# Gravitons **URL:** \ **Category:** Factual Questions\ **Created:** [October 29, 2000, 10:59pm UTC](https://boards.straightdope.com/t/gravitons/38851 "2000-10-29T22:59:32Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![howardsims](https://avatars.discourse-cdn.com/v4/letter/h/e8c25b/32.png) [@howardsims](https://boards.straightdope.com/u/howardsims)\ **Post date:** [October 29, 2000, 10:59pm UTC](https://boards.straightdope.com/t/gravitons/38851/1 "2000-10-29T22:59:32Z")
As I understand it… An atom, when energized, emits a photon and returns to a lower energy state. This photon hits another atom and is absorbed byt it. This second atom then becomes energized and in turn emits a photon… cascading all along. Now then… Atoms are always emitting gravitons. And if a graviton strikes another atom, it applies a force to that second atom and then keeps right on going. Meanwhile the second atom is also emitting gravitons. So gravitons are never absorbed like photons. After billions of years of this… why aren’t we up to our eyeballs in gravitons? And how can it be that one fundamental particle requires an atom to give up energy when it produces it yet another does not? ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [October 29, 2000, 11:31pm UTC](https://boards.straightdope.com/t/gravitons/38851/2 "2000-10-29T23:31:33Z")
IIRC we have not found such a partical as a gravaton. We use the term as a basic unit of gravity but don’t know if they exist. It is hard to say how a partical we don’t know about interacts with particals we do know about. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [October 29, 2000, 11:55pm UTC](https://boards.straightdope.com/t/gravitons/38851/3 "2000-10-29T23:55:33Z")
The graviton is still hypothetical because no one knows yet how to completely reconcile general relativity with quantum physics. Quantum theory states that energy of any sort (which would have to include gravitational potential) must come in discrete quanta. In order for gravitons not to flatly contradict the observed nature of gravity, they would have to be bosons of zero rest mass with a spin value of 2. And that’s about as much as is known right now. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 30, 2000, 1:00am UTC](https://boards.straightdope.com/t/gravitons/38851/4 "2000-10-30T01:00:02Z")
[QOUTE]they would have to be bosons of zero rest mass with a spin value of 2.[/QOUTE] So, does that mean they’d get sucked into a black hole like neutrinos ? yuck ! ---
**Author:** ![Scylla](https://avatars.discourse-cdn.com/v4/letter/s/a5b964/32.png) [@Scylla](https://boards.straightdope.com/u/Scylla)\ **Post date:** [October 30, 2000, 1:08am UTC](https://boards.straightdope.com/t/gravitons/38851/5 "2000-10-30T01:08:52Z")
We don’t yet have a quantum theory of gravity. Gravitons are to quantum mechanics as Swiss army knife is to Maguyver. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 30, 2000, 4:35am UTC](https://boards.straightdope.com/t/gravitons/38851/6 "2000-10-30T04:35:08Z")
Here’s a link to a page about[LIGO](http://www.ligo.caltech.edu/LIGO_web/about/factsheet.html), a project to detect gravitational waves. If you read through it, you will find that one of its objectives is to confirm the predictions that gravitons have zero rest mass and spin 2. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [October 30, 2000, 4:46am UTC](https://boards.straightdope.com/t/gravitons/38851/7 "2000-10-30T04:46:13Z")
How come there’s never a supernova around when you need one ? ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [October 30, 2000, 3:32pm UTC](https://boards.straightdope.com/t/gravitons/38851/8 "2000-10-30T15:32:13Z")
> [@](#): > > \*Originally posted by howardsims \* > \*\*why aren’t we up to our eyeballs in gravitons? > \*\* We are. If they exist, they are the fundamental particle of spacetime. I think. Einstein basically showed that gravity is the same thing as spacetime (i.e., gravity is everything and everywhere). Quantum Mechanics hypothesizes that gravitons are the fundamental particle of gravity. But I may be incorrectly mixing theories here. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 30, 2000, 8:13pm UTC](https://boards.straightdope.com/t/gravitons/38851/9 "2000-10-30T20:13:32Z")
The key here is the distinction between real particles and virtual particles. The photon emitted by an electron when it looses energy is a real particle, which can be detected directly and counted and all the rest. On the other hand, there’s also a continual stream of photons travelling between the nucleus and the orbiting electrons, which cause the electromagnetic force in the first place. These are virtual photons, which means that we can’t directly detect them. They’re all over the place, but most folks don’t care about them in day-to-day life. It’s a similar situation with gravitons: The particles that actually mediate the gravitational force between myself and the Earth are virtual particles, and there’s plenty of those. However, because particles interact so much more weakly than by electromagnetism, it’s a lot harder to produce real gravitons (or at least, any significant number of them with any significant energy). ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [October 30, 2000, 10:08pm UTC](https://boards.straightdope.com/t/gravitons/38851/10 "2000-10-30T22:08:38Z")
> [@](#): > > \*Originally posted by dtilque \* > \*\*Here’s a link to a page about[LIGO](http://www.ligo.caltech.edu/LIGO_web/about/factsheet.html), a project to detect gravitational waves. If you read through it, you will find that one of its objectives is to confirm the predictions that gravitons have zero rest mass and spin 2. \*\* Here’s a photo & a quick blurb about a ground-based attempt to detect gravity waves. [http://antwrp.gsfc.nasa.gov/apod/ap001030.html](http://antwrp.gsfc.nasa.gov/apod/ap001030.html) ---
**Author:** ![Nukeman](https://avatars.discourse-cdn.com/v4/letter/n/ce7236/32.png) [@Nukeman](https://boards.straightdope.com/u/Nukeman)\ **Post date:** [October 30, 2000, 11:12pm UTC](https://boards.straightdope.com/t/gravitons/38851/11 "2000-10-30T23:12:06Z")
Phobos: “But I may be incorrectly mixing theories here.” Im not sure Phobos, but in general, relativitymdoesnt ‘like’ particles (as it doesnt agree with quantum physics) and quantum physics doesnt allow for gravity. Gravitons are just a theory to explain away gravity for quantum theory, like superstring theory etc. Physicists are trying to create a Grand Unified Theory in which relativity and quantum physics are combined. ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [October 30, 2000, 11:23pm UTC](https://boards.straightdope.com/t/gravitons/38851/12 "2000-10-30T23:23:53Z")
> [@](#): > > \*Originally posted by Nukeman \* > \*\*Phobos: “But I may be incorrectly mixing theories here.” > Im not sure Phobos, but in general, relativitymdoesnt ‘like’ particles (as it doesnt agree with quantum physics) and quantum physics doesnt allow for gravity. Gravitons are just a theory to explain away gravity for quantum theory, like superstring theory etc. > \*\* Yeah. I know you can’t apply one theory to the domain of the other, but in and of themselves, they don’t conflict each other (since they explain different aspects of the universe). The question I was speculating on was whether it was possible to equate each theory’s fundamental aspect (gravity & gravitons). Perhaps not…perhaps a new theory of quantum gravity is needed (not necessarily a G.U.T.). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 31, 2000, 12:56am UTC](https://boards.straightdope.com/t/gravitons/38851/13 "2000-10-31T00:56:04Z")
> [@](#): > > Yeah. I know you can’t apply one theory to the domain of the other, but in and of themselves, > they don’t conflict each other (since they explain different aspects of the universe). Well, we’ve never seen a situation where both are in full force, but such situations are possible, for instance in the very early Universe. It’s also important to note the distinction between the two theories of relativity: Special relativity, which deals with speeds near the speed of light (or even not so near), is fully consistent with Quantum Mechanics, and in fact, is an integral part of QM. General relativity, by contrast, which deals with the curvature of spacetime and gravity, is not consistent with QM.