[nyssos]

> Since DM is a substance that, for all intents and purposes, defies detection by any means at our disposal, it makes no further predictions

This is completely untrue. All serious dark matter candidates are observable. For example:

- MACHOs should show up in gravitational lensing surveys. We did the surveys, they didn't, MACHOs were rejected. Exactly the way it's supposed to work.

- Axions convert to photons in sufficiently intense magnetic fields. ADMX has ruled out part of the parameter space for axions and is undergoing upgrades to test the rest of it.

- Other WIMPs still interact via the weak force, and therefore with nucleons. There are many experiments looking for WIMP scattering. A few of them have gotten signals but not enough to be convincing.

Dark matter candidates are not just "mass with no further properties" sitting out there to make the model fit. They're proposed extensions to the standard model (which is nothing but proposed extensions to quantum electrodynamics which ended up working out), and therefore very tightly constrained by the standards of any other scientific field.

[uoaei]

Unfortunately those are all candidates which are conjured ex post facto to explain the "mass with no known properties" that is inferred. As you say, none of them are convincing. It's also just bad science to reach for factors that are just-so explanations of the observed phenomena.

[nyssos]

They are not. MACHOs definitely exist, it just turns out there aren't nearly enough of them. Axions were proposed as a solution to the strong CP problem years before anyone went looking for dark matter candidates. Sterile (i.e. right-handed) neutrinos are motivated by the need to explain why left-handed neutrinos, contrary to the predictions of the standard model, have mass. Supersymmetry was originally an attempt at strong-electroweak unification.