"The only thing that could have happened, happened" In this episode, the universe as we know it starts to come into focus. Dr. Katie Mack teaches John Green about the cosmic dark ages, the possibility of a multiverse, and the connection between the hot, dense early universe and today.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