1758 - Rudjer Josip Boscovich developes his Theory of forces, where gravity can be repulsive on small distances. So according to him such strange classical bodies, similar to white holes, can exist, which won't let other bodies to reach their surfaces
1917 - Paul Ehrenfest gives conditional principle a three dimensional space
1918 - Hans Reissner and Gunnar Nordström solve the Einstein-Maxwell field equations for charged spherically-symmetric non-rotating systems
1918 - Friedrich Kottler gets Schwarzschild solution without Einstein vacuum field equations
1923 - George Birkhoff proves that the Schwarzschild spacetime geometry is the unique spherically symmetric solution of the Einstein vacuum field equations
1939 - Robert Oppenheimer and Hartland Snyder calculate the gravitational collapse of a pressure-free homogeneous fluid sphere and find that it cuts itself off from communication with the rest of the Universe
1963 - Roy Kerr solves the Einstein vacuum field equations for uncharged symmetric rotating systems, deriving the Kerr metric
1964 - Roger Penrose proves that an imploding star will necessarily produce a singularity once it has formed an event horizon
1965 - Ezra Newman , E. Couch, K. Chinnapared, A. Exton, A. Prakash, and Robert Torrence solve the Einstein-Maxwell field equations for charged rotating systems
1968 - Brandon Carter uses Hamilton-Jacobi theory to derive first-order equations of motion for a charged particle moving in the external fields of a Kerr-Newman black hole
1969 - Roger Penrose discusses the Penrose process for the extraction of the spinenergy from a Kerr black hole
