From Matthew R. Francis at Symmetry:
One reason to think of dark matter as a thermal relic is an interesting coincidence known as the “WIMP miracle.”WIMP stands for “weakly-interacting massive particle,” and WIMPs are the most widely accepted candidates for dark matter. Theory says WIMPs are likely heavier than protons and interact via the weak force, or at least interactions related to the weak force.
Both the primordial light known as the cosmic microwave background and the behavior of galaxies tell us that most dark matter must be slow-moving (“cold” in the language of physics). That means interactions between dark matter particles must be low in strength.
“Through what is perhaps a very deep fact about the universe,” Buckley says, “that interaction turns out to be the strength of what we know as the weak nuclear force.”
That’s the WIMP miracle: The numbers are perfect to make just the right amount of WIMPy matter.
The big catch, though, is that experiments haven’t found any WIMPs yet. It’s too soon to say WIMPs don’t exist, but it does rule out some of the simpler theoretical predictions about them. More.
Is it worth asking whether dark matter (and WIMPS generally) are the phlogiston of modern science? That is, a substance whose existence was never demonstrated but postulated on the basis of a now-exploded theory?
The current problem is that the universe looks fine-tuned, but that is not an ideologically acceptable view. So any speculation whatever may be adduced as an alterative explanation. Including speculation around postulated entities we never witness.
In short, the evidence is on the side we refuse to consider and the speculation we adduce as an alterative is without evidence. Eventually, one must decide.
See also: A proposed dark matter solution means gravity is an illusion
Copernicus, you are not going to believe who is using your name. Or how.
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