For the first time ever, scientists have captured high-speed footage of lightning striking a building. It's dramatic as hell, but the video could also change the way lightning rods are used to protect buildings.
The unprecedented video — captured by physicist Marcelo Saba and his team from Brazil's National Institute for Space Research — shows branches of lightning hurtling down from the sky. But just milliseconds before the leading streamers strike a pair of buildings, lightning rods expel their own upward-moving streamers to complete the connection. The result is a fantastic blast of light, and no harm done to the buildings.
Researchers have captured lightning strikes in super slow motion before, but this marks the first time scientists have captured high-speed footage of lightning as it interacts with lightning rods. As the authors note in their new study, now in Geophysical Research Letters, the observations could advance our understanding of how lightning rods work to protect structures, and how engineers might be able to improve lightning protection standards.
When deciding where to place a lightning rod atop a building, engineers typically use models and theories based on lab observations of long electrical discharges, or from observations of lightning rods on top of very tall structures. Still, scientists aren't entirely sure how rods work to protect buildings, particularly small to medium sized ones, owing in part to a lack of observational evidence.
It's exceptionally difficult to capture the precise moment when lightning strikes a lightning rod. Cameras have to be very close to the observed structure, and long observation times are required to catch these fleeting moments in time.
In the new video, the downward branch of lightning can be seen connecting to the upward leader initiated from the tip of the lightning rods on twin buildings located in São Paulo City, Brazil. These structures are under 60m in height, offering good examples of what happens to similar buildings around the world.
With the high frame rate — recorded at 7000 frames per second (fps) — the researchers were able to see details that would otherwise be impossible to document, including the striking distance and speed of the connecting leaders. In this case, the downward leader was moving at an astonishing 100km/s, while the discharge from the rod was moving upwards at about 0.05km/s.
After watching this video, and seeing that dramatic flash, we all need to stop taking lightning rods for granted.