Talk:Chronology of the universe

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Nucleosynthesis[edit]

RE: At this time, there are about three times more hydrogen ions than helium-4 nuclei.

This is a subtle mis-statement. At the end of the nucleosythesis period, Helium nuclei (almost all He4 and the tiniest amount of He3), account for approximately 25% of the MASS of ordinary matter in the universe - excluding the left over supersymmetric matter.

This proportion is well known. It can be directly observd in various ways, because the proportion of different nuclei only changes in the interior of stars,and in gas clouds ejected by previous generations of stars within galaxies. Everywhere else, the proportion remains almost the same, only disturbed by antiprotons from the decay of the lightest supersymmetric particle. (A topic on which I published a Physical Review Letter with John Hagelin and his student in 1989).

Because most of the hydrogen is in the form of protons, H1, and very little as deuterons, H2 deuterium nuclei, the statement above would mean that the total mass of Helium nuclei (alpha particles) would be 33% more than the total mass of protons (Hydrogen nuclei)!

The sentence would be better rewritten as:

At this time, there are approximately three times more hydrogen ions by mass than helium-4.

Alex Hankey, Physicist — Preceding unsigned comment added by 122.167.131.202 (talk) on 14:30, 24 July 2007

Temperature[edit]

There is very little info about the temperature of the Universe during the various epochs. — Preceding unsigned comment added by 174.88.8.190 (talk) 21:31, 17 October 2014 (UTC)

Capitalization of universe[edit]

There is currently a discussion about the capitalization of Universe at Wikipedia talk:Manual of Style/Capital letters § Capitalization of universe. Please feel free to comment there. sroc 💬 13:15, 19 January 2015 (UTC)

Discussion of capitalization of universe[edit]

There is request for comment about capitalization of the word universe at Wikipedia talk:Manual of Style/Capital letters#Capitalization of universe - request for comment. Please participate. SchreiberBike talk 00:31, 4 February 2015 (UTC)

Notification of request for comment[edit]

An RfC has been commenced at MOSCAPS Request for comment - Capitalise universe.

Cinderella157 (talk) 03:23, 22 March 2015 (UTC)

Fate of the Solar system[edit]

Pardon me but shouldn't this:- "the core of the Sun will become hot enough to trigger hydrogen fusion in its surrounding shell" say "the core of the Sun will become hot and dense enough to trigger helium fusion with hydrogen fusion continuing in its surrounding shell" ? — Preceding unsigned comment added by Ianchristie (talkcontribs) 03:22, 27 March 2015 (UTC)

https://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Stars[edit]

Hello can you view the entitled link please and let me know your thoughts. I'm kind of stuck in order to grasp the article as a whole... Regards. -- Space Ghost (talk) 06:25, 28 June 2015 (UTC)

The universe started ionized - at high energies you have nothing but high-energy particles, no neutral combinations. The "recombination" era is when the initial ionized era ends. Tarl.Neustaedter (talk) 21:23, 28 June 2015 (UTC)
Tarl.Neustaedter: Okay, noted, I'm guessing, this means that population III stars formed from this ionized place, but before the III stars formed, the ionized place went through stages e.g., the 'Dark Age'/transparent age, Abiogenisis molecules were also involved which became transparent along... Correct me if I'm wrong please. About 'reionization epoch', the article states the universe is composed of plasma in the 'reionization epoch' section? Which plasma is it talking about? -- Space Ghost (talk) 18:59, 29 June 2015 (UTC)
You need to read the article Reionization. Population III stars is simply a way of describing stars which formed before a lot of metals were around, so they were formed of primordial materials of Hydrogen, Helium and Lithium. It wasn't an organized process of event 1, then event 2, then event 3 - it was a messy process with varying conditions across the universe . Recombination took place because the universe cooled from expansion, allowing particles to drop to low enough energies to form atoms. Re-ionization took place because energetic events were taking place (galaxy formation, quasars, supernovas), which required aging stars, dumping energetic photons back into the mix. The first pop III stars probably formed before recombination started, but were still forming long after the re-ionization took place. Tarl.Neustaedter (talk) 20:19, 29 June 2015 (UTC)
Tarl.Neustaedter: Hello, sorry for delaying in getting back to you, I got involved into an unexpected thing. Anyway, thank you for the summary. I appreciate it.
What you stated, III stars started before recombination epoch, Galaxy/Galaxy formation and evolution article state that, about 300,000 after the Big Bang. What I'm trying to understand now, i.e., the universe was composed with ion after the Big Bang occurred, and ionized era ended as recombination era started. Now that I'm thinking that III stars were created before the recombination era started, protogalaxies started to occur from this period onwards right? reionization occured during this period, right? If so, why 'Dark Ages'? the universe was busy, right? (I'm gonna read through the article you stated; I skipped it last time because it was long...) -- Space Ghost (talk) 19:35, 1 July 2015 (UTC)

Per WP:TALK#USE, this conversation has gone on a bit far, so I'm going to close the discussion. The purpose of talk pages is to discuss improvements to the articles, not for a general discussion of the subject matter. That said:

  • The first stars (and galaxies) were almost certainly created well before recombination, during the so-called dark ages. Even when the universe was entirely plasma, gravitational collapse almost certainly still occurred. After all, stars are mostly plasma themselves (at high temperatures all atoms disassociate into nuclei and free electrons - plasma). We can't know for sure when the first stars and galaxies were created, we can't see that far back.
  • The dark ages were called that because the universe was occupied by plasma, and was thus opaque. Any photons generated were simply absorbed by free electrons and then re-emitted. We see the remnants of this glowing cloud in the cosmic microwave background radiation today.
  • When recombination occurred, temperature dropping enough that free electrons could be captured by nuclei, photons could then travel longer distances before being absorbed and re-emitted. It wasn't a sudden process, it was a gradual process. The stated timeframe of 377,000 years is approximate and probably not uniform - some places taking longer than others. When most of the matter of the universe had recombined to make neutral particles, the universe became mostly transparent.
  • Today, most matter is again plasma, but intergalactic matter is at low enough density that we can get photons from most of the way across the universe.

Regards, Tarl.Neustaedter (talk) 05:01, 2 July 2015 (UTC)

Tarl.Neustaedter: Okay, thank you. I appreciate what you done so far. Made me understand things in a simple way... -- Space Ghost (talk) 07:38, 2 July 2015 (UTC)

Clarifying the Summary[edit]

I found a number of confusing/misleading turns of phrase in the summary, and corrected them. Unfortunately I forgot to log in until just before the last one - the others show up as IP 81.2.68.136. MrDemeanour (talk) 17:53, 24 July 2015 (UTC)