Tell me why we cannot hear sound in space?


To get to the bottom of this question, we need to know two things.

Firstly, how sound travels, and secondly what’s actually out there in space. 

Space is Silent. Why space is silent?

 Sound is a vibration that typically diffuses as an audible wave of pressure. It is a mechanical wave,  a disturbance that moves and conveys energy from one place to another through a medium. And the medium can be any series of interconnected and interactive particles. Sound needs any of the three states of matter (solid, liquid or gas) as a medium for travel. So the first foremost condition of the sound to travel is the physical medium in any of the form- solid, liquid and gas.

The speed of sound 

The speed of sound is the distance traveled per unit time by a sound wave as it propagates through an elastic medium. The speed of sound depends on the medium through which it travels. Sound travels faster through Solid as compared to liquid and gases. The density of the medium also affects the speed of sound, the denser the medium, the slower sound will travels through it.

What is Space?

Now moving to space, first of all, what we consider space is?

The area of the universe outside Earth’s atmosphere is what we consider as space. ‘Outer space‘ begins about 100 km above the Earth, where the shell of air around our planet disappears. It is regarded as the boundless three-dimensional extent in which objects and events move in a relative position and direction.

The biggest fact about space is that it is nearly a perfect vacuum. Among the large objects like stars, planets, comets, moons, asteroids and other heavenly bodies, there are millions of miles of emptiness. This empty space which is also called interstellar space is practically devoid of all matter, so it’s effectively a vacuum. Because of this vacuum, the sound cannot travel in space. 

Why space is silent?

No, sound waves can travel only through matter. Since there’s almost no matter in interstellar space, its a vacuum with no medium to let the mechanical waves to travel, space remains to be silent.

So if next time someone asks you- Can you hear on Moon? Immediately reply to him – No

Radio Waves can travel in Space

The interesting fact is that Radio waves can travel through space. Radio waves are not mechanical waves, they are electromagnetic waves which can transmit energy through a vacuum.

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