17:30
Why We are Alone in the Galaxy | Marc Defant | TEDxUSF
16:34
Einstein Was Right: Gravitational Waves 101 | Rainer Weiss | TEDxNatick
24:02
Is Time Travel, Especially Into the Past Possible? | Matt Szydagis | TEDxSchenectady
16:06
Cosmology and the arrow of time: Sean Carroll at TEDxCaltech
18:00