Traveling Sharks

The huge shark in "Jaws" liked to hang around Martha's Vineyard. But it turns out that great whites prefer to roam. Marine biologist Peter Pyle attached electronic tags to four great whites off the coast of northern California two years ago. "We kind of had an idea they'd head south to Baja," where there's a feeding ground off the coast, he says. Pyle was shocked to find the sharks heading due west instead, eventually ending up in Hawaii, 2,500 miles away.

The trip has biologists astonished. Since the sharks cruise at a poky 2mph, the journey took months. And there were no snack stops; great whites feed on mammals, not fish. Even in Hawaii, endangered monk seals are few and far between. Why did the sharks make the trip? Reproduction isn't a likely motive: pregnant females have been seen only in the far western Pacific (scientists now suspect these may be the sharks' only spawning grounds). Here's another odd thing: the creatures all seemed to spend a few days at an empty patch of ocean midway between Hawaii and California. Pyle and his colleagues can't figure out why. But he plans to do more tagging to find out where marine predators go and what they do along the way.

SAND PUZZLES

Scientists are always telling us about things we can't possibly understand ("dark matter," anyone?). So why can't they explain everyday things? Consider the sand under your toes. Each grain is shaped slightly differently. Put thousands, millions, billions of them together and they jostle and bump with unspeakable complexity. Ever notice how a pile of sand tends to "avalanche" until it attains a certain slope, which is always the same? Know why? Neither does anybody else.

The more experiments physicists do, the less sand conforms to their expectations. Here's a cutting-edge problem: make one pile of sand with a funnel and another with a sieve. They look almost identical, but they aren't. The pile formed by the funnel has less weight at its center than its edges. The sieve distributes the weight uniformly, mystifying scientists.

LITTLE MONSTERS

Each time your foot sinks into the sand, you're squashing perhaps 30,000 animals. They'd scare your pants off--if only you could see them. Many look like worms or shrimp, but most resemble nothing else on this planet. Tiny Loricifera has two legs, a hairy mouth and a springlike body. It hides in its shell until a bacterium wanders by, then pops up and snatches it. Tardigrade, also called "water bear," has eight legs and sticky pads that cling to dead plants in the sand.

These beasts, called meiofauna, are the smallest of multicellular organisms, about the size of a (single-celled) ameba. They live anywhere there's sand and water. Amazingly, there are as many different species of meiofauna--about 3 million--as of all other earthly creatures combined, says biologist Paul Montagne of the University of Texas. Scientists suspect the creatures form a crucial link in the food chain, but they're only beginning to find out what that might be, and why there are so many different kinds.

Cloudy Thinking

To most of us, clouds are things of drama, romance and whimsy. To Caltech chemical engineer John Seinfeld, they're a cog in Earth's vast weather factory. At the beginning of the assembly line, salt particles escape from ocean waves and waft up to cooler altitudes, where moisture from the air condenses on them. Droplets form, and many droplets make a cloud. But human industry throws a monkey wrench into this process. The air's moisture also gloms onto "organic particles" (soot) from smokestacks, cars and kitchens. And since there's only so much water to go around, clouds form out of a finer mist, Seinfeld says. Such clouds reflect more of the sun's radiation back into space, making the Earth cooler. Pollution, it seems, has an upside: it compensates for warming due to greenhouse gases. Don't pop that cork just yet. Clouds may not produce as much rain. And nobody knows how big the cooling effect will be.

The Perfect Stone

Consider the hours you've spent searching for the perfect skipping stone. If engineers would just tell us what one looks like, we'd find them more quickly, thus increasing fun efficiency. Alas, the physics aren't simple. The stone spins, which is complicated enough, and it strikes water, which adds turbulence to the equation. Surely, though, the rocket scientists at NASA have cracked tougher problems?

We asked the folks at NASA's Langley Research Center in Hampton, Va., about the physics of skipping stones. First stop: the "aeroshell braking" department, the people who can make a spaceship that slows itself down by skimming along the Martian atmosphere. This isn't so much like skipping stones as dragging your feet from your bicycle, they said. Next we tried the "tow tank," a tub of water used to test spaceships that fall into the ocean. NASA dismantled the tow tub six months ago and sent the engineer who ran it back to the Navy. As this article went to press, they were still tracking him down.

Killer Jellies

Every so often, a diver or surfer washes up on some tropical shore, killed apparently by the bends or a heart attack or just plain drowning. Australian scientists now suspect the Irukandji, a tiny jellyfish the size of a peanut, may be a hidden cause. The jelly carries enough venom in its half-meter-long tentacles to fell an elephant. The poison causes savage pain, cramps and nausea--and even death. Two stricken tourists in Australia died earlier this year; hundreds were treated for stings. Warming oceans, which make the jellies grow faster and bigger, and fertilizer runoff, which nourishes them, are creating a global jelly boom. Where will killer jellies show up next?