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ST. CONSTANTINE'S DAY - Firewalkingambience: FireHeres a program from our archives.This week, villagers in Northern Greece are celebrating St. Constantine's Day, in a ceremony that climaxes with revelers dancing barefoot across a bed of hot coals. They carry relics sacred to St. Constantine, and it's said that those holy items protect them from the flames. But is there also a scientific explanation for this phenomenon? I'm Jim Metzner, and this is the Pulse of the Planet.Dr. Kenneth Kihlstrom is a professor of physics at Westmont College who's been known to walk across coals himself as a demonstration to his students. He told us that, aside from faith, St. Constantine's followers have several physical principles protecting the soles of their feet.Kihlstrom: There are basically three reasons why it works. The first is heat capacity. If you're baking bread in an oven, if you put your hand in the oven and just touch the air you don't get burned. If you touch the bread it feels warmer, but if you touch the side wall of the oven you burn yourself badly. The difference is that wall of the oven has a much higher heat capacity than either the bread or the air. And so the first thing that helps is that the coals have a relatively low heat capacity.Kihlstrom: The second issue is thermal contact. That when you walk on the coals, there's usually a little bit of a layer of ash on them, basically the heat doesn't transfer very efficiently from the coals to your feet.You'd not want to camp out on the coals. And so generally you walk reasonably briskly across. Because the coals are hot, and given enough time, even with the poor thermal contact and the lower heat capacity, eventually it will burn your feet, and it doesn't take that terribly long.Whether you're carrying icons or a physics textbook under your arm, firewalking is not recommend as a casual pastime.I'm Jim Metzner, and this is the Pulse of the Planet.