for National Geographic News
Each May in some northern Greek villages revelers walk barefoot across a bed of burning wood coals as part of a three-day celebration in honor of Saint Constantine and Saint Helen.
"They believe that the power of Saint Constantinethe religious powerallows them to do it and that that is a miracle," said Loring Danforth, an anthropologist at Bates College in Lewiston, Maine.
The festival is just one of the many events around the world in which people walk across a fire pit without getting burned.
Danforth has extensively studied fire-walking rituals, including the event in northern Greece and the more recently established fire-walking movement in the U.S.
As interest in fire walking has grown, he said, scientists have attempted to demystify the phenomenon and tease apart the allure of the ritual. But no amount of debunking can take away from the empowerment a fire walker can feel, Danforth says.
David Willey is a physics instructor and an expert on the science of fire walking at the University of Pittsburgh in Pennsylvania. He said people are able to walk across a bed of burning coals because "wood is a lousy conductor."
"There're three ways heat can get transmitted: conduction, convection, and radiation," he said.
Conduction is the transfer of heat from one substance to another via direct contact. In convection heat is transferred through air or fluid circulation. In radiation it is transmitted as if spreading out in straight lines from a central source (think of the sun or a heat lamp).
Conduction is the main way heat is transmitted to a person's feet during a fire walk.
In fire walking, a person's feet, which Willey said are also poor conductors, touch ash-covered coals.
Since the fire walker is indeed walking, the time of contact between feet and coals is minimaltoo quick for the coals to burn or char the feet, Willey said.
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