I've heard that space is teeming with death rays capable of destroying all life on Earth. Please tell me this isn't true.
—Angus McMahon, Frankfurt, Kentucky
Last January 23, astronomers working in Los Alamos, New Mexico, captured an event on film that was so mind-bendingly creepy it could have been dreamed up by Arthur C. Clarke: the brightest and most violent explosion ever detected in the history of science, a cosmic detonation whose force was estimated to be second only to the Big Bang itself. Scientists identified it as a mammoth gamma ray burst, an eerie phenomenon first discovered in 1967 and believed to be a gasp of radiation released just seconds before a dying star collapses into a black hole. Thanks to high-tech space cameras, astronomers are now capable of observing one or two GRBs every day. But do these celestial flameouts pose a mortal threat to us earthlings? The easy answer is no: By the time the January 23 megaburst traveled nine billion light-years to reach us, it had diffused so thoroughly that all that was left was a harmless fireworks display.Not so, however, should one of these cataclysms occur right here in our own galaxy. "It would quite simply be the worst natural disaster you could ever imagine," says NASA astrophysicist Peter Leonard. "The rays would destroy the ozone layer and cook the planet in a kind of cosmic sterilization bath, leaving the Earth radioactive for millions of years." According to astronomical models, it's only every 200 million years or so that a dying star collapses close enough to Earth —within 3,000 light-years—to deal us a catastrophic blow. (Some maverick scientists have even begun to speculate that the last one may have killed the dinosaurs.) Happily, the next Armageddon-style burst is probably still millions of years away, but if it arrives early, we likely won't be able to deflect the galactic death rays, much less see them coming. "It's difficult to make out the gun," notes Leonard, "when you're staring down its barrel."
I live at sea level, and when I go climbing in Colorado I get nosebleeds. Why?
—Linda Flegel, Vancouver, British Columbia
A variety of factors conspire to make mountains a bane to nasal cavities. Everyone knows that high-altitude air is extremely dry (thin, cold, low-pressure air holds less moisture) but the subtleties of the schnozz are more complicated:"The skin inside your nose isn't like the skin on your arms and legs," says Dr. Murray Grossan, a Los Angeles ear, nose, and throat specialist. "It's paper-thin and loaded with blood vessels." A few hours in the mountains, and the dry, oxygen-lean air will transform it into a chapped and bleeding mess. Humidifiers and saline spray can be a bloody nose's best friend, but if the problem lingers, consider consulting your doctor: You may be suffering from a deviated septum.
Why are polar bears so mean?
—Dave Cooper, Bermuda
While it's true that the largest land carnivore on earth has been known to dine on hapless Homo sapiens, polar bears don't hold any personal grudges against us. Unlike other bruins, these fierce Arctic roamers stay active in the winter and thusmust consume enormous amounts of high-calorie seal blubber—they can scarf down as much as 10 percent of their body weight in half an hour—to keep their half-ton masses fueled in the frigid temperatures. Because there's not much action on the monochromatic ice pack, they're programmed to treat every movement as a sign of a potential meal. So if you happen to pop up on their horizon, chances are they'll investigate—not a pleasant scenario: They can sprint at 25 miles an hour and have been known to gnaw on seals' heads before feasting, just to make sure they're really dead. Lucky for us, however, fewer than ten people have been killed by polar bears in the past 30 years.
Recently, I saw what appeared to be three suns in the western sky. What was that about?
—Deb McCorvey, Littleton, Colorado
You were the lucky witness to "sun dogs." Also known as parhelia or mock suns, this rare optical effect (thought to be the likeliest explanation behind many UFO sightings) can be seen year-round but is more likely to occur during winter months. In the hour or so after sunrise or before sunset, when the sun is low in the sky, the angled rays can refract through hexagonal ice crystals in high, cold cirrus clouds, causing a shimmery, orange-rimmed duplicate on one or both sides of the fiery orb. "You're seeing images of the sun that have been displaced 22 degrees," explains Margaret LeMone of the National Center for Atmospheric Research, who goes on to offer a savvy explanation of the canine sobriquet. "They seem to follow the sun around like a dog." Legend has it that the Mandan Indians of North Dakota interpreted this dazzling triptych in a more practical way: It's so cold on the Great Plains that the sun lights little fires on each side of it to stay warm.