1590 – Galileo Galilei formulates modified Aristotelean theory of motion (later retracted) based on density rather than weight of objects.
1600s
Geometric diagram for Newton's proof of Kepler's second law.
1602-1608 – Galileo Galilei experiments with pendulum motion and inclined planes; deduces his law of free fall; and discovers that projectiles travel along parabolic trajectories.
1846 – Urbain Le Verrier and John Couch Adams, studying Uranus' orbit, independently prove that another, farther planet must exist. Neptune was found at the predicted moment and position.
1855 – Le Verrier observes a 38 arc-second per century excess precession of Mercury's orbit and attributes it to another planet, inside Mercury's orbit. The planet, called Vulcan, was never found. Le Verrier's figure is revised by Simon Newcomb to 43 arc-second per century in 1882.
1876 – William Kingdon Clifford suggests that the motion of matter may be due to changes in the geometry of space.
1884 – William Thomson (Lord Kelvin) lectures on the issues with the wave theory of light with regards to the luminiferous ether.
The U.S. Navy's nuclear-powered Task Force 1 underway for Operation Sea Orbit in the Mediterranean, 1964.
1902 – Paul Gerber explains the movement of the perihelion of Mercury using finite speed of gravity. His formula, at least approximately, matches the later model from Einstein's general relativity, but Gerber's theory was incorrect.
1906 – Max Planck coins the term Relativtheorie. Albert Einstein later uses the term Relativitätstheorie in a conversation with Paul Ehrenfest. He originally prefers calling it Invariance Theory.
1907 – Albert Einstein introduces the principle of equivalence of gravitational and inertial mass and uses it to predict gravitational lensing and gravitational redshift, historically known as the Einstein shift.
Einstein's 1911 argument for gravitational redshift
1911 – Max von Laue publishes the first textbook on special relativity.
1911 – Albert Einstein explains the need to replace both special relativity and Newton's theory of gravity; he realizes that the principle of equivalence only holds locally, not globally.
1912 – Friedrich Kottler applies the notion of tensors to curved spacetime.
1916 – Karl Schwarzschild publishes the Schwarzschild metric about a month after Einstein published his general theory of relativity. This was the first solution to the Einstein field equations other than the trivial flat space solution.
1919 – Arthur Eddington leads a solar eclipse expedition which detects gravitational deflection of light by the Sun, which, despite opinion to the contrary, survives modern scrutiny. Other teams fail for reasons of war and politics.
1953 – P. C. Vaidya Newtonian time in general relativity, Nature, 171, p260.
1954 – Suraj Gupta sketches how to derive the equations of general relativity from quantum field theory for a massless spin-2 particle (the graviton). His procedure was later carried out by Stanley Deser in 1970.
1955-56 – Robert Kraichnan shows that under the appropriate assumptions, Einstein's field equations of gravitation arise from the quantum field theory of a massless spin-2 particle coupled to the stress-energy tensor. This follows from his unpublished work as an undergraduate in 1947.
1960 – Thomas Matthews and Allan R. Sandage associate 3C 48 with a point-like optical image, show radio source can be at most 15 light minutes in diameter,
1963 – Maarten Schmidt and Jesse Greenstein discover quasi-stellar objects, later shown to be moving away from Earth due to the expansion of the Universe.
1964 – Steven Weinberg shows that a quantum field theory of interacting massless spin-2 particles is Lorentz invariant only if it satisfies the principle of equivalence.
1971 – Introduction of the Khan–Penrose vacuum, a simple explicit colliding plane wave spacetime.
1971 – Robert H. Gowdy introduces the Gowdy vacuum solutions (cosmological models containing circulating gravitational waves).Image of Cygnus X-1 by the Chandra X-ray Observatory (2009)
Computer simulation of a black hole accretion disk published in 1979 by Jean-Pierre Luminet1974 – James W. York and Niall Ó Murchadha present the analysis of the initial value formulation and examine the stability of its solutions.
1974 – R. O. Hansen introduces Hansen–Geroch multipole moments.
1975 – Roberto Colella, Albert Overhauser, and Samuel Werner observe the quantum-mechanical phase shift of neutrons due to gravity. Neutron interferometry was later used to test the principle of equivalence.
1975 – Chandrasekhar and Steven Detweiler compute the effects of perturbations on a Schwarzschild black hole.
1975 – Szekeres and D. A. Szafron discover the Szekeres–Szafron dust solutions.
1976 – Penrose introduces Penrose limits (every null geodesic in a Lorentzian spacetime behaves like a plane wave),
1978 – Penrose introduces the notion of a thunderbolt,
Variations in the temperature of the cosmic microwave background measured by the COBE satellite. The plane of the Milky Way Galaxy is horizontal across the middle of each picture.
1980 – Vera Rubin and colleagues study the rotational properties of UGC 2885, demonstrating the prevalence of dark matter.
1986 – Bernard Schutz shows that cosmic distances can be determined using sources of gravitational waves without references to the cosmic distance ladder. Standard-siren astronomy is born.
1988 – Mike Morris, Kip Thorne, and Yurtsever Ulvi obtain the Morris-Thorne wormhole. Morris and Thorne argue for its pedagogical value.
1995 – John F. Donoghue show that general relativity is a quantum effective field theory. This framework could be used to analyze binary systems observed by gravitational-wave observatories.
1995 – Hubble Deep Field image taken. It is a landmark in the study of cosmology.
1998 – The first complete Einstein ring, B1938+666, discovered using the Hubble Space Telescope and MERLIN.
1998-99 – Scientists discover that the expansion of the Universe is accelerating.
2015 – Advanced LIGO reports the first direct detections of gravitational waves, GW150914 and GW151226, mergers of stellar-mass black holes. Gravitational-wave astronomy is born. No deviations from general relativity were found.
2017 – LIGO-VIRGO collaboration detects gravitational waves emitted by a neutron-star binary, GW170817. The Fermi Gamma-ray Space Telescope and the International Gamma-ray Astrophysics Laboratory (INTEGRAL) unambiguously detect the corresponding gamma-ray burst. LIGO-VIRGO and Fermi constrain the difference between the speed of gravity and the speed of light in vacuum to 10−15. This marks the first time electromagnetic and gravitational waves are detected from a single source, and give direct evidence that some (short) gamma-ray bursts are due to colliding neutron stars.
2017 – MICROSCOPE satellite experiment verifies the principle of equivalence to 10−15 in terms of the Eötvös ratio . The final report is published in 2022.
2017 – Scientists begin using gravitational-wave sources as "standard sirens" to measure the Hubble constant, finding its value to be broadly in line with the best estimates of the time. Refinements of this technique will help resolve discrepancies between the different methods of measurements.
2018 – Advanced LIGO-VIRGO collaboration constrains equations of state for a neutron star using GW170817.
2018 – Luciano Rezzolla, Elias R. Most, and Lukas R. Weih used gravitational-wave data from GW170817 constrain the possible maximum mass for a neutron star to around 2.17 solar masses.
2018 – Kris Pardo, Maya Fishbach, Daniel Holz, and David Spergel limit the number of spacetime dimensions through which gravitational waves can propagate to 3 + 1, in line with general relativity and ruling out models that allow for "leakage" to higher dimensions of space. Analyses of GW170817 have also ruled out many other alternatives to general relativity, and proposals for dark energy.
2018 – Two different experimental teams report highly precise values of Newton's gravitational constant that slightly disagree.
2019 – Advanced LIGO and VIRGO detect GW190814, the collision of a 26-solar-mass black hole and a 2.6-solar-mass object, either an extremely heavy neutron star or a very light black hole. This is the largest mass gap seen in a gravitational-wave source to-date.
2020s
The size of Sagittarius A* is smaller than the orbit of Mercury.
2020 – Principle of equivalence tested for individual atoms using atomic interferometry to ~10−12.
2021 – Jun Ye and his team measure gravitational redshift with an accuracy of 7.6 × 10−21 using an ultracold cloud of 100,000 strontium atoms in an optical lattice.
2021 – EHT measures the polarization of the ring of M87*, and other properties of the magnetic field in its vicinity.
2021 – EHT releases an image of Sagittarius A*, measures its shadow, and shows that it is accurately described by the Kerr metric.