Using Lasers To Make It Rain

World water use is rising faster than our world population. Tiny island nation Tuvalu has been crippled by drought and may be just the first island nation to run dry. Texas has been hit by massive dust storms thanks to that state’s record drought. That’s just a drop in the bucket in current drought news, and it’s enough to make one start wishing (or praying) for clouds on demand.

Luckily, thanks to Jérôme Kasparian, making rain appear out of thin air may soon be a reality.

Kasparian, a French physicist at the University of Geneva, has focused his research on the effects of powerful laser pulses on the atmosphere. With help from a team of scientists, Kasparian has pioneered a novel method for using these laser pulses to create water droplets in humid but otherwise rain-free air. The technique is called laser-assisted water condensation, and may be the key to bringing rain with the flip of a switch.

Traditional cloud seeding has required blasting the atmosphere with small particles of things like dry ice or silver iodide. The water molecules in the atmosphere coalesce on the tiny particles to form rain drops, just as natural rain is seeded by dust. While these methods occasionally work, the tradeoff is flooding the air with chemicals that can spread wherever the winds take them. Seeding is costly and not always effective. There’s also the whole aspect of having your rainwater being contaminated from the start with sprayed chemicals.

The laser method is potentially superior. Unlike chemical seeding, lasers are far more easily aimed and much more accurate. They also have the distinct advantage of being able to be turned on and off at will. The team uses a laser capable of producing extremely short pulses of light. Each pulse carries several trillion watts of energy.

The laser is powerful enough to knock electrons off of atmospheric molecules, created charged particles that water can stick on to form droplets. Kasparian’s team has gone as far as to test the laser in skies above Berlin. Using a second laser to measure and confirm any changes to the atmosphere, the team found that their laser actually produced results. Kasparian said that it’s not a magic cure-all; the laser system can’t create rain in dry air, and it’s not powerful enough to completely change the weather. But, as it stands right now, the system is capable of producing localized showers over a distance of a few miles.

In the second episode of our “Upgrade” series, Motherboard heads to Geneva to watch Kasparian’s laser in action and learn how he and his team are leading us to a future where agriculture and people’s thirst won’t be fully at the mercy of finicky weather.

 

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