Longevity or "L" is the last term in the Drake Equation, a formula designed to estimate the number of communicative civilizations in our galaxy.

CNN: Should we fear space aliens?

And while out in the San Francisco Bay Area, we swing by the SETI institute to find out how the organization is actively looking for extraterrestrial life in the universe, including a discussion with SETI founder and developer of the Drake Equation, Frank Drake.

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