1846 - Urbain Le Verrier and John Couch Adams, studying Uranus orbit, independently prove that another, farther planet must exist. The planet will be found at the predicted moment and position, and will be called Neptune.
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 will never be found.
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
1921 - T. Kaluza demonstrates that a five-dimensional version of Einstein's equations unifies gravitation and electromagnetism
1937 - Fritz Zwicky states that galaxies could act as gravitational lenses
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%