Building a Space Ark | How the Universe Works

Humans must expand to other planets and that requires building a spacecraft capable of crossing interstellar space. The craft will have to house thousands of people, and it’s too big to be built on Earth. | For more How the Universe Works, visit http://science.discovery.com/tv-shows/how-the-universe-works/#mkcpgn=ytsci1 Catch all new episodes of HOW THE UNIVERSE WORKS Wednesdays at 9/8c on Science Channel! Subscribe to Science Channel! | http://www.youtube.com/subscription_center?add_user=sciencechannel Check out SCI2 for infinitely awesome science videos. Every day. | http://bit.ly/SCI2YT Download the TestTube app! | http://testu.be/1ndmmMq