CryptozoologyDear SasquatchPhysics

Dear Sasquatch: Firewalking

Dear Sasquatch:

My mom and my brother went to one of those Unleash the Power of Your Mind seminars, where they have people walking on hot coals. They said it was a whole “mind over matter” thing. I told them I thought the coals were probably not that hot or something and they said they were tested at 1200 degrees F. How is this possible? Is it a mind over matter thing?
 
—Casey S.


Dear Casey:

The trick behind these Unleash Your Wallet seminars is not the power of the mind but the power of physics.

Temperature is not as important in firewalking as thermal energy is. The classic example is a cake in an oven. You can stick your hand in the oven and you can touch the cake without burning yourself, but if you touch the pan or the rack, you’ll burn yourself instantly. Yet everything is the same temperature.


Heat is essentially the transfer of energy. More energetic molecules in a hot substance collide with less energetic molecules in a colder substance, transferring energy and therefore heat. In solids, this transfer is called conduction. In liquids and gases, convection is involved, which basically means that the liquid or gas molecules move away from the source of heat, taking the energy with them and therefore dispersing the heat. (Radiation is another form of heat transfer, which we’ll get to in a minute.)

Temperature measures the average motion of molecules, which is the same in the cake, the pan, the rack, and the air. But the molecules in metal are denser than in air and cake, meaning there’s a lot more of them, so the thermal energy of the metal is higher. It also means that the vibrations of the individual molecules will pass more quickly from one to the other because they are closer together. (Metal also has free electrons, which move faster when heated, causing the molecules in the metal to move even faster and colliding with other substances in contact with the metal.)

So metal is a good conductor of heat while air and the cake are not. That’s why insulation in houses tends to be airy rather than dense, because the air helps slow the energy transfer between the outside and the inside. Molecules cannot transfer through a vacuum at all, which is how a thermos works, with a layer of vacuum preventing the molecules from transferring heat out of or into the liquid inside.

Coal is like cake, although not nearly as delicious. It is a poor conductor of heat. So you can touch it with your bare feet without getting burned, although you have to keep walking quickly. Sustained contact can produce burns, as has happened to firewalkers before. Also, if your soles are thin or you run (which pushes your foot deeper into the coals), you are more likely to burn your feet.

The coals also transfer heat through radiation, which means the energy is carried on electromagnetic waves, which is how the sun heats the Earth. But firewalkers are protected from this form of heat transfer in part by the layer of ash that forms as the wood burns into coal. Ash is a poor conductor and therefore it insulates your feet from the heat.

So mind over matter is a completely unnecessary theory to explain why people can firewalk without burning their feet. Although I hope it goes without saying that you should not try this at home. Aside from the obvious fire hazard, the coals need to be prepared properly (such as burning long enough to form a layer of ash), and medical care should be on hand for people who walk too slowly or run as well as those with thin soles—or, hypothetically, particularly hairy feet.

 
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skeptisquatch

Skeptical Sasquatch is an amateur tabloid photographer and filmmaker, beauty expert, and jetsetter (for security purposes). Tired of all the lies spread about him by cryptoloonologists and various crackpots, he joined Teen Skepchick to speak for himself about the skeptical issues of the day and to add species diversity.

You can find him on Twitter at https://twitter.com/Skeptisquatch (@skeptisquatch) and on Facebook (http://www.facebook.com/SkepticalSasquatch).

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