Ptolemy
A very non specific question about heat loss in a vacuum.

If you threw a human into space (with out worrying about his/her lungs bursting out) is there a rule of thumb about how fast he/she would cool down.

As there is molecules heat transfer can only be through radiation, and assuming he/she is not in the sun's path, there is no radiation adding heat and no molecules hitting him/her to add heat through kinetic energy.

So would they lose heat very quickly or would they be like coffee in a thermos flask and be perfectly insulated in space and only lose heat very slowly.

(This is probably very basic)

Staff Emeritus
Heat can be radiated via emission of IR (infrared) radiation. That's how the heat from the sun gets here. IR is an EM radiation, just like visible light, so it requires no medium for transmission.

Zz.

Ptolemy
Yes, I was aware of that and hoped I made that clear when I (mis)wrote
"As there [are no] molecules heat transfer can only be through radiation"

[] represents my poor original writing corrected.

So as an analogy would it be correct to say that the rate of heat loss of coffee in thermos vacuum flask and the rate of heat loss of the same coffee in a sealed container outside of the sun's rays would be roughly the same?

ie, the heat would radiate away very slowly (comparitively) and that this rate would be determined by...? (the propensity of that particular material to produce IR radiation? Is that a fixed physical property?)

Ta

Ptolemy
I guess in the thermos flask on Earth you would also have the coffee being heated by IR radiation from the outside.

Is it possible to estimate the rate of those two heat exchanges?

Staff Emeritus