Albert Abraham Michelson (1852–1931) grew up about as far from a physics laboratory as nineteenth-century America could offer: in Murphys Camp, a California gold-rush town, and then Virginia City, Nevada, where his immigrant father sold supplies to silver miners. There was no obvious route from there to anywhere, so the teenage Michelson manufactured one — he travelled to Washington and petitioned President Ulysses S. Grant in person for a place at the Naval Academy. Grant had no appointments left and gave him one anyway, an act cheerfully beyond the legal quota. The Navy got a middling seaman with a genius for optics; physics got the man who would spend the next half-century measuring light more precisely than anyone alive, and who won measurement its first American Nobel Prize.

The man who timed light for fifty years

In 1877, while teaching physics at Annapolis, Michelson realised he could improve Foucault's rotating-mirror measurement of the speed of light — and improving that one number quietly became his life's project. His 1879 result, made with about $2,000 of borrowed equipment, was accurate to a few parts in a hundred thousand and stood for a generation. He came back to the problem again and again for five decades, each time with longer baselines and better mirrors: in 1926 he timed light over a 35 km round trip between two Californian mountain peaks, and at his death in 1931 he was mid-campaign on a measurement inside a mile-long evacuated pipe, dictating corrections from his sickbed. His weapon of choice throughout was interference: he understood earlier and more deeply than anyone that the wavelength of light is nature's finest ruler, and the instrument he invented to exploit it — the Michelson interferometer, which splits a beam, sends the halves on separate journeys, and reads their reunion as fringes — could resolve displacements of a few billionths of a metre using 1880s hardware. He even used it to redefine the metre itself in wavelengths of cadmium light, and to measure the diameter of the star Betelgeuse — the first star ever sized — with interferometer arms bolted to a telescope.

The most productive failure in physics

The experiment that made him immortal was, by its own goals, a flop. In 1887, with the chemist Edward Morley in a Cleveland basement, Michelson floated an interferometer on a sandstone slab in a trough of mercury and set out to detect the "luminiferous aether" — the supposed medium of light waves — by comparing light's speed along and across the Earth's motion. The apparatus could sense a hundredth of the expected effect. It found: nothing. No drift in spring, none in summer, none at any orientation of the slab. Michelson called the experiment a failure and mostly avoided the subject afterwards, which is one of history's better jokes, because that null result cracked the foundations of Newtonian space and time: it forced FitzGerald's and Lorentz's contraction hypotheses and cleared the ground for Einstein's special relativity, in which light's speed is the same for everyone and no aether is needed. The "failed" experiment is now the most celebrated null result in science — proof that a sufficiently precise no can outrank a thousand yeses. Michelson, with equal irony, remarked in 1894 that physics' grand principles seemed firmly established and future truths would be sought "in the sixth place of decimals". He then supplied the sixth-decimal measurement that helped demolish those principles.

The lineage

The 1907 Nobel Prize in Physics — the first to an American in any science — cited not a theory but his "optical precision instruments" and the measurements made with them: a prize for the art of measuring itself. The instruments outlived the man spectacularly. His interferometer, scaled from a basement slab to arms four kilometres long, is precisely the geometry with which LIGO felt spacetime itself stretch in 2015 — gravitational waves detected as a fringe shift a ten-thousandth of a proton's width, Michelson's mercury trough reborn with lasers and seismic isolation. And shrunk instead of stretched, folded into a feed-forward form by Ludwig Mach and Ludwig Zehnder, it lives by the thousand on silicon chips as the Mach–Zehnder interferometer — the workhorse of photonic computing. Every datacenter modulator flickering phase into brightness is running the trick Michelson perfected: when you need to measure (or compute) something impossibly small, let light interfere and read the fringes. Off duty he painted watercolours, played violin, and ran a feared billiards table — precision, in every medium he touched.