try, this cannot be done from inside the box, causing them to resent any thoughts who can see the box for what it is due to their lack of containment within the box. --Neptunerover (talk) 19:44, 14 December 2009 (UTC)
Concerning pills: Oh yeah, I'm always forgetting, but what's that have to do with anything? --Neptunerover (talk) 19:44, 14 December 2009 (UTC)

## Seperation of variables.

A graviton is a term used to seperate the inter-atractive forces exerted on each other by substances from those same substances. A seperation of variables to be able to formulate an equation through point systems.

Example: Kinetic Energy, (KE), is defined as a function of mass and velocity, f(mv). That is, a point mass and a point velocity vector. Mass implies density. Velocity implies a space change. Mass and velocity are placed as seperate variables in the equation but have no real independant existance of their own without the other.

The real, real, real reality, nothing doesn´t move anything and velocity is a vector operator on a particle system.

A graviton is a vector operator on a mass, has no physical existance without that mass, and is a virtual particle that balances the energy and force equations due the interaction between masses.

fractalhints,(190.38.108.246 (talk) 15:37, 1 January 2010 (UTC))

## Do gravitons transmit centrifugal force?

Here's what I don't understand: according to general relativity, objects move in straight lines through curved spacetime. The acceleration from gravity is due solely due to geometry - due to the limitations of our Euclidean frame of reference. Now centrifugal force is also purely geometrical, and describes how objects are accelerated due to the limitations of a rotating frame of reference. So it seems like using gravitons to describe centrifugal force is no different from using them to describe gravity - i.e. absurd, as both are fictitious, geometric "forces" that are really just imposed accelerations in special frames of reference. Unless it is an underlying assumption of anyone speaking about gravitons that general relativity's spacetime curvature doesn't really exist?? Wnt (talk) 07:40, 7 January 2010 (UTC)

It's a little-known fact among non-theoretical physicists that not only the gravitational interaction, but also the electromagnetic interaction, can be expressed as the curvature of spacetime. That is, there are two different pictures here:
1. The usual introductory picture. Spacetime is a 4D Lorentzian manifold with a metric tensor and associated affine connection determined only by gravity. In the absence of non-gravitational fields, test particles move along geodesics, but if there is an electromagnetic field, then charged particles do not move along geodesics because there is a nonzero (and "real") electromagnetic force on them. Gravity is a "fictitious" force but electromagnetism is a "real" force.
2. Spacetime is a different kind of manifold (either 4D with a different kind of connection or 5D, I'm not sure of the details...), whose curvature is determined not only by gravity, but also by electromagnetism. All test particles move along geodesics, even charged particles in EM fields (we're ignoring nuclear forces here). Therefore both gravity and electromagnetism are "fictitious" forces in this picture. See [7] and [8] for examples of this picture.
The important point is that these two pictures are mathematically equivalent, and will give you the same answer to any physical question. The path of a test particle is the same whether you calculate it as a non-geodesic path in the first picture, or a geodesic path in the second picture. But regardless of any of this, the photon is a real particle. It is a quantum of electromagnetic radiation. The graviton (in a theory of quantum gravity) would be a quantum of gravitational radiation. —Keenan Pepper 14:48, 7 January 2010 (UTC)

## Gauge boson?

This article classifies the graviton as a gauge boson (infobox on the right). But the linked article for gauge boson says it is unclear whether the graviton is a gauge boson or not. So which is it? Shouldn't Wikipedia at least be consistent? 70.247.160.102 (talk) 01:40, 21 February 2010 (UTC)

## How does it escape a black hole?

Does it travel faster than light? Nothing traveling under the speed of light can escape a black hole and if it doesn't leave a black hole the hole will not attract other objects. —Preceding unsigned comment added by 154.20.199.45 (talk) 01:53, 9 April 2010 (UTC)

## Masslessness

In the introduction, I find this statement:

In physics, the graviton is a hypothetical elementary particle that mediates the force of gravity in the framework of quantum field theory. If it exists, the graviton must be massless (because the gravitational force has unlimited range) and must have a spin of 2.

However, later in the article, I find this statement:

For example, if gravitational waves were observed to propagate slower than c (the speed of light in a vacuum), that would imply that the graviton has mass.

So, a graviton *must* be massless, but if it's measured to propagate slower than light speed, it isn't massless? The article needs to reconcile these positions, or it will confuse non-experts (like me). 70.247.174.86 (talk) 15:35, 26 June 2010 (UTC)

This is a very good question, and I think the answer is subtle and complicated. For the photon, the situation is clear: as a spin-1 particle, the m → 0 limit of the massive theory is the same as the massless theory (the spin state corresponding to longitudinal polarization decouples), so if the photon had a mass of, say, 10−1000 eV, there would be no conceivable way to detect that. The best we can say from experiment is that the mass is less than some tiny value, and the only reasons to believe the mass is exactly zero are philosophical in nature (e.g. Occam's razor).
For the graviton (or any spin-2 field), however, the m → 0 limit of the massive theory is quite different from the massless theory. For example, the precession of the perihelion of Mercury for massive gravitons of very small mass would be exactly 2/3 of the value for massless gravitons.[9] This is known as the "van Dam-Veltman-Zakharov discontinuity" and it seems to me that it's a good experimental reason to believe that the graviton mass is exactly zero (or, since a theory of quantum gravity doesn't exist yet, that the gravitational potential in the classical limit is exactly 1/r and not a Yukawa potential).
So it seems like there's a good justification for making statements like "if gravitons exist, their mass should be exactly zero", but on the other hand people have come up with different ideas for theories (different kinds of mass term in the Lagrangian, or whatever) that have a massive spin-2 particle as a graviton, so it's all really up in the air, like most quantum gravity stuff. The thing we can say for sure is that if you try to come up a massive graviton theory, there are extra issues to be dealt with that don't exist for the case of a massive photon.
If Advanced LIGO detects gravitational radiation, people are definitely going to look at the time of flight between the two detectors and use that to make statements about the speed of gravitational radiation (and therefore graviton mass). —Keenan Pepper 07:41, 4 July 2010 (UTC)

could there be virtual Graviton and real Graviton? in addition if photons could be generated and absorbed by electron what particle (or particles) could generate Graviton?--e:Y,?:G 06:05, 4 September 2010 (UTC) —Preceding unsigned comment added by E:Y,?:G (talkcontribs)

Excuse my ignorance, but how does this gibe with this:
in 1971, the physicists Alfred Goldhaber and Michael Nieto at the Los Alamos Laboratory estimated the maximum mass of the hypothetical in 1971, the physicists Alfred Goldhaber and Michael Nieto at the Los Alamos Laboratory estimated the maximum mass of the hypothetical graviton particle - the carrier of the force of gravity. Their answer of 10-62 grams seemed incredibly insignificant. Over a decade later they published an improved version of his original paper. They noted that they had originally made an error in their 1971 paper, so that the calculated mass was actually over a billion times larger. In all that time, no one had ever caught the published error!- the carrier of the force of gravity. Their answer of 10-62 grams seemed incredibly insignificant. Over a decade later they published an improved version of his original paper. They noted that they had originally made an error in their 1971 paper, so that the calculated mass was actually over a billion times larger. In all that time, no one had ever caught the published error!
That's the maximum mass - it's a limit on how massive the graviton could possibly be and still be consistent with some set of data. Waleswatcher (talk) 03:26, 27 April 2012 (UTC)

## Edits by 98.237.137.191

A user with IP address 98.237.137.191 is trying to add material to the article that asserts that the existence of the graviton can be tested based on their propagation through different materials. The idea seems to be that gravitons will be affected differently by different materials, and therefore the strength of gravity (for instance of the sun) will be affected by intervening material.

(1) The source is an article "published" in a crackpot web-based "journal" with no peer review. It appears to have been written by the owner of the webpage, who (based on the IP's location) is potentially the user 98.237.137.191.

(2) According to wiki's policy of due weight, content in articles must be proportional to its weight in the relevant community. Not one professional researcher in gravity subscribes to thsi idea (see (3)), hence it should not be mentioned.

(3) The paper referred to is complete nonsense.

(a) It seems to be predicated on the idea that the force of gravity arises from a stream of gravitons that propagate from the gravitating object. This is false. Gravitational fields are coherent states of gravitons, they cannot be analyzed as if they were a propagating stream.
(b) It makes no attempt to estimate the size of the effect. In fact, it contains no equations at all. While there are non-linear effects in both classical and quantum gravity, their size in this context (different internal structure of a material) is ridiculously small, many, many orders of magnitude below detectability.

For these reasons, I'm deleting the material. Waleswatcher (talk) 12:51, 2 February 2012 (UTC)

I concur that the cited journal is certainly not a WP:RS and that the cited article is below any acceptable level for a refereed science journal. Materialscientist (talk) 13:02, 2 February 2012 (UTC)

This is 98.237.137.191, and yes I am the author of the paper. Please explain to me why gravitons can't be viewed as a stream. Also, how would you know how gravitons behave? They have never been detected and are purely theoretical! It seems only logical that gravitons, if they exist, would propagate through space just as other force carriers do.

Also, no size of the effect is needed when the principles make sense, which imho, are correct. — Preceding unsigned comment added by 98.237.137.191 (talk) 14:16, 2 February 2012 (UTC)

Also, just because a journal doesn't have peer-review and require you to have a PhD, doesn't make everything on it "crackpot." — Preceding unsigned comment added by 98.237.137.191 (talk) 14:24, 2 February 2012 (UTC)

Jake — Preceding unsigned comment added by 98.237.137.191 (talk) 14:13, 2 February 2012 (UTC)

I'm not going to discuss physics with you here - a wiki talk page is not an appropriate forum for that, nor do I expect it would be fruitful. What is important is that the material you added to this article violates at least two of wiki's guidelines, and therefore it cannot remain. Waleswatcher (talk) 15:00, 2 February 2012 (UTC)

You started the discussion of the physics involved: "Gravitational fields are coherent states of gravitons, they cannot be analyzed as if they were a propagating stream." I merely responded. — Preceding unsigned comment added by 98.237.137.191 (talk) 16:54, 2 February 2012 (UTC)

The silence speaks volumes.50.132.90.41 (talk) 22:17, 2 February 2012 (UTC)

## Dubious

Is there any formal proof of the UV non-renormalizability, at least for the "ordinary" graviton? I thought the jury was out on this, especially for some of the better studied supergravity models, with a SciAm feature going so far as to urge a serious reconsideration of the issue. Here are some recent refs related to this. [10][11][12] Teply (talk) 22:16, 6 August 2012 (UTC)

These links are all about supergravity rather than general relativity 128.243.253.116 (talk) —Preceding undated comment added 14:18, 9 November 2012 (UTC)

## GRAVITON disproved?

I have read about the graviton and find it difficult to relate to reality. I thought about the implications and found that a modification of previous experiments will disprove the graviton theory. The following are my thoughts:

The graviton theory suggests that the density of gravitons around a planet would be the same at the same distance from the planet. As gravitons are equal in their capacity to transfer energy, the volume of each sphere would be subjected to the same amount of energy. When that energy is expressed as force, the less massive sphere would be accelerated at a greater rate than the more massive sphere. This is because the more massive sphere would require a greater force to accelerate it at the same rate as the less massive sphere. Since the volumes of both spheres are equal, the amount of energy available to both spheres transmitted by gravitons must be equal at the same distance from the surface of the planet. Thus the less massive sphere should impact the surface of the planet sooner than the more massive sphere. Since the observations indicate that both spheres impact the planet's surface at the same time, the graviton theory is disproved.

I do not know if this fits the criteria for being posted in the main article, so I am submitting it here. It could be that I am missing something in the complexity of the graviton theory, but nothing I have seen so far has caused me to change my opinion. I still believe that Einstein's explanation is the most correct.

James thirteen (talk) 14:36, 19 January 2013 (UTC)

Sorry, but your argument is not valid. The graviton is the boson of a QFT, and the current knowledge is that the graviton prabably does exist, but there has not been found the way to renormalize the QFT of Gravity (or Supergravity). --ARoth (talk) 18:44, 25 May 2013 (UTC)

## New reference

http://pdg.lbl.gov/2013/tables/rpp2013-sum-gauge-higgs-bosons.pdf J. Beringer et al. (Particle Data Group), PR D86, 010001 (2012) and 2013 partial update for the 2014 edition (URL: http://pdg.lbl.gov) gives the graviton Mass m < 7 × 10−32 eV — Preceding unsigned comment added by 2001:4870:800E:101:511:C7B5:AE7A:9312 (talk) 19:02, 30 July 2013 (UTC)