Finding 40,000 Asteroids Before They Find Us

Astronomers have just catalogued the 40,000th near Earth asteroid, a milestone that marks humanity's transformation from passive targets to active defenders of our planet. These space rocks, ranging from house sized boulders to some the size of mountains, follow orbits that bring them uncomfortably close to Earth. Each discovery adds another piece to our planetary defence puzzle, though current surveys have found only about 30 percent of the mid sized asteroids that could still cause regional de