Say Alice decided to orbit dangerously close to a couple of black holes circling each other. She is in a heavily enclosed astronaut suit, as is Bob, who is floating much further away.

  1. Assuming Alice cannot hear anything from any other source, would she be able to hear the black holes due to the gravitational waves travelling through the air in her suit? We'll assume Alice is a tough girl so she isn't getting ripped to shreds.

  2. If the answer to the first question is yes, and assuming that the waves are still strong enough for Bob to hear them, would the sound he hears differ in frequency?

  3. If the answer to the first question is yes, would changing the polarization of the gravitational wave affect the sound?

My formal physics knowledge is limited to high school, although I have some outside experience through sites like these and Youtube. I'd appreciate if answers could be kept to an undergraduate level or lower.

Thanks for the help!

  • 3
    $\begingroup$ "Yes", "yes", "yes". Quotation marks are for Alice being tough enough to live trough that ordeal, but Alice could be a satellite, so it's OK. Now what? $\endgroup$
    – CuriousOne
    Commented Mar 29, 2016 at 1:05
  • $\begingroup$ Wow, thanks for the quick response! I'm guessing for #2 Bob would hear a lower frequency sound, but how would the polarization affect the frequency in #3? $\endgroup$ Commented Mar 29, 2016 at 1:08
  • 1
    $\begingroup$ Just like with electrical antennas the coupling between the antenna and the polarized wave depends on the shape and direction of the antenna, so one can have different sensitivities in different directions. To me that's "affecting the sound", but that's close to an opinion piece, of course. $\endgroup$
    – CuriousOne
    Commented Mar 29, 2016 at 1:12

1 Answer 1


1-yes. Air and suit would vibrate

2-yes , lower frequency sound, also lower amplitude

3-sound waves are not polarized , since they are longitudinal waves, but she could have sensors sensitive to different GW polarizations and the sensors could trigger different kinds of "bells", she could "hear" different sounds.

  • $\begingroup$ Could you elaborate on why the sound is lower frequency in the second case? Unless we are talking about cosmological distances (hundreds of millions of light years) where the expansion of the universe comes into play, the frequency shouldn't change. $\endgroup$
    – user10851
    Commented Mar 30, 2016 at 17:26
  • $\begingroup$ @ChrisWhite of course! but in principle the further the wave goes from the hole, the more gravitationally redshifted it will be. This is a gedanken experiment, so everybody is equipped with infinitely sensitive sensors....and hears. $\endgroup$
    – magma
    Commented Mar 30, 2016 at 17:36

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