How is space “cold” when it’s a vacuum? Isn’t temperature transferred between mass? If anything, shouldn’t you overheat when in a vacuum, because your body generates heat?
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>Isn’t temperature transferred between mass?
Through conduction and convection, yes, but not only. There’s also radiation. Everything with heat emits electromagnetic radiation. And there is nothing in our universe with zero heat. Nothing is 0K.
So, everything will emit some heat, nevermind how little. Something is “hot” or “cold” depending on the balance of this emission. If you emit more heat than something next to you, it will receive more heat from you than you receive from it. The effect is that it will gain heat while you lose heat. But as it heats up, it radiates more heat. You cool down and radiate less heat. At some point you reach equal heat, you both radiate as much as you absorb. If you’re isolated, there’s nothing colder than you, that’s it. You’re in equilibrium.
Now to answer the questions you’ve actually asked:
Space is “cold” because without additional source of heat, like sunlight, you will radiate more heat into space that you will absorb. You will absorb some, because even “empty” space isn’t empty. There’s radiation there, the Cosmic Background Radiation. Everywhere, every bit of space. And it’s about 4K, or about -269 C. Pretty cold.
But can you overheat in space? Yes, you can, even without sunlight. Because radiating heat is, while unavoidable, very slow and inefficient compared to conduction and convection. So if you heat up, either internally or by absorbing sunlight, it will he very difficult to get rid of it at the same rate as you gain it.
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