"Armageddon" Giant Asteroids Potential Threat to Earth - It's Closer Than You Think (Video)

Heads Up! No Major Asteroid Impacts With Earth Since 2001 Were Detected In Advance http://www.forbes.com/sites/ericmack/2014/04/05/heads-up-no-major-asteroid-impacts-with-earth-since-2001-were-detected-in-advance/

Ancient Gigantic Asteroid Boiled Oceans, Burned the Sky, and Shook Earth for a Half-Hour http://www.wired.com/2014/04/giant-asteroid-impact/

The 1908 Tunguska event, when a stony asteroid, about 40 meters in diameter entered the atmosphere over Siberia and exploded over a remote and unpopulated region. Recent work has determined that the explosion was equivalent to a 10 megaton bomb. Had the impact occurred in a more populated region of the planet, say New York or London, millions of people would have been killed without any warning.

What these impact events provide is convincing evidence that being hit by another “big one” is simply a matter of time. How large is a “big one?” What is the average frequency of impact? Why haven’t we seen one in our lifetimes?

http://en.wikipedia.org/wiki/Giant_impact_hypothesis

http://http://en.wikipedia.org/wiki/Near-Earth_object