The cold vacuum of space isn't the lack of heat in matter. It's the absence of matter. That rare molecule hitting the spacecraft will transfer thermal energy to it. But the effect will be practically nothing because it will be counteracted by the overwhelming mass of the craft which is being cooled by the vacuum of space and being heated on the inside by its nuclear reactor so that it doesn't get too cold to operate.

[–] atx_aquarian@lemmy.world 1 points 1 day ago (1 children)

And I'd guess what they're asking is how a vacuum would cool something if there's no matter providing collisions where energy transfer can happen. I.e., isn't vacuum the ultimate insulator? If I understand correctly, objects in a vacuum cool by radiating only (i.e., energy leaving as photons), and perhaps we only think of space as cold because the absence of a medium (i.e., atmosphere) means no pressure and no additional energy being provided in said medium.

[–] FauxPseudo@lemmy.world 1 points 1 day ago

The craft radiates heat into the void. Not conduction but radiation.