Though not a new phenomenon, flat Earth theory has enjoyed a huge resurgence recently. A YouGov poll indicated that a third of Americans aged 18 to 24 were unsure of the shape of our planet, in spite of scientific proofs from Pythagoras to Nasa. Why has this happened now, and what does it tell us about society today? Subscribe to The Guardian on YouTube ► http://is.gd/subscribeguardian Today in Focus podcast ► https://www.theguardian.com/news/series/todayinfocus Support the Guardian ► https://theguardian.com/supportus Sign up for the Guardian documentaries newsletter ► https://www.theguardian.com/info/2016/sep/02/sign-up-for-the-guardian-documentaries-update The Guardian ► https://www.theguardian.com/ The Guardian YouTube network: Guardian News ► http://is.gd/guardianwires Guardian Football ► http://is.gd/guardianfootball Guardian Sport ► http://bit.ly/GDNsport Guardian Culture ► http://is.gd/guardianculture #flatearth #conspiracy #globeearth #nasa #pythagoras #science