Albert Abraham Michelson: The Man Who Found Nothing
In 1887, in Cleveland, Michelson and Edward Morley built an instrument sensitive enough to detect the Earth's motion through the luminiferous ether — the invisible medium that nineteenth-century physics assumed light must be waving in. They found no motion at all. The null result is among the most consequential in the history of science, and its author spent the rest of his life doing what he had always done: measuring things more exactly than anyone had measured them before.
From Strzelno to Virginia City
He was born on 19 December 1852 in Strelno, then in Prussia and now Strzelno in Poland, into a Polish-Jewish family that emigrated to the United States when he was a small child. His father ran a store, and the boy grew up in the raw mining towns of the American West — Murphy's Camp in California, Virginia City in Nevada. For high school he lived in San Francisco with an aunt, Henriette Levy, finishing public school there in 1869. His sister Miriam became a novelist. The family was non-religious; Michelson stayed a lifelong agnostic.
An Appointment from President Grant
In 1869 he received a special appointment to the United States Naval Academy from President Ulysses S. Grant. Over four years as a midshipman he distinguished himself in optics, heat, climatology and technical drawing, graduating as an ensign in 1873. Two years of sea duty in the West Indies followed, then a return to Annapolis in 1875 to teach physics and chemistry.
It was there, in 1877, that a class demonstration turned into a career. Asked to show the students how the speed of light could be measured, Michelson improved on the apparatus so aggressively that in 1879 he published a formal figure: 299,910 kilometres per second, plus or minus 50. That year he was posted to the Nautical Almanac Office in Washington to work with Simon Newcomb, then went to Europe — Berlin, Heidelberg, the Collège de France, the École Polytechnique — before resigning his commission.
Chasing Light
The speed of light became the spine of his life. His 1883 value was 299,853 ± 60 km/s. Between 1920 and 1926 he ran a beam between Mount Wilson Observatory and Lookout Mountain, twenty-two miles away, and got 299,796 ± 4 — a precision that would have been unimaginable to his younger self, though the Santa Barbara earthquake of 1925 may have shifted the baseline underneath him. His last campaign, begun in 1929, ran the light through an evacuated tube near Santa Ana. He died with only 36 of a planned 233 measurement series complete; the result, 299,774 ± 11 km/s, was published in 1935, four years after his death. Over fifty years he had cut the uncertainty in the fundamental constant of the universe from fifty kilometres per second to eleven.
The instrument that made it possible was his own. In 1881 he built the interferometer, which splits a beam of light in two, sends the halves down perpendicular paths, and recombines them so that the interference fringes reveal differences in path length far smaller than a wavelength.
The Most Famous Null Result in Science
Appointed to the Case School of Applied Science in Cleveland in 1883, he refined the interferometer and in 1887 joined forces with Edward Morley of neighbouring Western Reserve University. The logic was simple: if the Earth ploughs through a stationary ether, light sent along the direction of travel should take measurably longer to return than light sent across it. Rotate the apparatus and the fringes should shift.
They did not shift. The experiment has been called the canonical demonstration that no detectable ether exists. Hendrik Lorentz responded by devising the contraction equations that would become part of the mathematics of special relativity. Whether it moved Einstein directly is less clear than legend suggests; Einstein himself said, "I was not conscious it had influenced me directly… I guess I just took it for granted that it was true." Michelson, for his part, had set out to measure the ether, not to abolish it, and never fully warmed to the relativistic world his experiment helped usher in.
Chicago, and the First American Nobel
He moved to Clark University in Worcester in 1890 and in 1892 to the new University of Chicago, where he was founding professor and first head of the physics department until retiring in 1929. He served as president of the American Physical Society in 1900, of the American Association for the Advancement of Science in 1910–11, and of the National Academy of Sciences from 1923 to 1927. He rejoined the Navy during the First World War and designed a rangefinder; he also built the echelon spectroscope, a high-resolution instrument for splitting spectral lines.
In 1907 he became the first American to win a Nobel Prize in any of the sciences. The medals piled up around it: Rumford (1888), Matteucci (1903), Copley (1907), Elliott Cresson (1912), Henry Draper (1916), the Royal Society's Albert Medal (1920), the Prix Jules Janssen (1922), the Gold Medal of the Royal Astronomical Society and the Franklin Medal (both 1923).
Measuring a Star
In 1920, with Francis G. Pease at Mount Wilson, he did something no one had done: measured the diameter of a star other than the Sun. Using a periscope arrangement that fed light from two sub-pupils up to twenty feet apart into the main pupil of the 100-inch Hooker Telescope, they resolved the red giant Betelgeuse. Every large interferometric array working today — the VLTI in Chile, CHARA on Mount Wilson, the Navy's NPOI — descends from that arrangement.
Why Albert Is Called a Genius
The quality in question is not theoretical insight; Michelson proposed no laws and wrote no equations that bear his name. It is instrumental imagination — the ability to see that a question others treated as unanswerable was really a problem of building a better ruler, and then to build it. The interferometer was a genuinely new idea about how to compare two quantities, and it converted an abstract cosmological question into fringes a person could count by eye. That same faculty produced the echelon spectroscope, the naval rangefinder and the stellar interferometer, and it kept squeezing the error bars on the speed of light for half a century.
The Nobel committee honoured precisely this: the instruments first, the results second. He was the first American scientist his European peers treated as an equal, and the presidencies of three national bodies say his colleagues thought so too.
The honest counter-case is that Michelson did not understand the significance of his most famous result. He was hunting the ether and was disappointed not to find it; Lorentz and Einstein supplied the meaning. He was, by his own account, driven less by grand questions than by pleasure — asked why he studied light, he is said to have answered "because it's so much fun." Call him the greatest experimentalist of his age rather than one of its great theorists, and the record fits without strain.
Legacy
He died in Pasadena on 9 May 1931, aged seventy-eight, with his final light-speed experiment unfinished. His name is on buildings at the University of Chicago, Case Western Reserve and the Naval Academy, on the Michelson Laboratory at the naval weapons station at China Lake, and on the Michelson–Morley Award and lecture series at Case Western. The larger monument is procedural. The interferometer he built in 1881 to chase a medium that turned out not to exist is now standard equipment wherever physicists need to compare two lengths with impossible accuracy, and the array he improvised on Mount Wilson in 1920 is the ancestor of every telescope that resolves a star as a disc rather than a point.
Achievements
- Albert Medal — 1920
- Matteucci Medal — 1903
- Nobel Prize in Physics — 1907
- Foreign Member of the Royal Society — 1902
- Copley Medal — 1907
- Rumford Prize — 1888
- Held posts at Case Western Reserve University, Clark University and University of Chicago
- Educated at Humboldt-Universität zu Berlin and United States Naval Academy
- Fields of research: astronomy and physics
