The Science of Lightning
How it strikes | Thunder | Estimating distance | Facts
During any given minute, there are more than a thousand thunderstorms around the Earth causing some 6,000 flashes of lightning. Every minute!
Most of the electrical energy in a thunderstorm is dissipated within the clouds, as lightning hops between the positively and negatively charged areas. Lightning becomes dangerous, though, when it reaches for the Earth.
As the stepped leader nears the ground, a positive streamer reaches up for it. Only then, once this channel is made, does the visible lightning happen. A return stroke runs from the ground to the clouds in a spectacular flash.
The air around a lightning bolt is superheated to about 54,000 degrees Fahrenheit (five times hotter than the sun!). This sudden heating causes the air to expand faster than the speed of sound, which compresses the air and forms a shock wave; we hear it as thunder. Since the bolt is actually several short bursts strung together, multiple shock waves are created at different altitudes; this is why thunder seems to rumble -- each shock wave takes a different amount of time to reach your ear.
Because light travels faster than sound (186,291 miles per second vs. 1,088 feet per second) you see lightning before you hear the thunder. When you see it, count the seconds before the thunder arrives. Divide this number by 5, and you'll know approximately how many miles away the lightning was (5 seconds = 1 mile).
- A lightning charge contains 30 million volts at 100,000 amperes.
- The total energy in a large thunderstorm is more than that in an atomic bomb.
- About a hundred U.S. residents are killed by lightning every year.
- Benjamin Franklin's famous kite experiment, in 1752, showed that lightning was electricity.
- The Empire State Building in New York City is struck by lightning about 25 times every year.
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