Sound is unable to travel through truly empty space. The phenomenon known as sound is the perception of alternating waves of compression passing through a medium. Unlike light, which is able to propagate without a medium, sound waves must have a medium, such as air, water or rock, to carry them.Continue Reading
True sound waves are only able to spread through a medium that puts molecules in contact, or near contact, with each other. As the wave of sound passes, the affected molecules press against nearby, unaffected molecules. The result is a moving wave of compression that, in an atmosphere, can be picked up by a human ear. In a vacuum, no air exists to carry the compression wave. In near-empty space, any event, such as an impact or explosion, that creates a moving wave of sound inside an atmosphere is left without surrounding matter to carry away the energy as sound.
Electromagnetic waves are able to propagate through empty volumes. The "sounds" that are sometimes picked up by space probes are heavily processed interpretations of electromagnetic radiation caused by such phenomena as charged particles moving through planets' magnetic fields. The variable intensity of this radiation can be assigned equivalent values along a spectrum of sound frequencies, which creates the "sound" of distant planets, galaxies and other astronomical phenomena.Learn more about Universe