Albert Abraham Michelson
German-born American physicist, first US Nobel laureate in science (1907). With Edward Morley, used a precision interferometer in 1887 to measure Earth's motion through the luminiferous aether — and got a null result every time. The negative result they could not explain became Einstein's positive postulate twenty-four years later.
Biography
Albert Abraham Michelson was born in Strelno, Prussia (now Strzelno, Poland), in 1852, the son of a Jewish merchant family who emigrated to Murphys Camp in California's Gold Country in 1855 and later San Francisco. He won an at-large appointment to the US Naval Academy from President Ulysses S. Grant in 1869, graduated in 1873, and was retained as an instructor in physics and chemistry. Stationed at Annapolis, he built his first ether-drift apparatus in 1881 — a single-arm interferometer that yielded an inconclusive null. To pursue the experiment with greater precision, he resigned his commission, studied in Berlin under Helmholtz, and accepted a chair of physics at the Case School of Applied Science in Cleveland.
In Cleveland from 1885, Michelson partnered with Edward Williams Morley, a chemist and experimentalist of remarkable mechanical patience at neighbouring Western Reserve University. Together they built the Michelson-Morley apparatus: an interferometer floating on a stone slab on a pool of mercury, isolating it from vibration; two perpendicular optical arms 11 metres long folded by mirrors; and a sodium-flame source whose monochromatic light produced an interference fringe pattern visible through a telescope. They turned the apparatus 90° in steady increments and watched for fringe shifts. None came. They published the result in 1887 in the American Journal of Science. The aether — the luminiferous medium that all of nineteenth-century optics had assumed — refused to make itself measurable. Lorentz and FitzGerald independently proposed that real material contraction in the aether might explain the null; Einstein's 1905 paper would discard the aether entirely and elevate the constancy of c to a postulate.
Michelson went on to a Nobel Prize in 1907 — the first awarded to an American in science — for his measurements of the speed of light, which he progressively pinned down to a precision of one part in ten thousand using rotating-mirror techniques. He also pioneered the Michelson stellar interferometer, which in 1920 enabled the first direct measurement of a stellar diameter (Betelgeuse, 0.05″). The Michelson interferometer principle would reappear a century later in LIGO, the gravitational-wave observatory whose 4-kilometre arms sense displacements smaller than 10⁻¹⁸ m. Michelson died in Pasadena in 1931, working until the end on his final speed-of-light measurement, conducted in a kilometre-long evacuated tube at the Irvine Ranch.
Contributions
- 011887 Michelson-Morley experiment with Edward Morley — null result for aether-wind effect; the empirical foundation for special relativity.
- 02First American Nobel laureate in science (1907), for optical precision instruments and the metrological measurements of c.
- 03Speed-of-light measurements progressively refined from 299,853 km/s (1879) to 299,796±4 km/s (1926, Mt Wilson–San Antonio Peak).
- 04Michelson stellar interferometer — first direct measurement of stellar angular diameters (Betelgeuse, 1920).
- 05Interferometric metrology defining the metre in terms of optical wavelengths — pre-laser standard later realized in 1960.
Major works
joint paper with Edward Morley reporting the null result that became special relativity's empirical foundation.
popular Lowell Lectures volume; the Michelson interferometer principle for a non-specialist audience.
late synthesis of his interferometric methods, written in his last years at Caltech.