Why do things get cold in space?

Question

I thought an atom had to touch another atom in order to lose entropy.

So since space is a vacuum, shouldn’t something drifting along in space not ever touching another object retain its heat forever?

In: 1

Answer 1

The primary mode of heat transfer in space is radiative – the atom emits a photon that carries energy off into the abyss.

This is how the sun’s energy reaches earth across the vacuum, and this is how a rock lost in deep space will eventually cool down to cryogenic levels.

Far from any stars or galaxies the only incoming energy you’ll receive the same way is the feeble heat still echoing from the big bang itself, a feeble 3 kelvin.