I figure Dark Matter is simply neutrinos that have slowed down. They don’t weigh much so there must be an incredible amount of them. The slowing down part is what is hard to figure out since nothing much effects them. Perhaps this 5th force is responsible for that.
Maybe they started out faster than light, hit the edge of the universe, and got bounced back like a reflection wave.
The 4 types of wave interactions ways that waves may interact with matter are reflection, refraction, diffraction, and interference. Maybe Neutrinos interact with each other in an interference pattern that knocks them down to sublight speed.