Coldness of space - Explain please

[The Boston Dangler]

Assuming our spaced victim didn't explode, he (let's call him Larry) would continuously thaw and freeze as passes in and out of shadows. Since Larry has a weight problem (too much Taco Bell) his core will remain frozen well into his trip around the sunny side of a spaceship, Earth, et cetera. With nearly 3 feet of inside-out lung projecting from Larry's mouth, his rapid and wild spinning would pevent the left half being solid while the right is blistering mush.
Thankfully, Larry's orbit will be totally unstable, with a clean finish. Unless, of course Larry is orbiting the Moon. Then he has one final trick up his sleeve. Given a shallow impact angle, he can scatter fragments over a decent slice of moon.

Still, it's a better way to die than Michael Hutchins.

 

[AgentJean]

Your lungs and eyes will explode before you freeze.
Remember that while you try sucking on some vacuum.

 

[Calin]

Originally posted by: BladeVenom
Convection works in space since it isn't a complete vacuum. It's about 1 atom per cubic centimeter.

This adds up to about 23 millions atoms per 23 cubic meters. Compare this to the 10^26 atoms (see Avogadro number) that are in 23 cubic meters of gas at normal pressure, and you could get an idea of the completeness of the vacuum

 

[Sc4freak]

It still works, though, despite the fact that space is 100 quintillion times less dense than an atmosphere 😛

 

[FP]

Originally posted by: sao123

Originally posted by: KF
The last time I read a thread like this the consensus went more the other way. Since I didn't quite follow the explanation, I should probably shut up. But...

The claim then was that heat sinks in the vacuum of space are much more effective, and rather than having trouble getting rid of heat, spacecraft have trouble holding it. Basically, although heat transfer by conduction and convection are nil, radiation into nothing is far more effective than radiation into air. I would have thought that air was nearly as tranparent to radiation as a vaccuum and there would be little difference in transfer by radiation. However, air is warm and therefore radiates into a heatsink too, which does not happen with a vacuum. So the temperature of the air also matters for radiation as well as conduction.

A thermos bottle has a mirror coating to reflect radiation, so you can't conclude much from the comparison.

That 2.73 Kelvin is the what the temperature of the blackbody radiation of the big bang fireball has been red-shifted to by the expansion of space itself since matter condensed out and allowed radiation to pass through. Whatever molecules might be in the vacinity of stars or planets could be a different temperature.

I recall the early days before any astronaut had been put in space. There were pictures in such as LIFE magazine showing volunteers that had been put through "explosive decompression" at the very instant the pressure dropped. There was no suggestion it would be deadly. They looked weird and bloated, but they didn't explode and die.

Let me give you a familiar explanation to prove you wrong from the start...

how do you cool down a computer better?
A plain Heatsync. (pure radiation)

or

A Heatsync with attached fan. (radiation + convection)


Now which would cool better in a complete vacuum?
Neither... they would both cool at the same rate... (radiation only, since convection cannot happen without a medium)


Air has nothing to do with radiative cooling, using air requires convective cooling.

Doesn't a heatsink work through conduction, not radiation?

 

[f95toli]

Well, it is conduction from e.g. the processor to the heatsink. However, you still need to get rid of the heat meaning you have to cool the heatsink and that is done using radiation and conduction (mainly the former).
A heatsink is just an "intermediate" stage when you are trying to cool something.

 

[silverdj]

I always that it was cold in space because unlike the earth, space does not have an ozone layer or anything to keep heat in. If it was warm in space, then we would probably have already figured out a way to live there. That is just my opinion though and its not very educated.

 

[jagec]

Originally posted by: sao123
Without regard to heat radiation.... would not the pressure laws dictate that (assuming that skin was strong enough to withstand 0 pressure without bursting) due to the drop in pressure create a proportional change in temperature?

PV = nRT

obviously thats the gas law, but i believe similar results happen in liquids and solids...so temperature is a measure of kinetic energy, and pressure is a measure of inter molecular static forces... would not a change in one, require a proportional change in the other, without violating conservation of energy laws?

So a drop in pressure could freeze you instantaniously?

You're not going to expand appreciably in space, so your temperature isn't going to drop much.

Originally posted by: sao123
Now which would cool better in a complete vacuum?
Neither... they would both cool at the same rate... (radiation only, since convection cannot happen without a medium)


Air has nothing to do with radiative cooling, using air requires convective cooling.

He's referring the temperature of the surroundings, which DOES affect radiative cooling pretty drastically. The higher the surrounding temperature, the less net heat will radiate away from an object, regardless of what medium surrounds it.

Originally posted by: f95toli
Well, it is conduction from e.g. the processor to the heatsink. However, you still need to get rid of the heat meaning you have to cool the heatsink and that is done using radiation and conduction (mainly the former).
A heatsink is just an "intermediate" stage when you are trying to cool something.

Nope, heatsinks are almost entirely convective. It's far more effective.