Stanley A. Rice on Carl Sagan

“As astronomer Carl Sagan thought about what Fermi said [Fermi paradox], he began to be alarmed. ...This could only mean that advanced civilizations destroy themselves before they get that far, a viewpoint Sagan published in 1966.”

“Sagan's first wife, Lynn Margulis, was one of the principal architects of the Gaia Hypothesis. Put their viewpoints together, and the conclusion you would reach would be that nuclear war could have a significant enough effect that it could even kill Gaia.”