Fire-walking is the act of walking barefoot over a bed of hot coals. This feat appears to defy the laws of nature—one would expect to burn one's feet—but according to physicists it is perfectly explainable by application of natural laws; the supernatural is not involved nor need be posited in explanation. This is ipso facto substantiated by the fact that anyone can perform firewalking without any 'mind over matter' preparation.

Application

Fire-walking is practiced

• by fakirs and similar persons,
• in management seminars and motivational seminars, such as those conducted by Anthony Robbins, Peggy Dylan, Tomorrow's Youth et. al.
• by Eastern Orthodox Christians in Greece and Bulgaria during some religious popular feasts. The African-born Hindus walk on fire regularly as part of important religious festivals and !Kung Bushmen of the Kalahari desert have firewalked since their tribal beginnings. The !Kung use fire in their powerful healing ceremonies.
• by Japanese Taoists
• as a rite of purification, healing, initiation and transcendence has been a thread in the cultural tapestry of our planet.

Organizers of firewalking ceremonies often claim that in order to prevent one's feet from burning, meditation, calling on spirits/gods or other supernatural intervention is necessary.

The oldest recorded firewalk occurred over 4,000 years ago in India. Two Brahmin priests were competing to see who could walk farther over hot coals. The victor's triumph was recorded in

During the booming economics of the early 1990's, the firewalk caught the attention of managers and corporations as a way to inspire creativity and empower visions of higher horizons in their employees. The firewalk was touching a new culture from small spiritual groups to thousands in corporate conferences. The firewalk as a tool for personal empowerment and a ritual for spiritual communion had been born in the West.

Physical explanation

When two bodies of different temperatures meet, the hotter body will cool off, and the cooler body will heat up, until they are separated or until they meet at a temperature in between. What that temperature is, and how quickly it is reached, depends on the thermodynamic properties of the two bodies. The important properties are:

• temperature,
• mass,
• specific heat capacity, and
• thermal conductivity.

The product

The bodies in question here are:

• human feet, which mainly consist of water;
• burning coals.

Several factors act together to prevent the foot from burning:

• Water has a very high heat specific capacity (4.18 kJ/K kg), whereas coals have a very low one. Therefore the foot's temperature will change considerably less than the coal's.
• Water also has a high thermal conductivity, and on top of that, the blood in the foot will carry away the heat and spread it. So effectively the mass of the cooler body is increased. On the other hand, coal has a poor thermal conductivity, so the hotter body consists only of the parts of the coal which is close to the foot.
• When the coal cools down, its temperature sinks below the flash point, so it stops burning, and no new heat is generated.
• The coals are often covered with ash, which is a poor heat conductor.
• The coals are a very uneven surface, and the actual surface area of foot touching the coals is very small.
• Firewalkers do not spend very much time on the coals, and they keep moving (one second per foot before lifting is a conservative estimate)

This does not mean that it is impossible to burn your feet. Fire-walking is still dangerous.

• People have burned their feet when they remained in the fire for too long (enabling the thermal conductivity of the coals to catch up).
• Also, there should be no foreign objects in the coals. Metal is especially dangerous since it has a high thermal conductivity.
• The coals should have burned for a while. Coals contain water, which increases their heat capacity as well as their thermal conductivity. The water must be evaporated already when the firewalk starts.
• The feet should be dry. Wet feet can cause coals to cling to them, increasing the exposure time.

It has been claimed that the Leidenfrost effect, which is based on a layer of water vapor between the hot and cold body, is involved in firewalking. This claim remains controversial. Some detractors state that if the Leidenfrost effect was operating the effect would create greatly reduced friction, making the coals slippery to the feel, which has not been observed.

External links and references

• KFC
• The Straight Dope:
• Feuerlauf

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