Sonicsaurus? Dino's tail made big bang


Q. What makes a bullwhip's tip crack like a gun? (Brontosaurs, take note.) –L. LaRue

 A. The undulation traveling from the handle toward the end of the whip reaches supersonic velocities, unloosing a sonic boom (like a plane breaking the sound barrier or a bullet from a gun), says University of Arizona mathematician Alain Goriely.

Whips are specially designed for their flexibility (kangaroo leather preferred) and tapered so an initial impulse of moderate speed can easily accelerate to supersonic velocities within a few feet– "roll 'em out rawhide," as oldtime bullwhippers prodded cattle onward.

The first scientific proof of this supersonic motion came from Zephyrin Carriere in 1927, using high-speed digital photographs to show the tip reaching near Mach 3 (3 times the speed of sound in air).

Curiously, the tail of Brontosaurus had a length and shape suggestive of its being able to crack in the air, says Goriely. Some computer simulations have indicated this possibility. But could its bone structure have withstood such a supersonic flagellation?

"This may be an amusing topic of scientific controversy for many years to come," he says.

Q. Do rainbows look the same on other planets in our solar system? -J. Garland

A. The recipe for an Earth rainbow is sunlight interacting with liquid water droplets in the air, creating red at one bow's end, violet at the other, green in the middle, says California Institute of Technology cosmochemist and planetary scientist Geoffrey A. Blake. Ice crystals also scatter light, but not with the same brilliant colors.

So, if there were liquid water in the atmosphere on other planets, the answer would be yes. Venus has clouds of a water/sulfuric acid mix, and they might well generate rainbows if you are at an altitude where direct sunlight is available. This is not so on the Venusian surface.

The atmosphere of Mars is too dry and thin for liquid water to be stable for long, but if the gulleys recently discovered there are indeed due to liquid water, then rainbows might briefly exist on the "red planet." On very cold moons like Titan (Saturn) or Triton (Neptune), there may be liquid organics that behave much like water.

"Beautiful rainbows are a universal phenomenon on planets with liquid water."

Q. Thousands of senior citizens have had total hip-replacements, with metal parts. Is it possible they could be a target for a bolt-out-of-the-blue (lightning strike)?– G. Erlich

A. Groundless is the way to describe these fears, says New Mexico Tech physicist Richard Sonnenfeld. The human body is already a good grounded conductor, 90 percent water and loaded with salt, no hardware needed. Only if the concerned seniors were somehow wearing their metal hips or limbs on their head like a hat, then the sharpish metal (limb especially) would enhance the surrounding electric field and could entice a strike.

In actual fact, should a strike occur, the metal might provide a lower-resistance path to ground and spare delicate tissues. "More realistically, being soaked by rain so the current flows over clothes and skin is a common life-saver," says Sonnenfeld. Main real fear from implants is the lightning-like speed with which security will descend upon them if they trip the metal detectors at airports.

Q. Which word in English has the most definitions? –J. B. Hingeley

A. Get set to answer this and, yes, that's the answer: "Set." This short word has some 450 definitions in the 20- plus-volume Oxford English Dictionary (OED), says the online Others in the running are run estimated at 400, go: 370, take: 340, stand: 330, get and turn: 290, put: 270, fall: 260 and strike: 250.

"Set" has so many meanings and nuances that its listed definitions and sample usages run longer in counted words than Ernest Hemingway's novel The Old Man and the Sea. You can set a precedent, set to music, set an emerald in a pendant, set bail, set sail, set store by, set up shop, set someone straight, set the stage for, set up housekeeping, set aside a conviction, watch the sun set, set about solving a problem, set forth ideas, set foot in, set off for Europe, hope swindlers don't set you up... the list runs on so long we have to run just now.

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