Ep. 6: The Story of Dark Matter

"How do we know that dark matter is there?" In this episode, Dr. Katie Mack and John Green unpack the full story of dark matter. Head to https://policygenius.com/crashcourse to get your free life insurance quotes and see how much you could save. This show is a production of Complexly. If you want to help keep Crash Course free for everyone, forever, you can join our community on Patreon at  http://www.patreon.com/crashcourse