Firing a laser into the sky can prevent rays from hitting a specific point. This is revealed by a study conducted by a team of French scientists who used lamps to prevent this type of electrical discharge from reaching a telecommunications tower located on a mountain in Switzerland.
The solution, which is still being tested, could help with the development of lightning protection at airports, launch pads or large buildings, for example.
Physicist Aurélien Houard from the Laboratory of Applied Optics at the French National Center for Scientific Research in Paris and his colleagues used laser equipment near a telecommunications tower more than 2.4 km high.
The aim was to analyze the functionality of the laser during thunderstorms and to see if it can deflect lightning away from the infrastructure the Telekom tower is struck by lightning about 100 times a year. The tests were conducted between July and September 2021.
Houard and his colleagues wanted to create better protection against lightning by fighting electricity with light.
“Although this research area has been very active for over 20 years, this is the first field result experimentally demonstrating laserguided beams,” the scientists wrote in a paper published in Nature Photonics.
So far, the best protection against lightning is lightning rods, a metal rod invented in the 18th century by Benjamin Franklin, a scientist who discovered that lightning is a zigzag current.
Lightning rods are connected to metal cables that descend from buildings and are anchored into the ground to dissipate lightning energy.
The results of the study
The experimental study was carried out on the Säntis in northeastern Switzerland. Short, intense laser pulses were fired into the clouds during a series of thunderstorms, successfully deflecting four electrical discharges that would have struck the top of the tower.
Another 12 bolts struck the tower during periods of thunderstorms when the laser was off.
On one occasion, when the sky was clear enough to capture the action with two highspeed cameras, a beam was recorded following the laser’s path for 50 meters.
Sensors on the telecommunications tower also recorded the electric fields and Xrays generated to detect lightning activity. The situation was reconstructed in a video.
“These preliminary results should be confirmed by further studies with new settings,” the study states.
According to the researchers, shots of up to a thousand pulses per second were used, much faster than other lasers used in previous experiments, allowing the green beam to intercept any precursors of rays forming over the tower.
How does the laser work?
Houard and his colleagues explain that the laser shot into the sky changes the refractive properties of the air, causing the laser pulse to shrink and intensify until it begins to ionize air molecules. This process is called filamentation.
Air molecules are rapidly heated along the laser’s path, absorbing its energy and then ejecting it at supersonic speeds. This leaves “durable” channels of less dense air that provide a path for electrical discharges.
“At high laser repetition rates, these longlasting charged oxygen molecules accumulate and retain a memory of the laser’s path” for the beam to follow, the researchers explained in the publication.
Meters of electrical discharge have previously been targeted with lasers in the lab, but this is the first time the technique has worked in a real thunderstorm.
*With Science Alert information