Forging new path with laser-guided lightning

Scientists say they have used a laser beam to guide lightning for the first time, hoping the technique will help protect against deadly bolts - and one day maybe even trigger them.

Lightning strikes between 40 to 120 times a second worldwide, killing over 4,000 people and causing billions of dollars worth of damage every year.

Yet the main protection against these bolts from above is still the humble lightning rod.

Now, in a study published in the journal Nature Photonics, scientists describe using a laser beam to guide a lightning bolt for more than 50 meters. "We wanted to give the first demonstration that the laser can have an influence on lightning - and it is simplest to guide it," said Aurelien Houard, a physicist at ENSTA Paris.

For the experiment, a car-sized laser was lugged up the 2,500m peak of Santis mountain in northeastern Switzerland.

The peak is home to a communications tower that is struck by lightning around 100 times year.

A telescope is used to focus the laser beam to maximum intensity at a spot around 150m in the air - just above the 124m tower.

During a summer storm in 2021, the scientists photographed their beam driving a lightning bolt for around 50 meters.

Three other strikes were also guided, interferometric measurements showed.

Lightning is a discharge of static electricity that has built up in storm clouds or between clouds and the ground.

The laser beam creates plasma, in which charged ions and electrons heat the air.

The air becomes "partially conductive, and therefore a path preferred by the lightning," Houard said.

In theory, this technique could also be used to trigger lightning.

That could allow scientists to better protect strategic installations, such as airports or rocket launchpads, by igniting strikes at the time of their choosing.