[SaberTail]

You say MOND is better because it's simpler.

We already have examples of particles that do not interact electromagnetically but have mass, and therefore interact gravitationally. They're neutrinos. How is a new theory of gravity simpler than particles that are similar to ones we know exist?

[AnimalMuppet]

Depends on which hat you're wearing. If you're wearing an astronomical or GR hat, new particles are simple. Just add their mass, and space curves differently, and you're done. But if you're wearing a particle physics/standard model hat, new particles are a huge deal. They change all kinds of things. Some of those things that change have rather large effects on cosmology.

[lll-o-lll]

I say that MOND can describe certain observations in a simpler way, which it can. For those same observations Dark Matter is more complex because you have to add a number of parameters to make it fit.

I didn’t say it’s better than Dark Matter; it’s not either or. I have no dog in this fight. I simply regard what Sabine has said “combine these two theories you idiots!” (paraphrased), and think “she’s probably got a point”.

[throwawaymaths]

It has one parameter. "Particle we can't see" has as many parameters as it takes to model the density and flow of those particles at any given place in the universe.

[mr_mitm]

That's a common misconception (at least on HN).

I debunked this idea in the last DM thread: https://news.ycombinator.com/item?id=34365591

[throwawaymaths]

Yeah and you're still wrong. The comparison is inapt because for all other cosmological phenomena our information is multimodal and this not currently the case for LCDM. Take the argument to the extreme: suppose dark matter has no weak force interaction. It will then be literally impossible to uncouple our observations of dark matter from our inference of it's distribution, and then LCDM is strictly unfalsifiable and may be used to explain almost anything.