While there is still debate within the scientific community as to the
exact nature of the process, most believe that cloud-to-ground
lightning originates when conditions within a thunder head strip
electrons from rising water vapor to create an electrical field. Free
electrons gather at the bottom of the cloud while positive ions move to
the top.
This electrical field is so intense that the negative
electrons in the cloud repel electrons on the ground. These ground-level
other electrons get pushed far enough into the strata that the surface
of the planet becomes positively charged. Once that occurs, air
molecules around the cloud ionize, discharging the electrical field via a
short-circuit back to Earth, neutralizing the charge difference. That's
lightning—and you don't want to be anywhere near it when it strikes.
Humans are good conductors. Being comprised of atoms that can
transmit electrons is great for our neural network's basic
functionality. But it's very bad when we drop a hairdryer in the tub,
crack open an industrial capacitor, or become a human lightning rod on
the links.
Lightning strikes do, however, differ from the
industrial shocks you'd receive from high-voltage equipment. First, the
level of voltage is greater in lightning—most industrial shocks generate
20-60kV, but a bolt of lightning generates 300kV. Second, the duration
of a lightning strike is much shorter. Man-made shocks last about a half
second (500 miliseconds), on average, until the worker is either blown
clear or the circuit breaker trips. A lightning strike courses through
you in in just 3 milliseconds. Finally, most industrial electrical
injuries hit the worker's hands, arms, and shoulders while natural
lightning most often strikes the head, shoulders, and upper torso.
When
a bolt of lightning does strike a human frame, very bad things happen.
In addition to the 300kV of energy coursing through you, the power of
the strike heats the surrounding air to 50,000 degrees F, causing third
degree burns at the bolt's entry and exit points. It can also create
lightning bolt-shaped burn marks, called Lichtenberg figures,
which are caused by bursting blood vessels. The heat and force can
singe and shred clothing. Lightning strikes have blown people clear out
of their shoes.