Where Are They?

The universe should be teeming with life, so where is everybody else? This mystery is known as the Fermi Paradox, after the nuclear physicist Enrico Fermi. In our search for answers, we interview top astronomers, biologists, philosophers, and science-fiction creators. We investigate possible evidence of alien life, from strange clouds on Venus to unidentified signals from deep space. And we prepare for the possibility: If we ever make contact, how will we talk to ET?