Talk:Flatness problem/GA1

GA Review

Protonk comments

Images

Image:End of universe.jpg doesn't provide source information (Aside from a name). This is the source. It is also my opinion that this image should be moved up to the top of the article.

Source added, and image moved. Olaf Davis | Talk 16:38, 10 September 2008 (UTC)[reply]

Image:Flatness problem density graph.svg. This is a much better image, and is also free.

But that image is showing something else: size of the universe vs. time for different matter/dark energy compositions. The current one shows the density parameter vs.time for different total densities to indicate how it diverges from 1. Olaf Davis | Talk 07:52, 9 September 2008 (UTC)[reply]

Sources

Citation method is inconsistent. The citations should appear in the same format, but I don't care what that format is.
Citations (if the notes layout is used, versus the notes/refs layout) should cite the work in a manner that allows the reader to find the source, then following citations of the same material can be abbreviated. Stompor et al 2001 is cited in an abbreviated fashion only.

Fixed. Olaf Davis | Talk 16:29, 10 September 2008 (UTC)[reply]

MOS issues

"The flatness problem is a cosmological fine-tuning problem within the Big Bang model." Per WP:LEAD this sentence should probably be rewritten a bit to include the discipline more explicitly.

Done. Olaf Davis (talk) 18:02, 19 June 2009 (UTC)[reply]

Fine-tuning is linked twice in the lead.

Fixed. Olaf Davis | Talk 07:50, 9 September 2008 (UTC)[reply]

The first citation in the lead is not necessary. The second might be.

Removed first cite. Olaf Davis | Talk 07:50, 9 September 2008 (UTC)[reply]

the lead should be longer.

Done. Olaf Davis (talk) 18:02, 19 June 2009 (UTC)[reply]

Energy Density and Spacetime Curvature section titles shouldn't be capitalized.

Fixed. Olaf Davis | Talk 07:50, 9 September 2008 (UTC)[reply]

Current Value of Ω Same same

Fixed. Olaf Davis | Talk 07:50, 9 September 2008 (UTC)[reply]

Non MOS issues

"The flatness problem arises because of the effect which the density of the universe has on its geometry..." This sentence is awkwardly worded.

It seems to have disappeared at some point. Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

"Since the total energy density of the universe departs rapidly from the critical value over cosmic time,[2] the early universe must..." Jumps into detail WAY too fast. Think of the lead as an executive summary. Anyone, regardless of training, should be able to read it and give a good summary of the article contents. I don't mean that the lead should be oversimplified, but the explanatory summary in the article should have its best elements used in the lead summary.

I've had a go at rewriting this - hopefully it's clearer to the layman now. Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

Fine-tuning, if linked prominently from this article, should be improved, or at least sourced.

Is that really a requirement for GA status? As far as I was aware even FAs weren't held to that standard... Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

Energy Density and Spacetime Curvature This should be merged with the following section.

Done, it seems. Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

"One such observation is that of anisotropies in the Cosmic Microwave Background (CMB) radiation..." This sentence and the sentence that preceeds it aren't very helpful. The two paragraphs describing experimental validation of background lensing should be rewritten to better describe what it is and how it offers a look at the value of Ω.
"This tiny value is the crux of the flatness problem..." This paragraph should start a new section.

Fixed. Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

"Some cosmologists agreed with Dicke..." Who?
"But there was also a school of thought..." What school of thought? Who were its adherents?
"Enough cosmologists saw the problem as a real one..." How many is enough? And who?
"...for various reasons to be proposed." Remember, when writing, don't say you are going to do something, do it. If you need to mention that you will introduce possible "reasons", just introduce them in a short summary.

I think you've misinterpreted what I meant. I've reworded it. Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

Criticisms of the Anthropic Principle No need for this header. Just include the criticism in the prose.

Done. Olaf Davis (talk) 17:29, 19 June 2009 (UTC)[reply]

"Since many physicists and philosophers of science do not consider the principle to be compatible with the scientific method..." The article can and should state clearly why the anthropic principle is not compatible with the scientific method.
"...another explanation for the flatness problem was needed." I am of the opinion that this kind of a segue should only be used if the failure of the anthropic principle to explain this anomaly is what spurred the inflation principle. Is that what happened? Or did a set of people consider the anthropic principle sufficient to explain this particular issue and another set of people work in parallel on a more testable proposition?
"The idea of inflation was first thought of..." a stronger verb is needed here.

Changed to 'proposed'. Olaf Davis (talk) 16:47, 19 June 2009 (UTC)[reply]

"This solving of the flatness problem is considered one of the major motivations for the existence of an inflationary epoch." What does this mean?

Reworded to "This success in solving the flatness problem is considered one of the major motivations for inflationary theory." Olaf Davis (talk) 16:47, 19 June 2009 (UTC)[reply]

"These have included non-standard interpretations..." What does non-standard mean in this context?
As a matter of fact, the "Post inflation" section should be fleshed out and explained fully.
In the post inflation section, is it fair to say that dark energy and dark matter are still to be treated as heterodox?

It wasn't my intention to imply that they are. In fact I'm not quite sure that the text does imply that. Olaf Davis (talk) 13:42, 20 June 2009 (UTC)[reply]

Why don't we mention Zel'dovich?

What about him do you think needs mentioning? Olaf Davis (talk) 13:42, 20 June 2009 (UTC)[reply]

"... as the scale factor $a$ grows exponentially" Does it grow exponentially or is this just a turn of phrase?

It's actually exponential. I've tried to clarify this by explicitly saying a ~ exp (t) above. Olaf Davis (talk) 13:42, 20 June 2009 (UTC)[reply]

The explanation of the Friedmann equation and the resulting expected values for $Omega$ should be clarified and expressed more formally. Step the reader through the derivation, even it if appears simple. You rely on their intuitive understanding of this formula later in the article, so don't rush past this.

Overall

This article is a good attempt at explaining a rather esoteric problem to a general audience but it has a few major problems. First (and this is the root of the other problems), it is too short to cover the subject appropriately. Second, it doesn't provide sufficient context for the subject. I can't judge the article POV because I have little information about the history of the problem among the community of physicists and the status of the solutions among the same. Third, the article has a spotty expectation of reader familiarity of the subject. Let's take these one by one:

too short/little context. The article can spend some more time discussing the roots of the flatness problem including what people thought at the time about it. There are several histories of science that cover the topic in some detail out there. the article can also spend some more time on solutions to the problem. The cosmic inflation section shouldn't get too long, lest it needlessly recapitulate detail elsewhere, but the post inflation solution section can be broken up and explanded. Likewise with the explanation of EFE and the curvature of space. The Freidmann equation can be laid out more fully and then the dark energy terms dispensed with (with some explanation why this was done). Likewise the article should make clear why this is a problem for physicists. It isn't an anomaly, in the Kuhnian sense. It is more of a curiosity until you look closer. Explain how we understood cosmology at the time and why a formula for the density of space could create such a fuss. Crucial to this is explaining the problem of divergence. This is partially why I suggested an image change. Other physicists need a mention here (some are noted above).
Reader familiarity. Assume that your reader is willing to click on well targeted wikilinks in order to understand an article. Don't talk down but don't speak entirely in the language of the discipline. I understand that this is not a particularly difficult concept as presented but the explanation of it should still proceed step by step. This is more of a clarity issue than a difficulty level issue. You will find that if you take the time and space to be clear, the level of material that can be presented will be increased.

I'm going to place this article on hold. The problems this article has to overcome are significant but not insurmountable. If they aren't one in ~7 days, no one should be ashamed if this article is not listed. The problems can be fixed and this article will be a GA soon. If not in the next seven days than soon thereafter. Thanks for giving me the chance to review an article like this. Protonk (talk) 03:47, 9 September 2008 (UTC)[reply]

Thanks for the very detailed review Protonk! I'll try and address your points soon. I probably won't have time to get to all of them this week, but it's not like there's a rush. Olaf Davis | Talk 07:45, 9 September 2008 (UTC)[reply]

No rush. the week thing is more for you than for me. It stops me from putting an article on hold and then indefinitely refusing to promote it. Protonk (talk) 13:47, 9 September 2008 (UTC)[reply]

Not promoting

I know there is no rush, but holding this article for 15 days is a little much. I would probably feel differently if the issues were being actively addressed, but it has been 9 days since the last change to the article. This article has a lot of potential but it isn't a good article yet. If you disagree with this decision feel free to post here or on my talk page. If you feel it was flagrantly unacceptable, you may bring this article to Good Article Review. Thank you and better luck in the future. Protonk (talk) 04:34, 25 September 2008 (UTC)[reply]

No, that's perfectly reasonable. I would have been addressing them more actively but I've had scant internet access recently - hopefully that will change soon and I can get back to work. Olaf Davis | Talk 22:04, 25 September 2008 (UTC)[reply]