This is a question regarding sound waves and space.

I know that sound waves must travel through a medium "air", enter our brains, and then we can decipher what exactly the sound is.

But in space, there is no air, and so does that mean that no sound waves are being produced, or that there are waves, but we cannot hear them because they never reach us

And how can we tell? We cannot "hear" space, so who says its because theres no air, rather then just because "its not being produced in the first place?"

  • 1
    $\begingroup$ If there is no medium, there are no sound waves. In space there is a medium (the interstellar and intergalactic medium) which may mediate sound waves, but because it's so dilute, the waves have extremely long wavelengths (like, lightyears). The baryon acoustic oscillations is a great example. I started writing an answer, but you may bbe satisfied with this physics.SE answer. $\endgroup$
    – pela
    Sep 11 '17 at 7:43
  • 1
    $\begingroup$ Baryon acoustic oscillations is a signature of the acoustic oscillation in early universe, when the universe was so dense that there were acoustic waves (sound). Now it is too dilute so you don't have any, you just see its signature when you observe the disposition of galaxies in the universe. $\endgroup$
    – Richard
    Sep 11 '17 at 8:10
  • 1
    $\begingroup$ Very low density, so very low frequencies only: gizmodo.com/there-actually-is-sound-in-outer-space-1738420340 $\endgroup$ Sep 11 '17 at 14:12