[wanda]

It was not my intention to trigger anyone. I only wanted to say why dark matter is given the time of day. If I came across as condescending or as a know-it-all, I apologise, it was not what I wanted at all.

I also must apologise for my use of the term "emergent property" regarding gravity — judging by your response, I seem to have alluded (unintentionally) to a whole other theory of gravity; I only wanted to say that gravity itself is the curvature of the geometry of spacetime rather than a force in the conventional way it is described.

Also, regarding alternatives still requiring dark matter, it is my understanding that MOND and its derivatives explain galaxy rotation curves but not other phenomena that dark matter is purported to resolve (galaxy cluster formation/structure, gravitational lensing, CMB). If I am wrong about this, I would welcome correction. On the other hand, if your comment simply meant that there are alternatives to DM and MOND that require no DM, fair enough, I should have been clearer and said that some of the foremost competitor theories still require DM.

But I stress again, I am not fighting DM's corner or saying that alternatives are wrong. My stance on it is irrelevant, and I have no more belief in it than any other explanation, belief is irrelevant and doesn't enter into the matter. I was just saying that I understand why a theory that inflates mass arbitrarily, and understandably ruffles some feathers as a result, is given any credence at all.

Personally, I understand your frustration with DM, it does not seem like very good science to let unexpected or inexplicable observations make us simply add parameters without making further predictions to test if that's the right thing to do. Does seem like we're manipulating facts to fit the theory where we should be altering the theory to fit the facts.

Since DM is a substance that, for all intents and purposes, defies detection by any means at our disposal, it makes no further predictions, it just lets us push the square block into the round hole — what we should be doing is finding the square hole.

[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.