Theories get the credit, and instruments do the work. Nearly every major revision of the scientific picture of the world in the last four centuries began when somebody built a device that revealed something nobody had been able to detect before. The pattern repeats with unusual regularity. A new instrument…

Around 1940, Alan Turing sat down to write a manual. New recruits were arriving at Bletchley Park with mathematical training and no idea how the German cipher machines worked or what was being done about them, and somebody had to explain it. The result runs to about 150 typed pages…

In 1927 a Belgian priest and physicist published a paper in a Brussels journal showing that a universe governed by general relativity must be either expanding or contracting, deriving the relationship between a galaxy’s distance and its recession speed, and calculating the rate from the observational data then available. Two…

In February 1851, visitors to the Panthéon in Paris were greeted by a notice inviting them to come and watch the Earth turn. Inside, a brass sphere weighing twenty eight kilograms hung from the centre of the dome on a wire sixty seven metres long, swinging slowly back and forth…

On the evening of 13 March 1781, an organist from Bath was working through a survey of double stars from his back garden when he noticed an object that did not look right. Unlike a star, it showed a small disc, and it grew larger when he increased the magnification.…

In February 1858, on a small island in the Moluccas, a thirty five year old English collector lay ill with fever and worked out the mechanism of evolution. Within days he had written it up. He then posted the essay to the one man in England he thought would appreciate…

In 1835 the philosopher Auguste Comte offered an example of knowledge that would forever lie beyond human reach. We might learn the shapes, distances and motions of the stars, he wrote, but their chemical composition was a question no method could ever answer. Twenty four years later the method was…

In 1814, in a book about probability, Pierre-Simon Laplace described an imaginary intelligence that knows the position and velocity of every particle in the universe at a single moment, and possesses the analytical power to process that information. For such an intelligence, he wrote, nothing would be uncertain, and the…

In the first ten days of September 1854, more than five hundred people died of cholera within a few streets of each other in Soho, London. A local physician named John Snow marked each death on a street map and saw that the deaths formed a ring around a single…

On 6 November 1919, at a joint meeting of the Royal Society and the Royal Astronomical Society in London, the results of two eclipse expeditions were announced. The following morning The Times ran the headline “Revolution in Science”, and within days Albert Einstein, previously known to a few hundred physicists,…