1576 | Thomas Digges modifies the Copernican system by removing its outer edge and replacing the edge with a star filled unbounded space. |

1610 | Johannes Kepler uses the dark night sky to argue for a finite universe. |

1720 | Edmund Halley puts forth an early form of Olbers' paradox. |

1744 | Jean-Phillipe de Cheseaux puts forth an early form of Olbers' paradox. |

1826 | Heinrich Olbers puts forth Olbers' paradox. |

1917 | Willem de Sitter derives an isotropic static cosmology with a cosmological constant as well as an empty expanding cosmology with a cosmological constant. |

1922 | Vesto Slipher summarizes his findings on the spiral nebulae's systematic redshifts. |

1922 | Alexander Friedmann finds a solution to the Einstein field equations which suggests a general expansion of space. |

1927 | Georges-Henri Lemaitre discusses the creation event of an expanding universe governed by the Einstein field equations. |

1928 | Harold Robertson briefly mentions that Vesto Slipher's redshift measurements combined with brightness measurements of the same galaxies indicate a redshift-distance relation. |

1929 | Edwin Hubble demonstrates the linear redshift-distance relation and thus shows the expansion of the universe. |

1933 | Edward Milne names and formalizes the cosmological principle. |

1934 | Georges-Henri Lemaitre interprets the cosmological constant as due to a "vacuum'' energy with an unusual perfect fluid equation of state. |

1938 | Paul Dirac presents a cosmological theory where the gravitational constant decreases slowly so that the age of the universe divided by the atomic light-crossing time always equals the ratio of the electric force to the gravitational force between a proton and electron. |

1948 | Ralph Alpher, Hans Bethe, and George Gamow examine element synthesis in a rapidly expanding and cooling universe and suggest that the elements were produced by rapid neutron capture. |

1948 | Hermann Bondi, Thomas Gold, and Fred Hoyle propose steady state cosmologies based on the perfect cosmological principle. |

1951 | William McCrea shows that the steady state C-field can be accommodated within general relativity by interpreting it as a contribution to the energy-momentum tensor with an unusual equation of state. |

1961 | Robert Dicke argues that carbon-based life can only arise when the Dirac large numbers hypothesis is true because this is when burning stars exist; first use of the weak anthropic principle. |

1963 | Fred Hoyle and Jayant Narlikar show that the steady state theory can explain the isotropy of the universe because deviations from isotropy and homogeneity exponentially decay in time. |

1964 | Fred Hoyle and Roger Tayler point out that the primordial helium abundance depends on the number of neutrinos. |

1965 | Martin Rees and Dennis Sciama analyze quasar source count data and discover that the quasar density increases with redshift. |

1965 | Edward Harrison resolves Olbers' paradox by noting the finite lifetime of stars. |

1966 | Stephen Hawking and George Ellis show that any plausible general relativistic cosmology is singular. |

1966 | Jim Peebles shows that the hot Big Bang predicts the correct helium abundance. |

1967 | Andrey Sakharov presents the requirements for a baryon-antibaryon asymmetry in the universe. |

1967 | John Bahcall, Wal Sargent, and Maarten Schmidt measure the fine-structure splitting of spectral lines in 3C191 and thereby show that the fine-structure constant does not vary significantly with time. |

1968 | Brandon Carter speculates that perhaps the fundamental constants of nature must lie within a restricted range to allow the emergence of life; first use of the strong anthropic principle. |

1969 | Charles Misner formally presents the Big Bang horizon problem. |

1969 | Robert Dicke formally presents the Big Bang flatness problem. |

1973 | Edward Tryon proposes that the universe may be a large scale quantum mechanical vacuum fluctuation where positive mass-energy is balanced by negative gravitational potential energy. |

1974 | Robert Wagoner, William Fowler, and Fred Hoyle show that the hot Big Bang predicts the correct deuterium and lithium abundances. |

1976 | A.I. Shlyakhter uses samarium ratios from the prehistoric natural fission reactor in Gabon to show that some laws of physics have remained unchanged for over two billion years. |

1977 | Gary Steigman, David Schramm, and James Gunn examine the relation between the primordial helium abundance and number of neutrinos and claim that at most five lepton families can exist. |

1980 | Alan Guth proposes the inflationary Big Bang universe as a possible solution to the horizon and flatness problems. |