3
$\begingroup$

As far as I know stars emit a finite number of photons in all directions in a given period of time and as an observer goes further away he experiences less and less photons to the point where the photon sphere is so spread out that sometimes he will not experience any photons making the star appear to be blinking.

So my question is: Does the same apply to gravity and is it also "blinking" at very long distances? And if so, then could theoretically an observer (by chance) experience a long enough period between such blinks as to drift away as if he wasn't being influenced by gravity of this object?

Improve this question
$\endgroup$
1
  • $\begingroup$ I think a better comparison (rather than a star) would be two oppositely charged objects attracting each other, which are exchanging virtual photons to mediate the attraction. If there are gravitons, static gravitational attraction would be mediated by virtual gravitons. $\endgroup$
    – DavePhD
    Commented Apr 1, 2014 at 13:30

2 Answers 2

Reset to default
2
$\begingroup$

The two situations are different. In the first case the star is radiating energy in the form of electromagnetic waves. Actually it isn't a good approximation to think of the star radiating photons because the energy it radiates is delocalised. If you insist on treating it as photons you would have to describe it as a superposition of all the possible photon positions. This point is dealt with in more detail in the question Photons from stars--how do they fill in such large angular distances?. However it is certainly true that the interaction with the light from the distant star is periodic. Your CCD or photomultiplier tube would record intermittent signals not a continuous signal.

Anyhow, a mass like Earth, a star, a black hole or whatever is not continuously emitting gravitational energy in the way a star is emitting light - it is not continuously emitting gravitons.

If you treat gravity as a field theory, then the interaction between masses can be described by the exchange of virtual gravitons. However you should not take this literally as an exchange of particles like throwing tennis balls at each other. A virtual particle is just a mathematical way to describe a disturbance in a quantum field, and the interaction is built up from the sum of many such disturbances. The best article I've seen on this subject is from Matt Strassler's blog.

So there is no intermittent arrival of virtual gravitons, and no freedom from gravity in the time between their arrivals.

Improve this answer
$\endgroup$
1
  • $\begingroup$ Thanks, especially this article about virtual particles was really helpful. Still I have one question and that is how far can those disturbances of quantum field extend from the original localized ripple (i suppose graviton in this case)? Do they somehow extend to infinity on some endless and continuous field of gravitons? $\endgroup$
    – Ardath
    Commented Apr 1, 2014 at 17:10
0
$\begingroup$

According to my limited understanding: gravity isn't part of the Standard Model and gravitons are purely hypothetical. If they exist then I'd say you're right. But if General Relativity is right then gravity doesn't come in quanta and you would always experience a small but non-zero attraction due to the curvature of spacetime.

Improve this answer
$\endgroup$
3
  • $\begingroup$ Gravitons could well be the particle that mediates the information of curvature. In other words, it might be the graviton that tells spacetime to bend, and can exist in the GR framework. $\endgroup$
    – PhotonBoom
    Commented Apr 1, 2014 at 13:04
  • $\begingroup$ Good point. Anyway, I guess the real answer is: nobody knows. :) $\endgroup$
    – Pepijn Schmitz
    Commented Apr 1, 2014 at 15:08
  • $\begingroup$ Well yeah we need a quantum theory of gravity for that :) $\endgroup$
    – PhotonBoom
    Commented Apr 1, 2014 at 15:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.