¿ìè¶ÌÊÓƵ

THE Sun may be sending asteroids careering towards Earth. Normally these
cosmic boulders sit comfortably within the asteroid belt. But no one is quite
sure why so many sometimes sneak off into orbits bound for Earth. Now William
Bottke’s team at the Southwest Research Institute in Boulder, Colorado, points
out that as the spinning asteroids warm up on their sunward side, they lose the
heat again on their dark side. Computer simulations show that over hundreds of
millions of years, the radiated energy could be enough to nudge the rocks off
course (Science, vol 294, p 1693).