Sound does not travel in space. ('In space, no-one can hear you scream', as the tag line for 'Alien' went...) What would happen to the sound energy if, say, an astronaut decided to play a guitar during a space-walk?
1 Answer
In brief, sound energy is the vibration of molecules in air of other substances, usually caused by the vibration of something else. In space, there is no air to vibrate, so we could say there is no sound energy.
Explanation:
This is a great question!
Sound energy is a kind of energy that is transmitted through air, other gases, water, steel... most things, actually, at least if they can be compressed. Sound waves are cycles of compression and 'rarefaction' (the opposite of compression). They can carry energy from one place to another.
In deep space, there is no air. Strictly speaking, there could be sound energy in space that was passing through the steel walls of a spaceship, for example. But those vibrations could not be transmitted into vibrations in the air, because there is no air.
That means that energy, in the form of sound waves, cannot move through open space. There simply is nothing to compress and rarefy.
(Side note: even in deep space, there is a teeny-tiny amount of matter, maybe one hydrogen atom per cubic metre, but this is not enough to transmit sound.)
In answer to the question, then, sound energy is not created or destroyed in space. If an astronaut played a guitar in space, the energy her fingers put into the strings would cause the strings to vibrate, the strings would cause the body to vibrate, but all that energy would remain in the body of the guitar. It would not be carried away as sound in air, as it would on earth.
The energy would eventually go away - the guitar would not simply vibrate forever. It would go away as heat energy from the vibrations in the material. Heat energy is infrared radiation, part of the electromagnetic spectrum (like like), and those waves do not require air to travel through.
