We all know Ben Franklin's 1752 experiment with lightning - flying a kite in a thunder storm with a brass key tied to a kite string. But did you know that it was Franklin who invented lightning rods?
What is Thunder and Lightning
Thunderstorms form in cumulonimbus clouds. Drops of water, hailstones and specks of ice, rub and bump against each other as they do they become charged with electricity. After a while, the whole cloud fills up with electrical charges. There are positive charges (called protons) and negative charges (called electrons) in electricity and during the storm these charges separate. The positive charges form at the top of the cloud and negative charges form at the bottom of the cloud.
Positive and negative charges are attracted to each other and as they travel through the air they create an electric current which causes a spark, this is lightning. So lightning happens inside a cloud and between clouds. Intracloud lightning happens in the same cloud and is the most common type of lightning. Intercloud lightning happens between two different clouds and the strike travels in the air between them.
As the storm builds the negative electrical charge at the bottom of a cloud are attracted to the positive charge in the ground below. As the negative charge get stronger, the air cannot stop it from jumping from the cloud towards the positive charge on the ground. The giant spark of electricity is the lightning that we see.
As the lightning heats the air around it, the air expands outwards at great speed, and there is a hole left in the air, called a channel. When the lightning is gone, the air collapses back in, creating the sound that we hear as thunder.
Types of Lighting
Forked lightning appears as jagged or crooked lines of light. They can have several branches. Forked lightning can be seen shooting from the clouds to the ground, from one cloud to another cloud, or from a cloud out into the air. This lightning can strike up to 10 miles away from a thunderstorm and appear to be coming out of a clear blue sky. The phrase, "out of nowhere" or "out of the clear blue" might well describe some of these forked lightning strokes.
Sheet lightning appears as flashes of light that seems to light up or illuminate entire clouds. This makes the clouds visible far away. Intracloud lightning is sometimes called sheet lightning because it lights up the sky with a 'sheet' of light.
'Heat lightning' is simply ordinary lightning from faraway thunderstorms below the horizon. Heat lightning is created by thunderstorms that are usually more than 10 miles away. The reason it is called heat lightning is that it appears most often in the hot summer when the sky overhead is clear and most often is too far away to be heard.
Ball lightning is very rare. (In fact some scientists say it does not exist at all.) Reports of ball lightning have been made by passengers on planes and ships as well as from people that experienced it in their homes. These form of lightning appears as a glowing ball less than three feet wide. It lasts from a few seconds to several minutes and then disappears. Usually there is no damage from ball lightning except for burn marks left where it traveled through screens or windows. Therefore, its existence remains questionable and is currently given the same scientific credibility as UFOs. Many of the ball lightning reports have been found to be nothing more than power line arcs and other unrelated events.
St. Elmo's Fire appears as a blue or greenish glow above pointed objects on the ground. It was named for the patron saint of sailors. It is created when tiny positively charged sparks reach up in response to negative charges in the air or clouds above the ground. Instead of a lightning strike the glow appears from objects such as a ship's mast, a power pole, tall antennae, or the wings of an aircraft. If a thunderstorm is nearby, St. Elmo's Fire might be seen right before a lightning strike.
High-altitude lightning has been given other names such as "red sprites," "green elves," and "blue jets." This form of lightning appears as brightly colored flashes, high above thunderstorms. These flashes shoot up above the thunderstorm about the same time as other lightning discharges inside the storm cloud.
History and Mystery of Lightning
Lightning has always fascinated mankind. It was like fire in the sky, which sometimes fell to earth. As early man sought answers about their world, lightning became a part of the superstitions, myths and many early religions.
Lightning has been thought to be a weapon of mystical or powerful gods. The Greeks were amazed by lightning but feared it as they thought it was hurled by a god named Zeus. Thunderbolts were invented by Minerva the goddess of wisdom. Since lightning was a product of the gods any place that lightning hit became scared.
Moslems also attributed lightning and thunder to their god. The Koran says "He it is who showeth you lightning and launches the thunderbolts."
The Vikings thought that a god named Thor produced lightning as his hammer struck an anvil while he rode his chariot across the clouds. Thor also gave us Thurs-day.
Early statues of Buddha showed him carrying a thunderbolt that had arrows at each end.
Even Indian tribes in North America gave lightning a mysterious origin. They believed that lightning was caused by a mystical bird whose feathers flashed with light. They also thought that the flapping of the wings produced the thunder they heard.
During the Napoleonic wars, more than 220 British tall ships were damaged, by lightning. The solution, of course, was to install lightning rods recently invented by Ben Franklin. But since that device had been invented by a "rebel colonist" , His Majesty's Navy steadfastly refused. It took until the 1830's before the admiralty finally saw the light and forgot about old colonial rebellions.
Lightning Facts
- Average Lightning Stroke is 6 miles long.
- Lightning moves about 30,000 times faster then a bullet.
- 44,000 lightning storms occur every day throughout the world. Lightning strikes the earth 6,000 times a minute. Since your last breath, lightning has struck the earth 100 times.
- There are 1,800 thunderstorms in progress at any given time on Earth.
- The temperature of lightning's return stroke can reach 50,000 degrees Fahrenheit. The surface of the sun is not even that hot! (around 11,000 degrees Fahrenheit).
- Average Thunderstorm is 6-10 miles wide.
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A lightning flash is usually no more than an inch wide.
- Average thunderstorm travels at a rate of 25 miles per hour.
- A "Positive Giant" is a lightning strike that hits the ground up to 20 miles away from the storm. Because it seems to strike from a clear sky it is known as "A Bolt From The Blue". These "Positive Giant" flashes strike between the storm's top "anvil" and the Earth and carry several times the destructive energy of a "regular" lightning strike.
- On average, thunder can only be heard over a distance of 3-4 miles, depending on humidity, terrain, and other factors.
- Approximately 100,000 thunderstorms occur in the United States each year. Approximately 10% of all thunderstorms are severe enough to produce high winds, flash floods, and tornadoes.
- Thunderstorms cause an average of 200 deaths and 700 injuries in the United States each year.
- A lightning strike may contain more than 1,000,000 volts and over 200,000 amperes.
- Lightning does strike twice, and more. The Empire State Building, for example, averages over 20 hits per year.
- Lightning can sideflash, through air, for over a mile.
- A lightning channel may have five or more surges during the 1/5th of a second it discharges energy.
- Daytime lightning is difficult or impossible to see under local sun and/or hazy conditions.
- Night-time "heat lightning" can be seen up to 100 miles away (depending on "seeing" conditions).
- "Lightning Crawlers" or "Spider Lightning" can travel over 35 miles as it "crawls" across the bottoms or through squall line "frontal" clouds.This rare type of lightning is very beautiful as it zaps from "horizon-to-horizon". However it can turn deadly if it happens to strike the ground at the end of its super long path! Radar has detected Lightning "Crawlers" traveling at high altitudes (15000 ft to 20000 ft) as they zap from cloud-to-cloud. Lightning "Crawlers" over seventy five (75) miles long have been observed by Radar!
- The longest bolt of lightning seen to date was 118 miles long. It was seen in the Dallas-Ft. Worth area.
- How big around is a typical lightning bolt? Answer: About the size of a Quarter to Half-Dollar! Lightning looks so much wider than it really is just because its light is so bright!
- "Red Sprite" lightning is a newly-rediscovered type of lightning that zaps between the 40 mile span between the tops of severe storm clouds to the lower ionosphere "D" layer. Red Sprite Lightning looks like a giant "blood-red"-colored jellyfish having light-blue tentacles.
- Lightning bolts are classed as either "hot" or "cold." A hot strike lasts up to a tenth of a second, has a high amperage, and sets fire to flammable materials in its path. A cold strike is much faster, has a higher voltage in relation to amperage, and has an explosive rather than a flammable effect. A large bolt of cold lightning has enough power to lift a 44,000 ton OCEAN LINER six feet in the air.
- Lightning causes thunder. The lightning bolt you see is so hot that the air around it expands very quickly. Thunder is the sound of the expanding air.
- To estimate the distance between you and a lightning strike, count the number of seconds between when you see the lightning flash and hear the thunder. Each five seconds is roughly equivalent to one mile in distance, i.e. 10 seconds between flash and thunder means the lightning was about two miles away.
Sources:
http://en.wikipedia.org/wiki/Lightning
http://environment.nationalgeographic.com/environment/natural-disasters/lightning-profile/
http://stormhighway.com/types.shtml
http://www.ec.gc.ca/foudre-lightning/default.asp?lang=En&n=73364E34-1
http://www.nssl.noaa.gov/primer/lightning/ltg_basics.html
http://www.lightningsafety.noaa.gov/history.htm