Health & Science

How Jupiter got its new spot; Explaining the size of raindrops; Why the jockey crouch wins; How moths ‘jam’ bats’ sonar; Don’t take the moving walkway

How Jupiter got its new spot

Had it collided with Earth, the comet or meteor that crashed into Jupiter last week would have wiped out human civilization. But on the giant gaseous planet, the impact merely created a new scar in its multicolored atmosphere. Jupiter, the largest planet in the solar system, has an orbit that puts it at a minimum of 390 million miles away from Earth, about four times as far as we are from the sun. Its new blemish was first detected by Anthony Wesley, an amateur astronomer in Australia, who saw “something that wasn’t there when I last looked two days before,” he tells Discovery News. He alerted professional astronomers by e-mail, and they confirmed the sighting with high-power telescopes. The spot, which has since grown and changed shape, was roughly the size of Earth—but just a small mark on Jupiter’s massive face. Astronomers believe a comet or meteor, perhaps a few hundred feet across, crashed into the planet, exploding like a bomb when it hit the swirling Jovian atmosphere. “If anything like that had hit the Earth it would have been curtains for us,” says Wesley. Indeed, if not for Jupiter, the smaller, inner planets would likely be hit more often. Jupiter’s massive gravitational pull attracts comets and stray chunks of space debris from the outer solar system that might otherwise stray into our neighborhood. “We can feel very happy that Jupiter is doing its vacuum-cleaner job and hoovering up all these large pieces before they come for us,” Wesley says.

Explaining the size of raindrops

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The average rainstorm serves up a surprisingly wide array of raindrops, from fine droplets to chubby plops. What accounts for the variety? The standard explanation was that raindrops collide as they fall from clouds, breaking into smaller drops or combining to form those big plops. But the truth is simpler and more elegant, a pair of French investigators has discovered. With high-speed video, they recorded water falling through the air. The drops start off as little spheres, but are quickly flattened by air resistance and then inflated, like parachutes. Continued air resistance then bursts the parachutes into myriad droplets of varying size—a process that takes place in a fraction of a second. “Each drop breaks up individually, independently of its neighbors, on its way to Earth,” Emmanuel Villermaux tells Australia’s ABCScience. The original drops may start off at 6 millimeters across, but after breaking up, they range from 1 millimeter to 4 millimeters.

Why the jockey crouch wins

The ubiquitous “monkey crouch” of the modern jockey transformed horse racing when it first appeared a century ago; race times have since improved by roughly 6 percent. Now scientists know why. Biomechanics researchers at the University of London’s Royal Veterinary College attached motion sensors to the saddle and the jockey’s belt as horses were run through their training. These revealed that as the horse moves up and down in its gallop, the jockey isolates himself from the motion by remaining in his crouch. The horse, in turn, is spared the effort of lifting the jockey’s weight every time its back moves up. That saved energy translates into faster times. But maintaining that crouch is “very hard work,” co-author Alan Wilson tells; a jockey’s heart rate can rise to 190 beats per minute. “It’s a bit like skiing moguls.”

How moths ‘jam’ bats’ sonar

Bats are famous for catching insects via sonar, emitting clicks and then listening for the echoes much like submarines on the hunt. Now, biologists have found the first conclusive evidence of sonar “jamming” in nature, says National Geographic News. Wake Forest University researchers studied tiger moths, which, like many night-flying moths, have evolved the ability to hear bat sonar. Tiger moths, native to an area from Colorado to Central America, emit a rapid burst of high-pitched clicks that appear to baffle their predators. With high-speed video, researchers observed big brown bats pursuing and missing tiger moths in an enclosed space, as the moths’ high-frequency sounds—450 clicks in one-tenth of a second—interfered with the bats’ echo-location system. “It demonstrates a new escalation in the bat-moth evolutionary arms race,” said researcher Aaron Corcoran.

Don’t take the moving walkway

Most modern airports are equipped with “travelators,” those long, moving walkways intended to speed you and your luggage through the crowds to your departing flight. If you’re in a rush, skip ’em, says New Scientist. Princeton researchers found that on a travelator, you’re likely to slow your walking speed to about half the speed of the walkway, to conserve energy and make better sense of the disorienting information arriving from your eyes and feet. As a result, you’ll barely travel faster than unaided walkers—and only if you have no baggage and there’s no one ahead of you. When the moving walkway is crowded, you’ll go considerably slower than if you just walked, says Seth Young, an Ohio State researcher who has also studied travelators. “Moving walkways are the only form of transportation that actually slow people down,” he says.

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