Sound cannot travel through the vacuum of outer space.

Sound is a pressure wave that needs a medium — molecules to bump into one another — to propagate. Air carries sound on Earth through vibration; water carries it even faster because its molecules are packed more tightly together. Outer space, by contrast, is a near-perfect vacuum, with far too few particles for pressure waves to travel through in any conventional sense.

That means the dramatic explosions and engine roars of space movies are pure invention. It’s also why astronauts communicate by radio rather than shouting: radio waves are electromagnetic radiation, not sound, and travel through a vacuum just fine. Space isn’t silent in every sense, though — telescopes have detected electromagnetic emissions from cosmic phenomena that scientists convert into audible tones for study, but that’s a translation of data into sound, not sound waves actually propagating through space itself.