“In space, no one will hear you scream. This is the catchphrase, as famous as it is realistic, of the film Alien. Indeed, the sound cannot propagate in the quasi-interstellar vacuum.
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Light is what is called “a electromagnetic wave “. It can spread even in the void. the his, on the other hand, is a mechanical wave. A bit like a wave on the water surface ; it spreads step by step.
Sound wave and noise in space
L’sound wave therefore needs matter to spread, by a succession of compressions and dilations of the environment in which it is produced. This medium can equally well be solid, liquid or gaseous.
Propagation, speed of sound and density of matter
In interstellar space, the density of matter is much too low – of the order of one particle per cubic centimeter compared to some 1020 particles per cubic centimeter on the side of the Earth – so that the sound can take support there and propagate. That’s the reason why we can’t hear any sound in space. Blaise Pascal spoke quite rightly about “eternal silence of infinite spaces”.
It should also be noted that the denser a body, the faster it allows sound to propagate. So in theairthe speed of sound is around 340 meters per second (m/s), in water it goes up to around 1,500 m/s and in steel it reaches 5 km/s!
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