Observations by NASA's WISE space telescope, for example, suggest that about 4,700 asteroids at least 330 feet (100 m) wide come uncomfortably close to our planet at some point in their orbits. To date, astronomers have detected less than 30 percent of these objects, which could destroy an area the size of a state if they slammed into Earth.
And researchers have spotted less than 1 percent of asteroids at least 130 feet (40 m) wide, according to officials with the B612 Foundation, a nonprofit organization dedicated to predicting and preventing catastrophic asteroid strikes.
Space rocks of this size can cause severe damage on a local scale, as the 1908 "Tunguska Event" shows. That year, a 130-foot-wide object exploded over Siberia's Podkamennaya Tunguska River, flattening roughly 825 square miles (2,137 square km) of forest.
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Overall, scientists think 1 million or more near-Earth asteroids are lurking out there, and just 9,600 have been identified to date.
I suspect we're moving into a more chaotic part of the galaxy. We've been lulled into a false sense of security. The galaxy is full of stuff and fluff, signifying no-thing. But we've been riding through a calm part of it for a long time. Unless of course this is all just a big simulation or hologram or what have you, created by some kid in a far away dimension, just for fun. The kid may have grown bored with this game and is not sweeping away the space rocks.