The physics of fire walking

Ezra Klein reports on the mishap last week at a Tony Robbins fire walk event where 21 people were burned, some seriously. Klein explains the physics behind how in the usual course of these events people don't get burned. While the coals on the bottom might be up to 1000 degrees they wait until the top coals form ash. Tests have shown that the top coals are around 300 degrees. Still hot enough to burn, so how do people not get burned? First off charcoal doesn't conduct heat very well. Plus they walk over them really fast so that the foot is in contact with the ash for less than a second at any one time. Another factor not reported in the story is that one starts out on a wet grass surface, which adds a layer of water, further insulating the foot. Like one licks their fingers before using them to put out a match quickly with those fingers.

Klein doesn't take away from the benefits of positive thinking, just that it somehow transforms your physical capacity to not burn through some magical power of the mind. It's a stunt designed to trick one into self-confidence. And the stunt went wrong likely due to physics last week, probably due to not allowing enough ash to form on the top layer before taking the walk and/or not enough wetting of the feet beforehand. No amount of positive thinking is going to prevent burns under the wrong physical conditions, Tony.