Benjamin Franklin is credited with inventing the lightning rod, and for some 270 years it has remained the main tool for protecting buildings from destructive and potentially deadly thunderbolts. But now an ambitious experiment on a Swiss mountaintop has demonstrated that a laser beam also can help guide the path of lightning, extending the effectiveness of the Franklin rod high into the sky.
Lightning rods are made of metal, which conducts electricity much better than the surrounding air and helps guide lightning to the ground harmlessly. The protection offered by a traditional lightning rod covers an area with a radius roughly equal to the height of the rod.
The idea behind laser-guided lightning is to extend that protective area by making the lightning rod function as if it soared hundreds of feet taller, to heights that would be impractical and costly for a physical object.
The report, published Monday in the journal Nature Photonics, claims that powerful lasers could be deployed to help protect sensitive sites such as airports and launchpads.
Decades of laser experiments in laboratories previously showed that, in principle, lasers would be useful for taming the heavens. The report states that this is the first time the concept has been demonstrated in the real world amid an actual tempest.
Joseph Dwyer, a University of New Hampshire physicist who was not part of the research and has expertise in the physics of lightning, praised the report as “a big step forward.”
“People have been trying to do things like this with lasers for a long time,” Dwyer said. “Using lasers instead of a lightning rod, or using lasers to trigger or steer lightning, is a fascinating idea. It seems like a no-brainer but it turns out to be really hard to do.”
The experiment was performed on Säntis Mountain, in northeast Switzerland. A 407-foot (124-meter) communications tower there, equipped with a lightning rod, is struck roughly a hundred times a year.
The researchers positioned a car-size device for generating a high-power, rapid-fire laser next to the communications tower and fired pulses into the sky during stormy weather. The laser created not only a beam of light, but also a channel of thinned-out air that beckoned the lightning.
As the laser fired, air molecules absorbed and expelled the laser energy very rapidly, leaving behind long-lived channels of heated air with reduced density. Those channels functioned as a preferred path for the lightning. (WashingtonPost)
