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 Wilhelm 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, termed a de Sitter
            universe
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 Lemaître 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 Lemaître 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 proto and electron
1948 - Ralph Alpher, Hans Bethe ("in absentia"), and George Gamow examine element synthesis
            in a rapidly expanding and coolin 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 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 - Andrei 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.
2001 - Evidence that the fine structure constant does vary over the lifetime of the universe
            becomes conclusive.
2003 - NASA's WMAP takes first detailed "baby picture" of the universe by means of the Cosmic
           microwave background radiation.
           The image reveals the universe is 13.7 billion years old (within one percent error) and that
            the inflationary theory is correct.