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I've heard that a fast moving object such as a jet plane traveling much faster than speed of sound can produce shockwaves which is also known as sonic boom, also Cherenkov radiation is produce by electromagnetic waves through a medium instead. How about gravitational wave which is predicted by Albert Einstein in his paper on General Relativity, this time what can serve as a medium?

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    $\begingroup$ This could only happen if there is a medium in which the speed of gravity waves is slower than the speed of light. I am not aware that our observations of gravity waves are sufficiently advanced that we have observed different velocities in different media... $\endgroup$ – Floris Jan 18 '16 at 5:53
  • $\begingroup$ @Floris is there any theoretical prediction of a medium where gravity waves would be slower? $\endgroup$ – Ruslan Jan 18 '16 at 6:31
  • $\begingroup$ @Ruslan - I'm not aware of any. That's not the same thing as "no". I am just not the right person to answer that authoritatively. $\endgroup$ – Floris Jan 18 '16 at 6:44
  • $\begingroup$ First, I should point out that Cerenkov emission occurs because a charged particle, not an EM field, moves faster than the local speed of light in a medium. Second, the gravitational wave itself would not produce this effect, it would be a massive particle (i.e., the analog of a charged particle in Cerenkov emission). Third, I am not sure what the answer might be since I have no idea whether the phase speed of gravitational waves depend upon anything... $\endgroup$ – honeste_vivere Jan 18 '16 at 18:10
  • $\begingroup$ @honeste_vivere: sorry for my mistake I didn't fully understand how Cherenkov radiation works, so do you meant the charged particle outrun it's electrical field(something to do with photon) in a medium? If that's the case I'll amend my question, thanks. $\endgroup$ – user6760 Jan 18 '16 at 23:11

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