Get it up: How levitation really works


Q. Levitation– floating in midair as if by turning off gravity– sure looks like fun in magic shows. Is it true a real frog has been levitated? And if a frog, why not you? ­H. Houdini

 A. To the world's amazement, researchers at the Nijmegen High Field Magnet Laboratory in Holland did manage to suspend a frog in midair with a balancing force of magnetism, as close perhaps as we'll get to a sci-fi anti- gravity machine, they said.

The key is diamagnetism, a quantum phenomenon by which it turns out everything from wood to pizza to "frogs and even humans can be lifted by a magnet– providing it is strong enough," says Roger Highfield in The Science of Harry Potter: How Magic Really Works.

All the billions of electrically charged atoms within, moving rapidly about and generating magnetic fields, make a body levitatable. "When the little frog underwent this form of levitation, it looked comfortable inside the magnet and later happily rejoined its fellow frogs in the laboratory."

A hamster too was levitated; and a human spent several hours (nonlevitating) inside the magnet without harm.

To levitate the frog required a field 100,000 times the Earth's magnetic field; a human would need a vast magnet and field many times stronger than an MRI scanner. And adds Sir Michael Berry, wizard of quantum mechanics, since the bodyis not uniform– tissues, bones, etc. have different magnetic properties– we would feel pushings and pullings all over.

"If the magnetic force on flesh is greater than on bone, it would be as though we were held up by our flesh, bones hanging down, a bizarre reversal of the usual and possibly the basis for an expensive type of face-lift."

Still, concludes Berry, "I would enthusiastically volunteer to be the first human levitatee." You too?

Q. World War II statistician Abraham Wald had an assignment: Figure out where to put extra armor on planes to keep them from being shot down. He studied hundreds of returning aircraft and graphed the location of any bullet holes. As data accumulated, most of the composite plane outline filled up. So where to recommend armor placement? Near the hole clusters? ­ R. Baron

 A. Not at all, reasoned Wald. Put the armor in the few spots with no bullet holes. That's where bullets hit the planes that didn't make it back, says David S. Moore in Statistics: Concepts and Controversies. General statistical rule: "After you plot your data, think!"

Q. Are dreams in color or black and white? One man reported dreaming in vivid colors like the movies, another said black and white, a third likened his dreams to paintings or tapestries. When did the three live? ­ S. Freud

A. Black and white was a common idea of the 1950s, the golden age of black and white movies and early TV, says John Whitfield of Nature.Com. Surveys of the era had people saying they rarely if ever dreamed in color. But before and since, most people have reported colorful dreams, says University of California-Riverside professor of philosophy Eric Schwitzgebel.

It's not that dreams were any different then but our knowledge of our stream of experience is very poor, so people of the '50s naturally likened dream imagery to the "artificial dreams" surrounding them in black and white. Before the 20th century, dreams were often compared to colorful paintings or tapestries.

The media today probably influence our dreams just as much, adds Schwitzgebel. Although few people mention touch in dreams– the reason we pinch ourselves to be sure we're awake-in the future this may change as virtual realities surround us more and more, touchy-feely as well as visual.

"We might start thinking our dreams are really great."

Q. What larger lesson is there in a trick used by a San Francisco restaurant to boost sagging clam sales? ­S. and B. Phillips

A. When the head waiter took pains one evening to point out to patrons a special on clams, report Robert Ornstein et al. in New World, New Mind, he found few takers– until he modified his approach: "The clams are very popular tonight, so if you want to start with them, I suggest you tell me now." Bingo! A run on clams!

Creating an artificial sense of scarcity is the essence of "Get them while they last" sales pitches, auctions and bidding wars. And even in romance: A classic study of a Virginia singles bar showed patrons' looks ratings of the opposite sex soared as closing time neared, when the opportunities for meeting someone and striking up a conversation were growing scarcer by the minute.

Send strange questions to brothers Bill and Rich at