Enjoy the amazing Planet Earth footage of polar bears, since the incredible animals might be even harder to find in the coming decades. The U.S. Geological Survey announced on Friday that by the year 2050, thinning sea ice in the Arctic will cut the polar population by two-thirds.

The problem is that the bears will lose 42 percent of the territory they roam in the summer, which is when they hunt and breed. Only 16,000 bears remain today, and there won't be any left in Alaska by the century's midpoint.—Gregory Mone

Californians living in fear of the "Big One"—and Californians living in denial about it—should check out these new computer simulations of the 1906 San Francisco earthquake. Seismologists from the U.S. Geological Survey unveiled these very cool, highly detailed computer simulations that show the seismic waves propagating outward from the epicenter, which lies offshore from San Francisco, and all across the Bay Area. Download the movies here and be sure to watch one of the closeup simulations, say, of downtown San Francisco. According to the USGS Web site, the colors and shading indicate the maximum shaking intensity at each location and the current shaking at the time, noted in seconds on each movie frame. Scary. —Eric Adams

We all know why North American birds fly south in the fall. But why don't they simply stay in their lush southern surroundings year-round?


George Peer
Mississauga, Ontario, Canada