Olaf Hajek

A: "You can sleep while you're walking," says Jerry Siegel, a psychologist at UCLA's Sleep Research Center, "but of course, you can't get REM or restful sleep." In other words: Yes, worry about walking off a cliff at the end of a long hike; no, you can't trek the whole AT in dreamland. EEGs show that during a groggy state called microsleep, activity in the cortex momentarily slows down and then seconds later speeds up to normal. Your brain goes offline, online, and then offline again. Ultimately, however, after prolonged periods of semiwakefulness, your fatigued body and brain will agree on the need for deep sleep—crucial for restoring muscles, organizing memories, and regulating moods—and you'll simply conk out. People can delay microsleep and the impulse to rest by exerting themselves (think of adventure racers), but, as Michael Perlis, director of the University of Rochester's Sleep Research Laboratory, points out, if you were strong enough to run on adrenaline for weeks, you'd be terminally fit: "Total sleep deprivation is probably fatal."

Q: Are there mammals besides humans that do not naturally know how to swim?
—Karen Stewart, Meridian, Idaho

A: Well, scientists would argue that humans do innately know how to swim. Most infants are capable of flailing their arms and legs enough to keep their heads above water for at least a short time. "Babies don't swim very well because their motor skills are not fully developed," admits Frank Fish (pure coincidence), an expert on the energetics of swimming at West Chester University. "But all humans have a layer of fat, smooth skin, and the ability to breath-hold"—attributes that make us quite aquatically suited. Similarly, most four-legged mammals can turn their walking strides into an ungainly dog paddle if necessary. The notable exceptions are giraffes and apes. The reason for the giraffe's inability to swim is painfully self-evident: Like a keel without a hull, the long-necked creature simply cannot stay upright in water. Orangutans, gorillas, and their ape relatives, meanwhile, will ineffectually thrash around in deep water or simply gurgle and sink. (After more than half a dozen accidental ape drownings in the last decade, modern zoos have caught on and surrounded their moats with electric fences.) Of course, there is little scientific data on this apparent evolutionary oversight. "Throwing a chimpanzee in the water and watching it drown is not the sort of experiment we like to do," says Fish.

Q: How much does the earth weigh? Does anybody know?
—Deborah Hardt, McGrew, Nebraska

A: Technically, the earth weighs nothing, thanks to that old scientific chestnut that defines weight as a measure of the earth's gravitational pull on another mass. The real question is: How strongly is the earth and its terrestrial matter attracted to itself—or, more simply put, what is the earth's own mass? The answer is incomprehensibly huge and impressive enough to toss out with great effect at cocktail parties: 5,972 sextillion metric tons. In pounds, that would be 13,160 followed by 21 zeros. The figure only came to light a year ago as a bonus factoid while Jens Gundlach, a University of Washington professor of physics, was busy solving a different mathematical conundrum altogether: finding the precise value of the 300-year-old unknown called Newton's Gravitational Constant. How'd he do it? The calculations are about as unfathom-able as the figure itself, so let's just say he used gold-plated Pyrex dishes, stainless-steel balls, a host of microcomputers, a pen, a notepad, and a cranium full of brains. "The last equation took about ten seconds," boasts Gundlach. "I just did it on a piece of paper." OK, next time how about the weight of the atmosphere?

Q: Twice I've seen winged red ants streaming out of their anthills, and twice I've smelled something really sweet in the air. What was it?
—Susan Popovitch, Simsbury, Connecticut

A: "I couldn't be sure without knowing the kind of ant," says Harvard University professor of science Edward O. Wilson, author of The Ants and Journey to the Ants, who is reluctant to guess which of the 150 species of wood ant you may have seen. "But it's not uncommon for red worker ants to release chemical substances during the queen's nuptial flight." The citronella-scented pheromone he's referring to is secreted for a wide variety of reasons: to show coworkers the way to a food source, to sound alarms when the queen is threatened by an enemy, and to enhance sexual attraction. Indeed, ants of all kinds use hundreds of odoriferous pheromones—most of which are expelled in such tiny quantities that human noses can't detect them—to communicate nearly everything. For example, when some ants die, they secrete a funereal incense called oleic acid, thus alerting their cohorts to remove the body from the nest. Virgin queens attract males of the same species with parfum de 2-5-dimethyl-3-isopentylpyrazine. And if the ants are streaming out of those hills to bite or sting your legs, you've probably crushed their home and someone signalled "Charge!"—with a blast of 4-methyl-3-heptanone.   

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