The Planck epoch is the earliest period of time in the history of the universe, before the time passed was equal to the Planck time (tₚ) ; that is from zero to approximately 10⁻⁴³ seconds. The Planck scale is the physical scale beyond which current physical theories may not apply and cannot be used to calculate what happened. At this time scale, every physical quantities like temperature, energies etc were in the range of Planck units values. During the Planck epoch, the temperature and average energies within the universe were so high that even subatomic particles could not form and even the four fundamental forces that shape our universe were combined and formed one unified fundamental force.
Traditional Big Bang cosmology predicts a gravitational singularity before this time, but this theory relies on the theory of general relativity, which is thought to break down for this epoch due to quantum effects. Due to the extraordinarily small scale of the universe at that time, the quantum effects of gravity were the strongest and it is believed that cosmology and physics are assumed to have been dominated by the quantum effects of gravity. At this scale, the unified force is assumed to be unified with gravitation. Immeasurably hot and dense state of the Planck epoch is succeeded by the grand unification epoch, where gravitation force is separated from the unified fundamental force.