> Well, not really. The physical justification is, the multitude of observations that appear consistent with the theory that there is some form of matter out in space that does not interact with photons. It's not something someone just had a dream about one night - it's a real-world observation, with telescopes.

This is it. Everything points towards it being some kind of invisible matter. Scientists know that the very idea is preposterous!

But you can't make up some 'cleaner' hypothesis without also holding that idea up to the same standards as Cold Dark Matter, and to date they have tended not to.