Do the planets really make a faint "music" that you can hear?

--Rita Sousalous, Davenport, Iowa

It's a beautiful idea, this antiquated notion of the "music of the spheres," but like so many beautiful ideas, it's completely imaginary. The theory, thought to have been originated by Pythagorean mathematicians of ancient Greece, went thus: As the planets whirled around Earth with perfect proportionality and rhythm, their constant spinning motion created an ethereal, heavenly hum--a low-pitched tune audible to the naked ear. The notion endured for centuries: In 1619, German astronomer Johannes Kepler assigned notes and harmonic relationships to the different planets, inspiring classical composers such as Josef Strauss and Gustav Holst to write musical scores based on those notations. Today, of course, we know that the universe is a place of volatility and violence: exploding stars, apocalyptic asteroids, cataclysmic black holes. We can't exactly hear any of this celestial ruckus (it's common knowledge that sound cannot travel in the vacuum of space), but when astronomers train their radio telescopes on the heavens they pick up an endless cacophony of static, clicks, bumps, and fizzes--a discordant world that's more Johnny Rotten than Josef Strauss.

How do deer run so quickly through dense woods without poking out their eyes on branches?

--T. Mascarich, Clifton, New Jersey

"I've never encountered a blind deer," says eminent Canadian deer researcher Valerius Geist of the University of Calgary, "even though many can run nearly 50 miles per hour." There are several reasons why those big, orblike eyes go unscathed. For one, bucks and does don't make a habit of wandering through alien forests, hewing instead to well-trod trails in familiar necks of the woods. In its lifetime, a deer moves over a limited geography, and it comes to memorize every tiny obstacle in its territory. Moreover, deer, being naturally frugal with their energy, rarely run at all unless spooked by a predator. Mainly, though, our ungulate friends are able to avoid blinding arboreal pokes because they're equipped with thick, hardy eyelids and lightning-fast reflexes. "Deer are far superior to humans at detecting minute changes in their environment and then performing precise reactions in a limited time frame," explains Geist. "Among bow hunters, there are well-documented stories of deer spotting arrows in midflight and then blithely sidestepping them. So a little tree branch is not going to pose a problem."

I've heard that scuba diving is bad for your bones. Should I find a new sport?

--Angus Miller, Spokane, Washington

The average scuba enthusiast has little to worry about, but commercial divers who make frequent 100-foot-plus descents have been known to suffer from a crippling affliction known as dysbaric osteonecrosis--or, more ominously, "bone death"--a degenerative condition that can make bones dangerously brittle and cause excruciating pain in the joints. Though the science isn't yet fully understood, here's what we do know: Under pressure, nitrogen is squeezed out of the bloodstream into the surrounding tissues. When a diver rises slowly, the nitrogen is reabsorbed gradually into the blood. Should he ascend too quickly, however, gas bubbles will linger in the tissues, blocking the flow of blood to the bones and resulting in a painful, perhaps fatal, case of the bends. But that's just the short term. Osteonecrosis occurs after lengthy exposure to great depths, when areas of the bone--especially around the knees, shoulders, and hips--start to weaken from lack of blood. Unless the person stops diving altogether, the bone will become prone to chipping or breaking or, in the most extreme cases, will degenerate into severe arthritis. Such is the fate of 20 percent of Maine's commercial scallop divers, a sad and hobbled class of retirees who make Joe Namath look spry.

Why does moss grow on rocks? What's the appeal?

--Carlo Codato, Stamford, Connecticut

In a word, stability. without such an anchorage, moss would be nothing more than a vagrant consigned to tumble in the wind. Hence the plant's brilliant survival strategy of attaching hundreds of its microscopic rhizoids--sticky, Velcro-like hairs--to tree roots, cathedral walls, rocks, or any other stationary object. Once a tuft of moss finds a suitable stone and sets up housekeeping, the acids in its tendrils begin to dissolve the rock, affording the plant a firmer foothold against the elements and providing it crucial sustenance through calcium and other minerals in the stone. "They can get nutrients from windblown dirt, fallen leaves, and dripping water," explains Alan Whittemore, a bryologist at the Missouri Botanical Garden. "Even a rat that comes along and leaves a single dropping can provide a robust meal." Bon appétit.

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