Climate Central: As teaching moments go, it doesn't get much better than this. NASA scientists have known for nearly a year that a small asteroid called 2012 DA14, about 150 ft. across, would whiz past Earth at the nail-biting distance of 17,000 miles or so -- significantly closer than the 22,500-mile altitude occupied by geosynchronous satellites. It happened right on schedule on Friday morning, with no consequences at all for Earth.
But nobody had a clue that a space rock about a third as large would scream...