[teraflop]

The main difference is that the aether was only ever a theoretical construct, whereas we have lots of indirect observational evidence that "dark matter" is a phenomenon that really exists. We don't know what it consists of, but it certainly seems like there is more of it in some places than others, and it has mass and momentum (see e.g. the Bullet Cluster that was already mentioned in this thread), so "matter" seems as good a name for it as any.

[edna314]

Ok, I would be curious about evidence that dark matter has momentum, because my favorite theory at the moment is that spacetime itself has certain topology on large scales, which isn’t tied to any masses. If one could show that dark matter has momentum, I would reconsider, but I don’t think that is what Bullet Cluster shows.

Edit: even if it turns out that dark matter is the best theory, it would still be a conceptual disaster. But so is QM. Nature seems not to care what we find conceptually appealing.

[DiogenesKynikos]

Quantum mechanics is incredibly elegant and appealing as a theory. It's just counter-intuitive.

[edna314]

Is this why there are a bazillion of theories of the foundations of QM? I get that the mathematics is incredibly elegant, but concepts behind the mathematics are not really “understandable” to quote Feynman.

[DiogenesKynikos]

The Many-Worlds Interpretation is the simplest one, because it makes no assumptions beyond, "The basic rules of Quantum Mechanics are correct." It's also very counter-intuitive, but very elegant.