Thompson's Position on Dark Matter
Tim's approach seems to be exactly the opposite from my perspective. The "conservatism" is aimed at "protecting the status quo" rather than filling in the gaps of the "dark" parts of his current theory and understanding. It's almost as through he INSISTS that some sort of exotic matter MUST exist. Maybe, and maybe not. We won't know however if we never actually attempt to ELIMINATE the need for exotic types of matter and we constantly favor a "dark matter=exotic matter" approach.
I've seen a lot of people fiercely defending dark matter in the form of particles likes WIMPs, so I empathize with your sentiment. But I haven't read much of the thread, so I don't know Tim's stance.
Here is my official stance.
It is a
fact that the motion of matter in the universe is observed to be significantly inconsistent with the standard physical assumptions. Therefore, the standard physical assumptions need to be either modified, or simply replaced with new assumptions. There are in essence only two real candidates for new or modified assumptions: (1) There is more matter in the universe than we see, providing an unseen source for more gravity than we would have expected, or (2) The standard laws of gravity need to be modified to conform with observation. Of course, both (1) & (2) could be simultaneously true. The first assumption comes in two parts: (1a) There is more ordinary (i.e., baryonic) matter than we see, and (1b) There is additional, as yet undetected nonbaryonic matter. And, of course, Both (1a) & (1b) could be simultaneously true.
In my opinion, and in the consensus opinion of the main stream science community, both (1a) & (1b) are true. It is known that there is more baryonic matter in the universe than previously thought, although Mozina has thus far done a poor job of finding the correct sources to justify this already mainstream conclusion. However, it is also known that all of this previously undetected
baryonic dark matter combined falls far short of the mark required to avoid the necessity of more exotic
nonbaryonic dark matter (so long as we simultaneously assume that (2) is incorrect and that the law of gravity does not need to be modified). Hence, the bulk of mainstream research is concentrated on figuring out ways to directly or indirectly detect the nonbaryonic dark matter which has thus far remained undetected. However, it should also be noted that there is significant research, exemplified by numerous journal papers, devoted to (2) above, attempting to eliminate the need for any dark matter at all by modifying the laws of gravity. As far as I know, being outside my own area of expertise, these attempts have failed to find a universal solution; e.g., one form of modified gravity might work to solve "this problem" but not "that problem", and so forth, while the assumption of both baryonic, but predominately nonbaryonic dark matter produces universal solutions that simultaneously solve all of the problems (at least in principle), limited of course by observational uncertainty.
If Mozina thinks I am trying to "protect the status quo", or that I "insist" that some form of exotic matter must exist, then he is quite wrong, for neither of these positions he suggests are of any interest to me at all. I do insist that the current state of observation strongly suggests the presence of nonbaryonic dark matter, and I do insist that this is in fact the simplest, most empirical, best scientific solution to the problem of conforming theory with observation, given the current state of knowledge.
I am definitely not arguing here that the status quo must be protected from new ideas. I am simply arguing that Mozina has yet to come up with anything particularly reasonable to say about anything relating to the physical sciences in general, or the more specific sciences of cosmology & astrophysics.