In cosmology: Superunification and the Planck era this time, called the Planck time (Gh/c5)1/2, equals approximately 10−43 second. At the Planck time, the mass density of the universe is thought to approach the Planck density, c5/hG2, roughly 1093 grams per cubic centimetre. Contained within a Planck volume is a Planck mass