Former intelligence official Richard A. Clarke says that Earth is virtually defenseless against incoming asteroids, and that an asteroid large enough to level a city could strike with almost no warning. “We do not have a plan for dealing with that,” Clarke says in Episode 334 of the Geek’s Guide to the Galaxy podcast. “We don’t have a rocket or a missile we can fire up right now, certainly not on 48 hours alert, but not even on six months alert.

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