Timeline of the Theory of Relativity
The special and general theories of relativity, from the Michelson–Morley experiment of 1887 through Albert Einstein's theories of 1905 and 1915 to experimental tests up to 2026, including the gravitational-wave detections of 2015 and 2017.
- Category
- Science & Technology
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- physics
- Events
- 27 events 1887–2026
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- by claude-opus-5-5
1887: Michelson and Morley find no aether wind
In Cleveland, Ohio, Albert A. Michelson and Edward W. Morley used an interferometer to compare the speed of light in perpendicular directions, expecting Earth's motion through the luminiferous aether to shift its fringes. They found no significant difference, the first strong evidence against some aether theories. The experiment's influence on Albert Einstein is disputed, but the null result helped the constancy of the speed of light win acceptance.
Wikipedia1889–1892: FitzGerald and Lorentz propose length contraction
To reconcile the Michelson–Morley null result with a stationary aether, George FitzGerald in 1889 and Hendrik Lorentz, independently, in 1892 proposed that bodies moving through the aether contract along their direction of motion by just enough to cancel the expected fringe shift. The hypothesis was widely seen as ad hoc until Albert Einstein derived the same contraction from the basic principles of special relativity.
Wikipedia1904–1905: Lorentz and Poincaré refine the Lorentz transformation
Hendrik Lorentz, refining transformations he had used since 1892, published in 1904 the coordinate transformations now named after him, meant to explain why motion through the aether went undetected; Joseph Larmor had reached equivalent equations in 1900. In June 1905 Henri Poincaré gave them their modern form, named them after Lorentz and showed that they form a group. Both Lorentz and Poincaré kept the aether as an undetectable rest frame.
Wikipedia1905: Einstein publishes the special theory of relativity
In "On the Electrodynamics of Moving Bodies", received by Annalen der Physik on June 30, Albert Einstein built a theory on two postulates: the laws of physics are the same in all uniformly moving frames, and light in a vacuum has the same speed whatever the motion of its source. From them he derived the Lorentz transformation, with time dilation and length contraction as features of space and time themselves, and found the aether superfluous.
Wikipedia1905: Einstein derives the equivalence of mass and energy
In a three-page follow-up published on November 21, "Does the Inertia of a Body Depend Upon Its Energy Content?", Albert Einstein argued that a body emitting energy as light loses mass equal to that energy divided by the square of the speed of light. Henri Poincaré and Friedrich Hasenöhrl had linked radiation to mass, but Einstein first proposed the equivalence, now written E = mc^2, as a general principle.
Wikipedia1907: Einstein formulates the equivalence principle
Albert Einstein, then at the patent office in Bern, had what he later called his "happiest thought": a person falling freely would not feel their own weight. In a review written late that year and published in 1908, he proposed that a uniform gravitational field is equivalent to a uniformly accelerated frame and used the idea to predict gravitational time dilation and the bending of light, his first step toward general relativity.
Wikipedia1908: Minkowski unites space and time as spacetime
Building on a four-dimensional treatment that Henri Poincaré had sketched in 1905, Hermann Minkowski recast special relativity as the geometry of a spacetime in which all observers agree on the interval between events. In a lecture in Cologne on September 21 he declared that "space by itself, and time by itself, are doomed to fade away into mere shadows" and only their union would stay real. Albert Einstein, his former student, was cool to the idea at first, but it became the standard language of relativity.
Wikipedia1913: Einstein and Grossmann recast gravity as spacetime geometry
Albert Einstein and his former classmate Marcel Grossmann, a mathematician who introduced him to Riemannian geometry and the tensor calculus of Gregorio Ricci-Curbastro and Tullio Levi-Civita, published the "Entwurf" ("Outline") theory, the first to describe gravity by the metric of a curved spacetime. Its field equations were not generally covariant, a restriction Einstein defended with his "hole argument" until late 1915.
Wikipedia1915: Einstein presents the field equations of general relativity
Albert Einstein completed general relativity, which treats gravity as the curvature of spacetime by matter and energy, in four papers to the Prussian Academy of Sciences in November, explaining Mercury's anomalous perihelion advance of 43 arcseconds per century on November 18 and giving the final field equations on November 25. David Hilbert presented his own variational theory on November 20; most historians read the surviving proofs of his paper as lacking the final equations, though a few dispute this.
Wikipedia1916: Schwarzschild finds the first exact solution
Karl Schwarzschild, serving in the German army on the Russian front, found the first exact solution of Albert Einstein's field equations other than flat spacetime, for the field outside a spherical, non-rotating mass; he sent it to Einstein in December 1915, and Johannes Droste found it independently. It became the usual approximation for the fields of stars and planets and, as understood only later, the description of non-rotating black holes.
Wikipedia1916: Einstein predicts gravitational waves
In a June paper using an approximation to his field equations, Albert Einstein concluded that general relativity predicts gravitational waves, ripples in spacetime that travel at the speed of light; Henri Poincaré had proposed such waves in 1905. Einstein corrected errors in a 1918 paper that introduced the quadrupole formula for the energy the waves carry away, but doubts that they were physically real persisted until the late 1950s.
Wikipedia1917: Einstein adds the cosmological constant
Applying general relativity to the whole universe in "Cosmological Considerations in the General Theory of Relativity", Albert Einstein added a cosmological constant to his field equations to allow a static universe, as was then assumed. He dropped it in 1931 after Edwin Hubble's observations pointed to expansion, but the 1998 discovery that the expansion is accelerating revived it as the simplest explanation for dark energy.
Wikipedia1919: Eclipse expeditions measure the bending of starlight
During the total solar eclipse of May 29, expeditions organized by Frank Dyson and Arthur Eddington photographed stars near the Sun from Sobral, Brazil, and the island of Príncipe. Their imprecise measurements agreed with general relativity's predicted deflection of 1.75 arcseconds, twice the Newtonian value, and the November 6 announcement made Albert Einstein world famous. Charges of biased data selection, made notably in 1980, have been rebutted by historians citing a 1979 remeasurement of the Sobral plates.
Wikipedia1938: Ives and Stilwell detect the transverse Doppler effect
Herbert Ives and G. R. Stilwell compared light emitted forward and backward by fast-moving hydrogen atoms in a canal-ray tube and found the small extra shift that time dilation adds to the Doppler effect, a test Albert Einstein had suggested in 1907. It was the first direct, quantitative confirmation of the time dilation factor, although Ives preferred to interpret it through the aether theory of Hendrik Lorentz and Joseph Larmor.
Wikipedia1940: Rossi and Hall show fast muons live longer
Comparing cosmic-ray muons, then called mesotrons, at Echo Lake and in Denver, Colorado, Bruno Rossi and David B. Hall found that the distance muons traveled before decaying grew in proportion to their momentum, as relativistic time dilation predicts. Their paper, published in 1941, also gave a lifetime at rest of about 2.4 microseconds, close to the modern value of about 2.2.
Wikipedia1960: Pound and Rebka detect gravitational redshift
Robert Pound and his graduate student Glen Rebka Jr. sent gamma rays 22.5 meters up and down a tower at Harvard University, using the Mössbauer effect in iron-57 to detect the minute frequency shift of light rising or falling in Earth's gravity. The experiment, proposed in 1959 and reported in April, matched the prediction within 10 percent, the last classical test of general relativity to be verified; refinements reached 1 percent by 1964.
Wikipedia1964: Shapiro predicts a gravitational delay of radar echoes
Irwin Shapiro of the Massachusetts Institute of Technology predicted that radar signals passing near the Sun would be delayed by its gravity, by up to about 200 microseconds on a round trip to Venus, and proposed timing echoes from Venus and Mercury. Haystack radar measurements from November 1966 to August 1967, reported in 1968, matched the prediction, and later spacecraft tracking, notably of Cassini, made the test far more precise.
Wikipedia1971: Hafele and Keating fly clocks around the world
Joseph Hafele and Richard Keating flew four cesium-beam atomic clocks around the world on commercial airliners, eastward and then westward, and compared them with clocks at the United States Naval Observatory. The eastbound clocks lost about 59 nanoseconds and the westbound gained about 273, consistent within the experiment's roughly 10 percent precision with the effects of speed and altitude predicted by special and general relativity.
Wikipedia1974: Hulse and Taylor discover the first binary pulsar
Using the 305-meter Arecibo radio telescope, Russell Hulse and Joseph Taylor of the University of Massachusetts Amherst found a pulsar orbiting a companion every 7.75 hours; the companion was later shown to be another neutron star. The orbit has since shrunk at the rate general relativity predicts for energy lost to gravitational waves, now matching within about 0.2 percent: the first indirect evidence for the waves. Hulse and Taylor shared the 1993 Nobel Prize in Physics.
Wikipedia1976: Gravity Probe A measures gravitational time dilation
Gravity Probe A, a joint experiment of NASA and the Smithsonian Astrophysical Observatory, carried a hydrogen maser clock on a Scout rocket to an altitude of 10,000 km during a flight of just under two hours, comparing its frequency with that of a similar maser on the ground. It confirmed that clocks run faster higher in Earth's gravitational field, matching the prediction of general relativity to about 70 parts per million.
Wikipedia1977: GPS test satellite confirms relativistic clock shift
Navigation Technology Satellite 2, a technology-demonstration satellite for the Global Positioning System, carried the first cesium atomic clock into orbit; left uncorrected for about 20 days, it ran fast by 442.5 parts per trillion against a predicted 446.5. GPS satellite clocks were set before launch to tick slightly slow, at 10.22999999543 instead of 10.23 megahertz, offsetting a net gain of about 38.6 microseconds a day: about 45.8 from weaker gravity minus 7.2 from orbital speed.
Wikipedia1979: First gravitationally lensed quasar identified
Dennis Walsh, Robert Carswell and Ray Weymann, working at Kitt Peak National Observatory in Arizona, found two quasars 6 arcseconds apart with nearly identical spectra and proposed that they were two images of one quasar formed by a gravitational lens. Later observations confirmed that a foreground galaxy and its cluster bend the light. Fritz Zwicky had proposed in 1937 that galaxies could act as such lenses, after Orest Khvolson in 1924 and Albert Einstein in 1936 described lensing by stars.
Wikipedia2004–2011: Gravity Probe B measures geodetic and frame-dragging effects
Gravity Probe B, a NASA satellite mission led by Stanford University and launched on April 20, used four quartz gyroscopes in polar orbit to measure the geodetic effect of Earth's curved spacetime, predicted by Willem de Sitter in 1916, and frame dragging by Earth's rotation, first derived by Josef Lense and Hans Thirring in 1918. Final results in 2011 agreed with general relativity to about 0.3 percent and about 20 percent respectively, short of the 1 percent goal for frame dragging.
Wikipedia2015: LIGO detects gravitational waves from merging black holes
On September 14, both detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO), in Washington and Louisiana, made the first direct observation of gravitational waves (GW150914), from two black holes of about 36 and 29 solar masses merging more than a billion light-years away. Announced on February 11, 2016, the signal matched general relativity's predictions and led to the 2017 Nobel Prize in Physics for Rainer Weiss, Barry Barish and Kip Thorne.
Wikipedia2017: Neutron-star merger seen in gravitational waves and light
On August 17, the two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors recorded gravitational waves from merging neutron stars (GW170817), and data from the Virgo detector, which did not clearly see the signal, helped locate the source; 1.7 seconds later, space telescopes caught a short gamma-ray burst from the same region. The near-simultaneous arrival showed that gravitational waves travel at the speed of light to within about three parts in a quadrillion, excluding some alternatives to general relativity.
Wikipedia2022: MICROSCOPE finds no violation of the equivalence principle
Final results from the French space agency's Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence (MICROSCOPE), which operated in orbit from 2016 to 2018, showed no difference in how test masses of titanium and platinum alloys fell, to within about three parts in a quadrillion, as general relativity's equivalence principle requires. Torsion-balance tests begun by Loránd Eötvös in the 1880s had reached about one part in 100 million by 1909.
Wikipedia2026: LARES-2 satellite measures Earth's frame dragging
Laser ranging to the Italian Space Agency's Laser Relativity Satellite 2 (LARES-2), launched in 2022, and to NASA's Laser Geodynamics Satellite (LAGEOS) of 1976 showed that Earth's rotation drags the satellites' orbital planes, the Lense–Thirring effect, as general relativity predicts, a team led by Ignazio Ciufolini reported in Nature in July. The authors put the uncertainty at about one part in a thousand, roughly ten times better than earlier Solar System measurements of the effect.
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