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The Straight Dope


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I would like to know two answers. First, I would like to know how those swamis lie on a bed of nails, and I would also like to know how they do that weird rope trick thing. --Anonymous

Why no name, sport? Taking a little time out from mailing anthrax letters? No need to be shy, though. While the bed-of-nails trick may have struck the rubes as an impenetrable mystery a hundred years ago, today we live in the age of science. Not only do we understand how Eastern mystics did this stunt, college professors routinely use it to wake up the jocks in Physics 101.

The trick, when you think about it, is obvious. You'd impale yourself if you put all your weight on a single nail, but it's a different story when your weight is spread across hundreds. What you've got here is a demonstration of pressure as force per unit of area. According to one calculation, a 70-kilogram individual lying on a grid of nails spaced at 2.5-centimeter intervals would exert a downward force of only 40 grams per nail, not enough to break the skin. In fact, there's enough safety margin that real daredevils have a volunteer stand on them or pile on concrete blocks (sometimes atop of an additional bed of nails, points down), which the volunteer then whacks with a sledgehammer. No damage, although you have to wonder whether doing this for a roomful of freshmen who just got their physics midterms back isn't pushing your luck.

As you can appreciate, lying on a bed of nails requires some preparation. You have to make sure none of the nails sticks up higher than the others, lest it bear more weight. (Variation of greater than one millimeter is asking for trouble.) You also don't want to just hop on the rack. One bed of nails I've seen has armrests on either side so you can let yourself down easy and a sandbag to be used as a headrest. In theory you could also rest your head on a balloon--balloons benefit from distribution of force too--but I've never seen anyone try this. You might suggest it next time Professor Macho goes into his act.

Despite the precautions, things can go wrong. Physics legend Jearl Walker--you remember Jearl, the guy who used to plunge his hand into a vat of molten lead to demonstrate the Leidenfrost effect--tells of performing physics demonstrations as part of motivational talks for IBM salespeople ("If I can plunge my hand in a vat of molten lead, the least you pups can do is sell some computers"). The bed-of-nails demo was customarily preceded by a stunt in which Jearl "fell" off the stage to the floor below. (I'm not sure what principle of physics this demonstrated, but it's a can't-miss principle of comedy.) One day Jearl took his pratfall a bit too hard, breaking a rib. Demonstrating the show-must-go-on spirit that's the hallmark of true scientists, he gamely proceeded to do his bed-of-nails act, in which the local IBM boss would stand on his chest, sandwiching him between two beds of nails. Unfortunately for Jearl, this particular IBM boss weighed 230 pounds. "When he stood up on the top bed of nails, the pain in my chest went ballistic," Jearl relates. "I could hardly breathe." Somehow he got through it, then dragged himself to a doctor's office and got patched up. He was back giving bed-of-nails demonstrations the following week.

Explaining the rope trick isn't so easy. In fact, some think there was never any such thing--the controversy has raged for more than a century. In the classic account a fakir tosses a rope skyward and it proceeds to stand straight up. His assistant, a limber young lad, scrambles up the rope and disappears into thin air at the top. The fakir admonishes the boy to return, to no avail. The frustrated mystic grasps a scimitar or what have you, climbs the rope, and slashes at the sky. The boy's apparently severed limbs drop to the ground. Covered with blood, the fakir descends and tosses the limbs into a basket. The boy then pops out of the basket intact. I ask you, is that entertainment or what?

An early account of the rope trick appeared in the Chicago Tribune in 1890 under the byline Fred S. Ellmore. The story gained worldwide notoriety, and numerous similar accounts appeared over the years. But no one could ever come up with a convincing eyewitness account, photographs, etc, nor was there a satisfactory response to the reward offered by a British magicians' association for an actual performance. Then a few years ago University of Edinburgh researcher Peter Lamont took a closer look at that 1890 Tribune article. Four months later, he found, the editors had confessed in print that the whole thing was a hoax to sell more newspapers--Fred S. Ellmore, get it? This may not be the last word on the subject--when last heard from, Lamont was traveling to India to see what more he could learn--but right now it's looking like India doesn't have the market cornered on fakers.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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