I suppose the real title should be, "can relativity explain the NEED for Dark Matter"? Now I'm not a physicist, so if I get a detail wrong here or there please do not get stuck on that but rather try to answer the question... It is my understanding that dark matter is "needed" (in one case) to account for the stars on the edges of spiral galaxies not flying off into deep space. Without dark matter, the gravity of the galaxy could not hold the stars in place, as they are moving much too fast. Tests regarding Mercury's orbit proved that gravity slows the passing of time. Would that mean that, since the centers of galaxies are much more massive than the edges, the center of galaxies would appear to orbit slower when perceived from a distance and the outer stars moving relatively faster? If this is true, could this effect be strong enough to make it seem as if the stars on the edge are moving "too fast"?