accelerating universe age of the universe albert einstein arno allan penzias boomerang experiment big bang big bang nucleosynthesis big crunch cosmic gravitational wave background cosmic inflation cosmic microwave background radiation cosmic neutrino background cosmological constant dark energy de sitter space dust solution edwin hubble energy friedmann equations fritz zwicky future of an expanding universe galaxy filament galaxy formation and evolution general relativity george gamow george smoot lambda-cdm model large-scale structure of the cosmos metric expansion of space milne model observational cosmology physical cosmology radius of curvature redshift robert woodrow wilson scientific consensus shape of the universe sloan digital sky survey space speed of light stephen hawking structure formation timeline of cosmology timeline of the big bang tired light ultimate fate of the universe universe vera rubin wilkinson microwave anisotropy probe