“The Earth has been lawned with life for something over 3.5 billion years. That's a span of time great enough to encompass some honest-to-goodness catastrophe. For example, 700 million years ago, Earth underwent a planet-wide deep freeze, with ice covering the oceans from the poles to the equator.”

American astronomer and author

G. Seth Shostak is an American astronomer and author, best known as the senior astronomer for the SETI Institute. He has spent his career working in astronomy and public discussion of the search for life beyond Earth. His work at SETI places him at the center of research and outreach on extraterrestrial intelligence. As an author and scientist, he often writes and speaks about astronomy, the search for signals from other civilizations, and related questions about the universe.