Jul 182011
 

I’ve been in Las Vegas the last few days, taking in my first TAM. For those who don’t know, TAM stands for The Amazing Meeting, an annual conference put on by the James Randi Educational Foundation. This years meeting was “TAM 9 From Outer Space” with presentations having a space-based theme. One speaker was Bill “The Science Guy” Nye. I hadn’t seen Bill Nye in person in many years, and I thought his presentation was great. Funny and inspiring at the same time. His talk reminded me of a strange criticism I once heard.

Years ago I was watching a sideshow performer demonstrate an amazing new stunt that involved red hot metal. To get his steel red hot he had to use a small forge which ran on propane and air. This was back in the 1990’s, long before the Station Nightclub fire which killed 100 people. That fire pretty much put the kibosh on indoor performances that involved fire of any kind. This gentleman was going to walk on red hot steel, or so he said. As with any sideshow stunt that has any element of danger, the stunt must be hyped beforehand for maximum effect. The hype in this case took a strange turn, as the performer began to criticize Bill Nye.

Unfortunately I don’t know what Bill Nye said in the first place. Frankly I never caught his TV show, only his early work with Almost Live, a local TV comedy show based in Seattle. I suspect, but do not know that Nye probably offered the common “explanation” for fire walking, namely that it’s a matter of the low heat conductivity of the wood embers that fire walkers walk on. A classic analogy is that it’s possible to leave your hand in a hot oven as long as you don’t touch the hot metal. Both the air and the metal in the oven are at the same temperature, but the metal is a much better conductor of heat.

In any event, the sideshow performer suggested that Bill Nye was wrong, that it was possible to walk on hot steel without searing the skin. At this point we should consider the social nature of such a performance. The goal of a showman’s pitch is to create tension, to hype the act, and hopefully to leave a lasting impression in the minds of the audience members. It shouldn’t be intended as formal physics presentation! Consider that when an audience enjoys a comedian, a certain suspension of disbelief is in effect. We are OK with a comedian telling a story that may be complete fiction, as long as the punch line is funny. An audience accepts this kind of thing in a comedian that wouldn’t be accepted in a scientist. But was the criticism of the sideshow performer valid? Is the “official explanation” of firewalking wrong? Well, sort of…

As our sideshow performer kept his bally going, his steel slats began to glow red hot. Coupled with the roaring sound of the forge on stage it was an awesome psychological setup. Soon his slats were set into a frame on the floor. In what must have been no more than a second or two the act was over. Indeed, our brave performer had “walked” on the hot steel slats. Only he didn’t really walk so much as hop. And therein is the crux of this whole essay, namely that sometimes simple “explanations” for phenomena fall short, and that the true description is more complex. What our performer was effectively utilizing was a low exposure time. Had he actually “walked” on the hot slats he would have surely gotten burned.

This is not to take anything away from our performer! It was an outstanding stunt, one which I’d never seen before and one which I haven’t see other performers doing. But for our purposes, let’s take a closer look at the physics involved, and what we can learn from it. A good resource on the subject is the Wikipedia article on Thermal Conductivity. A key passage is this:

For general scientific use, thermal conductance is the quantity of heat that passes in unit time through a plate of particular area and thickness when its opposite faces differ in temperature by one kelvin.

Note the critical variable of “unit time.” If we lower the time of exposure to a heat source, we lower the quantity of heat that flows to that which is being heated. A commonplace demonstration of this is running fingers through a candle flame. If you keep your fingers moving you can avoid a burn. The variable of time is often missing in explanations of firewalking. Indeed, the stunt is firewalking, not “firestanding!” Walking provides a series of exposures to the heat instead of one continuous exposure.

It should also be pointed out that skeptics have done an excellent job of debunking the claim that some sort of special mental or “spiritual” state is required to walk on hot coals. Skeptics Ben Radford and Joe Nickell have both performed this feat, and neither needed “chi” powers or motivational seminars to do it. I was amused at Radford’s account of his own fire walk, as he had organized it as something of a house party affair!

I actually began to think about these issues many years ago, way back in high school. Sometime in the late 1970’s I recall reading in Scientific American magazine the suggestion that firewalking could be “explained” by the “Leidenfrost effect.” Indeed, suggestions are still being made that this is the correct explanation. In my opinion this makes no sense as an explanation for the simple reason that any putative hovering water droplets would quickly be smashed into the sole of the foot or the wood embers by the walker’s body weight!

There is a temptation to glom onto “explanations” of seemingly mysterious phenomena. It’s unsettling to witness things that we don’t understand or can’t explain. But when incorrect or incomplete explanations are offered, it can backfire. A classic example in UFOlogy is “swamp gas” which became a term of derision for UFO advocates. I think skeptics are entirely justified in calling out those who would charge money for staging fire walking demonstrations, especially when it’s couched in terms of nonsense like “chi” energy. Today practitioners of marshal arts would call chi “bullshido.”

I would like to suggest that we get our physics correct when we suggest what is really going on…

 Posted by on 07/18/2011 Pseudoscience

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