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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?

Ardath
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  • 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. – DavePhD Apr 01 '14 at 13:30

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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.

Community
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John Rennie
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  • 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? – Ardath Apr 01 '14 at 17:10
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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.

Pepijn Schmitz
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