Why is the ozone hole over the South Pole, rather than above the equator or spread around the globe?

—Maureen Purvis, Carrboro, North Carolina

Only above Antarctica will you find a 150-mile-per-hour wind cycle called the polar vortex that lasts the entire four-month Antarctic winter, keeping high-altitude temperatures in the frigid 120- to 140-degree-below-zero-Fahrenheit range. Such frigid temperatures produce stratospheric clouds that act like a net to trap enough ozone-depleting toxins to destroy 60 percent of the area's ozone annually. (While the Arctic is chilly enough to produce a more volatile polar vortex and occasional stratospheric clouds, Arctic Circle ice and landmasses like Greenland influence weather patterns that disperse the clouds before the ozone damage becomes too great.) The process works like this: Chlorofluorocarbons (chlorine-producing gases), most of which are released from air conditioners, cleaning solvents, and refrigerators, rise into the earth's lower atmosphere. These gases are blown towards the equator, where tropical winds spout them up like a fountain 50,000 feet above the earth, and even stronger winds carry them toward the poles. There, the sun's ultraviolet rays react with the cloud-trapped compounds, releasing radical chlorine atoms, which cause a series of chemical reactions including the breakdown of ozone molecules (0₃) into oxygen (0₂) and chlorine monoxide (C_1O). The result is a patchier ozone layer above Antarctica spanning 9.8 million square miles, allowing harmful ultraviolet rays to penetrate the stratosphere. Come spring, the thinned ozone moves north, and a new hole appears the next winter. "Think of the atmosphere as a bucket of white paint and the ozone hole as a red dollop in the center," says Paul Newman, a NASA atmospheric physicist. "Stir, and it comes out pink."

Is wool a moth's favorite food? What nutritional value does it offer them?

—Greg Silverman, Minneapolis, Minnesota

Of the 10,000 or so known species of moth in North America, only three dine on wool: the webbing clothes moth, the casemaking clothes moth, and the carpet moth. They do so during their larval stage as caterpillars to load up on their main dietary requirement: a protein called keratin that's found in hair, feathers, hide, silk, and your now-holey favorite ski sweater. (Most of the continent's other 9,997 moth species subsist on flower pollen and tree leaves, as well as cotton, corn, and tomato plants.) It's a primal appetite that entomologists trace back 50 million years, to a time when this trio of picky eaters lived in damp underground caves and got their keratin fix from the skin and hair of bat carcasses. As soon as humans started building houses with dark, musty cellars and closets stocked with wool and leather boots, it was only natural for moths to move the feast indoors.

Is it true that a fungus is killing off all the chocolate plants in South America?

—Ellie Anna Hoffman, Duluth, Minnesota

First, a few clarifications: Chocolate per se doesn't grow on trees. But cocoa—the small, dark bean we have to thank for hot fudge and chicken molé—does, and in the past ten years some five to six million cocoa farms have suffered serious declines in production. Second, cocoa farming is not strictly a South American affair. The Ivory Coast is the world leader in domesticated cocoa crops (yielding half of the three-million-ton-per-year global supply), followed by Ghana, Indonesia, Brazil, and Nigeria. That said, the devastation comes courtesy of three aggressive fungi. Witches' broom, which sends a spray of orange shoots into the plants' stems, infiltrating every bean pod, has reduced production 70 percent in Brazil over the past 15 years. Frosty pod rot, prevalent throughout South America, produces white spores that devour the cocoa bean's interior like termites, and Indonesia's nefarious black pod rot spawns growth-thwarting cankers on a tree's trunk. On the sweeter side, the fungi's effects are being combatted by pruning diseased trees, spraying them with fungicides, and breeding resistant cocoa trees—tactics that make a global chocolate crisis an unlikely scenario.

Is the "second wind" for real?

—Julia McCunn, Minneapolis, Minnesota

This question rates up there with "Why do athletes cramp?" as one of the great mysteries of sports physiology. That's because the second wind—a burst of energy that kicks in after a period of fatigue—seems to be brought on by subjective factors (like finding a comfortable pace in a training run or hearing the roar of cheering crowds during a race) that are nearly impossible to replicate in a lab. "We could test an athlete forever," laments Jeff Potteiger, director of the University of Kansas's Human Performance Laboratory, "and he might never get a second wind." Even so, there are a few popular theories. One defines second wind as what happens when you're warmed up and in your aerobic groove; it typically takes 20 minutes for your heart rate and blood flow to speed up enough to meet your muscles' increased oxygen demand—at which point your heart, lungs, and muscles begin working together with maximal efficiency. Other experts attribute it to an increase in the release of beta endorphins—protein compounds that block pain and fatigue and give the body that enviable euphoric feeling.   

Illustration by Rick Sealock

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