Throughout history, man has been fascinated by lightning. Ancient peoples thought it was the work of the gods. In medieval Europe, church bells were rung during thunderstorms in the belief that it would prevent lightning from striking the spire (a practice which resulted in the deaths of literally hundreds of bell ringers). In more recent times, Ben Franklin proved that lightning is merely electricity with his famous kite experiment and invented the lightning rod in order to protect buildings from its effects.

Today, we don't pay that much attention to lightning. We know that it's basically just a gigantic version of what happens when you scuff your feet on a carpet and touch a metal doorknob. Sure, it's pretty to look at (and it makes some great pictures, but why should we concern ourselves with it? But, in fact, lightning kills more people in the United States than any of the more spectacular disasters we hear about, such as tornadoes, floods, and hurricanes. How does such a powerful phenomenon happen, and what can we do to protect ourselves from it?

A Lightning Bolt

The structure of a typical lightning bolt is surprisingly complex. It begins with a large thunderstorm. Through a process that is not yet fully understood, charge separates within the cloud, causing the top to become positively charged and the bottom negatively charged. This negative charge attracts a "shadow" of positive charge on the ground below. When enough charge accumulates, a lightning bolt occurs.

A lightning bolt happens in a series of stages. First, a faint step leader emerges from the base of the cloud. It moves toward the ground in steps of 50 meters or so, pausing very briefly between steps. Often it branches as it goes down, which is why so many lightning bolts "fork". When the step leader nears the ground, it attracts "streamers" of positive charge from the ground. When it finally connects with one of these streamers, a brilliant return stroke occurs as the charge drains out of the ionized channel left by the step leader. The charge nearest the ground goes first, causing the return stroke to propagate upward. Often this is followed by another relatively faint cloud-to-ground dart leader, which is rapidly followed by another return stroke. This process can take place up to 40 times, which is why many lightning bolts are seen to flicker.

Effects of Lightning

A typical lightning bolt can discharge millions of volts and tens of thousands of amps in a fraction of a second. This enormous energy heats the air through which it passes to a temperature of 50,000 degrees (five times as hot as the surface of the sun!). Naturally, this kind of power does nasty things to whatever it hits. Lightning bolts have been known to heat up the sap of a tree so rapidly that the tree literally explodes. When it strikes a person, lightning can stop the heart, cause serious burns, damage the nervous system, and stop breathing. Despite all of these potentially life-threatening effects, however, the vast majority of those who receive prompt medical attention (usually CPR) survive being hit by lightning.

Not so lucky, however, are the trees, houses, and other structures struck by lightning. In eighteenth-century Europe, church vaults were often used to store gunpowder, with predictable results when lightning struck the steeple: explosions that destroyed cities and killed thousands of people. While we're a little more informed today, lightning still causes many millions of dollars in property damage every year. The main culprit is fire, but much damage is also done to electrical systems and electronic equipment.

Lightning Safety

The best way to avoid being killed by lightning, not surprisingly, is to avoid being struck. Just because you're not right under a storm doesn't mean you're safe, though - lightning bolts can reach more than ten miles away from a storm. Since thunder can only be heard at a distance of three to four miles, it's possible to be hit by lightning before you even know a storm is nearby. So if you're outdoors during thunderstorm season, pay attention to the weather - it could save your life.

When a thunderstorm approaches, here are some safety precautions to follow:

• Go inside a home or large building, if you can.
• Avoid using electrical appliances such as telephones, computers, or television sets.
• If no building is available, try to get into a car. The metal frame will conduct the lightning safely into the ground.
• If stuck outside, do not take shelter under a tall, isolated tree.
• Stay away from open water.
• If you are trapped in an open field and you feel your hair stand on end, lightning is about to strike. Drop to your knees and bend forward putting your hand on your knees. Do not lie flat on the ground.

Useful Links

The Lightning Page Lots of useful information and links (once you get past all the preaching).

Exploring: Weather Good background information on lightning.

Lightning in Virginia Good source for general information and safety precautions.

Federal Emergency Management Agency Lots of useful safety information.

Space Shuttle Observations of Lightning Not as practical, but pretty interesting.

And, of course, this page would be incomplete if I didn't tell you where to find some more cool lightning pictures. Try these Weather Photography Links or Cori Prazen's Lightning Links.