[edna314]

I'm not entirely sure which one of the two, Dark Matter or MOND, is conceptually the bigger disaster. Dark matter pretty much sounds like the invisible ether that was suspected to carry EM waves. A physical theory that depends on the scale at which you look at space seems similarly awkward to me.

[mnl]

You could have said the same stuff about the neutrino after Pauli introduced it in 1930 to explain the missing pieces in the beta decay. The alternative could have been giving up on the conservation of energy-momentum, but then if you have a continuous energy spectrum in an apparent two-body decay, it makes sense to think there's a third body there that makes it all work as expected despite you being unable to detect it at the time.

It took 26 years to confirm, and that's thanks to having man-made high flux sources. Detection of solar neutrinos had to wait until the 60s. Funnily there was a puzzle with those, as around two thirds of the ones you could expect seemed to not being there (again). This mismatch took another 40 years or so to confirm, so now we know that there are neutrinos indeed and that they show flavour oscillation, that's why if your experiment is looking for a particular leptonic flavour, well you're missing the other two.

So this is not the first time such there must be something there I can't see, yet I can say something about so it all fits together does the job. Hopefully it won't be the last time.

[edna314]

Very nice breakdown of the history of the neutrino! I fully agree. Whether a theory is a conceptual desaster or not is completely unrelated to its success. And I totally get that the hope of physicists is that such theories continue to be successful, since it means new physics which can be discovered. But, still if there is a theory that manages to explain observations, without postulating an otherwise unmeasurable quantity, Ockham’s razor tells you that it would be reasonable to prefer those.

[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.