Is there more than one universe? Physicist Brian Greene shows how the unanswered questions of physics (starting with a big one: What caused the Big Bang?) have led to the theory that our own universe is just one of many in the "multiverse."
The SETI Institute's Jill Tarter wants to accelerate our search for cosmic company. Using a growing array of radio telescopes, she and her team listen for patterns that may be a sign of intelligence elsewhere in the universe.
What's six miles wide and can end civilization in an instant? An asteroid â€” and there are lots of them out there. With humor and great visuals, Phil Plait enthralls the TEDxBoulder audience with all the ways asteroids can kill, and what we must do to avoid them.