The number usually quoted for Enigma is 158,962,555,217,826,360,000 possible settings. It is roughly the number of grains of sand in a cube two kilometres on each side, and it is correct. It is also almost irrelevant, and understanding why requires following the current through the machine one keypress at a…

On 9 October 1604 a star appeared in the constellation Ophiuchus, near the foot of the serpent handler, where no star had been the night before. Within days it was brighter than Jupiter. It stayed visible to the naked eye for about a year and then faded out. Four centuries…

In December 1932 a twenty seven year old mathematician sat in a room in Warsaw with a pile of intercepted German radio traffic, a set of stolen operating manuals, and no machine. By the end of the month Marian Rejewski had worked out the internal wiring of the Enigma’s rotors…

The Moon is tidally locked, so the same hemisphere has faced the Earth for as long as there have been eyes to look at it. Until October 1959, roughly forty one percent of the lunar surface had never been seen by anybody, ever, and there was no way to find…

Marie Curie is one of the most written about scientists in history and one of the least read. Almost everyone knows the story. Very few people have looked at the actual papers, partly because they are in French, partly because they are scattered across twenty years of Académie des Sciences…

In 1919 the Smithsonian published a sober sixty nine page monograph by a physics professor at Clark University called A Method of Reaching Extreme Altitudes. It was mostly about the mathematics of multistage rockets and the efficiency of propellants, and it was rigorous enough that the Smithsonian had funded the…

Sputnik 1 was an aluminium sphere 58 centimetres across with four trailing antennas, weighing 83.6 kilograms, and almost all of the inside was battery. It carried no camera, no telescope and no experiment in the usual sense. It carried a radio transmitter, and the radio transmitter was the experiment. It…

In 1705 Edmond Halley published a thin book of comet orbits and put a bet in it. The comets recorded in 1531, 1607 and 1682 had, he argued, nearly identical paths, and the intervals between them were suspiciously close to seventy six years. They were not three comets. They were…

In 1892 Lord Rayleigh published a short note in Nature about a discrepancy he could not explain. He had prepared nitrogen two ways. Nitrogen extracted from air, with the oxygen and the water and the carbon dioxide removed, came out at 1.2572 grams per litre. Nitrogen produced chemically, by decomposing…

On the evening of 1 October 1847 there was a party downstairs in the Mitchell house on Vestal Street, Nantucket. Maria Mitchell, twenty eight years old and the island’s librarian, left the guests, climbed to the roof of the Pacific Bank where her father worked, and pointed a two inch…