Is Lightning That Lethal?

Nope – 90 percent of people hit by lightning survive. One reason is that, unlike high-voltage accidents that happen indoors, lightning strikes last “less than a half-millionth of a second [and] often scorch the skin but don’t cause internal burns.” More fascinating details:

Just as crucial, most of the electricity in a lightning bolt does not pass through the body. Rather, it dissipates over the skin in what’s known as a flashover. Vernon Cooray, a lightning scientist at Uppsala University in Sweden, explains the phenomenon by contrasting the ways a human body and a tree react when struck.

Both trees and people are filled with a soup of water and minerals that conduct electricity pretty well. But because trees are covered in dry, inelastic bark, lightning traveling through the trunk has no escape route. It must stay its course. In the process, it superheats the water and sap inside the tree into explosive steam, which can rip apart the trunk and branches.

Compared with tree bark, human skin is much more pliant and moist. Sweat and rainwater make it extra conductive, providing an alternate external path for voltage. Most of the electricity can pass over strike victims rather than coursing through them. “The path through the body has much greater resistance than the path around the body,” says Vladimir Rakov, a University of Florida researcher and one of the world’s leading authorities on lightning physics. “Current always chooses the path of least resistance.”