Q: There are people who can perform the amazing feat of walking barefoot over red-hot coals without injury. Is this a case of mind over matter? –Dr. T. Scholl
A: Actually, physics protects the feet, says Jearl Walker of Cleveland State University. He should know: As a "hands-on" prof, he has shed footwear a number of times to demonstrate fire walking to his students.
The theory: red-hot wood coals, though at a high temperature, contain little energy. So if you quickstep across the bed, little heat gets conducted to the feet. It's like touching a cake right out of the oven. Even at 350 degrees, the cake is a poor heat conductor, so you won't get burned. But don't try touching the metal pan!
A second saving factor is foot moisture. Some firewalkers step through wet grass or pour water on their feet beforehand. Then as the water heats up and evaporates, it absorbs energy from the coals– similar to wetting your fingers to snuff a candle– while also possibly providing brief insulation as it vaporizes into a thin film.
But for his own fire walks, Walker eschewed foot dousing, figuring his fear of injury would stimulate sufficient foot perspiration to protect him. For his first four walks, everything went smoothly. Then on the fifth, Walker got complacent, his fear left him, and his "no sweat" effort got him two very badly burned feet.
Q: Can trees "cry out" in pain to warn other trees of danger? What could the other trees do about it? –P. Bunyan
A: Certain trees under attack by microbes or chewing insects send out airborne alert chemicals that drift over to nearby trees, says Penn State entomologist Jack C. Schultz. Thus signaled, these neighbors produce more tannin in their leaves, making themselves less palatable to the attackers.
A second line of defense is using chemical signals to attract parasites and predators of the attacking insects, as when emitted ethanol brings woodpeckers to home in on bark beetles. "So plants don't only warn each other,” Schultz says, “they also call in friends!"
Q: Bible readers and heavy metal fans know "the number of the Beast" is 666, the devil's number. How would this be written in Roman numerals? –O. Scratch
A: DCLXVI. See the pattern? Here in sequence are the symbols for 500, 100, 50, 10, 5 and 1. So 666 had much the appeal in Roman numerals that a number like 123,456 has today, says Richard Phillips in Numbers: Facts, Figures and Fiction. "It is possible that for the writer of the book of Revelation, 666 was just a convenient large number."
Q: Nervous triskaidekaphobes want to know: How long from one Friday the 13th to the next? –N. Webster
A: Going by computer-crunched perpetual calendar data, there is little respite for the superstitious. At worst, there's but a four-week break, from Friday, February 13, to Friday, March 13, in a non-leap year. This happens when January 1 is a Thursday, as in 1998, next in 2009.
No calendar year is without a Friday-the-13th, and while some have two or three, there are never as many as four. Dreaded triple-threat years are non-leap years beginning on a Thursday and leap years kicking off on a Sunday.
Longest breather is 61 weeks, as from August 13, 2001, to October 13, 2002; then again from 2012 to 2013. Curiously, there are exactly seven (lucky?) possible intervals: four, 13, 26, 35, 39, 48, and 61 weeks.
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