Dark matter is one of the artifacts of the standard model of physics, a model dominated by the twin pillars of Jachinite relativity and Boazite quantum mechanics. Well, consider the following interesting article from phys.org:
There's a number of statements here that I wish to draw attention to, because they perfectly illustrate the predicament that western theoretical physics has got itself into. Note the following statements:
"Like his previous study featured on PhysOrg about a cyclic universe successively dominated by matter and antimatter, Hajdukovic’s paper on a dark matter alternative is also an attempt to understand cosmological phenomena without assuming the existence of unknown forms of matter and energy, or of unknown mechanisms for inflation and matter-antimatter asymmetry. In the case of the fast rotational curves of galaxies, he explains that there are currently two schools of understanding the phenomenon.
“'The first school invokes the existence of dark matter, while the second school invokes modification of our law of gravity,' he said. 'I suggest a third way, without introducing dark matter and without modification of the law of gravity.'”
In other words, the whole notion of dark matter and dark energy come from theoretical and mathematical artifacts of the standard model; they are not the result of observation and experiment, but rather, the result of observation interpreted through the lens of the assumed model.
It was this whole approach that was brought into physics by Einstein's two theories of relativity, which sought a different interpretation of the results of an experiment, the celebrated Michelson-Morley experiment. As many physicists of the time suspected, there was a problem both with the way the original experiment was set up (Georges Sagnac), and the way it was interpreted (Herbet Ives).
What is interesting here is that Hajdukovik is hypothesizing something quite similar to German physicist Burkhardt Heim, namely, that there is a direct relationship between electromagnetism and gravity, in that matter and anti-matter are also a gravitational dipole and the result of a broken symmetry:
"His ideas (like those in the previous paper) rest on the key hypothesis that matter and antimatter are gravitationally repulsive, which is due to the fact that particles and antiparticles have gravitational charge of opposite sign. (Though like matter, antimatter is gravitationally attractive with itself.) Currently, it is not known whether matter and antimatter are gravitationally repulsive, although a few experiments (most notably, the AEGIS experiment at CERN) are testing related concepts.
“Concerning gravity, mainstream physics assumes that there is only one gravitational charge (identified with the inertial mass) while I have assumed that, as in the case of electromagnetic interactions, there are two gravitational charges: positive gravitational charge for matter and negative gravitational charge for antimatter,” Hajdukovic explained.
"If matter and antimatter are gravitationally repulsive, then it would mean that the virtual particle-antiparticle pairs that exist for a limited time in the quantum vacuum are “gravitational dipoles.” That is, each pair forms a system in which the virtual particle has a positive gravitational charge, while the virtual antiparticle has a negative gravitational charge. In this scenario, the quantum vacuum contains many virtual gravitational dipoles, taking the form of a dipolar fluid."
Whether or not Hajdukovic's proposal will ultimately be born out will have to rely on the basis of experimentation. But that's the point. It's at least a testable hypothesis. If true, then the standard model will have to undergo some adjustment. But it is an adjustment that could conceivably lead to new forms of energy and propulsion technologies, for a broken symmetry leading to such a gravitational dipole -like electromagnetic circuitry - is conceivably an engineerable phenomenon.