Johnny Galecki plays Dr. Leonard Hofstadter in The Big Bang Theory.
 Meanwhile, during these decades, two questions in observational cosmology that generated much discussion and disagreement were over the precise values of the Hubble Constant and the matter-density of the universe (before the discovery of dark energy, thought to be the key predictor for the eventual fate of the universe)
The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature

