The Planck epoch would have occurred immediately after the Big Bang.
In physics, the Planck scale refers to a very large energy scale (1.22 x 10 19 GeV) or a very small size scale (1.616 x 10 -35 meters), where the quantum effects of gravity become important in the description of particle interactions. On the Planck size scale, quantum uncertainty is so intense that concepts like locality and causality become less significant. Physicists today are very interested in learning more about the Planck scale, as a quantum theory of gravity is something we currently don’t have. If a physicist were able to come up with a quantum theory of gravity that agreed with the experiment, it would practically guarantee him the Nobel Prize.
If a physicist were able to come up with a quantum theory of gravity that agreed with the experiment, it would practically guarantee him the Nobel Prize.
It is a fundamental fact of the physics of light that the more energy a photon (particle of light) carries, the shorter the wavelength it has. For example, visible light has a wavelength of about a few hundred nanometers, while much more energetic gamma rays have a wavelength the size of an atomic nucleus. Planck energy and Planck length are related in the sense that a photon would need to have an energy value on the Planck scale to have a wavelength as small as the Planck length.
To make things even more complicated, even if we could create such an energetic photon, we wouldn’t be able to use it to accurately measure something on the Planck scale – it would be so energetic that the photon would collapse into a black hole before returning any information. . So many physicists believe that the Planck scale represents some kind of fundamental limit on how small the distances we can probe. The Planck length may be the smallest physically significant size scale there is, in which case the universe can be thought of as a tapestry of “pixels” – each with a Planck length in diameter.
The Planck energy scale is almost unimaginably large, while the Planck size scale is almost unimaginably small. The Planck energy is about a quintillion times greater than the energies achievable in our best particle accelerators, which are used to create and observe exotic subatomic particles. A particle accelerator powerful enough to probe the Planck scale directly would need to have a circumference similar in size to the orbit of Mars, built out of as much material as our moon.
Since such a particle accelerator is not likely to be built in the foreseeable future, physicists are looking for other methods to probe the Planck scale. We look for gigantic “cosmic strings” that may have been created when the universe as a whole was so hot and small that it possessed Planck-level energies. This would have occurred in the first trillionth of a second after the Big Bang.