Cloud seeding: Making your own rain and snow

Today, 13 November, marks the date back in 1946 when Vincent J Schaefer, American chemist and meteorologist, performed the first cloud seeding experiment, artificially inducing snow by sprinkling clouds with pellets of dry ice from an airplane.

While this first attempt was not completely successful – the artificially created snow evaporated as it fell through the dry air and disappeared before it hit the ground – it showed that the concept of cloud seeding is possible. This resulted in the GE Research Laboratory (where Schaefer was working at the time) receiving funding for further research into cloud seeding and weather modification.

New Zealand – getting enough rain and snow the natural way!
(© All Rights Reserved)

While initial experiments in cloud seeding was done using dry ice, later substances used include silver iodide, liquid propane and, more recently, salt. Cloud seeding has been done to different extents around the world, in Asia, North America, Europe, Australia and Africa, with China having the world’s largest commercial operation in this domain.

In some of the most recent experimental work in the field of cloud seeding, German scientists at the University of Geneva experimented with firing short infrared laser pulses into the air, the idea being that the pulses might encourage the formation of atmospheric particles which could act as seeding particles in the clouds. According to lead researcher Jerome Kasparian, “the laser pulses generate clouds by stripping electrons from atoms in air, which encourage the formation of hydroxyl radicals. Those convert sulphur and nitrogen dioxides in air into particles that act as seeds to grow water droplets.”

While this work is still at an experimental stage, it has shown promising results in laboratory conditions. A field experiment, where the pulses were aimed at the skies over Berlin, has also shown notable increases in the density and size of water droplets in the area, when measured using weather LIDAR and it is believed that, using the right frequencies and intensities, generation of rain by this means might become a real possibility.

This really feels like science fiction, doesn’t it? Quite incredible to imagine, really!

And of course it immediately reminded me of Kate Bush’s song ‘Cloudbusting’. So herewith, in commemoration of the pioneering work of Vincent Schaefer, father of cloud seeding, the wonderful short film produced for ‘Cloudbusting’ by Kate Bush and Terry Gilliam, starring Donald Sutherland as Wilhelm Reich and Bush as his young son Peter.


Gordon Gould, laser shows and space battles

If you were young in the late 70s/early 80s, you may have a special appreciation for today’s subject. Remember those high-tech night club laser shows that were so popular at the time? Well, today we celebrate the invention of the laser.

On this day back in 1957, the American physicist Gordon Gould, noted down the principles of ‘Light Amplified by Stimulated Emission of Radiation’, or ‘LASER’ in a dated notebook entry. His notes also included various applications for laser light, and he was the first to coin the term ‘LASER’ at a conference in 1959.

(© All Rights Reserved)

Sadly Gould’s patenting savvy at the time didn’t match his physics skills, and his 1959 patent application was denied by the US Patent Office. The USPO subsequently went on to grant a patent in 1960 to Bell Laboratories, whose scientists, Charles Townes and Arthur Schawlow, were independently and in parallel to Gould, also working on the concept of lasers.

This effectively ‘robbed’ Gould of his share of the benefits – money, prestige, science acumen – derived from the invention. Not willing to accept this fate, Gould took the matter to court, an action that set in motion 28 years of lawsuits. He won a minor patent in 1977, but it was only in 1987 that he succeeded in achieving a major victory, claiming patents for a number of laser devices.

To this day, science historians are not in agreement about who to give primary credit for the invention of the laser, but there is no doubt that Gould deserves a large portion of the credit.

Since its discovery, many different types of lasers have been developed, producing emissions in ways too intricate to try and discuss in a blog post. However, the key feature of a laser beam is its high degree of spatial and temporal coherence. ‘Spatial coherence’ means there is very little diffraction in a laser beam, so it can be focused on a tiny spot over a significant distance. ‘Temporal coherence’ means the wave phase of the light beam is correlated over a large distance, producing a polarised wave at a single frequency.

Lasers are not just important scientific tools – they’re also a great subject for science photography.
(© All Rights Reserved)

Of course lasers are far more useful than simply creating special effects light shows. They have become a ubiquitous part of modern society, being used in electronics, information technology, medicine, industry and military applications. In any single day you may encounter lasers in barcode scanners, CD players, computer hard disks, laser printers and more.

Thanks to their precise focusing ability, lasers are used in a range of medical applications, including surgery, treatment of kidney stones, eye treatments etc. They are also used in cosmetic skin treatments. Their accurate cutting ability makes them extremely useful in many modern industrial cutting and part-making applications. They are also an integral part of many military systems, including guidance and electro-optical defence systems.

And perhaps most importantly, judging by countless science fiction movies over the years, lasers will be absolutely indispensable as the weapon of choice to defend our planet and obliterate enemy space ships!