Will 2012 be the end of the world? Astronomer says threat from space is real

Will 2012 be the end of the world? Astronomer says threat from space is real: "Is it time to start worrying about the apocalypse?

Some say the Mayan calendar portends the end of the world, but others say a threat to Earth could come from space.

Astronomer Chris Impey, writing for The Independent, recently gave us some frightening doomsday scenarios.

Impey said every 100 years or so a meteor crashes into the Earth with the force of a nuclear blast. Every 1,000 years or so, our planet passes through the trails of thick comets that can create firestorm conditions.

After that, Earthlings can look forward to an event that happens roughly every 100,000 years—a large projectile many miles across. If it hit the ocean, it could cause global tidal waves that made the last large tsunami look like an overflowing bathtub."