1665 - Isaac Newton introduces an inverse-square universal law of gravitation uniting terrestrial and celestial theories of motion and uses it to predict the orbit of the Moon and the parabolic arc of projectiles.
1684 - Isaac Newton proves that planets moving under an inverse-square force law will obey Kepler's laws
1686 - Isaac Newton uses a fixed length pendulum with weights of varying composition to test the weak equivalence principle to 1 part in 1000
1855 - Leverrier observes a 35 arcsecond per century excess precession of Mercury's orbit and attributes it to another planet, inside Mercury's orbit. The planet was never found. See Vulcan.
1876 - William Clifford suggests that the motion of matter may be due to changes in the geometry of space
1882 - Simon Newcomb observes a 43 arcsecond per century excess precession of Mercury's orbit
1937 - Albert Einstein, Leopold Infeld, and Banesh Hoffman show that the geodesic equations of general relativity can be deduced from its field equations
1968 - Irwin Shapiro presents the first detection of the Shapiro delay
1968 - Kenneth Nordtvedt studies a possible violation of the weak equivalence principle for self-gravitating bodies and proposes a new test of the weak equivalence principle based on observing the relative motion of the Earth and Moon in the Sun's gravitational field
1976 - Robert Vessot and Martin Levine use a hydrogenmaser clock on a Scout D rocket to test the gravitational redshift predicted by the equivalence principle to approximately 0.007%
1979 - Dennis Walsh, Robert Carswell , and Ray Weymann discover the gravitationally lensed quasar Q0957+561
1982 - Joseph Taylor and Joel Weisberg show that the rate of energy loss from the binary pulsar PSR1913+16 agrees with that predicted by the general relativistic quadrupole formula to within 5%
