Nothing to carry the sound
Why Is Space Silent?
Sound needs a substance to travel through, and space has almost nothing at all.
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Step 1 of 5
Sound is a wave that travels through something.
A noise is a pattern of squeezing and stretching passed from one particle to the next. Without particles the pattern cannot go anywhere.
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Step 2 of 5
Space is very nearly empty.
A cubic centimetre of air holds a staggering number of molecules. The same volume of deep space might hold a single atom.
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Step 3 of 5
With nothing to pass the wave, it stops.
A bell ringing in a vacuum still vibrates, but there is nothing next to it to accept the push, so no sound leaves it.
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Step 4 of 5
Radio still works, because light needs nothing.
Astronauts talk by radio, which is a form of light. Light is a wave in electric and magnetic fields and needs no material at all.
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Step 5 of 5
Touching helmets would genuinely work.
Press two helmets together and the vibration travels through the solid material instead, which is why the trick appears in space films.
Sound travels at about 340 metres a second in air, 1,500 in water and 5,000 in steel — but nowhere at all in a vacuum.
The short version
Space is silent because sound must be passed from particle to particle, and space has essentially no particles to do the passing.
Try it yourself
Put a ticking phone alarm in a sealed jar and listen, then imagine removing the air too. The remaining sound travels through the glass.
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