Stealth bugs

Q: How do insects successfully evade attacking bats? Do bats do as well avoiding stealth fighter planes? ­-V.T. Impaler

 A: From the fossil record, bats have been using sonar stalking for at least 50 million years, so bugs have had time to evolve defenses, says Dartmouth's Howard C. Hughes in Sensory Exotica: A World Beyond Human Experience.

Certain moths can detect when a sonar beam has found them; then, off they fly at a sharp right angle to the approaching bat. If a similar maneuver doesn't succeed for a green lacewing, it "freezes" its wings and drops straight from the sky. These seem to work, says Hughes, as zoologists estimate insects with sophisticated sonar detection are only half as likely to fall prey to bats.

Jamming the bat's receiver is another option, i.e., adding confusion with counter-signals. Or some un-tasty insects may use ultrasonics to advertise their presence so as not to be mistaken for a more desirable morsel.

Too bad that bugs haven't hit upon a form of "stealth" technology, becoming undetectable by bat signals. This has been so successful for military aircraft, rendering them "invisible" not only to radar but bio-sonar as well, that the "U.S. Air Force discovered stealth fighters left outside overnight were often littered with injured or dead bats that had apparently flown into them during the night!"


Q: Could a skydiver survive if her chute failed and she fell two miles onto terra firma? If another diver were nearby, could two people ride to safety on the same chute? –Gravity granny

 A: A Cleveland diver hit a pocket of air turbulence, became entangled in her own parachute lines, then fell 10,000 feet onto a swampy field. In spite of serious injuries, she lived to jump again a year later.

A couple of things helped save her: her trailing unopened chute likely acted as drag to reduce her "terminal velocity"– the point where gravity and air friction offset each other and no further acceleration occurs. For a free falling person this might be 100-200mph, depending on weight, body shape, and positioning.

Another key factor was that her fall was not broken suddenly– a "hard landing" would have subjected her to tons of lethal force. Instead, her stopping was spread out over a longer time by her crashing through some tree branches and sinking into mud. (She made a hole more than a foot deep.) Thanks to this, the impact force on her was reduced.

As for linking up with a companion diver for rescue, this would be tricky, say Joshua Piven et al. in The Worst- Case Scenario Survival Handbook. Diver A (in trouble) must signal fast, before Diver B's chute has opened, then A could hook arms through B's chest straps or harness, and hold on for dear life. Preparation must be for a mighty jolt, 3-4 times normal body weight G-forces when Diver B's chute opens, probably enough to dislocate or break the arms.


Q: Could a top Olympic sprinter beat a racehorse? B. Baffert

 A: What distance? Track superstar Jesse Owens took part in an exhibition in 1936 where he edged out a horse over a 100-yard course, helped by the thoroughbred's momentary fright at the starting gun going off near its ear.

Plus, from the biomechanical standpoint, it takes the horse longer to gain speed because its mass is much greater, says sports scientist Gideon Ariel. So over the first 50 meters (of a 100-meter race), the human sprints ahead, but over the last 50 meters the horse closes the gap. For the full 100 meters, the time is about the same.

"But over 200 meters, the horse will beat any human to date." (Approximate top speeds: 43mph vs. 27)


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