exchemist
Valued Senior Member
I suppose I ought to point out that I've changed my mind about what I said in post 58, thanks to the further discussion about whether dark matter can be said to have a temperature, which we have had in Beaconator's thread here: http://www.sciforums.com/threads/was-the-majority-of-the-universe-created-by-fusion.165572/
On further reflection it seemed to me that dark matter particles (if it exists as particles) may be unable to collide, since they do not respond to the EM interaction, which is where the repulsion between atoms and other normal matter particles comes from. If they can't collide, they can't redistribute their kinetic energy into a Boltzmann distribution, and if they can't do that, a temperature cannot be defined for them.
On further reflection it seemed to me that dark matter particles (if it exists as particles) may be unable to collide, since they do not respond to the EM interaction, which is where the repulsion between atoms and other normal matter particles comes from. If they can't collide, they can't redistribute their kinetic energy into a Boltzmann distribution, and if they can't do that, a temperature cannot be defined for them.