Since the earth is in a vacuum and therefore there is no thermal transfer of hea
ID: 1318888 • Letter: S
Question
Since the earth is in a vacuum and therefore there is no thermal transfer of heat to anything else, how can it even cool down? It seems like its average temperature would always be constant, ignoring outside sources of heat.
However, if you then consider that there is constant radiant heat transfer from the sun to the earth, now you have a net gain in energy/heat.
I also read somewhere that the solar wind actually blows a bit of our atmosphere into space, but that seems like a miniscule amount of heat loss compared to how much heat is gained from the sun.
Will the earth ever cool at all?
Explanation / Answer
All matter radiates electromagnetic radiation according to its temperature. It is called black body radiation.
The power emitted goes as T^4 , where T is the temperature in degrees Kelvin.
If there is no replenishment of the energy lost the body in vacuum will approach absolute zero after a calculable time.
The earth gets replenished mainly by the sun, a bit from internal fission too.
Absolute zero cannot be reached in finite steps as this formulation of the third law of thermodynamics states:
It is impossible for any process, no matter how idealized, to reduce the entropy of a system to its zero point value in a finite number of operations.