Even as a kid, I remember hearing the popular myth that lightning cannot, or does not, strike the same place twice. It’s funny how these myths withstand the test of time, but nothing could be further from the truth.
Lightning doesn’t have a memory, and if an object has been struck once, it is no less likely to be struck a second time. Ask some of the employees at Cape Canaveral in Florida. The shuttle launch pad gets hit time and time again, sometimes more than once in the same storm. How about the Empire State Building in New York city which gets struck by lightning about 25 times each year. Even a park ranger by the name of Roy Sullivan was struck by lightning 7 times!
lightning is simply trying to balance a charge separation; positive and negative. Very tall objects such as skyscrapers, mountains and radio towers are more likely to be struck because they narrow the gap between the charge separation of the ground below and the oppositely charge cloud above. When the charge builds up enough to overcome the resistance of the air, the opposite charge will rush upwards along the structure more easily than through the air and as a result the gap between the two charges is lessened increasing the chance of a strike.
Ironically, objects that are taller than their surroundings aren’t always the lightning bolts first choice. Lightning may miss an 80 foot tree and instead strike the rooftop of a house right next to it. It might strike the ground instead of a building or some other smaller object just a short distance away.
If the tallest objects were always struck then every tree, telephone pole and house on the open prairie would have the scars of being struck, lightning rods would always work and predicting where lightning strikes would be a very simple science. Millions of dollars in damages could be prevented each year and harnessing the power of lightning would be a very simple task. A day out golfing would be much safer!
The fact is, objects closer to the ground play a much smaller role in determining what a lightning bolt is going to strike because lightning doesn’t know what it’s going to make contact with until the last 50 to 100 feet. That is to say, lightning doesn’t know at 50,000 feet that its going to strike your neighbors satellite dish.
Lightning zig-zags down to the ground by forming “step-leaders”, re-evaluating at each step where it’s going next. Sometimes left, sometimes right, sometimes down, sometimes up. Once the step-leader approaches a grounded object, a “streamer” composed of the opposite charge shoots upwards. One can shoot up from a telephone pole, a tree, a car or all three simultaneously. Whichever streamer connects with the descending step leader first will complete the circuit and trigger a massive rush of electricity creating a lightning bolt.
The taller object might not be the closest target and it might not throw up as tall a streamer. The tallest object may be just a 100 feet further away than a shorter one and the shorter one will get hit because its streamer made contact with the step leader first.
While watching a thunderstorm, you might have noticed lightning sometimes looks like it’s pulsating or flashing several times very quickly. Sometimes all the charge doesn’t dissipate in one flash over. The electric current will pulse down the channel hitting the same place several times in quick succession. In essence, lightning is hitting the same place many times in a row in a very short amount of time.
But just because an object is hit once, doesn’t not make it immune from being struck again. It’s a myth that lighting won’t strike the same place twice.