In physical cosmology, the Planck epoch (or Planck era), name after Max Planck, is the earliest period of time in the history of the universe, from zero to approximately 10-43 seconds (one Planck time), during which quantum effects of gravity were significant. One could also say that it is the earliest moment in time, as the Planck time is perhaps the shortest possible interval of time, and the Planck epoch lasted only this brief instant. At this point approximately 1.37×1010 years ago the force of gravity is believed to have been as strong as the other fundamental forces, which hints at the possibility that all the forces were unified. Inconceivably hot and dense, the state of the universe during the Planck epoch was unstable or transitory, tending to evolve and giving rise to the familiar manifestations of the fundamental forces through a process known as symmetry breaking. Modern cosmology now suggests that the Planck epoch may have inaugurated a period of unification or Grand unification epoch, and that symmetry breaking then quickly led to the era of cosmic inflation, the Inflationary epoch, during which the universe greatly expanded in scale over a very short period of time.