Make sure you have seen part one on our main channel: https://www.youtube.com/watch?v=c4pgWd8V8HU Professor Elisabeth Werner is based at the Department of Mathematics at Case Western Reserve University. NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile Videos by Brady Haran Support us on Patreon: http://www.patreon.com/numberphile Brady's videos subreddit: http://www.reddit.com/r/BradyHaran/ A run-down of Brady's channels: http://www.bradyharan.com/ Sign up for (occasional) emails: http://eepurl.com/YdjL9