What is Gravitons: Definition and 173 Discussions

In theories of quantum gravity, the graviton is the hypothetical quantum of gravity, an elementary particle that mediates the force of gravity. There is no complete quantum field theory of gravitons due to an outstanding mathematical problem with renormalization in general relativity. In string theory, believed to be a consistent theory of quantum gravity, the graviton is a massless state of a fundamental string.
If it exists, the graviton is expected to be massless because the gravitational force is very long range and appears to propagate at the speed of light. The graviton must be a spin-2 boson because the source of gravitation is the stress–energy tensor, a second-order tensor (compared with electromagnetism's spin-1 photon, the source of which is the four-current, a first-order tensor). Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field would couple to the stress–energy tensor in the same way that gravitational interactions do. This result suggests that, if a massless spin-2 particle is discovered, it must be the graviton.

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  1. N

    Gravitons detected around black holes?

    Could Gravitons be causing this Black Hole turbulence? http://perimeterinstitute.ca/news/turbulent-black-holes In the article above they talk about how the Gravity around Black holes is bumpy or has Gravity turbulence. Does this discovery give any evidence to the undiscovered Graviton? Because...
  2. FysixFox

    A tad confused about gravitons

    I'm a bit of a non-classical physics newbie here, so let me check my (rudimentary) understanding of some things first. In quantum physics, there are the leptons, quarks, and bosons. All particles are excitations of a field. Bosons in particular are the fields that mediate different kinds of...
  3. J

    How many gravitons are there in the observable universe?

    It is thought that there are approximately 10^80 protons in the observable universe, but there are approximately 10^90 photons in the observable universe. If my googling is correct, there are also approximately 10^90 neutrinos in the observable universe, but their temperature is only 1.9 degrees...
  4. H

    How can gravitons be linked to general relativity?

    Hi, this might be a silly question, but it does confuse me when I read about general relativity. From what I know about quantum mechanics, a force always needs a force carrier. For example photons are force-carriers for electric or magnetic force; the so-called ‘gravitons’ are the force-carriers...
  5. P

    Negative gravitational energy - negative energy gravitons?

    We know that gravitational energy is negative (zero energy universe theory). If the mediator particles (bosons) of the gravitational interaction are gravitons, then the energy of the gravitons would be negative?
  6. T

    Gravitons: Existence & Effects on Gravity

    I read about the concept of the above, but is their any proof that a) they exist and/or b)they are the cause of gravity?
  7. J

    Do photons interact with gravitons?

    Does QED predict that the hypothetical graviton particle will interact with light? I mean it would have to interact in some way, right? We already have evidence that it does. (Eddington and such). I was just under the impression that the graviton needs some sort of mass to interact with.
  8. C

    Gravitons: Explaining Need & Function in Relation to GR

    If general relativity states that objects move along geodesics in spacetime, why is there a need for gravitons? What do they do? If they are passed back and forth between energetic objects to create the gravitational interaction, this seems to completely disregard GR, but if objects move along...
  9. K

    Spooky action at a distance - gravitons

    What is the explanation for gravity being weaker than expected?
  10. K

    Suppose gravitons do leak into Calabai Yau spaces

    Suppose gravitons do leak into Calabai Yau spaces thereby dragging 3 dimensional space in with them and suppose in the absence of gravitons Calabai Yau space just naturally leaks into 3 dimensional space. The dragging of 3 dimensional space into Calabau Yau spaces would decrease the distance...
  11. S

    How Do Gravitons Facilitate Interaction Between Mass Particles?

    I have some basic questions about gravitons. If you have two particles with mass, do they "exchange" gravitons, if so what is the frequency?
  12. R

    How do gravitons mediate the force of gravitation in universe ?

    How do gravitons mediate the force of gravitation in universe ?
  13. S

    Exploring Cosmic Strings: Dimensions & Gravitons

    I have reading about cosmic strings and have some questions about them, are they in any way related to other dimensions even though they are one dimensional? Also do they have anything to do with gravitons and the cause of gravity?
  14. E

    Higgs boson interactions and gravitons

    How is it possible that the Higgs boson interacts with itself? Now that it is almost certainly discovered, how can a particle that gives mass to other particles, give mass to itself? Does it make a 'loop' with other Higgs bosons? How can the Higgs boson interact with other particles in such...
  15. D

    Why is the linearized vierbein a 2nd rank tensor in flat spacetime?

    Why are gravitons tensorial spin 2 particles while Newtonian gravity is a scalar?
  16. W

    Gravitons: Do They Exist & Would Volume Increase Effects?

    If a graviton existed wouldn't volume increase the effect of the gravity? For instance light we know(I think this is pretty solid) is a particle. We can see evidence of this by say a solar sail. We increase the surface area that light can hit and the energy of light hitting the sail can be...
  17. Y

    Do quarks temporarily lose mass when giving off gravitons?

    Imagine a quark, which has x mass. The quark gives off a graviton, which has y energy. My question is, before the graviton "snaps" back, would the quark lose mass equivalent to y energy? That is, xnew = xold - y Where xold is the mass of the quark, xnew is the mass of the quark after...
  18. B

    What is the status of research on gravitons and Higgs bosons?

    What is the present state of research on gravitons and Higgs bosons? How much has the research advanced?
  19. M

    Why Do We Consider Gravitons if Gravity Is Space-Time Curvature?

    If gravity manifests itself as a warpage in space-time, "forcing" bodies to travel in curved paths in the vicinity of more "massive" objects, why is graviton exchange/mediation necessary?? If not necessary, then why is the existence of the graviton particle (which has yet to be discovered)...
  20. W

    Gravitons in Loop Quantum Gravity

    How do you understand about Gravitons in Loop Quantum Gravity? All I know about it is from what I heard that "LQG hopes that its predictions for experiments occurring far below the Planck scale will be almost identical to that of gravitons on flat spacetime". So do you consider it a pure...
  21. W

    Flat spacetime + gravitons = Curved spacetime?

    Hi, does flat spacetime + gravitons automatically lead to curved spacetime? In an old 2002 google thread sci.physics.research which is moderated...
  22. Crazymechanic

    Where do gravitons come from and can we create them?

    So I understand it this way.gravitons are not experimentally proved but they are proposed theoretically.So they are the gravitational force carriers just like photons are for electromagnetic field.right? but the main question is Where do gravitons come from? We all know that the more something...
  23. Orion1

    Gravitons and Cold Dark Matter

    What would be the distinguishing theoretical differences between gravitons with an infinitesimal rest mass (non-zero) and cold dark matter? Reference: Dark matter - Wikipedia Graviton - Wikipedia
  24. Z

    Stern-Gerlach experiment with Gravitons

    It has long been predicted that gravitons will be spin 2. If that is true, then if we have a sufficient magnetic field, what is to stop us from recreating the Stern-Gerlach experiment and using a magnetic field to diffract them? Now, we have made very strong magnetic fields and to my...
  25. C

    Are Gravitons Always in a Definite Spin State?

    As John Bell showed us a particle is not in a spin state until we measure it. So would a Graviton always be in a definite spin state because it would always be interacting with the gravitational field.
  26. R

    Must Gravitons Exist? Quantum Gravity Theories

    Are there any theories of quantum gravity that don't incorporate gravitons?
  27. Y

    Gravity: Exploring Gravitons & Interactions with Spacetime

    I have a question about gravity. Why do we think that gravity is caused by a specific particle. Why isn't gravity considered a phenomenon related to the way matter interacts with spacetime.
  28. Islam Hassan

    Gravitons vs Attraction Due to Curvature of Spacetime

    If one day gravitons are discovered, would their action be complementary to the gravitational attraction due to curved spacetime? Can gravity arise from both curved spacetime and exchange of gravitons? IH
  29. L

    Gravitons: Explained for New Learners

    I am new to all this "stuff", so please forgive me If GR describes gravity as a straightline movement through a curved space-time, why does there need to be a "carrier" at the quantum level? What would it be carried between? When people say at the quantum level GR stops working, is there a...
  30. Q

    Gravitons and the Field Theory Metric

    We know the background metric has the description; g_{\mu \nu}\sim\eta_{\mu \nu}+h_{\mu \nu} I would like to know what the physical meaning is of the difference then? h_{\mu \nu} - \eta_{\mu \nu} When I've read field theories describing gravitons, they are usually denoted as...
  31. D

    What are gravitons exactly and how will they help us prove string

    I recently watched the documentary, "The Elegant Universe," by Brian Greene. During the show, gravitons were mentioned. What are gravitons exactly and how will they help us prove string theory? Was he trying to explain that gravity is a lot stronger than we perceive it to be? Thank you in...
  32. J

    Do gravitons interact with photons?

    Does string theory predict that gravitons interact with photons? Can a particle traveling linearly at the speed of light curve space-time around it? I guess a photon could instantaneously have rest mass it if were energetic enough to convert to an electron-positron pair and back again...
  33. S

    If gravity is not a force, why does it need to be carried by Gravitons?

    According to General Relativity, gravity is not a force. It arises from the curvature of space-time due to presence of matter. Matter curves space-time in a way that the paths of things appear to be bent giving rise to th effects of gravitiation. But if gravity is not a force, why do we need...
  34. E

    Suppose gravitons and Higgs were quasiparticles like phonons

    It's well known that gravitons expressed in QFT is perturbatively non-renormalizable at high energies. Higgs bosons suffers from quadratic radiative corrections. Recently Verlinde proposed gravity is the result of entropy. This has led researches to speculate on the microscopic structure of...
  35. W

    Understanding the Nature of Gravity: Debunking the Need for Gravitons

    OK, So as Einstein showed us that the effect that we call gravity is actually caused by the warping of spacetime. I.e. The Sun, for example, does not "pull" on the Earth directly. The Sun warps spacetime, thus altering the route which the Earth takes as it travels through spacetime - the...
  36. S

    Does Spin of Particles Change in a Gravity Field?

    hi, I wonder whether if we suppose the graviton has a spin of 2, would that mean that the spin of particles that are modified by the gravity field would need to increase or decrease their spin by 2? because gavity still exists on Earth but i don't believe particles modify their spin by 2 in a...
  37. C

    Magnetic fields and gravitons ?

    This might sound crazy , but could a magnetic field exchange gravitons with something else , or can a magnetic field emit gravitons , And when a photon is emitted from the B field is the gravitational field from the B field transferred to the photon and then carried away by the photon .
  38. C

    Understanding LQG: How Gravitons Interact with Spacetime

    How does LQG work? I know there are gravitons in it but how do they interact with spacetime? Why is it a theory of quantum gravity but not everything? Thanks, Cosmolojosh
  39. I

    What is the connection between General Relativity and gravitons?

    Recently I've been doing some research in physics, and I've come across a problem: what exactly is the connection between General Relativity and gravitons? I know that General Relativity talks about the bending of spacetime and how that causes gravity, and that the graviton is supposedly the...
  40. U

    Gravitons & Inertia: Do They Cause Each Other?

    Among those who believe in gravitons, is it believed that gravitons cause inertia? This would seem logical to me since gravitational mass is, as far as we can tell, the same as inertial mass.
  41. FeDeX_LaTeX

    Force carrier particles i.e. gravitons, photons

    Hello; How do force carrier particles work? For example, if I drop an object, the force of gravity is carried by gravitons. Does this mean that there is a long stream of gravitons underneath/all around the object? Because the wave would need to be carried through the medium of gravitons. Is...
  42. N

    Exploring Quantum Gravity Theories and Gravitons

    Are quantum gravity theories trying to progress on the assumption that there are such things as gravitons?
  43. A

    Gravitons and General Relativity: A Recap of the Debate

    If gravitons are proven to exist, does that mean that Einstein was just lucky in coming up with the right formula for general relativity and that the theory of relativity would be proven wrong?
  44. M

    Gravitons moving out of our dimension

    Is my understanding correct. Gravity is a week force because gravitons escape out of our dimension into other dimensions. If so would gravitons not also be able to re-enter our dimesion. Therefore cancelling out this theory
  45. FeDeX_LaTeX

    Exploring the Hypothetical Graviton: Is It Truly Massless?

    I was just reading a Wikipedia article about a hypothetical particle known as the graviton. It stated that it was massless -- but how is this possible? I thought that every particle has to have a mass.
  46. N

    Why Even Talk About Gravitons Even Existing?

    From what I have read out there, of the four fundamental forces that have been detected in our universe, gravity seems to be the weakest at the atomic level and smaller. I figure this is most likely true because at the atomic level and smaller - the weak and strong forces (those causing beta...
  47. P

    Hi, i have a question about Gravitons

    hi, i have a question about "Gravitons" do gravitons exist? I'm wondering what is gravity made up of. as they say light is made up of photons, then what is gravity made up of? or is it only that fabric of space-time that takes place here?
  48. E

    Is quantum gravity viable without gravitons?

    The logic of spin-2 gravitons is that GR predicts gravitational waves, and in QM, all waves are also particles. Gravitational waves are seen as waves of spacetime whereas gravitons are mediated as particles on fixed spacetime. Spin-2 gravitons can reproduce GR using QFT in the weak field...
  49. C

    Can Gravitons Escape Black Holes?

    Maybe a simple or stupid question so bear with me (it is late and I just thought of this). Assuming the existence of gravitons and assuming they are mass-less and travel the speed of light - how can they escape a black hole? Please point me in the right direction.
  50. G

    Can gravitons bend space-time?

    Can gravitons bend space-time? How can it be shown experimentally? Ideas?
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