Sending lightning with lasers

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Lightning may look pretty, but every year it kills thousands of people, does massive amounts of damage to buildings and infrastructure, and causes power outages.

The only protection we have is lightning rods, which were invented 300 years ago and only protect a small area.

The cost of lightning damage to buildings is difficult to determine worldwide, but insurance company payouts for repairs to homes and businesses in the US in 2020 were about $2 billion ($2.87 billion).

Insurance data from the UK suggests the cost of covering lightning strikes is rising.

Swiss scientists used a laser to move lightning.

The problem is likely to get worse as the climate crisis sparks a wave of wildfires worldwide, increasing lightning strikes.

A 2014 study suggested that the number of strikes increases by 1 percent for every degree (Celsius) of global warming.

Light bars have their uses, but scientists are looking for a better way to determine where lightning strikes, and lasers may be the answer, according to a new study.

How they did it

This latest experiment was conducted near a telecommunications tower on Switzerland’s Säntis mountain, which is often struck by lightning — about 100 times a year, even though the tower itself is protected by a lightning rod.

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The results of the study showed that the lightning flowed almost in a straight line near the laser pulses, but the lightning strikes were more randomly distributed when the laser was off.

While this study isn’t the first attempt at directing lightning trails, it’s the first to show it’s possible.

The scientists attributed this to the powerful laser they used and the high altitude. At high altitudes, the air is less dense. This makes it easier for current to pass through, meaning future sea-level experiments would need a more powerful laser.

The laser on the top of the Säntis (2500 m) was focused above a 124 m high transmission tower, equipped with a traditional lightning rod.

To understand how the scientists used light to change the path of electricity, you need to understand what lightning actually is: a flow of charged particles from one location to another.

Particles in clouds are usually electrically neutral when they form, but build up both positive and negative charge. The cloud wants to become neutral by exchanging charge with the ground.

The type of lightning most people are familiar with is the erratic strikes of bright light seen between the ground and clouds, but there are other types.

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Lightning can move between clouds. It can also move from clouds upwards to the upper atmosphere. This can even produce wisps of red sky glow where the thinner atmosphere warms. This heat energy is then released as light.

As the charge builds up in the cloud, it reaches incredibly high voltages (roughly equivalent to eight million car batteries linked together) that rip a path through the sky. The electrical current required to split apart the components of air is generally about 300 million volts per square meter.

The pushing force of this enormous voltage in electrically charged (ionized) air allows the charge to flow down from the cloud and discharge into the ground or nearby buildings. This current will follow the most electrically conductive path.

This is why lightning rods are sometimes used to protect buildings from lightning. Metal is more electrically conductive than air, so if you stick a large rod in the ground, lightning has an easier path than through air. However, it can only protect a small area.

Many researchers believe that some thunderstorms may be caused by cosmic rays (high-energy particles from outside the solar system).

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These particles pass through the atmosphere and interact with air to create an ionized path through their direction of travel. This is a theory that researchers are divided on whether it affects the total number of lightning strikes around the world.

The scientists used a powerful laser to create ionized trails in a similar way to the cosmic ray theory.

Firing fast (1000 times per second) energetic pulses with a laser heats and ionizes the air, making it briefly conductive. The lightning strike will have less resistance along this path and will thus be more inclined to flow in that direction.

If this technology is perfected, it could one day help protect infrastructure such as airports and nuclear power plants.

It could even be used in a more advanced form to protect homes with a laser at a safe distance. However, it’s unlikely to be rolled out in your area any time soon, if only because of power costs.The conversation

Ian Whittaker, senior lecturer in physics, University of Nottingham Trent

This article is republished from The Conversation under a Creative Commons license. Read the original article.