The fundamental phenomenon of dilation explains dark matter. Mass that is dilated is smeared through spacetime relative to an outside observer. It's the phenomenon our high school teachers were talking about when they said "mass becomes infinite at the speed of light". A graph illustrates its squared nature, dilation increases at an exponential rate the closer you get to the speed of light. Time dilation is just one aspect of dilation, it's not just time that gets dilated. Dilation will occur wherever there is an astronomical quantity of mass because high mass means high momentum. This includes the centers of very high mass stars and the overwhelming majority of galaxy centers. The mass at the center of our own galaxy is dilated. This means that there is no valid XYZ coordinate we can attribute to it, you can't point your finger at something that is smeared through spacetime. In other words that mass is all around us. Dilation does not occur in galaxies with low mass centers because they do not have enough mass to achieve relativistic velocities. It has been confirmed in 6 very low mass galaxies including NGC 1052-DF2 and DF4 to have no dark matter. In other words they have normal rotation rates. All binary stars have normal rotation rates for the same reason.