Gazing up at the night sky is simultaneously humbling and utterly thrilling. This hour, we’ll hear from TED speakers who share an infectious sense of wonder and curiosity about our place in the universe and what lies beyond our skies.

Physicist Brian Greene explains how the prevailing theories about the fabric of space changed dramatically in the last century — twice. The most recent shift in thinking came about from a strange mistake, and revealed hidden truths about the nature of our universe. Later in this episode, Greene talks more about why this discovery hints at the existence of other universes.

What's six miles wide and can end civilization in an instant? An asteroid — and there are lots of them out there. Blogger Phil Plait explains all the ways asteroids can cause great destruction, and what we must do to avoid them.

Astronomer Jill Tarter wants to know if we're alone in the universe. She's spent her career hunting for signs of sentient beings elsewhere in space and explains why searching for cosmic company is important to the entire human race