A high-speed photo of a lightning rod at work during an electrical storm in São José dos Campos, Brazil, helps researchers understand how the devices compete to attract strikes and protect buildings from damage.
The image shows lightning heading toward the ground at 230 miles per second, according to the researchers. Their analysis of the lightning rod’s reactions to the bolt was is published in Geophysical Research Letters in December 2022.
When the bolt was about a hundred feet off the ground, “lightning conductors and tall objects on top of nearby buildings produced upward positive discharges, competing to connect with the downward stroke,” said the study’s lead author Marcelo Saba, a researcher at Brazil’s National Space Research Institute. in a FAPESP release.
“The last image before the connection was taken 25 thousandths of a second before the lightning struck one of the buildings,” Saba added.
Lightning conductors were invented in the mid-18th century by Benjamin Franklin. They are metal (often copper) used to safely spread electrical discharges on the ground, according to Britannicarather than allowing them to hit structures that can easily ignite. (Luckyy for Mr. Franklin, lightning may have been less common then than today.)
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Despite the 30-plus lightning rod in the imaged area, Saba said a failure in their installation caused the lightning to strike a chimney, causing a 30,000-amp discharge that damaged the structure.
Lightning seeks the path of least resistance to the ground, not the most direct path, hence its characteristic zigzag shape. That’s also why it’s just as happy to be discharged on an unfortunate chimney as it is to land on a lightning rod.
Lightning is basically an electrical spark in the atmosphere. As noted by NOAA, when there are significant opposite charges in the atmosphere, the air loses its insulating properties and the air sparks from lightning. (This is why you don’t need a thunderstorm for lightning to occur, it can also come from volcanic eruptions and nuclear explosions.)
In the picture, you can see lightning rods on at least three different buildings trying to connect with the downward lightning charge. As the lightning shoots down from the sky, the various rods and tall objects produce upward charges to connect with the bolts.
You could try 40,000 times to get the same photo, but you still couldn’t compete with the 40,000 frames per second camera. Besides a quick science lesson, it’s a hair-raising spectacle.