Why We are Alone in the Galaxy | Marc Defant | TEDxUSF
17:51
UFOs and Aliens – What Science Says | Donald Prothero | TEDxResedaBlvd
14:22
Beyond the singularity: The search for extraterrestrial technologies | Andrew Siemion | TEDxBerkeley
20:10
The Unusual Earth Orbit Circling Above Our Ancient Past | Roger G. Gilbertson | TEDxColoradoSprings
17:59
What if Everything You Know is Wrong: Bob McDonald at TEDxVictoria 2013
16:06
Cosmology and the arrow of time: Sean Carroll at TEDxCaltech
17:33
Artificial Intelligence: it will kill us | Jay Tuck | TEDxHamburgSalon
14:59
I've studied nuclear war for 35 years -- you should be worried. | Brian Toon | TEDxMileHigh
15:48