Whatever dark matter is, is not what was expected. From Dan Hooper at Physics:
The latest results from two dark matter searches have further ruled out many theoretically attractive dark matter particle candidates.
The lack of a definitive detection of dark matter particles, in both underground experiments and at the Large Hadron Collider [4–7], has had a palpable effect on the community of scientists that study particle dark matter. Even though a discovery could very plausibly be right around the corner, there is a widespread view that many of the most theoretically attractive candidates for dark matter should have been detected by now, based on their predicted properties. In the absence of such a discovery, the field has begun to redirect efforts toward new, and sometimes very different, ideas. Although this state of affairs can certainly be frustrating at times, it has also had the positive effect of ushering in an explosion in dark matter model building.
…
Because of the progress of experiments such as XENON1T and PandaX-II, the field of dark matter research is currently in a state of major disruption. The dark matter, it turns out, is not what many of us in the particle theory community imagined it was likely to be. With this disruption, however, has come both great excitement and great opportunity. We know much more about dark matter’s nature than we did only a few short years ago. And the years ahead offer considerable promise for further advances, and perhaps with a little luck, the discovery that so many of us have been waiting for. More.
Our physics color commentator Rob Sheldon offers,
Dark matter WIMP searches are coming to a close with a bang. $M is being spent on 3, humongous, underground Xenon experiments, each bigger than the last. US was first to report with its LUX experiment, $10M 370kg of Xe, then comes China with its 584kg of Xe, and finally EU with its 2000kg of Xe. These experiments are millions of times more sensitive than previous searches, and could detect one event per year.
What have they seen?
Nothing.
How do these nations justify the spending?
“Because of the progress of experiments such as XENON1T and PandaX-II, the field of dark matter research is currently in a state of major disruption. The dark matter, it turns out, is not what many of us in the particle theory community imagined it was likely to be. With this disruption, however, has come both great excitement and great opportunity. We know much more about dark matter’s nature than we did only a few short years ago. And the years ahead offer considerable promise for further advances, and perhaps with a little luck, the discovery that so many of us have been waiting for.”
Nice spin, but I sure wish they would spend that money for more lucrative goals—The Philosopher’s Stone, for example. Sounds like Sabine Hossenfelder’s criticism is valid–our education system is cranking out bad theoretical physicists. I would add, “bad metaphysicists” too.
See also: Could that hole in the sun be dark matter?
Are we really closing in on dark matter? At this point, it may be useful to stop and ask, is there a date on dark matter’s IOU? Is there any point at which we can reevaluate without starting a blame circus? Because, if not, this is really a quest for something in inner space, not outer space and it is not clear what we are looking for.
and
Rob Sheldon: Dark matter has finally been found—in pop science mags