A new study by a research team from Cornell University’s Carl Sagan Institute suggests we should also look for signs of alien civilizations that have destroyed themselves. It would be a grim task, but the ability to detect extinct civilizations would not only tell us something about the prospect of intelligent life in the galaxy, it might also tell us something about our own fate as well.
“In a way, it doesn’t really matter if we have evidence for living or extinct life,” says study co-author Jack O’Malley-James. “Finding evidence for a civilisation that has destroyed itself still gives us evidence that there is other life out there. Furthermore, looking for the kind of destructive events that could only be caused by intelligent life tells us something about whether intelligent life is out there.”
more here: http://io9.com/how-we-could-detect-an-alien-apocalypse-from-earth-1723355339