Name: Dana F.
I am curious about the temperature of space between galaxies.
Would it be close to, near or at 0 degrees K? >If there is no energy to heat, it should be.
Intergalactic temperature at some point in space primarily depends upon
how much radiation a probe at that location, because radiation (as opposed
to convection, or conducting) is the major mechanism for transferring energy
in "outer space". The amount of energy (the number and energy of individual
photons) the probe absorbs and converts into heat depends of course on the
absorbance/reflectivity of the probe's surface, but assume that the probe is
100% efficient in absorbing incoming photons of all energies. Then, the
incident energy is the energy of the various photons times the number of
photons of that given energy. If the probe is not near any other stars,
galaxies, etc. that give off a lot of photons, you are correct, the
temperature of the probe will by near 0 kelvins. The energy density falls
decreases as R^-2 the inverse square of the distance from the photon source
(assuming there are no other absorbing inter-galactic clouds and the like).
If the probe is near a photon source, and the other assumptions above apply,
the temperature of the probe will be higher.
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Update: June 2012