Talk:Reionization

message: I added the link back to the disambiguation page for the time being, as it give some explanation. I may write create a recombination stub in the next few days and redirect the link there. James McBride 09:14, 15 August 2007 (UTC)
replies: text: My bad. I went back and looked at the previous version, and I guess I had looked at the wrong recombination. I thought the link had been removed, instead of redirected to the Big Bang timeline. James McBride 08:36, 16 August 2007 (UTC)
thread_title: Recombination disambiguation

message: I would like to see a few more images in the article. In particular, the graph of the CMB polarization angular anisotropy map and an example Gunn-Peterson trough. A non-copyrighted version of the first should be possible, as it was generated by WMAP, but I only was able to find the image at other sites. James McBride 09:14, 15 August 2007 (UTC)
thread_title: Adding more images

message: I think editors should give serious consideration to deleting the image given at http://imagine.gsfc.nasa.gov/Images/sats_n_data/exhibit/reion.diagram.jpg
1) The universe does not become opaque at the surface of last scattering. It's called that for a reason, and it's not because the universe suddenly starts scattering - the universe becomes transparent then, not opaque (exception being specific neutral hydrogen absorption features as mentioned in the GP trough sections)
2) The universe does not become neutral either for that matter. It was neutral already, but ionized. It becomes unionized at that point, which is not the same as neutral
3) The universe does not become transparent again at reionization. It'd be opaque again, except that the free electron density is low enough that the Thomson scattering cross section remains low and the universe stays opaque.
In other words, that diagram from NASA is pretty badly wrong in a number of fundamental points. I'd get rid of it myself, but I'd probably be accused of vandalism for getting rid of something from a reputable source, even when it's got fundamental errors in it  —Preceding unsigned comment added by 91.84.172.216 (talk) 00:29, 21 February 2008 (UTC)
replies: text: I agree that the language used is rather poor. There is some use of opaque and transparent in the sense used in the diagram in some of the literature, but I was initially rather confused by that. Perhaps the article would be stronger without the diagram. James McBride (talk) 02:42, 22 February 2008 (UTC)

text: Wow, that is great! I just uploaded the new version, and also made a couple of changes in the text you added to reflect the new image. James McBride (talk) 20:20, 30 December 2009 (UTC)
thread_title: Current image deletion

message: I suggest that the name of this entry should be changed to "Reionization event," to more clearly indicate its specific subject matter. --Steve, Sm8900 (talk) 14:53, 26 February 2010 (UTC)
replies: text: Only if you have a reliable source that uses the term "reionization event". Seems to me that something that is spread over two phases, one of which lasts more than 800 million years, is more like a process than an event. Gandalf61 (talk) 15:21, 26 February 2010 (UTC)
replies: text: I believe the two events are considered to be separate events. this article covers them as distinct though related events. I will try to find sources. --Steve, Sm8900 (talk) 16:01, 26 February 2010 (UTC)

text: Seeing your edit, I think I may understand the source of confusion. The universe started ionized. It became neutral during recombination. It was then reionized during a single period of time, lasting some hundreds of millions of years, known as reionization. I have frequently heard reionization called the "epoch of reionization," but almost never called the "reionization event." As such, I would strongly oppose any move to change the name to reionization event. James McBride (talk) 20:07, 26 February 2010 (UTC)
replies: text: Well, how about a parenthetical note to indicate the topical area? Reionization is a word and scientific term with multiple uses and applications, like any other word in the English language. also, it can refer to a reionization process of any object or in any set of conditions. As an article title, it seems rather imprecise. An article title like "Reionization (cosmology)" or "Reionization (astrophysics)" might perhaps be more clear and accurate. --Steve, Sm8900 (talk) 14:57, 2 March 2010 (UTC)
replies: text: I feel like the first sentence of the article makes clear the scope of the term as used in the article. As there is no other article on reionization, I am not sure what the purpose of renaming would be. Reionization would still redirect to reionization (cosmology) anyway. And, as a final note, the first non-cosmology hit for a simple search of reionization is on the 9th page. James McBride (talk) 04:07, 3 March 2010 (UTC)
thread_title:  Name change 

message: It seems that several citations are lacking from the first few paragraphs. Really, there aren't any until
the end of the second paragraph in the 'Quasars and the Gunn-Peterson trough' section. Can anyone cite
a reference to this: "which occurred at a redshift z = 1089 (379,000 years after the Big Bang)"? The article 
seems to assume that we already know a lot, whereas we probably don't. Richard Nowell (talk) 17:08, 19 June 2014 (UTC)
thread_title:  More Citations Please 

message: As of Jul 10, 2014 the 2nd P of the Background has some strange (inappropriate) wordings and sentences.
First:"The second phase change occurred once objects started to condense in the early universe that were energetic enough to ionize neutral hydrogen. As these objects formed and radiated energy, the universe reverted from being neutral, to once again being an ionized plasma."
Why are the Population III stars called "objects"?!? AFAIK, there is no controversy that the first objects to radiate significant amounts of emr were mostly Pop. 3 stars (whether black holes also formed then and were significant source of emr (from their accretion disks) is something I don't have a handle on (but doubt)). (Whether Pop. 3 stars formed in galactic structures or whether galactic structures formed around those stars, has not (to my knowledge, but it may be out-dated) been conclusively answered. Regardless, it is irrelevant here.)
Second: Isn't "The second phase change" actually called the "Reionization"? Why is that being avoided??
Third:"the universe reverted from being neutral, to once again being an ionized plasma." Wow! Talk about awkward!
The Universe is space and time and everything in it. PART, and ONLY part, of it is baryonic matter. To confuse the plasma in the matter(?) dominated Universe with the Universe itself is so egregiously WRONG as to be, to me, incomprehensible.  Have you not heard of Dark Matter??? How about Dark Energy?? Wow! This MUST be changed!!
Here is a hint: the plasma is roughly 25% of the matter in the Universe and only 4% of the total energy content. So, whether or not you ignore Dark Energy, equating the Universe to the plasma in it is a blunder of epic proportions.
Fourth:"At that time, however, matter had been diffused by the expansion of the universe, and the scattering interactions of photons and electrons were much less frequent than before electron-proton recombination. Thus a universe full of low density ionized hydrogen will remain transparent, as is the case today."
"matter had been diffused" is gobble-de-gook. Why not:"By that time the expansion of the Universe had diluted the concentration of matter so that it was too diffuse to obstruct light transmission. Today's Universe is and will remain transparent."  — Preceding unsigned comment added by Abitslow (talk • contribs) 15:57, 10 July 2014 (UTC)
thread_title:  Background - 2nd Paragraph needs work 

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thread_title:  External links modified (January 2018)