Why is there no sound in space?
Sound is a vibration that travels by air molecules bumping into each other. Space is almost completely empty, with nothing to pass the vibration on. So even a roaring rocket makes no sound you could hear just a short distance away in space.
Sound is molecules bumping into each other
When something makes a sound, it shakes the air next to it. Those air molecules push on the next ones, which push on the next, and the wave travels until it reaches your ear.
Share this stepAir thins out above the Earth
The atmosphere gets thinner the higher you go. Far above the clouds there are fewer and fewer molecules to carry the vibration, and the sound fades away.
Share this stepIn empty space, nothing passes it on
Space between planets and stars is close to a perfect vacuum, with almost no molecules at all. With nothing to bump into, the vibration has no way to travel, so there’s complete silence.
Share this stepNo air, no sound.
Vibrationno moleculessilence
Light and radio waves don’t need anything to travel through, which is why we can see the stars and astronauts can talk by radio. The roaring explosions in space movies are added for drama.
Common follow-up questions
How do astronauts talk to each other in space?
By radio. Inside the spacecraft there’s air, so they can talk normally. Out on a spacewalk, two astronauts can even hear each other faintly by touching helmets, since the sound travels through the solid material.
Is space completely silent?
For our ears, yes. But space isn’t perfectly empty, and in thin gas clouds very slow pressure waves exist. NASA has turned such signals into sound so we can hear them.
Could you hear an explosion in space?
Not from a distance. Only if pieces or gas from it hit you or your spacecraft would the vibration reach you through solid material.
Why do space movies have sound?
Because silent battles feel strange to audiences. A few films, like 2001: A Space Odyssey, show space realistically silent.
