Got no objections to inventing particles to take up and carry off whatever bit of stuff has to conserved: neutrinos, virtual particles, gluons, what-have-you.

I don't really even object to inventing five times the mass of the known universe.

It just feels, as I said, un-parsimonious. It feels quite a lot like inventing God to patch a "missing link" in your evolutionary succession. Maybe you'll find God there somewhere, but it doesn't seem like the first thing to try.

So, maybe dark matter really will turn out to be an ordinary axion or something detectable only if you manage to squint just right, and God just loved those so much that almost everything is them, and we are all made out of just leftover scraps. Maybe there are dozens of elementary axions, with relationships and exciting interactions we can never figure out because we can't touch them in any way but gravitationally.

But I still want to know how they cool.