In our last episode, Dr. Katie Mack and John Green discuss what the ultimate fate of the universe might look like. 

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In this episode, Dr. Katie Mack gives John Green an idea of what to expect for the future of our universe. 

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In our journey through the history of the entire universe, we have finally reached the present. Before we continue moving forward in our timeline, John has some questions for Katie that he's been holding back. 

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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 

In this episode, Katie Mack and John Green discuss why life was able to happen. 

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In this episode, Katie Mack and John Green discuss the wonder keeping the stars apart... dark energy.

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"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.

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In this episode, John and Katie take a break from talking through the universe's timeline to focus on a mystery of our cosmos: black holes.

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"Is free will still in the equation?"

In this episode, the universe begins to become visible to itself. Dr. Katie Mack teaches John Green about the moment the stars turned on, while John seeks to answer one question... do humans matter to the universe? 

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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 

"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.

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"That?s why we?re here. Something broke."

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In episode 2 of their journey through the history of the universe, Dr. Katie Mack and John Green discuss the fundamental forces of nature, the tiny ovens we know as particle colliders, and how we all can exist.

"Part of me was there?" 

Dr. Katie Mack teaches John Green about the beginning of the Universe - including that we are not just made of stardust; we are also made of Big Bang stuff, with pieces of us directly born in the vast, first cacophony.

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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 

Join Dr. Katie Mack, a theoretical astrophysicist, and #1 New York Times bestselling author John Green as they walk through the history of the entire universe - including the parts that haven?t been written yet. The Universe debuts on April 24th.