why is space cold when everything generates heat? expanding: why isn’t the expansion of space creating heat at the edges?
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Heat transfers through one of three methods – conduction (hot object touches cooler object,) convection (warm fluid flows because it has lower density than cool fluid,) and radiation (warm object emits heat energy in the form of infrared waves.)
Space is cold because there’s no fluid to have convection current. But there is lots of radiation in space – which is why we have to put radiation shielding on satellites and spacecraft. As soon as that radiation hits something, it’ll warm it up… but space is cold because there’s no “something” for the radiation to hit.
Sorry, space isn’t expanding at the edges any faster than it is anyplace else. It’s expanding at the same slow rate everywhere, but space is very, very large and over enough distance small changes accumulate. The space containing the Earth expands at the rate of about 1mm/year. Space is a bazillion times bigger than the Earth, and over large distances this expansion accumulates.
Goodness that’s a bit to unpack there…
Simple answer: you have temperature and volume. Increase the volume, you lower the temperature.
Ok, now have a thing expand for 13.8 billion years (at a fairly rapid pace) and you’ve diluted the heat, therefore reducing the temperature.
Now check *why* the cosmic background temperature is what it is.
Keep asking questions – I’m happy to answer
Space itself is neither cold nor hot. Space itself is not a thing so it has no temperature, only stuff *in* space has temperature. There are also no “edges” where the universe is expanding, that’s not how the expansion of space works. Space is expanding in the sense that everything in space is moving farther away from everything else, it is NOT like an explosion with some outer edge that expanding.
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