Scientists direct laser bolts for the first time | Physics

Scientists have directed lightning bolts with lasers for the first time in the field, according to a demonstration made during severe storms on top of a Swiss mountain.

The feat, which involved firing powerful laser pulses into a thundercloud over several months last year, paves the way for laser-based lightning protection systems at airports, launch pads and tall buildings.

“Metal rods are used almost everywhere for lightning protection, but the area they can protect is limited to a few meters or tens of metres,” said Aurélien Houard, a physicist at the École Polytechnique in Palaiseau. “The hope is to extend this protection to a few hundred meters if we have enough laser power.”

A bolt of lightning is a huge electrical discharge that usually ignites over a distance of two to three miles. The charge carried in the bolt is so intense that it reaches 30,000 degrees Celsius, five times hotter than the surface of the sun. More than a billion screws hit the Earth each year, causing this to happen Thousands of deaths10 times the number of injuries and damages amounting to tens of billions of dollars.

Traditional lightning rods date back to Benjamin Franklin who used to chase thunderstorms on horseback before they showed up. The famous kite experience In 1752. But recently, scientists have been looking for other ways to protect buildings and objects from devastating blows.

Writing in the journal Nature photonicsHoward and his colleagues in Switzerland describe how they transported a powerful laser beam to the summit of Mount Santis in northeastern Switzerland and placed it near a 124-meter-tall communications tower that is struck by lightning about 100 times a year.

Scientists waited for the storms to gather and, between July and September last year, fired fast laser pulses at thunderclouds for a total of more than six hours. Instruments set up to record lightning strikes showed that the laser deflected four upward lightning discharges over the course of the experiments.

Only one strike, on July 21, occurred in conditions clear enough for researchers to photograph the lightning’s path from two directions using high-speed cameras several kilometers away. The footage shows the bolt following the path of the laser for about 50 metres, indicating that the pulses helped deliver the blow.

The laser deflects the lightning bolt by creating an easier path for the electrical discharge to flow downward. When laser pulses are fired into the sky, the change in the refractive index of the air causes them to contract and become so intense that they ionize the air molecules around them. This leads to a long string of what researchers call filaments in the sky, where air molecules heat up rapidly and race away at supersonic speeds, leaving a channel of low-density ionized air. These channels, which last for fractions of a second, are more conductive than the surrounding air and thus make for an easier path for lightning to follow.

The laser is powerful enough to be a danger to the eyes of airborne pilots, and during the trials air traffic was closed over the test site. But scientists believe the technology could still be useful, since launch pads and airports often have specific areas where no-fly restrictions apply. “It’s important to consider this aspect of safety,” Howard said.

He added that more powerful lasers that operate at different wavelengths can direct lightning at longer distances and even trigger lightning before it becomes a threat. “You avoid going somewhere else where you can’t control it,” Howard said.

“The cost of the laser system is very high compared to the cost of a simple rod,” said Professor Manu Haddad, director of the Morgan Beauty Lightning Laboratory at Cardiff University. “However, lasers could be a more reliable means of guiding lightning discharges, and this could be important for lightning protection of sensitive ground installations and equipment.”

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