8 ways the world could suddenly end: Stephen Petranek at TEDxMidwest
17:30
Why We are Alone in the Galaxy | Marc Defant | TEDxUSF
17:59
What if Everything You Know is Wrong: Bob McDonald at TEDxVictoria 2013
24:02
Is Time Travel, Especially Into the Past Possible? | Matt Szydagis | TEDxSchenectady
20:29
Why I changed my mind about nuclear power | Michael Shellenberger | TEDxBerlin
20:10
The Unusual Earth Orbit Circling Above Our Ancient Past | Roger G. Gilbertson | TEDxColoradoSprings
22:14
Crows, smarter than you think | John Marzluff | TEDxRainier
14:59
I've studied nuclear war for 35 years -- you should be worried. | Brian Toon | TEDxMileHigh
17:42