Picture an immense concert hall filled with 64,000 computers – not machines but people who compute figures. This entire hall functions as a map: “The ceiling represents the north polar regions. England is in the gallery, the tropics in the upper circle, Australia in the dress circle and the Antarctic in the pit.” As weather data pours in from around the world, coloured stage lights cue the human computers to work in unison. Towering above them in a pulpit is “a conductor of an orchestra in which the instruments are slide rules and calculating machines. But instead of waving a baton he turns a beam of rosy light upon any region that is running ahead of the rest and a beam of blue light upon those who are behindhand.” Lewis Fry Richardson’sfanciful proposalfora “slide-rule orchestra” was the culminatingvision of one of the most ambitious attempts ever made at weatherforecasting.

FOR a man who liked to be alone, Lewis Fry Richardson had come up with an idea guaranteed to make him feel uncomfortable. In 1913, he was superintendent of the Eskdalemuir Observatory, a remote weather station in Scotland. It was the perfect job for someone who counted solitude among his hobbies. Three years earlier, however, an event had taken place that had him yearning for a vast crowd of people – so long as everyone in it was handy with a slide rule.

On 20 May 1910, under the direction of the Norwegian meteorologist Vilhelm Bjerknes, weather stations across Europe simultaneously collected measurements from weather balloons at six different altitudes over a 6-hour stretch. The idea of all that data would make …