Scientists are close to discovering how to do something that humans throughout history have dreamed of accomplishing: summoning rainfall.
By shooting laser beams into the air, researchers from the University of Geneva realized that in the right conditions the lasers can trigger the growth of micron-sized water droplets. The experiment, detailed in the Nature Communications Journal, may be a precursor to actually manipulating the presence of significant rainfall.
The researchers spent 133 hours firing laser beams across Switzerland's Rhône river while employing a variety of temperatures, humidity levels and other atmospheric conditions. At a relatively low humidity of 70 percent, the intense pulses of light created nitric acid particles in the air that behaved like atmospheric glue, according to The Guardian, causing the water molecules to bind together into droplets while preventing them from re-evaporating.
Within a few seconds, the drops reportedly grew. While still miniscule, they were large enough to encourage scientists to carry on with their research.
We have not yet generated raindrops - they are too small and too light to fall as rain. To get rain, we will need particles a hundred times the size, so they are heavy enough to fall, Jerome Kasparian, a physicist at the University of Geneva, told The Guardian.
Rain clouds form when airborne pockets of tiny particles condense water vapor around them. Enough of these could seeds produce clouds and subsequently, rain.
Kasparain said shooting lasers into the sky may be particularly effective if researchers aimed to create water droplets in air masses drifting towards mountains. In that scenario, the air would cool as it rose, causing the droplets to expand and eventually fall.
Similarly, the lasers could also be used to stave off rainfall by creating so many microscopic droplets that none grow large enough to fall, a method that Kasparian said one day could be used to reduce flooding or weaken a monsoon.
This isn't the first time scientists have developed weather modification techniques. The process, known as cloud seeding, has been around for years and involves firing hazardous chemicals - such as silver iodide - into the air. The silver iodide provides a surface for water vapor to condense on and theoretically prompts downpours from cloudy skies.
However, silver iodide is a chronic pollutant and may cause skin rashes, irritation of the mucous membranes, anemia, depression and other ailments after chronic ingestion.
Some nationalities are particularly invested in the race to control the weather. Wired Magazine reports that in China, the Beijing meteorological bureau has an office devoted to weather modification. In 2009, the department claimed it was able to successfully ensure blue skies for a Beijing parade celebrating 60 years of communism by launching 19 cloud-seeding jets and 432 explosive rockets to empty the sky of rain beforehand.