07.23The Physics and Fantasy of Firewalking
by Robert Novella
Many alleged powers of the mind, like reading another person’s thoughts or seeing the future, can be very subjective phenomena with ambiguous experimental results. Firewalking, however, cannot be denied. For centuries thousands of people have undeniably and routinely walked barefoot over long beds of hot coals. This coal, or wood embers, can be hundreds of degrees, sometimes well over one thousand degrees Fahrenheit. An increasing number of people assert that under normal conditions this is an impossible feat. They further contend that only some mysterious power of the mind or some similar paranormal force could possibly prevent serious burns. Such invocations are not necessary, however. The scientific principles of heat transfer and the nature of firewalking itself are all that is needed to account for this intimidating and intriguing pastime.
Firewalking is not a 20th century phenomenon; in fact it has been part of human culture for millennia. There is even mention of it in the Bible: “Can a man walk on red-hot coals without burning his feet?” (Proverbs 6:28). The earliest known reference is from a 3400-year-old Indian story. Then, as now, many cultures incorporate firewalking into religious and mystical rituals. There are Hindu, Tibetan Buddhist and American firewalkers. Interest in this country did not take off until the late 1970’s but the context of this endeavor was not religious, but part of self-help seminars and motivational courses. Tolly Burkin (Director of F.I.R.E – the Firewalking Institute for Research and Education) is credited with starting the firewalking craze in 1977, which has induced over 500,000 Americans to brave the coals. Firewalking apostles like Tolly Burkin and others, most notably Tony Robbins (author of Unlimited Power) offer successful firewalks as proof that their ministrations can help people overcome their fears and achieve the seemingly impossible.
The requirements and explanations of firewalking cover a broad spectrum, from a little silly to completely outrageous. Tony Robbins does not believe that paranormal forces need be invoked, all that he requires is conquering one’s fears and focused attention. Other explanations I have encountered inhabit the more extreme end of the spectrum. Veteran firewalker Karen Chow writes at her website that she has noticed that successful firewalkers are usually very excited beforehand. She concludes that fire protection is afforded these individuals due to a “lifting up (of the) vibration of your body so that it is about the same as the fire.” (Chow, ’99) In other words, being excited causes our atoms to vibrate in unison with the fire preventing an exchange of heat, leaving the feet untouched by the embers.
Many times spiritual or mystical powers are claimed to be required for a successful firewalk. Firewalkers in Lankadas carry effigies of Catholic saints for protection against the heat. Others claim that a week or two of special preparation is vital to success. A Sri Lankan firewalker recommends “fasting, prayer and meditation, devotional chants, frequent baths and celibacy” (Doherty, ’82).
Tom Margrave, a certified firewalk instructor since 1991, believes that life energy is the force that makes firewalking possible. This force, unknown to science, is described as “an animating force that is common to all living things. It is the organizing, anti-entropic essence of life and it is composed of consciousness.” This life energy “interacts with our physical body, and possibly the environment, in some special way in which damage to the body is precluded.” (Margrave, ’95)
By far, one of the most commonly cited and widely believed requirements for a successful firewalk is a firm, unwavering belief that the coals will not burn the feet. The power of the mind is said to be instrumental for success. In order to achieve the mental state necessary for this invulnerability, many hours or even days of special preparation are often necessary. This mind over matter power is said to somehow alter the environment preventing any burns. Alternative Medicine guru Andrew Weil in his book Health and Healing echoes these sentiments when he makes reference to abilities of “…the mind or power of consciousness to modify physical reality” (Weil, ’85). Michael Sky’s popular firewalking book Dancing With the Fire (Sky, ’89) contends that firewalking is compelling evidence of the human mind changing reality in ways that science cannot understand. He writes: “We contribute to the ongoing creation of reality through the special medium of human consciousness.” When I read such descriptions of the mind altering physical laws I can’t help thinking about Douglas Adams’ Hitchhikers Guide to the Galaxy novels in which characters are permitted to fly like Superman merely by ignoring gravity and steadfastly not thinking about how impossible this activity is.
I know that firewalking appears spectacular and burns seem inevitable, but are all these far out explanations justified? Is there a shred of evidence to support any of these claims? In a word, no. Life energies and mysterious mind powers are not required to explain this phenomenon because simple physics is all that is needed. It essentially boils down to the science of thermodynamics, the transfer of heat. What does science have to say about how heat energy moves from one object to another?
There are three distinct ways that heat energy moves around: convection, conduction and radiation. Each of these will be briefly examined to determine which might be a major player in firewalking. Convection transfers heat through the wholesale movement of a fluid such as water or air. As the fluid is heated, it expands, causing it to move away from its source of heat and taking energy with it. The familiar phrase “hot air rises” is an example of this phenomenon. As you might have guessed, since convection involves the movement of fluids it does not significantly impact firewalking.
Radiation transfers heat, by and large, through the transmission of infrared electromagnetic waves. Electromagnetism moves energy at the speed of light and manifests itself as radio waves, x-rays, microwaves etc. These waves are not composed of heat themselves but certain frequencies do cause atomic motions to increase which, by definition, increases the temperature. Like convection however, the amount of heat transferred to the feet by radiation is negligible during firewalks. The walk itself is too short and the ash covering the coals can also inhibit the transmission of heat through radiation. (See Firewalking Myths and Physics by David Willey)
Conduction transfers heat not through the motion of the medium itself, but the constituents of the medium, its atoms and molecules. As the molecules vibrate faster and faster, they transfer some of their energy to their slower moving neighbors. As these neighbor molecules start to vibrate faster they, in turn, pass some of their energy to other molecules, and so on. Heat is, after all, caused by this movement of atoms and molecules. Conduction also occurs through the movement of electrons, which greatly aid in the transfer of heat throughout the material. In this way the medium, and anything touching it, gets hotter and hotter as heat is conducted through it. If you hold a long metal rod over a hot flame, even though your hand may be many feet away from the source of heat, they can nevertheless get burned through the conduction of the heat energy through the metal and into your hand. This is the primary mechanism by which firewalking transfers heat from the coals to the firewalker’s feet.
Now that we know how heat energy gets to the firewalker’s feet we need to determine how significant that heat is in order to decide if severe burns should be inevitable. It turns out that not all conductors are created equal. Some materials conduct heat very efficiently while others take a relatively long time to conduct similar amounts of thermal energy. The canonical example of this phenomenon is a baking cake. Open an oven that has been baking a cake for about half an hour at 350 degrees. Everything in the oven, including the cake, the pan, and even the air, is 350 degrees. Now touch the cake. It is warm but it does not feel like 350 degrees. A brief touch is easily tolerable. The air in the oven is even more so. The metal pan, of course, is another story. Even the briefest of contacts conducts a tremendous amount of heat into your hand, resulting in blisters or very serious burns.
How can all of these objects be at the same temperature yet have such a different effect on our skin and on our perception of heat? The answer is conductivity. Some conductors are just very inefficient at moving heat from one place to another, regardless of its temperature. You might think that material of similar density should conduct heat relatively rapidly, but this is not the case. For example, wood and aluminum have similar densities but their rate of conduction differs immensely. Ease of conduction is greatly enhanced due to the availability of free electrons, mentioned above. Poor conductors move heat primarily by the vibration of atoms, which transfers heat throughout the medium. Very good conductors have an additional property; an abundance of free electrons. Electrons are the negative point charges that surround atoms. Some atoms have a tight grip on their electrons but other types of atoms have free electrons that are allowed to roam throughout the material transporting heat around as they do it. It is primarily these free electrons, in conjunction with the vibrating atoms that separate the good conductors from the bad. Together, both modes of conduction make for a potent combination. For example, most metals conduct heat thousands of times more efficiently than poor conductors do. This results in the extremely rapid conduction of heat from the metal into your hand quickly causing a burn.
Another consideration for the transfer of heat is partly due to the important difference between temperature and thermal (heat) energy. Temperature is defined as the average kinetic energy (energy of motion) of the atoms in a substance whereas thermal energy is the cumulative amount of energy contained in all the moving atoms. Since all objects in the oven have the same temperature, then a typical molecule in the air would have the same kinetic energy as a typical molecule in the metal pan. The metal pan, however, has about a million times more atoms per unit volume which therefore increases the amount of thermal energy in the metal by a million times. Therefore, even if a substance were a good conductor, the low amount of thermal energy it contains precludes the transfer of significant amounts of thermal energy.
Related to thermal energy is the concept of heat capacity. The higher the heat capacity of a substance the more energy is required to raise its temperature by one degree. Water, for example, has a tremendous amount of heat capacity because a lot of heat needs to be added in order to raise its temperature by one degree. Conversely, metal has a low heat capacity because it reaches a similar temperature with much less of an infusion of heat. Therefore, if water and metal have both been raised to the same temperature, then much more energy was required for the water, which results in a greater amount of thermal energy. The human body has a relatively high heat capacity (similar to water). In the oven, your high heat capacity hand is surrounded by low heat capacity air. Therefore a big drop in air temperature is matched by only a small increase in temperature in your hand.
We are now better prepared to more fully appreciate why firewalkers are not in as much danger as it would appear or they would have you believe. The wood coals typically used in firewalks may be at a high temperature but they are poor thermal conductors and have a low heat capacity. Therefore they do not contain much thermal energy and what heat there is does not conduct very efficiently. Wood is such a poor conductor of heat it is considered a good insulator, even if it is on fire. Before the advent of heat-resistant plastics, wood was used as handles for pans and soldering irons. Skin also is a poor conductor, being only four times more efficient than wood. Further decreasing conduction is the brief overall contact between the firewalker’s feet and the coals. A fourteen-foot firewalk will expose each foot to direct contact for only about a second in total. Further decreasing conduction is the uneven nature of the coals which reduces the amount of skin area that actually touches the coals. Finally, any ash that builds up on the coals acts as yet another good insulator. All of these factors bring the conduction of heat down to a snail’s pace for brief timescales. Many people are still impressed to hear that the firewalkers have walked over 1600+ degree coals but we now know that the simple facts of thermodynamics greatly diminish the supernatural appeal of this stunt. If these simple laws of physics are irrelevant to firewalking there’s a very simple test that could blow them out of the water. Simply walk on 1600-degree steel. I would completely reevaluate my position if this were successfully done. Of course, I would never have any part of such an irresponsible and dangerous experiment.
The low conductivity and heat capacity of the embers are the primary factors making firewalking possible and no other factors are necessary to explain this phenomenon. There are, however, many ancillary contributors that are worth mentioning. Blood, for example, is very efficient at distributing heat throughout the body. Any heat that does enter through our feet is quickly whisked away, preventing any appreciable buildup.
The perception of pain is a very subjective experience and can be affected by many factors, including emotions and different mental states. Many firewalkers experience little or no pain during the walk, but some do. Some firewalk teachers employ methods that can reduce the amount of pain experienced like increasing one’s confidence in success and removing much of the fear of firewalking. Other instructors teach breathing control, relaxation techniques, and methods of distraction that can all have an effect on the subjective experience of pain. Burns and thermodynamics, however, are not subjective.
There is one phenomenon that for years was declared the primary factor that prevents burns during firewalking, the Leidenfrost Effect. This occurs when a vaporizing liquid acts as an insulator or barrier to heat conduction. Have you ever seen a drop of water in a hot pan? The drop skitters around for quite a while, much longer than you would think it should given the hot surface it is on. The same sized drop will, counterintuitively, survive less time over a colder pan. This is due the vaporized water between the drop and the source of heat. Gases are poor conductors, therefore the steam under the drop insulates against the heat, greatly reducing the conduction of thermal energy through it. Another common example is wetting your finger before touching a hot iron. This sounds like a reasonable explanation for the firewalker’s immunity. Many firewalking rituals include spraying water near the embers to isolate and contain the heat. Walkers then inevitably pick up some of this water on their feet. It is also easy to imagine sweaty feet due to nervousness and proximity to the heat. This reason was even teneted by Jearl Walker, in Scientific American’s “The Amateur Scientist” column in 1977. This effect, however, is now widely regarded as insignificant at best for firewalkers. Many people, in fear of sticking embers, scrupulously dry their feet with no harmful side effects. This would not be possible if the Leidenfrost Effect played a significant role.
In my research I came across many different firewalks performed by skeptics that refuted the ubiquitous mind over matter contention. In 1985 The Southern California Skeptics held a public demonstration of firewalking at CalTech, the California Institute of Technology in Pasadena, California. Over one hundred and twenty people braved the 1200-degree heat that night without any special or prolonged mental preparation. Bernard J. Leikind describes in his article in The Encyclopedia of the Paranormal (Leikind,’85) a clever yet elegant experiment he performed with Tolly Burkin. He simply tied two pieces of raw, double-sized steaks to his feet to see how they would fare on the coals. After the firewalk the steaks emerged dirty but otherwise unsinged. It appears that, not only do cows share mind over matter abilities with the best firewalkers but they also can pull it off posthumously (sorry for that one, I couldn’t resist).
What is the response of true believers to science’s explanation for firewalking? The most common response I’ve come across sounds something like the following; “If science insists that the lack of burns is easily explained, then why are there occasional burn victims at all?” Veteran firewalker and author Michael Sky (mentioned above) also reflect this attitude.
“Each time I lead a firewalk I use the same amount of the same kind of wood, and I burn it for the same length of time, raking it into a path of the same dimensions, meticulously preparing it in the same way. And yet, from firewalk to firewalk, from experiment to experiment, sometimes there are burns and sometimes there are not. The fire has burned as a constant, unchanging stimulus. The only changing factor has been the psycho-emotional state of the individual walkers.”
Michael does seem to take great care in making sure that from firewalk to firewalk the experience is the same and I commend him for that. There are, however, many other variables that should be considered and accounted for besides the fire itself and the psycho-emotional state of the walkers. Some people simply have thin soles on their feet or they walked slower than others, perhaps they happened to be among the first to brave the coals that night before enough cooling has taken place, or maybe some hot spots have formed in the coals due to the wind. Before these factors are controlled for, not an easy job, it is not justified to discount the more prosaic but also more likely scientific explanation in favor of a supernatural one.
The apparent immunity to fire afforded to firewalkers ostensibly appears to be a phenomenon requiring a supernatural explanation. Resorting to a mind over matter explanation is not required, however. The ordinary mechanisms of heat transfer and the nature of the firewalk itself offer ample evidence that simple laws of physics are all that are being invoked. The wood coals are very poor conductors and contain relatively little thermal energy, little time is spent on the coals, and a small part of the feet is in contact with the coals at any one time. All of these factors conspire to greatly reduce the amount of heat conducted to the feet. Regardless of how it appears, firewalking is a testament to human culture’s fascination with fire and the supernatural, not our mysterious ability to transcend reality and bend it to our will.
1) Chow, Karen; http://www.geocities.com/HotSprings/1541/What.htm, 1999
2) Leikind, Bernard; Fire Immunity, Encyclopedia of the Paranormal, Prometheus Books, Amherst N.Y.
3) Doherty, Jim. 1982. Hot Feet-firewalkers of the world. Science Digest, August, p. 66.
4) Margrave, Tom; http://heartfire.com/firewalk/pages/experience.html#where. 1995
5) Sky, Michael; Dancing With the Fire : Transforming Limitation Through Firewalking. Bear & Company, of Santa Fe, New Mexico.
6) Walker, Jearl; Scientific American, “Amateur Scientist” Aug. 1977, 126
7) Weil, Andrew, M.D. Health and Healing (Boston: Houghton Mifflin, 1983), pp. 246 – 249.
Willey, David. Firewalking Myths and Physics; http://www.pitt.edu/~dwilley/Fire/FireTxt/fire.html