When gravitation is modelled after real life, there is no such thing as a gravitational shadow. Does this mean that gravitons travel through matter without being scattered?
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You can find a calculation of the graviton scattering cross section in this paper. – Ghoster Feb 26 '23 at 20:34
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Although it is widely expected that quantum gravity will involve particles called gravitons, this is not certain. We do not have a complete quantum theory of gravity. The current best theory of gravity (general relativity) has no notion of gravitons at all.
Even in a hypothetical theory with gravitons, gravitational attraction would be modeled by exchange of virtual gravitons, not real ones, and these should not be confused with real particles.
Real gravitons, if they exist, would form gravitational waves. These interact only weakly with matter. Gravitational waves can scatter off matter in some extreme circumstances (e.g. see this paper) but in most circumstances I think they would pass through matter.
Urb
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Eric Smith
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P.S. please help me get this straight... what is the difference between a virtual and real graviton? How many gravitons does it take to make a gravitational wave? 1? – shawn_halayka May 26 '21 at 00:20
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The distinction between real and virtual particles is pretty complex, but you can start by looking at https://physics.stackexchange.com/questions/147096/are-virtual-particles-only-a-fictive-tool-in-equations. In quantum field theory the whole notion of "particle" is not at all like the intuitive picture of a little ball; in QFT a particle is an excitation of a field. – Eric Smith May 26 '21 at 01:34
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As for "how many gravitons does it take to make a gravitational wave", this is very much like asking "how many photons does it take to make a radio wave". There's not really a good answer, but you could start at: https://physics.stackexchange.com/questions/90646/what-is-the-relation-between-electromagnetic-wave-and-photon – Eric Smith May 26 '21 at 01:36