Lasers to force rain

Scientists working on technique to use lasers to force rain

(PhysOrg.com) -- As with many of man's most basic ancient desires; to be able to fly, to become invisible etc. making it rain on command (or by prayer) has always been high on the list, and up to now, has proved more elusive than other advances in the sciences. Now however, physicists in Switzerland might have finally made a breakthrough. In their paper published in Nature Communications, they describe a method whereby a laser is used to create nitric acid particles in the air to which moisture will gravitate forming droplets.

Experimental setup. Image: NPG, doi:10.1038/ncomms1462

A group of scientist with a Teramobile mobile femtosecond-Terawatt laser system start firing it into the sky (on a very humid day - over 70%) for 113 hours. To ensure their results were constrained to one area, wind shields were used. They then sampled the aerosols alternatively at 2 cm distances in the areas where they expected to see nitric acid particles form. In so doing they found that their efforts did indeed result in the creation of nitric acid particles which caused water droplets to form on the order of a few microns in size.

The tiny drops are not heavy enough to fall as rain. But this is a good start.