A Hard Rain is Gonna Fall

In 1538 the sculptor and goldsmith Benvenuto Cellini attended the entrance into Rome of Duchess Margaret of Austria. It was raining. In his autobiography Cellini tells how he fired several large pieces of artillery at the thickest of the clouds. The rain stopped and by the fourth shot the sun was shining 'and so I was the sole cause of the festival succeeding to the joy of everyone'. Cellini was remarkably ahead of his time. Fast forward to 1992 and the Chinese army could be found firing more than 4000 anti-aircraft shells at clouds passing over Sichuan province in an attempt to stop it from hailing.

Weather manipulation has for centuries been a holy grail sought by meteorologists, farmers and the military. Thus some consternation was caused in Mexico last January when scientists from the National Center for Atmospheric Research in the US announced that they had succeeded in increasing the rainfall from certain storm clouds by up to 50%. The technique used was cloud-seeding, a notoriously imprecise procedure. Yet the significance of the Mexican experiment was that it provided the same results as research gained in the early 1990s - consistency has forever been weather modification's Achilles heel.

Weather control was traditionally seen as the preserve of the gods. However, in 102 BC Plutarch broke the mould by suggesting that the noise of a great battle produced rain as it mimicked the sound of thunder. The belief in warfare prompting precipitation persisted - despite Cellini's assertions - until the 20th century. Now control of the weather is a favoured science fiction plot device. Above the towering city blocks of 2000 AD's Judge Dredd stories hovers Weather Control, a vast metal ring that provides the weather for the city below and is used to quell civil unrest by providing a localized downpour or tornado whenever necessary.

Indeed the inventor of the cloud-seeding technique was Irving Langmuir, a Nobel prize-winning chemist and a man indelibly linked to both science and sci-fi. In the 1930s and 1940s Langmuir worked in General Electric's Research Laboratories in Schenectady, New York, renowned as a playground for some of the most brilliant scientific minds of the time.

It so happened that H. G. Wells visited this maelstrom of creativity and Langmuir offered him the idea for a story: an imaginary substance, an allotrope of ice that remains solid at room temperature. Wells never used the idea but Kurt Vonnegut, who also worked at GE, did. Langmuir's suggestion eventually became 'ice-nine', the subject of Vonnegut's 1963 apocalyptic tale Cat's Cradle. (Langmuir appears in the book as the monumentally distracted scientist Dr Felix Hoenikker.)

Langmuir had always been attracted to the edges of science. He coined the phrase 'pathological science' to describe scientific results that are falsified through a pathological wish to believe in them. Yet despite his own crusade against phoney science he had no qualms about leaping wholeheartedly into what was - notwithstanding the foundation of the Leningrad Institute of Rainmaking in 1932 - an uncharted branch of science.

His enthusiasm stemmed from an experiment undertaken in the 1940s. Langmuir created home-made clouds - tiny water droplets suspended in a deep-freeze box - into which he dropped a tiny grain of dry ice. Ice crystals formed, grew larger and then fell to the ground. Thus rain that wouldn't normally fall might be encouraged to do so. By replacing dry ice with cheaper and less bulky silver iodide, Langmuir claimed to have controlled rainfall over much of the United States for weeks in 1951. Weather control immed-iately leapt onto the political agenda, but later lost favour with the public when it was revealed that the US air force had seeded clouds in Vietnam in an attempt to flood North Vietnamese supply routes.

Despite scepticism, many types of weather modification are still practised. 'Hail suppression' bombards clouds with rockets containing silver iodide to shrink hailstones and prevent them from destroying crops. Lasers are used to burn off fog on runways, while 'lightning control' sends rockets trailing wires into thunderclouds to encourage storms to discharge their lightning into the wires rather than unfortunates on the golf course.

Nevertheless, deforestation and CO2 emissions have shown that mankind can cause massive climatic change without even trying. The apocalyptic visions depicted in the films The Day the Earth Caught Fire (1961) and Soylent Green (1973) reflect fears of an inadvertent climatic disaster caused by new technology. You only need to look at the latest proposals for weather control devices to break out in a Cold War sweat all over again. Ben Eastlund, an American physicist, has designed a system for eradicating tornadoes by blasting them with powerful beams of microwave radiation generated by huge solar-powered satellites orbiting the earth. What it will do to anybody caught in the path of the energy beams is less certain. Such is the stuff that electric dreams are made of.