Physics Girl: How the Edge of Our Galaxy Defies Known Physics[VIDEO]
Cosmologists believe that there is four times more dark matter than ordinary visible matter in our universe. But how do we know that dark matter exists?
Dr. Vera Rubin and Why Dark Matter Matters
Because of Dr. Vera Rubin, dark matter became a household term in the 1980’s, but we still aren’t sure what it is or even if it really exists.