[Doctor Stochastic]

Meteor hits (with attendant destructions) have happened, as have massive volcanic eruptions (Toba, for example). They're somewhat rare. Throwing the Earth off orbit would take a collision with something big. Gravitational theory shows these things to be extremely rare; like one every 5,000,000,000 years. Running Newton's equations for the solar system backwards does indicate a collision about 4,5000,000,000 years ago. This collision produced the Moon.

[dubyagee]

like one every 5,000,000,000 years. Running Newton's equations for the solar system backwards does indicate a collision about 4,5000,000,000 years ago. This collision produced the Moon.

Geez, looks like we're due for one pretty soon, huh? ; * ) Night, guys...