Dark matter

Well, this is depressing.

Not that the existence of dark matter has been confirmed; that's just interesting, although it's a little disappointing that the MOND theories are pretty much sunk. No, the depressing part is the last few words of the article, where it notes that the evidence "supports the view that dark matter particles interact with each other almost entirely through gravity."

The practical upshot of this is that dark matter not merely exists, but is boring — almost certainly sterile neutrinos or something very much like. It can't generate interesting structures like atoms, let alone chemical compounds, and certainly can't serve as a universal computational substrate. There are no sentient dark-matter entities on any scale of space or time, no possibility of invisible civilizations in the extragalactic halo.

I suppose it's just barely possible that it could form something vaguely starlike, after a long while left to “cool” — a massive gravitationally-bound clump of dark matter only held apart by neutrino degeneracy pressure. However, I suspect (admittedly with no better than cursory knowledge of the physics involved) that neutrino degeneracy pressure wouldn't suffice, and "something vaguely starlike" would just be a black hole.

Also by then the Big Rip might have happened already.