Imagine that an astronaut goes through a space-time warp, bringing him home after 250 million years have passed on Earth. Continents are unrecognizable and every trace of mankind has vanished. To envision what this spaceman would see, experts travel around the world rediscovering our past in order to make predictions about the future. Asteroid collisions, glaciations and sudden volcanism are what created our present world. What natural forces may be responsible for our demise?