During the Planck epoch, one cannot neglect quantum effects.

They play a role in some models of the evolution of the universe during the Planck epoch.

This period is therefore called the Planck era or Planck epoch.

As before, there have been 60.9 cosmological decades between the Planck epoch and the current epoch.

How closely we can extrapolate towards the singularity is debated-certainly no closer than the end of the Planck epoch.

Since the Planck epoch, the Universe has been expanding to its present form, possibly with a brief period (less than 10 seconds) of cosmic inflation.

There were an infinite number of cosmological decades between the Big Bang and the Planck epoch (or any other point in time).

The Universe expanded from a very hot, dense phase called the Planck epoch, in which all the matter and energy of the Universe was concentrated.

Thus, in inflationary cosmology there is no Planck epoch in the traditional sense, though similar conditions may have prevailed in a pre-inflationary era of the universe.

In modern inflationary cosmology, the traditional grand unification epoch, like the Planck epoch, does not exist, though similar conditions likely would have existed in the universe prior to inflation.

In theoretical physics, the Hartle-Hawking state, named after James Hartle and Stephen Hawking, is a proposal concerning the state of the universe prior to the Planck epoch.

In physical cosmology, the Planck epoch (or Planck era) is the earliest period of time in the history of the universe, from zero to approximately 10 seconds (Planck time).

Inconceivably hot and dense, the state of the universe during the Planck epoch was unstable, tending to evolve, giving rise to the familiar manifestations of the fundamental forces through a process known as symmetry breaking.

It proposed that prior to the Planck epoch, the universe had no boundary in space-time; before the Big Bang, time did not exist and the concept of the beginning of the universe is meaningless.

The Planck epoch is an era in traditional (non-inflationary) big bang cosmology in which the temperature is high enough that the four fundamental forces-electromagnetism, gravitation, weak nuclear interaction, and strong nuclear interaction-are all unified in one fundamental force.

This is still several orders of magnitude away from the Planck epoch, when the universe was at the Planck scale, but planned probes such as Planck Surveyor and related experiments such as IceCube expect to greatly improve on current astrophysical measurements.

Without an understanding of quantum gravity, a theory unifying quantum mechanics and relativistic gravity, the physics of the Planck epoch are unclear, and the exact manner in which the fundamental forces were unified, and how they came to be separate entities, is still poorly understood.

Strongly symmetric matter: If the predictions of supersymmetry and more so, string theory are correct then during the time of the Planck Epoch (10 seconds after the Big Bang) all four fundamental forces were of equal strength and united into a single fundamental force.

Modern cosmology now suggests that the Planck epoch may have inaugurated a period of unification, known as the 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.

Although this interval is still orders of magnitude longer than the Planck time, other experiments currently coming online including the Planck Surveyor probe, promise to push back our 'cosmic clock' further to reveal quite a bit more about the very first moments of our universe's history, hopefully giving us some insight into the Planck epoch itself.