Jill Tarter, co-founder of the SETI Institute, lists the scientific reasons why it is plausible for other life forms to exist in the Universe.

Michael Summers, Professor of Planetary Science & Astronomy at George Mason University, explains how creatures that survive in extreme conditions on earth give us a broader perspective on what's possible elsewhere.

Jill Tarter, co-founder of the SETI Institute, explains the technology behind artificial looking radio waves.

Jill Tarter, co-founder of the SETI Institute, debates the merits of transmitting signals to outer space. If we receive a response, who speaks for Earth?

Michael Summers, Professor of Planetary Science & Astronomy at George Mason University, wonders if alien life forms may be utterly different from life as we know it.

Jill Tarter, co-founder of the SETI Institute, describes the organization's historical search for extraterrestrial life.