I have a theory of Dark Matter. Perhaps the Universe has a contraction phase and expansion phase and maybe it happens simultaneously in cycles. During the contraction part, all matter combine so densely that it turns dark, cold and very slow moving. Example: When combining colors, the more colors in the mix the darker it gets. If all colors are combined, it turns black. During expansion, matter, colors seperate causing rapid acceleration, lighter colors, heat, little density. When colors are seperated to the extreme, it turns white. So, maybe Dark matter is extremely condense matter and light is expanded seperated matter.