What causes lightning? Lightning is a discharge of electrical current during storms in the earth’s atmosphere, or during volcanic eruptions that produce ash columns. Storm lightning can be classified into one of thee types based on where it occurs – 1) cloud-to-cloud from one part of a storm cloud to another, 2) cloud-to-ground from the bottom of a cloud to the earth, or 3) cloud-to-air from clouds to the air around a storm. Put simply, a bolt of lightning is a large-scale manifestation of the same static electricity that arcs from your fingertips to a doorknob after you drag your feet on a carpet inside a house.
Scientific study of lightning began in 1752 when Benjamin Franklin began to devise experiments to investigate whether lightning was indeed electricity. Franklin invented the lightning rod, and proposed a dangerous experiment to channel cloud-to-ground lightning into some instruments installed at the top of a tower to test his invention. Luckily for him, he never managed to try his idea out. A Swedish physicist named G.W. Richmann managed to actually give Franklin’s experiment a shot, and was struck and killed in 1753.
A bolt of lightning can contain hundreds of millions and even up to one billion volts of electricity. The average lightning bolt carries 20,000 amps. You might think that this is a huge amount of energy, and while it is not small, the average bolt of lightning would only power a household incandescent light bulb for about three months (National Lightning Safety Institute, 2011).
You might be surprised to learn that scientists don’t completely agree on how lightning forms. The leading theory holds that ice particles and water droplets circulating within a vertically-forming cloud (cumulonimbus) bump into one another on their way up through the cloud as warm air rises, and they shed electrons during these collisions. Gravity sorts the particles by size, with the majority of the larger particles and their lost electrons remaining in the bottom portions of the clouds, charging their bases negatively like a giant capacitor.
A bolt of cloud-to-ground lightning begins to form when the charge in the base of the cloud becomes sufficient to overcome the insulative capacity of the air between the storm and the earth. A “stepped leader” of electrons emanates from the bottom of the cloud in dendritic webs of about 50 meters each (~160 feet). When the leaders almost reach towards the ground, or more likely something protruding from the ground like trees, the top of a building, antennas, or hopefully not you, an opposite and equal positive electric charge called a “streamer” rises from the object.
The streamer and the bottom parts of the stepped leader join to form the bolt of lightning, with the entire process happening so fast that to the human eye, the bolt appears as one coherent flash that emanates from the cloud to the ground. The air surrounding the main channel of a lightning bolt becomes heated to ~54,000 degrees – three to five times the temperature on the surface of the sun. As the air expands, the superheated part lets loose a massive sound from the resulting shock wave, which we call thunder. Once the electricity has blazed a path through the ionized air, electricity can cycle through it rapidly, which explains the flickering nature of lightning light. You can tell how far away the lightning strike was from you by counting the number of seconds from the flash of light that elapse until you hear the peal of thunder. Lightning one mile from you should result in thunder heard five seconds later, so the distance away in miles can be estimated by counting the number of seconds and dividing by five.
According to National Geographic, around 100 bolts of lightning strike the surface of the earth every second. Maps are readily available online that show lightning strikes in near-real time:
The premise that lightning never strikes the same place twice is a complete myth. According to the National Weather Service, the Empire State building in New York City gets hit by lightning an average of 23 times per year, and during one storm it was struck eight times in 24 minutes. This map shows the distribution of lightning strikes across the earth, from 1995-2003. As you might imagine, the highest density strikes fall in the areas in the tropics where thunderstorms are most prevalent. The Democratic Republic of Congo has the most lightning strikes on the planet, and in the US, that distinction goes to Florida.
What should you do if you are caught out in a thunderstorm that is showering down lightning on you like the blows you used to get from the jocks in gym class when they stuffed you in the garbage? The best way to minimize potential harm to your body is to crouch down and stand on the balls of your feet. Many people who get struck by lightning and live to tell about it report that their hair stands up on their heads and on the backs of their necks prior to the bolt hitting them. If you feel this happening, crouch down and don’t lay flat. Lightning actually doesn’t penetrate the ground like you might think it would do, it spreads out along the ground, and the more points of contact you have by laying flat will equate to more burns and other injuries.
What happens to people that get hit by lightning? 20-30% of people that get hit by lightning die from their injuries. The National Weather Service recorded 3,239 deaths and 9,818 injuries from lightning strikes in the United States between 1959 and 1994. In 1926, lightning caused a major disaster in New Jersey when it struck a Navy ammunition dump, killing nearly 20 people and causing around $17 million in damage (1986 dollars – NLSI). There is a medical discipline devoted to studying the effects of lightning on people, called keraunopathy. Most deaths occur as a result of ventricular fibrillation, aka heart failure. A majority of cases suffer from some long-term neurological damage, and a great deal of patients have severe burns on their skin as well as internal organ damage. Basically – do everything you can to not get hit by lightning – the results are not pretty.
Check out these telephoto images of lightning hitting an antenna, even showing the shower of sparks as the current zaps the metal like an arc welder:
Lightning is no joke! Unless of course you need to harness its power to travel back in time to make sure your parents hook up so you exist in the first place and you accidentally do back to Christmas Day, 0000.