Astronomers debate the risks of an asteroid colliding with the earth and how much of society's resources should be devoted to detecting and preventing a collision.

The Bush administration is significantly loosening controls on commercial spy satellites, allowing them to capture images with high enough resolution to show people on the ground and using them as a much greater resource for national security organizations.

Potential deaths and decontamination costs tied to "dirty bombs" ? conventional explosives laced with radioactive materials ? have been underestimated, a prominent researcher says.

"Don't look now, but the ground has shifted on global warming. After decades of debate over whether the planet is heating and, if so, whose fault it is, divergent groups are joining hands with little fanfare to deal with a problem they say people can no longer avoid."