Talk:Chronology of the universe

What is the origin of "377 000 years after BB"?

The age of the universe at the recombination appears in this article as "377 000 years". I do not necessarily question that value, but in this article it is simply given as a well-known fact - no source, no reference to an article that explains it all. I assume that the value is based on some assumptions, but what are these assumptions? Where-ever I look in WP, "380 000 (something)" is stated as a fact, but nowhere how this value has been derived ... Hilmer B (talk) 16:37, 24 September 2018 (UTC)

See note in ref#3 (revision as of 09:40, 29 January 2020) for Hinshaw, Weiland & Hill 2009. Alan G. Archer (talk) 17:04, 2 February 2020 (UTC)

Lead sentence

The opening sentence currently reads The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. The earliest stages of the universe's existence are estimated as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.

An editor is trying to change it to The earliest stages of the universe's existence are estimated as taking place 13.800000001 billion years ago (in the year 13799997982 BC), with an uncertainty of around 21 million years (years 13820997982 BC to 13778997982 BC) at the 68% confidence level.

Thoughts? Personally, I think the current sentence is easier for readers to understand, and I think specifying the years BC is confusing, harder to read, and adds unnecessary complexity to the sentence. Also, 13.800000001 implies a misleading specificity to the estimate. Schazjmd (talk) 18:39, 8 August 2020 (UTC)

I think the warning ^{(This figure is unduly precise)} would apply. Tarl N. (discuss) 18:48, 8 August 2020 (UTC)

The article quotes an age of the Universe of 13.8 Gyr with an uncertainty of 21 million years. An uncertainty this large would make quoting ages and dates to the nearest year meaningless. Quoting a meaningless precision would make no sense. I believe the lead sentence should remain as "taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level". — Preceding unsigned comment added by TowardsTheLight (talk • contribs)

I've invited the IP editor to make their case here. Schazjmd (talk) 20:45, 8 August 2020 (UTC)

Each year the uncertainty range would effectively shift by one year, making it not the original uncertainty range. In 2020 it should be 13.800000001 years ago with an uncertainty of 21 million. In 2021 it will be 13.800000002 years ago. And so on. 2A01:119F:31B:5D00:CDA:B9B8:6D94:5EE (talk) 15:17, 22 September 2020 (UTC)

Currently the center of uncertainty is 13.800000005 years ago, not 13.800000004, not 13.800000006. It's in the year 13799997982 BC, with an uncertainty of around 21 million years (years 13820997982 BC to 13778997982 BC), not years 13820997981 BC to 13778997981 BC, not years 13820997983 BC to 13778997983 BC. 2A01:119F:31B:5D00:CDA:B9B8:6D94:5EE (talk) 22:16, 13 November 2024 (UTC)

You're assigning a degree of precision to the estimates that isn't reflected in the sources and, on a scale of 13+billion years, isn't even meaningful. Schazjmd (talk) 15:45, 22 September 2020 (UTC)

If it was 13.8 billion years ago in 2019, it would be 13.9 billion years ago in 100002019. So in 10002019 it would be 13.81 billion years ago, and in 1002019 it would be 13.801 billion years ago, and so on. 2A01:119F:31B:5D00:453A:2110:9DE4:8C78 (talk) 05:11, 30 September 2020 (UTC)

You're just repeating your insistence on an unsupported precision. You haven't convinced anyone that the change to the lead is an improvement to the article or helpful to readers. Schazjmd (talk) 15:01, 30 September 2020 (UTC)

First Molecules/Recombination conflict

The section of First Molecules is giving a timeline at about 100,000 years, which I understand comes from the linked article. However, the article is referencing a Nature Journal entry which only states that the molecules could only start forming during the recombination epoch, and doesn't give any specific time when this would be.

The following section on Recombination then gives a conflicting date of 370,000 years, which would make most readers assume that the first molecules would have formed much earlier than the recombination.

I'm not sure what the preferred way to resolve this conflicting information should be, but wanted to highlight this issue. --elentir (talk) 16:15, 9 November 2020 (UTC)

I found a source which discusses the recombination timeline for various ionization levels of both helium and hydrogen, with the earliest recombination to HeII around 18,000 years after the big bang and HeI at around 100,000 years, which matches the timeline for the earliest molecules. I think the Recombination section needs to be expanded to include this data as recombination covered a timespan of several hundred thousand years (~18,000y–~370,000y), finally ending with decoupling.

See graph on pg. 8 for best illustration of timeline. Signals From the Epoch of Cosmological Recombinationelentir (talk) 12:16, 11 November 2020 (UTC)

References

Semi-protected edit request on 17 March 2021

This introductory sentence is ambiguous and is not reflected in the detailed text of the article.

From about 9.8 billion years of cosmic time,[7] the slowing expansion of space gradually begins to accelerate under the influence of dark energy,

I think the editor meant to say this:

From about 9.8 billion years of cosmic time,[7] the expansion of space gradually begins to decelerate under the influence of dark energy,

But before making this change, please confirm my suspicion that the original sentence is not supported by the main text. If so, the sentence needs to be deleted entirely. Thank you.

 Not done: The page's protection level has changed since this request was placed. You should now be able to edit the page yourself. If you still seem to be unable to, please reopen the request with further details. Asartea ^{Talk | Contribs} 13:22, 17 March 2021 (UTC)

"the expansion of space gradually begins to decelerate under the influence of dark energy" <- this is definitely not correct. Dark energy is a positive acceleration on the expansion of the universe. Gravity is a negative acceleration (aka deceleration) on expansion. What the original sentence is getting at, while gravity was initially slowing expansion early on in the universe, around 9.8Gy the universe was big enough for the amount of dark energy to overcome the effects of gravity resulting in positive acceleration. elentir (talk) 11:19, 23 March 2021 (UTC)

I updated the stat and took a stab at clarifying it; as always, feel free to copy-edit it if there's a way to use simpler words without sacrificing accuracy. Rolf H Nelson (talk) 22:41, 27 March 2021 (UTC)