Geological periods describe varying phases in the last few hundred million years on earth.

Are there any names for the periods on a timescale 1-2 orders of magnitude greater, that is, for the stages of a/the universe?

I found some bits and pieces of information but nothing as clear as I did for geological periods, possibly because of the conjecture involved.

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    $\begingroup$ There's also en.wikipedia.org/wiki/Graphical_timeline_of_the_Big_Bang for the early times. $\endgroup$
    – PM 2Ring
    Commented Jan 25, 2021 at 5:01
  • $\begingroup$ @PM2Ring extremely useful. I think that's all the stages in the first ~100m years of the universe from the big bang. I found this on that page as well which speculatively shows periods beyond 100m years $\endgroup$
    – stevec
    Commented Jan 25, 2021 at 5:06
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    $\begingroup$ You have to know that the universe started very rapidly and made a lot of changes in the first second or so. Geology isn't so inequal. Of course Quaternary is shorter than Cambrian, for example, but these inequalities aren't so obvious. The line between geology and cosmology is nearly impossible to make. By the way, humans have developed three main points of the universe: start, now (Earth ...) and end. The periods are shorter and more detailed near these three points. But between them? There are just some long periods where almost nothing happens. $\endgroup$
    – User123
    Commented Jan 25, 2021 at 7:15
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    $\begingroup$ @MetinCelik In case your answer gets deleted as "link-only answer", here your link youtube.com/watch?v=uD4izuDMUQA $\endgroup$
    – B--rian
    Commented Jan 26, 2021 at 8:48
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    $\begingroup$ @B--rian good idea. Here is my comment from MetinCelik's answer: How farcically wrong I was to assume the universe's life would be "1-2 orders of magnitude greater (than the last few hundred million years)". According to Brian Cox: "as a fraction of the lifespan of the universe ... life as we know it is only possible for 1 thousandth of a billionth billionth billionth billionth billionth billionth billionth billionth billionth of a percent" $\endgroup$
    – stevec
    Commented Jan 26, 2021 at 8:56

1 Answer 1


Yes there are. They are mainly based on what dominates the energy density of the universe at the time and they are known as epochs.

Thus we have the inflationary epoch in the first tiny fraction ($\sim 10^{-32}$) of a second, when the energy density was dominated by an inflationary field.

Then we are in the electroweak epoch, when the weak nuclear and electromagnetic forces were united.

This is followed by the quark epoch when the electromagnetic and weak nuclear forces separate at about $10^{-12}$s, which is followed by the hadron epoch between about a millionth of a second and 1 second, when quarks were able to be confined into multi-quark hadrons.

Then the lepton epoch between about 1 second and a minute when most of the hadrons have annihilated with each other and the energy density is dominated by electrons, positrons and neutrinos, although this also coincides with the "epoch of primordial nucleosynthesis" when the first multi-nucleon nuclei were built.

From there until about 300,000 years, we have the radiation epoch, when photons dominated the energy density of the universe.

After that, the universe entered the matter-dominated epoch for about 5 billion years and now we are in the epoch where the universe is dominated by dark energy.

There are other schemes and other nomenclatures depending on what physics is being focused on. For example, people interested in the formation of the first stars will talk about the "epoch of reionization", which occurred some 100 million years after the big-bang. Those studying the cosmic microwave background talk about the "epoch of recombination", which coincides roughly with the transition from a radiation to a matter-dominated universe.

  • $\begingroup$ Of course, it's a little bit hard to describe the early universe in terms of "seconds" or "fractions of seconds", since the flow of time depends on the expansion of space, and with all of space and matter compressed into a singularity at the moment of the Big Bang, time is basically infinite. Or at least it's sort of nonsensical to even ask "What was there before the Big Bang?" since time itself can only be defined in terms of space-time expansion. (I'm probably mangling this a bit - is there an astrophysicist in the house?) $\endgroup$ Commented Jan 25, 2021 at 16:13
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    $\begingroup$ @DarrelHoffman Not sure what you are getting at. My usage of time (in seconds) is perfectly standard in cosmology. There is no discussion in my answer of time before the big bang. $\endgroup$
    – ProfRob
    Commented Jan 25, 2021 at 16:26
  • $\begingroup$ Right, it's just that time as you get close to the big bang (from this side) cannot be as easily measured using familiar terminology. The math kind of breaks down the closer you get to singularity. I'm not good at explaining it, I've just watched a lot of educational stuff on this, though it might just be one of those "different schools of thought" issues. $\endgroup$ Commented Jan 25, 2021 at 16:30
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    $\begingroup$ @DarrelHoffman It is the proper time measured since the scale factor was zero in a standard $\Lambda$CDM cosmology. See en.wikipedia.org/wiki/Cosmic_time . If you are talking about the possibility that anything could have happened prior to inflation then sure - that's why I started at that point. $\endgroup$
    – ProfRob
    Commented Jan 25, 2021 at 17:34
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    $\begingroup$ @James They're Planck units. ;) The Wikipedia Big Bang graphical timeline nicely deals with the time "compression" issue by using logarithmic time. $\endgroup$
    – PM 2Ring
    Commented Jan 25, 2021 at 17:59

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