The Wild File

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Q) Will the earth's interior ever cool off completely?

J.T. Leeson, Franklin, TN

A) Yes, but probably not before the sun becomes a red giant and swallows our planet, about ten billion years from now. In the meantime, things will get gnarly here on Earth Island. According to Paul Asimow, a professor of geology and geochemistry at the California Institute of Technology, the earth's outer core—a layer of liquid iron surrounding the solid inner core—is cooling and solidifying every year. Since the dynamo effect caused by the core's movement gives the earth its magnetic field, that field will eventually be gone. This is bad news for humans, because the field repels intense radiation from the sun that, if unimpeded, would cause skyrocketing cancer rates. Another dire consequence: The globe's upper mantle will cool and harden, making magma generation almost impossible, which in turn will lock up plate tectonics and put an end to volcanoes and earthquakes. That may sound good, but it's awful: Without these processes, new continental crust will stop forming and the continents will erode into the sea. Eventually, the entire earth will be covered with water. "Yes, the news is ultimately bad," says Asimow, not so soothingly. "But you already knew that."

Q) What is the world's tallest iceberg?
Mark Gaspard, Tennessee Colony, TX

A) Scientists obviously don't spend enough time rappelling down icebergs with measuring tapes in hand, because nobody knows. An iceberg's remoteness and constantly changing size make this a very elusive factoid. "But we do know," offers Greg Rose, of the National Ice Center, a government agency that tracks sea ice for commercial and defense purposes, "the tallest iceberg ever officially recorded." That was an unnamed 1957 beauty spotted just off the coast of Melville Bay, Greenland. From the surface up (about seven-eighths of a berg remains hidden underwater), it was 550 feet tall, or roughly one George short of the Washington Monument.

Q)Why are parrots such astounding mimics?
Kris Trotter, Middleton, NB, CANADA

A) Parrots, macaws, and cockatoos have proportionally bigger brains than other birds, as well as exceptional hearing, so they're simply better at discerning subtleties in human speech. Their vocal apparatuses and muscular tongues also make them better than other tweeters at producing human-like sounds. What evolutionary benefit do they gain from their chatterbox talents? According to Tim Wright, a zoologist at the Smithsonian National Zoo, in Washington, D.C., parrots' talkative ways are handy in the jungle, where members of flocks tend to get isolated from one another. Wright says parrots have distinct "languages" that help them identify friends and significant others (parrots are monogamous), but they also can mimic other parrots to increase their chances of integrating into new flocks if the need arises. As for their favorite topic, Wright believes it's office politics. "They talk about who's in charge and who are the peons," he says.

Q) What percentage of the U.S. is paved?
Jessica LeClair, Windsor Locks, CT

A) If you count only roads, says Richard Forman, a Harvard professor of landscape ecology, the number is 0.6 percent, an area roughly half the size of Virginia. If you throw in parking lots, sidewalks, building foundations, and all other "impervious surfaces," the number doubles to about 1.29 percent. That figure may be lower than you expected, but the local effects of too much hardtop can be huge, particularly on the weather. A 1999 NASA study of Atlanta showed that the city's overpaved center has created a "heat island" where daily summertime temperatures can average eight degrees higher than usual and thunderstorms can occur in the morning—an event almost unheard of before ten-lane highways came along.

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