Why there's no sound in space

All images: NASA

'No One Can Hear You Scream'

"In space, no one can hear you scream"- This is a tagline from the 1979 movie Alien. This is 100 per cent true as there is no sound or echo in space. But why so?

What is Sound?

Sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. Sound is carried by atoms and molecules. Astronomer Chris Impey says that in space, with no atoms or molecules to carry a sound wave, there is no sound.

'No Sound means No Echo'

Impey says that no sound also means no echo.

How Would Human Voices Sound in Neigbouring Planets?

Though hypothetical, our voice on Mars would sound tinny and hollow, like the sound of a piccolo, Impey says. On Venus, our voice would be much deeper, like the sound of a booming bass.