Precipitation: Gold goes and comes

 DRAWING BY DEBORAH DERR MCCLINTOCK

Q. You're a Danish Nobel prize-winning nuclear physicist fleeing the Nazis. You must leave behind your own gold medal and that of a Nobel-winning German friend who left his with you for safekeeping. So, where to hide them? ­R. Stiltskin

A. As German troops marched through the streets of Copenhagen, Niels Bohr dissolved the 8-ounce medals in nitric and hydrochloric acids, one of the few mixtures that will dissolve gold, then after the war precipitated the gold out and had the medals recast, says Sharon McGrayne in 365 Surprising Scientific Facts, Breakthroughs and Discoveries.

Q. How much do you weigh on a roller coaster? How about your terrified brain? ­W. Disney

A. You'll gain apparent "weight" fast at the bottom of a dip after a long hill or while taking an inside loop, pulling anywhere from 3 to 7g's, meaning your 3-pound brain will skyrocket to maybe 20 brain-pounds briefly, says Doug Davis, physicist at Eastern Illinois University.

It better be brief, because these numbers skirt at the edge, where dizziness and blackout are not out of the question. Needless to say, coaster designers try to tease the g's well shy of this.

These are largely downward forces on the brain; the opposite can occur in an outside loop or careening over a hillcrest, where you'll catch "negative g's"– net forces upward. Now the brain is jammed upward against the skull, and fewer g's can be tolerated in this direction.

"Negative g's" over a hilltop is usually a misnomer; half a g (half normal weight) is more like it, so you'll feel some "hang time" without actually being pitched skyward dangerously into the restraining mechanism, notes Davis.

Interestingly, one way NASA simulates zero-gravity for astronauts in training is to fly an aircraft up and down roller-coaster fashion, with hang time (weightlessness) occurring in 20-second bursts at the peaks.

Q. Is it possible for two kids to be full siblings, sharing 50 percent of their genes, without sharing either the same Mom or the same Dad? ­G. Mendel

A. Easy. Take two sets of identical twins A-1 and A- 2, B-1 and B-2. A-1 marries B-1, and they have kids. Ditto A-2 and B-2, making the two couples' kids full siblings, in spite of having neither parent in common.

Q. Cracking an old riddle, which came first, the chicken or the egg? ­E.M. Muffin

A. Here you must be precise with your terms, says Amherst College biologist Paul W. Ewald. If the question is, "Which came first, the chicken or the generic egg?" then it's the egg. The ancestors of chickens were laying eggs long before there were chickens.

If you're asking, "Which came first, the chicken or the chicken egg?" then the answer depends on exactly when the genetic mix that you call a "chicken" first arose: If the last necessary mutation occurred just after egg formation (say during early embryo development), then the chicken came first. But if the mutation occurred in the process of egg formation, then the chicken egg preceded the chicken.

However, any dividing line here between chicken and pre-chicken ancestors would have to be arbitrary. "Most evolutionary biologists prefer to say that both the chicken and the chicken egg evolved gradually together over many generations, in concert from the ancestral chicken and the ancestral chicken egg," Ewald says.

Send Strange questions to brothers Bill and Rich at strangetrue@compuserve.com.

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