There are many assumptions, and nobody really knows much about what is Dark Matter is.
Dark matter is matter that cannot be detected by electromagnetic radiation, hence dark. In physics and cosmology, dark matter is hypothetical matter that does not interact with the electromagnetic force
According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter and dark energy account for the vast majority of the mass in the observable universe.
While examining the Coma galaxy cluster in 1933, Swiss astrophysicist Fritz Zwicky, of the California Institute of Technology was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter.
Currently research by scientists attempting to discover exactly what this dark matter is with the world’s biggest atom smasher in Switzerland.
How much dark matter there is, and what effect it may have on the future of the Universe as a whole, scientists are hoping to make with the Large Hadron Collider (LHC) underground near Geneva.