In
physical cosmology, assuming that nature is described by a
Grand unification theory, the
grand unification epoch was the period in the evolution of the early
universe following the
Planck epoch, starting at about 10
-43 seconds after the
Big Bang, in which the
temperature of the universe was comparable to the characteristic temperatures of
grand unified theories. If the
grand unification energy is taken to be 10
15 GeV, this corresponds to temperatures higher than 10
27 K. During this period, three of the four
fundamental interactions—
electromagnetism, the
strong interaction, and the
weak interaction—were unified as the
electronuclear force.
Gravity had separated from the electronuclear force at the end of the
Planck era. During the grand unification epoch, physical characteristics such as
mass,
charge,
flavour and
colour charge were meaningless.