The Wild File


Q) Is it ever too cold to snow?
Peter Haggart, Moscow, Idaho

A) IT'S A POPULAR misconception that it can be too cold to snow. According to Andy Heymsfield, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, the key to getting snow in extreme cold lies in humidity. As long as the temperature is at or below 32 degrees Fahrenheit and the humidity is above 60 percent, says Heymsfield, then ice crystals—tiny dustlike motes of snow—will form inside the clouds and may be pulled to earth by gravity. How can there be humidity (i.e. liquid water suspended in the atmosphere) below the freezing point? Generally speaking, ice crystals form on tiny pieces of dust called ice nuclei. These nuclei lend a structure on which the water can crystallize. However, there are often not enough ice nuclei to go around inside the cloud, in which case the water remains in a liquid state—and can even become supercooled, reaching minus 40 degrees or below. When these supercooled droplets bump up against an existing microscopic ice crystal, the water attaches and finally freezes, forming the large and elaborate crystals we call snowflakes. Is it true that no two snowflakes are alike? Yes and no. But that's a whole other ball of, ahem, snow.

Q) Why aren't there fireflies on the West Coast?

James Becker, Portland, Oregon

A) TO BE PRECISE, about 30 of North America's 200 or so species of firefly live on the West Coast. Surprisingly, only one of those species—the landlubbing glowworm—actually glows. Scientists define a firefly as any insect belonging to the family Lampyridae (lam-PIER-ri-dee), which are slender soft-bodied beetles usually between 4.5 and 20 millimeters long, with mostly concealed heads. In other words, a bug doesn't have to be bioluminescent to be a firefly. Go figure. According to James Lloyd, an entomologist at the University of Florida, Gainesville, scientists know a lot about lightning bugs—for instance, that they light up in order to attract mates and, on occasion, to startle predators—but he's not aware of any rigorous studies on why Photinus pyralis, the most common six-legged lightbulb in the U.S., isn't found west of the Rockies. A widely proposed theory, says Lloyd, is that the snails, slugs, and worms that make up P. pyralis's preferred diet live only in the East; however, he adds that other factors, like humidity levels and soil types, may also be significant. Or it could simply be that non-flashy species already fill the Western biological niche in which P. pyralis would thrive. Until some researcher as curious as Mr. Becker tackles the problem—Lloyd is currently too busy naming several dozen new species to do it himself—Lloyd's guess is the best answer. "The wheels of science turn slow," he admits.

Q) Is it true that drinking hot tea or other beverages in hot weather cools you?
Bonnie Simon, Berkeley, California

A) THE LOGIC BEHIND this old wives' tale is convincing: Hot tea, for example, raises one's body temperature, causing the person to sweat more, especially in summer—with evaporation leading to a feeling of coolness. A similar myth holds that the hot-tea-warmed body signals the brain to dilate blood vessels in the skin, which radiates heat, and the person feels cool. But according to Lawrence Armstrong, professor of exercise and environmental physiology at the University of Connecticut, neither explanation holds water. The laws of thermodynamics dictate that the amount of body heat lost by sweating or radiation will usually equal— never exceed—the amount of heat gained by drinking the hot beverage. The blood-vessel hypothesis is equally flawed, because when blood vessels in the skin release extra heat, heat-sensitive nerves in the skin detect that extra heat and a person will feel flush and hotter. So it's a draw. (Eating ice cream on a cold day is similarly ineffective.) "I've tested this theory on dozens of people, and I've never seen anyone who actually felt more comfortable drinking hot tea in warm weather," says Armstrong. "You may be cooler psychologically, but not physiologically."

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