Like Thor’s high-tech hammer, powerful lasers can grab lightning and alter its path across the sky.
In the hilltop experiment, such a laser bend the lightning towards the lightning rodthe researchers reported online Jan. 16 Natural PhotonicsScientists have used lasers in the lab to solve electrical problems before, but this is the first demonstration that the technology works in real-world storms and could one day lead to better lightning protection.
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The most common lightning protection technology today is the classic lightning rod, which is a one-meter-long metal rod rooted in the ground. The metal’s electrical conductivity attracts lightning that might otherwise strike nearby buildings or people, safely delivering electricity to the ground. However, the shielding area of the lightning rod is limited by the height of the lightning rod.
“If you want to protect some large infrastructure like an airport or a rocket launch pad or a wind farm…then you need a lightning rod in the size of a kilometer or a few hundred meters,” says Aurélien Houard, Palaiseau Paris, France Physicist at the Polytechnic Institute. Metal poles this tall are impractical. But lasers can go that far, intercepting distant lightning and directing them to a metal rod on the ground.
Houard and his colleagues tested this idea atop the Säntis mountain in northeastern Switzerland. They installed a high-powered laser near a telecommunications tower topped with a lightning rod, which is struck by lightning about 100 times a year. During thunderstorms from July to September 2021, the lasers shined in the sky for about six hours.
The laser fires short, intense beams of infrared light into the clouds about 1,000 times per second. This series of light pulses strips electrons from air molecules and knocks some of them away, opening a channel of low-density charged plasma.Kind of like cutting a path through the woods and laying out the sidewalk, the combination of this effect makes it a Electricity flows more easily Along this line (Serial Number: 3/5/14). This creates a path of least resistance for lightning to travel through the sky.
Houard’s team tuned their laser so that it formed this conductive pathway over the spire. This allows the tower’s lightning rod to intercept bolts blocked by the laser before it travels all the way down to the laser device.
The tower is struck by lightning four times when the laser is turned on. One of the attacks took place in fairly clear skies, allowing two high-speed cameras to capture the moment. The images show the lightning snaking down from the clouds and following the laser light about 50 meters toward the tower’s lightning rod.
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To trace the paths of the three lightning bolts they couldn’t see, the researchers looked at the radio waves emitted by the lightning. These radio waves indicated that these three strikes were closer to the path of the laser than the other strikes that occurred when the laser was turned off. This implies that the laser also directs these three strikes to the lightning rod.
“It’s a real achievement,” says Howard Milchberg, a physicist at the University of Maryland, College Park, who was not involved in the work. “People have been trying to do this for years.” The scientists’ main goal in bending lightning to their will is to improve safety, he said. But “if this thing turns out to be really, really efficient, and the possibility of guided discharge increases a lot more than it does now, it might even be useful for charging.”
Atmospheric and space scientist Robert Holzworth is more cautious about imagining these applications. “They only showed the 50-meter [guiding] length, and most lightning channels are kilometers long,” says Holzworth of the University of Washington in Seattle. So scaling up a laser system to a useful range is likely to be a lot of work.
Using higher-frequency, higher-energy lasers could expand its range, Houard said. “This is the first step towards a kilometer-range lightning rod.”