Instead, there's a far simpler explanation: The motion of galaxies is due to the stretching of space between those galaxies. (livescience.com)
According to theory, the bulk of the matter in the universe consists of large, dark filaments of gas in the vast empty space between galaxy clusters. (sciencemag.org)
Partially dimmed x-rays (dips in graph) from a flaring blazar (right) reveal two filaments of hot, diffuse matter in the vast spaces between galaxies. (sciencemag.org)