For many years, the basic principles of thermodynamics stumped physicists. John Dalton hadn’t propounded his atomic theory yet, so the mountains of evidence in favor of atoms and molecules had not been convincingly compiled, thus the alternate (and correct) explanation of heat being the kinetic energy of atoms and molecules rattling (or in the case of gases, ricocheting) around didn’t exist. Therefore physicists hypothesized the existence of a mysterious substance called caloric, which was said to embody heat; heating and cooling was interpreted as a flow of caloric.
For many years, the propagation of light and radio waves stumped physicists. Such radiation clearly took the form of waves, yet what was waving? Sound waves and water waves involve matter making waves. Yet light travels just fine through interplanetary space. Therefore, they thought, the universe must be pervaded with a luminiferous ether, the oscillations of which caused light to propagate. Eventually Einstein’s theories of relativity obsoleted the need to hypothesize an ether into existence.
Numerous experiments were performed in attempt to detect both presumed substances, all to no avail. Eventually, alternate and better explanations for both phenomena were arrived at, ones that did not involve the conjuring into existence of hypothetical types of matter. However, the critical point is that for some reason, people seem to prefer imagining matter into existence over revising their theories of the rules for the behavior of observable matter.
This predilection explains religious mythology as well as scientific dead-ends. Dating back to prehistory, invisible realms were conjured from the imagination to explain the holes in our understanding of the natural world. Can’t understand storms, the change of seasons, or the apparent motion of the Sun, the Moon, and the stars? Invent gods and a realm in which they dwell to explain it all.
It is reasonable to assume that this aspect of human nature is still with us today. Which brings me to dark matter: it has a lot in common with the earlier caloric or luminiferous ether. There is absolutely no evidence in its favor save how our current understanding of the laws of physics fails to explain the behavior of galaxies and other very large-scale phenomena. Nobody has ever actually detected so much as the smallest iota of this “dark matter.”
The most logical explanation is that dark matter simply doesn’t exist. It is a scientific dead-end that our human nature has conned many of us into chasing. There are in fact some astrophysicists who have come to this very conclusion.
The rub is, so far, none of the known alternate explanations (that do not involve dark matter) have yet proven sufficiently convincing. This may be because the correct explanation has yet to be arrived at, or it may be because prejudice is preventing an existing (albeit not well-known) correct explanation from being well-accepted. I will freely admit I do not know enough about the subject to offer any informed opinion as to which of the two is more likely.
But, based on what the history of not just science but all of human culture tells me about human nature, I strongly suspect that dark matter will eventually be consigned to the same dustbin of scientific history that caloric and the luminiferous ether currently are in.