# What happened during the Planck Era of the Big Bang?

If you look at a big bang timeline before 10 to the -43 seconds you can see

Planck time - ????

So I googled it and was met with

Before 1 Planck Time Before a time classified as a Planck time, 10-43 seconds, all of the four fundamental forces are presumed to have been unified into one force. All matter, energy, space and time are presumed to have exploded outward from the original singularity. Nothing is known of this period.

I looked at another timeline and instead of "Planck Era" it said "Quantum Fluctuation"

So any ideas of what was going on during that time period? Did Higgs Boson fields sweep through the known universe?

• Didn't someone just ask the same question? physics.stackexchange.com/q/275428/5345 – Jim Garrison Aug 21 '16 at 21:09
• Yes but besides the unification of fundamental forces what was going on? – EasyPeasy Aug 21 '16 at 21:13
• @count_to_10, why not flesh that out into an answer? – Alfred Centauri Aug 21 '16 at 22:20
• @AlfredCentauri I took your advice, re an answer, but there is very little to expand upon, in the absence of evidence. I wish I knew more physics, in a nutshell. Thank you. – user108787 Aug 22 '16 at 5:48

The Planck length $\ell_p~=~\sqrt{G\hbar/c^3}$ is related to the Planck time by $T_p~=~\ell/c$, or the time it takes a photon to cross this distance. The Planck length may be the shortest distance one can isolate a qubit. As a result the universe at the Planck time, assuming it occupied then a single Planck length, can only be said to consist of at most one state or vacuum, or a qubit in a single state. Now use Shannon information $S~=~-k\sum_np(n)log(p(n))$, and we have only $p(1)~=~1$ for one qubit. As a result $S~=~0$, or equivalently there is no real information. This is assuming the Planck moment of the universe was where the universe occupied a single Planck volume.

In a sense we can then say that during the Planck time at the start of the universe, or the observable universe potentially in a multiverse, there was in fact as close to nothing as one gets in physics. It also means we can't really say much about that epoch of the universe. If at the first Planck moment there were a number of Planck volumes or areas on a horizon, these might define some sphere packing for a group or symmetry. If so, say the $248$ root vectors of $E_8$ or the $256$ of $CL(8)$, these might define a sort of sphere packing system for the fundamental symmetry of the universe.

The Planck era is defined as the time when the universe was the size of the Planck length, $10^{-33}$ cms, and less, and the universe's age was $10^{-43}$ sec, the Planck time, and less. It is the earliest epoch we identify after the Big Bang. The Planck temperature at the end of the epoch was about $10^{32}$ degrees Kelvin.

This was way before quarks, leptons, Higgs bosons, and inflation. Neither Quantum Theory (QT) nor General Relativity (GR) have anything to say about what is happening at these sizes, times, energy densities and temperatures, except that they are not applicable.

The wiki article summarizes the epochs, or times, when the universe was dominated by different kinds of physics, from the Planck epoch through the GUT epoch, inflation, electroweak and strong force separation, and on till the current epoch. It is at https://en.m.wikipedia.org/wiki/Chronology_of_the_universe

At Planck times and earlier after the Big Bang, GR effects or equivalently strong gravity effects predicted by GR, would be happening at the sizes and energies such that QT also applies. It needs a unification of GR and QT to have anY explanatory power, a theory of quantum gravity. At these times there are no photons, quarks, electrons, neutrinos, gluons or anything associated specifically with the 4 forces. This was before spacetime was defined by geometry and GR, or even before it existed. The two best known theories of quantum gravity, none proven or accepted, are string theory (ST) and its newer versions of superstrings and M theory, and loop quantum gravity. They both have elementary entities which can be about the Planck size, one is strings and the other loops.

I know quantum loop gravity less well, but when the spacetime is larger than the Planck length ST has strings in a 10 or 11 dimensional spacetime, which were all small dimensions unti the inflationary era where for some reason all but 4 dimensions remained small, and so now we see those 4 dimensions. At least that is one version. Others take multidimensional branes in a higher dimensional space. You can see the wiki references on string theory. But either way at the Planck length it becomes a sort of quantum foam, with no spacetime defined. Spacetime emerges as the scale factor increases and multiple Planck lengths enter in.

So, what happens at the Planck epoch (era) is not well understood. As the universe goes into the next era, the GUT era, 3 of the 4 forces, all but gravity which when we enter the GUT epoch decouples, are unified. ST aims to also explain it, i.e., a unification of the 3 forces (and actually gravity in the Planck era as well). The 3 forces then remain unified until the universe expands and cools some more, the strong force decouples, and later there is inflation and the electroweak force separates into the weak and electromagnetic force, and the Higgs boson emerges. There is more after that.

See the wiki and its references for string theory cosmology, but at inflation and later (maybe even before, up to the Planck epoch) there is commonality with the standard cosmology model. https://en.m.wikipedia.org/wiki/String_cosmology

The OP obviously still wants to nail down some sort of satisfactory answer to his/ her question Unification Of Forces In The Very Earliest Universe and so do I.

The answer to the previous question in the link above, although an excellent summary of the method by which forces differentiated, did not address the point of "what did the unified force era "look" like?

Fortunately for me as a total amateur, the properties of a unified force concept during the minutely short timespan that it existed, is not described by physics as we currently understand it. This allows me freedom to waffle away, but I will try and keep it as coherent as possible.

We have no evidence of what went on during a very short time within which nothing, apart from possibly a temperature drop, occurred. No matter existed and we have no idea of what effects a unified force may have had on the radiation present at this time.

So all we can do is guess, and I have never read of anybody even trying to guess, perhaps for the same reason as we keep saying just after rather than at the Big Bang and also because because of the short time involved. Without forces or matter, it sounds pretty uninteresting, especially if you can only guess with no chance of testing anything.

It's physics (Jim), but not as we know it, so what's the point of thinking about a plenum, full of radiation, but with completely unknown (and unknowable) properties?

Optimistically, there are two advantages to any understanding that the idea of a unified force may provide. They are both the worst examples of handwavy, "then a miracle occurred", type speculation, but if you got this far, I'm near the end of the answer.

The first advantage is that, in some way a unified force may help resolve the problem of Low Entropy at the just after the Big Bang. A unified force would have been "smoother", more homogenous and more isotropic that anything that has existed since and this smoothness may have, despite conjectures regarding inflation, symmetry breaking, vacuum fluctuations, mini black holes (and whatever else went on), carried on to maintain a low entropy state. Don't ask me how, it's just a wild guess.

The second advantage of a unified force is that, through gravitational wave detection techniques from inside the surface of last scattering in particular, we may discover more about phase transitions, symmetry breaking (Higgs Field, say) and how to solve the Hierarchy Problem.

If I could extend my solution set to include the cosmological constant discrepency, I would, but I fully admit it's all ridiculous extrapolation as it stands.

I don't think this piece is worth voting on, or even commenting on, because of the lack of evidence from nature and the lack of knowledge from me. If you can view it as "not even wrong", I'd appreciate it.