Talk:Graviton

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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)[reply]

This is a dead comment for certain but I would like to clarify for future readers: the graviton is massless and therefore doesn’t experience any gravitational force. A theory of quantum gravity will be needed to explain how it escapes the screwed-up spacetime behind the event horizon, but the graviton has no issue escaping a gravitational field. OverzealousAutocorrect (talk) 18:42, 13 February 2024 (UTC)[reply]

This is not correct explanation. Photon too is massless but it experiences gravitation due to having energy and cannot therefore escape black hole. IlkkaP (talk) 06:50, 24 August 2024 (UTC)[reply]

In the context of Einsteinian gravity it doesn't actually even matter if it has any energy, because even straight lines are curved by gravity according to the geodesic equation, but in the Newtonian case where gravity is a force it still relates only the rest masses of particles (hence why relativistic particles or objects don't have much higher gravitational mass; observed gravitational mass should not depend on reference frame). Photons can't escape black holes because time stops at the event horizon; it is impossible to observe any object fully cross the event horizon in a finite period of coordinate time (although it can be done in finite proper time; see MTW Gravitation), let alone escape from it after entering.

Either way, the OP is asking about quantum gravity which is not well understood at this time anyway. OverzealousAutocorrect (talk) 13:26, 24 August 2024 (UTC)[reply]

Still wrong. Neither gravitons nor photons can escape black hole (and if they could, one could send information from inside black hole to outside). However, this doesn’t exclude black holes having gravitational and electric fields around them (i.e. black holes have mass and electric charge). IlkkaP (talk) 18:15, 24 August 2024 (UTC)[reply]

We actually agree; I said in the comment you replied to that photons can't escape. All objects experience gravitation because gravitation is not a force but curvature of spacetime, and explaining why/how the graviton field works will require actually coming up with an accurate theory of quantum gravity, which we don't have. We also don't know that black holes can have electric fields; we have metrics that describe such black holes at the relativistic level, but whether or not the electromagnetic field behaves the same way at the quantum level is unknown because we've never directly measured the properties of a black hole at the quantum level. OverzealousAutocorrect (talk) 18:57, 25 August 2024 (UTC)[reply]

@IlkkaP @J Mark Morris @OverzealousAutocorrect Please limit your discussion to corrections or improvements in the article. See Wikipedia:Talk page guidelines. Wikipedia is not a forum. Try Physics StackExchange or Quora. Johnjbarton (talk) 19:08, 25 August 2024 (UTC)[reply]

Disputed reference

The published primary ref:

Tobar, Germain; et al. (22 August 2024). "Detecting single gravitons with quantum sensing". Nat Commun. 15 (1): 7229. arXiv:2308.15440. doi:10.1038/s41467-024-51420-8. PMC 11341900. PMID 39174544.

has been disputed by an expert in an unpublished work:

Carney, Daniel. "Comments on graviton detection." arXiv preprint arXiv:2408.00094 (2024).

Johnjbarton (talk) 16:10, 19 September 2024 (UTC)[reply]

Thanks for the addition. Now I am thinking would even the Jupiter size detector (if it didn't collapse to a black hole) be able to detect single gravitons, as the source above states that Bell like inequalities need to be violated (or something similar) before you can prove quantization and not just classical fields producing "clicks". IlkkaP (talk) 16:58, 19 September 2024 (UTC)[reply]

Graviton upper mass bound

In the infobox, Particle Data Group source gives graviton mass upper bound as 6×10⁻³² eV/c². Planetary trajectories and gravitational wave detections based upper bounds are of the order of 1×10⁻²³ eV/c². This difference should somehow be explained. As I understand it, the tighter bound is much more model dependent. How to source and explain this in the article? IlkkaP (talk) 17:16, 19 September 2024 (UTC)[reply]

Negative mass analogy?

The rubber sheet image with the red negative mass shows space curving upwards instead of downwards. Is this a correct analogy? It is still stretching, not compressing space as I assume a negative mass would do, right?? Tayste (edits) 21:17, 24 September 2024 (UTC)[reply]

The unsourced image has nothing to do with the article. Johnjbarton (talk) 01:59, 25 September 2024 (UTC)[reply]