Original sentence: In physical cosmology, the Big Bang is the scientific theory of the origin of the universe as an explosion of space itself, starting from an enormously dense state at some finite time in the past.The Big Bang theory developed from observations and theoretical considerations.The central idea is that the observed mutual recession of the galaxies (Hubble's law) implies that the galaxies were much closer together in the past
Edited sentence: In cosmology, the Big Bang is a geometric theory of the origin of the universe as an explosion of space itself, starting from an enormously dense state at some finite time in the past.The Big Bang theory developed from observations and theoretical assumptions.The central assumption is that the observed mutual recession of the galaxies (Hubble's law) implies that the galaxies were much closer together in the past