Experiment shows that firing a laser into the sky can deflect lightning

(ORDO NEWS) — Don’t try it at home, but by shooting a laser beam into the sky, lightning strikes can be prevented, according to a new study by a group of scientists who experimented with lasers on top of a Swiss mountain where a huge metal telecommunications tower stands. .

Physicist Aurélien Houard of the Laboratory of Applied Optics at the French National Center for Scientific Research in Paris and his colleagues weathered several hours of lightning activity to test whether a laser could deflect lightning strikes away from critical infrastructure. A telecommunications tower is struck by lightning about 100 times a year.

This is about the same number of flashes of lightning strike planet Earth or crackle between clouds every second. Combined, these strikes could cause billions of dollars in damage to airports and launch pads, not to mention people.

Our best defense against lightning strikes is the Franklin rod, nothing more than an invented metal capstan. in the 18th century by Benjamin Franklin, who discovered that lightning strikes are zigzag discharges of electricity.

These rods are connected to metal cables that run down buildings and anchor into the ground, dissipating lightning energy.

Howard and his colleagues wanted to develop a better way to protect against lightning strikes by fighting electricity with light.

“Although this area of ​​research has been very active for over 20 years, this is the first field result that experimentally demonstrates laser-guided lightning,” they write in their published paper.

With the increase in extreme weather events caused by climate change on the radar, lightning protection is becoming increasingly important.

The pilot campaign was carried out in the summer of 2021 on Mount Sentis in northeastern Switzerland. Short, intense laser pulses were fired into the clouds during a series of thunderstorms and successfully deflected four ascending lightning bolts from the top of the tower.

Experiment shows that firing a laser into the sky can deflect lightning
laser and telecommunications tower on top of Mount Sentis in Switzerland

Another 12 lightning strikes hit the tower during those thunderstorm periods when the laser was not working.

On one occasion, when the sky was clear enough to capture the action on two separate high-speed cameras, a lightning strike was recorded in the path of the laser at 50 meters (164 feet).

Sensors on the telecommunications tower also captured the electrical fields and X-rays generated to detect lightning activity and confirm its path, which you can see in the reconstruction in the video below.

For an idea first put forward in 1974 and extensively tested in the lab, it finally works as intended in the real world. Several earlier field trials, one in Mexico and another in Singapore, failed to find any evidence that lasers could reflect lightning strikes.

“These preliminary results need to be confirmed with additional campaigns with new configurations,” Howard writes. and colleagues.

While the researchers are still figuring out why the lasers worked in their trials and not in earlier experiments, they have a few ideas.

Laser Howard and his colleagues used speeds of up to a thousand pulses per second, much faster than other lasers used, allowing the green beam to intercept all lightning precursors forming above the tower.

But only laser events have been registered. seemed to deflect the positive lightning flashes that are produced by the positively charged cloud and generate the negatively charged ascending “leaders”.

So how does it work?

As Howard and his colleagues explain in their paper, a laser aimed at the sky changes the light-bending properties of air, causing the laser pulse to compress and amplify until it begins to ionize air molecules. This process is called filamentation.

Air molecules quickly heat up in the path of the laser, absorbing its energy, and then ejected at supersonic speeds. This leaves behind “long-lived” channels of less dense air that provide a path for electrical discharges.

“With a high repetition rate of the laser, these long-lived charged oxygen molecules accumulate, preserving the memory of the laser. the path that lightning will follow, the researchers write.

In the laboratory, lasers were used to control multi-meter electrical discharges, but this method first worked during a thunderstorm.

The operating conditions of the laser were adjusted in such a way that the onset of filamentary behavior started just above the top of the tower.

“This work paves the way for new atmospheric applications of ultrashort lasers and represents an important step forward in the development of laser-based lightning protection for airports, launch pads or large infrastructure,” conclude Howard and his colleagues.

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