Talk:Big Bang/Archive 19

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SZ and copernican principle

I deleted this sentence from the "Underpinnings" section. It was very unclear. SA offers an explanation above, but it seems to me that he describes a test of the big bang model as a whole (vis-a-vis one particular theory in which the CP does not hold) rather than of the Copernican principle itself. Anyway its a bit tricky because the SZ signal depends on cluster properties which are not usually independently measured. I will add a mention of tests of T/a to "observational evidence".

Also, since the underpinnings section mentions GR and had a spurious extra "assumption", I replaced this with the assumption ethat GR is right and stuck the disputed reference to alternatives in there. Maybe people will agree that this is less offensive in this context. PaddyLeahy 14:45, 7 May 2007 (UTC)

Another way to think about the SZ measurements is that they test the CP by measuring the local value of T0. That is, if observers a few Mpc "over there" measure a hotter CMB temperature (even if it obeys the correct T(a) relation) you'd see that in SZ.

I have an issue with the recent edit as it stands, since it jumps into alluding to problems with the big bang 1. before even completing the description of the theory (!!!) and, 2. without even mentioning the problems. Stylistically, the criticism of GR is in the wrong place (more on this below).

Also the edit is factually incorrect. GR is an absolutely essential element of the cosmological perturbation theory that lets you compute the CMB spectrum for l < 200 or so (eg, superhorizon scales at decoupling). So the implicit claim that it's only been tested on stellar scales is misleading.

Overall I'm very unhappy with the repeated "alternative gravity edits." I really fail to understand the POV that insists that the fact that GR is potentially wrong is an essential feature of the big bang model (despite the utter lack of evidence). Paddy, I applaud your edits in other areas, but the insistence that "alternative gravity," whose predictions are largely unknown, has made no unique predictions of its own, is not supported by the majority of cosmologists, and solves no pre-existing problem in the theory, strikes me as teach the controversy. Frankly, I think you would do well to read Will's book, then read it again, and then possibly a third time, and then start talking about the evidence for GR.

This irks me. Will's most recent book is 14 years old & therefore irrelevant for discussion of more recent theories (also way out of date on precision confirmations of GR on AU scales). You also apparently need to do some reading if you think that MOND has made no successful predictions and supplied no generic solutions of problems which need a posteriori "adjustment" with GR+DM: see the recent review by Mike Merrifield [1] (who is not a supporter of MOND). You keep requesting a list of "supporters" of MOND as if this were about competing football teams. Cosmologists are grown-ups. Read my comment under "NPOV" etc above. PaddyLeahy 22:53, 7 May 2007 (UTC)

Beyond just waking up each morning and removing these edits (which isn't really how things are supposed to work here), and posting/reading long diatribes on this talk page, I'm not really sure what we should do to reach a resolution. Does anyone else have thoughts on this? Wesino 20:56, 7 May 2007 (UTC)

Only that this is very mild compared to the archived diatribes of years past, so we must be doing something right. Art LaPella 21:28, 7 May 2007 (UTC)

Wow, glad I wasn't around.... Wesino 21:31, 7 May 2007 (UTC)

(later) Also, I am disturbed by apparent attribution errors -- see my comment at the end of the NPOV, MOND, and TeVeS section. Unfortunately, you'll have to scroll down a bit. Wesino 21:21, 7 May 2007 (UTC)

I'll cite chapter & verse on those in a minute... PaddyLeahy 22:53, 7 May 2007 (UTC)

For the last week I've been slowly correcting the problems I originally listed on this page and have now finished, so I hope the iteration will converge soon. I have not directly reverted changes that you (Wesino) and SA agreed on even when I disagreed. Wesino, I think you are confusing the amplitude of the argument about validity of GR that is going on on this page with what the article actually says. Also, you seem to think I'm an anti-GR zealot, whereas I submit that my comments here and edits to the article clearly give high probability to GR being right (if any edits don't read that way I'm happy for you to correct the article). No-one disputes that GR must break down by the Planck epoch. It is important to emphasise this because many presentations of the Big Bang identify the singularity (hence the "beginning of time") as the key element, whereas this article quite correctly makes the case that the essence of the theory is the early hot state from which all observable consequences flow... the singularity or any pre-big bang ideas are no more than interesting speculations at the moment. No one disputes that GR is one of the major assumptions of the Big Bang model (it is referred to as an assumption numerous times in the article, not as the result of my edits). Hence why not include a sentence or two on the evidence, as for the other assumptions? You might just as well complain that there is not the slightest evidence that the laws of nature are not universal, or that the cosmological principle is wrong, so why cite these as assumptions? Wesino, you keep demanding evidence that GR is wrong, whereas I want evidence that it is right before unequivocally commending it to the innocent public. No GR specialist worth their salt would cite the low-l multipole prediction as a strong test of GR; these are fitted with various cosmological parameters and several other gravity theories (yes, TeVeS is one) can also be fitted.

(sorry to intrude on your post, this just didn't fit below) Actually, the low ls are not "fitted" to GR. This is because GR has no free parameters (once you've fixed G_N). GR specialists have many other tests they can point to, but this is on the largest scales.

One way we might make some progress to a resolution is for you to respond to my comments about the different philosophies we seem to be adopting... if I'm mis-characterising your position, explain yourself more clearly. PaddyLeahy 22:53, 7 May 2007 (UTC)

(unindent) I'm not sure what the business about the Planck time has to do with this, I'll just ignore it for now (hopefully without causing offense). But I'll take you up on your suggestion to clarify my position, in the hopes of reaching some kind of resolution.

I'm also unclear of what your characterization of my position actually is, but I'll welcome the chance to clarify it in the spirit of moving things forward.

Our main responsibility, in the Big Bang article, is to clearly explain the Big Bang model as understood by the scientific community. We should take as our reference someone who is scientifically literate, and wants to learn what scientists mean when then talk about the "big bang," and why they believe it describes our world.

From this follow some subsidary points:

If the "alternatives" to GR are mentioned in this article, they should be much less space than discussions of dark matter, reflecting their proportion of the extant literature on these topics. Discussions of these models should be located in an appropriate section in the article, after the BB theory has been explained clearly and fairly.
If mentioned, it should not be claimed that these are full alternatives to GR. As I'm sure you'll agree -- since you yourself have made statements to this effect -- no one really knows what the predictions of these alternative models are. (Both MOND and TeVeS have free functions and many unknown parameters, for example)
If mentioned, it should also be noted that all of the "alternative" models under anything close to serious consideration require some form of dark matter in addition to modified gravity.
If mentioned, in fairness to CDM should be noted that most cosmologists and astrophysicists believe that observations such as the Bullet cluster rule out modified gravity models in favor of CDM.

When you ask for evidence that GR is right, I can only point you to sources such as Will's book (despite its "age"), or for that matter any textbook on GR, where you will find any number of successful experimental predictions of GR, from the early 20^th century to the recent announcements by the Gravity Probe B team. There are simply no experiments in conflict with the theory, and a great number that are completely in accord with it.

I am fully aware of the fact that nothing can ever be known "for certain," and I do appreciate your efforts to make sure that the status quo isn't calcified, and that people understand that science is in flux. But I feel that many of these "alternative gravity" edits are falsely portraying GR as a theory in crisis. They also overstate the case for the "alternatives." Even proponents of these models admit that dark matter is still required, as well as a number of other fields, interactions, free parameters, and free functions. Also GR has been tested, and passed, in vastly more settings than any of the alternatives. A fair and complete contrast of these models belongs somewhere -- but it's off-topic for the Big Bang article.

Personally, I am making an effort, however clumsy, to try an elevate this debate to something more than personal attacks. As one approach, I've gone to two primary source databases and cited statistics. I've also looked at the sources you've cited. I've also tried to engage on this talk page whenever possible instead of simply reverting.

I'm frustrated because I'm really not seeing any response to my arguments (and those of others). It's impossible to respond to an "argument by authority," for example, without getting into the details of who works where. (And shouldn't professionals be able to argue convincingly without appealing to their own authority?) For another, to the primary source statistics, there is a claim that my numbers are skewed (How? What is the opposing analysis? What ratio do you propose, and how do you get it?). There are also a number of uncited claims, and arguments by implication that a large number of respectable scientists are secretly MONDians and so on.

I'm frustrated because I have a fear that you're set on a position from which no argument will dislodge you, and a mission to make sure your PoV is known to all, despite the arguments of others and the opinions of nearly the entire scientific community. I really hope it's not the case.

I think what we need most of all here is some kind of constructive suggestions. Here's mine. How about collecting all the points about "alternative" gravity models from their present locations, and putting a bullet point in the "Speculative Physics Beyond the Big Bang" section? It wouldn't require making the text any shorter than now, and furthermore --

This allows a complete and uninterrupted explanation of the BB theory, while allowing for the fact that some feel alternatives are important, but in an appropriate place in the article,
It makes clear that these are still-controversial proposals,
We already talk about the possibility of GR breaking down in the SPBtBB section (thus modified gravity would fit naturally in the theme of "beyond GR" too)
We already talked about alternatives to GR (eg, string models -- yes these are alternatives because the EP is violated, courtesy the dilaton, and quantum gravity effects, which may modify GR)
In a narrow sense, when people talk about the canonical Big Bang model, they usually mean LambdaCDM+Inflation. So interpreted this way, modifying both gravity and CDM fits well here.

Of course, as is probably clear, I see no case for including "alternative gravity" suggestions in the article. However, I do understand there are other points of view regarding inclusion. Nonetheless I think that there is a strong case to be made that these do not belong in the parts of the article devoted to explaining the theory itself.

If this idea sounds good, let's go with it. Otherwise, I would welcome a clarification of your position, and especially suggestions for action. (Action that doesn't involve me talking a long walk off a short pier, that is). Wesino | t | 00:33, 8 May 2007 (UTC)

Taking your comments from the top: Mostly agree on your aim for the article, but rather than "why they believe" I'd say "How much they believe". To pick an example I hope you agree on, few would claim to be fully convinced by inflation at the moment.

Your conditions for mentioning alternates to GR require that the comment be very short and that a lot is said about it, presumably to discourage the reader from following the link. This seems a bit contradictory; I'm happy to go with short. You can always edit the article at the other end of the link if you think it's unbalanced (havn't touched it myself).

The point about successful tests of GR (which are referenced in the article) is that viable alternates give identical results in the strong-field regime (by design). The issue is the ultra-weak field regime, hence the literature debate we have both referenced. I'm not going to waste space defending MOND because it now isn't mentioned in the article and as SA pointed out it is not the only alternate theory currently under discussion in the literature. I also don't want to emphasise the personal by defending myself against charges of being unreasonable etc. I'll supply references if requested on points where the article is in dispute.

You seem to think the article contains several disputed references to alternates to GR, but I can only find one, i.e. the brief mention in "underpinnings" (I thought you were counting the edit I made to distinguish the Planck epoch from the singularity, but apparently not). If other places are in dispute, please give a list so I can see what we're talking about. As for the "underpinnings" mention, it doesn't seem to me to interrupt the flow, and seems naturally to fit in that section; it comes after the "overview" has explained the BB picture in a fairly detailed way; its very brevity suggests this is not considered a likely possibility; ie. it arguable satisfies your criteria. I'd value the input of other editors on this point.

I don't think "beyond the big bang" is the right place to put this...the name seems to imply that these are ideas which can be added to the BB picture outlined in the rest of the article without changing it significantly. (Also, I've lived long enough that I can't associate the BB purely with lambdaCDM+inflation, indeed none of those concepts seem essential to the basic idea). PaddyLeahy 10:49, 8 May 2007 (UTC)

I removed what seemed to be (perhaps unintentional) pandering to alternative gravity theories. If you look hard enough, you can find a minority-opinion alternative to just about anything in science, so why single out gravity? The existence of alternatives are not in-and-of-themselves notable enough to include in a summary article, and the fact that there are no consensus falsification tests for GR versus any alternatives means that we should stick right now to describing the status quo. Even obliquely calling GR into question is disingenuous from a summary perspective because there are many other points in cosmology which are far more debatable and yet whitewashed over simply because this is a summary general-knowledge encyclopedia article and not something published in A&AR. Unfortunately, the subtlety of identifying holes in standard theories does not translate well into mass-media publications. Take New Scientist magazine's consistent travesties in reporting as an example of how it can go very wrong. Imagine the audience for this subject: people who may have only a vague understanding of what the Big Bang theory is and carry a lot of baggage and misconceptions along for the ride. If we begin throwing around alternative gravity theories like it's our job, we'll end up obfuscating the idea rather than elucidating it. WP:WEIGHT is a policy for a reason: undue emphasis on minority opinions bogs down articles on straightforward subjects.

To put this another way, try reading a standard intro text on the Big Bang and see how often it mentions alternatives to GR. If a Frank Shu doesn't do it, why should we?

--ScienceApologist 14:11, 8 May 2007 (UTC)

As it happens I have 9 of these in my office. Excluding the one written in 1974 (pre-MOND) and the one written by Hoyle (pro-maverick), 2 mention modified gravity en passant and 5 regard dark matter as certain. I'm going to concede on this point because no other editors are supporting my position, but I would say that I think the position has changed since all these books were written. (i) A major objection to MOND has been overcome (i.e. that it has no relativistic generalisation) and (ii) strong test cases, notably the bullet cluster have become available. As I said a week ago, the jury is still out on the latter. It will be interesting to see what position the next generation of textbooks will take. PaddyLeahy 15:05, 8 May 2007 (UTC)

Indeed, this article will continue to evolve as the textbooks evolve. That's one of the beauties of Wikipedia. --ScienceApologist 17:44, 8 May 2007 (UTC)

theoretical underpinnings

From the FA review it seemed like one of the issues was that things got too jargony. While looking over the theoretical underpinnings it seemed like this might be a problem. Coordinate charts, conformal time, etc.

From the looks of it, it seemed like the section was just trying to explain the GR mathematical model for the BB, which would be in parallel with the article overview. I've tried to get these ideas across without the jargon getting too intense, and linked to articles that get more hard-core. Here's the diff if you'd like to peruse what I did.

I also took out the sentence that says we can't test alpha variation in the very early U.

Not sure about the use of hyphens, I'm worried about this after reading bits of the FA review. Can someone point me to the wp policy on --'s? Wesino | t | 17:57, 8 May 2007 (UTC)

Hyphen is the best Wikipedia hyphen guide I know of, although there seems to be little agreement on hyphens even on the Main Page, where such details are inspected more closely than they are here. Art LaPella 19:28, 8 May 2007 (UTC)

WP:DASH PaddyLeahy 21:54, 8 May 2007 (UTC)

Horizons

Big Bang#Horizons ends with "there will be future horizon as well". I almost added the word "a" before "future". Then I wondered why it's "will be". The horizon is a region of space that exists now; its definition is what depends on the future. Similarly, in the previous sentence, should "there was a past horizon" be "there is a past horizon"? Art LaPella 19:10, 8 May 2007 (UTC)

Huh, that's an interesting point. Maybe it would be better to say "spacetime has a future/past horizon," since that would reflect the fact that a horizon is a feature that depends on the whole history of the universe. Wesino | t | 19:16, 8 May 2007 (UTC)

I changed the section before seeing this discussion. I think those changes address your concerns and hope they're okay. Gnixon 20:22, 8 May 2007 (UTC)

A couple of issues the in History section -- comments invited

I'm reading through and there are a few things I'm not sure about, but which I think could stand correcting. Nothing major, just polish.

In "History," ...Alexander Friedmann, a Russian and Soviet cosmologist and mathematician,... There seem to be too many ands. Could we eliminate either (and Soviet) or (Russian and) since in 1922 these were redundant? Or is there a reason that Soviet+Russian are both important?

Early in the History section it talks about Hubble's 1924 measurement of the distance to "spiral nebulae," then later (next paragraph) started "Since 1924" I actually edited this second sentence to strengthen the impression that he started his measurements in 1924, but which more accurate? Should we say that he painstakingly developed the distance ladder, which enabled him to announce distances to Slipher's galaxies in 1924? What's right here?

Later on in "History" ...the oscillatory universe (originally suggested by Friedmann, but advocated by Einstein and Richard Tolman),[9] I know Tolman advocated this model (the reference is to the book where he discussed it) but is it true that Einstein did? I always thought that he was more of a static universe guy. Is there a reference to Einstein supporting the oscillatory universe (presumably after abandoning the static one)?

Any history buffs feel like chiming in? Wesino | t | 19:43, 8 May 2007 (UTC)

(Puts on other hat). First point no opinion (I guess the distinction is important to some Russians); second & third points are mine. Actually the only nebula measured in 1924 was Andromeda (my original text got changed) though others followed soon after; this was a Cepheid distance and Hubble used Harlow Shapley's calibration (which was in substantial error). From 1924 on Hubble pushed his distances out further and further. The Einstein ref is from Tolman's book: on oscillating models (§163) Tolman says: "The first of these models was originally considered by Friedmann as early as 1922, and has since been advocated by Einstein." The ref is "Einstein, Berl. Ber. 1931, p. 235." (which I havn't consulted). Einstein suggested various options after his original model was ruled out, e.g. also the Einstein-de Sitter model. Given that the citation in the text is to Tolman's book, you could argue this is documented already... PaddyLeahy 21:17, 8 May 2007 (UTC)

Okay, number three sounds fine to me – maybe we could include the Berl. Ber. ref, but I try not to cite things I haven't read, so I'm not sure I could do it personally! Tolman's word is fine with me. From what you say it seems number two is all right as well... For the first, I guess I'll take out "Soviet" since Russian implies Soviet in '22. Hopefully if someone has an issue they'll say something. Cheers, Wesino | t | 22:05, 8 May 2007 (UTC)

While on the subject of history, the article used to credit Gamow with the CMB prediction, but as pointed out by John Mather (The Vergy First Light) this is incorrect: the prediction was made by Gamow's student, Alpher and post-doc, Herman. I've now given the correct citation. Reading this "paper" for the first time just now was a revelation: no wonder the prediction went unnoticed, since it appears at the end of what is essentially an erratum (or correction) to Gamow's earlier Nature paper, which usually gets the credit, but doesn't actually mention that the big bang radiation would still be around today! PaddyLeahy 23:12, 8 May 2007 (UTC)

Initial state?

Last week I removed the word "initial" from the description of the early high-density state, on the grounds that the big bang concept does not depend on there being no "pre-history" to the universe. I see Gnixon has put it back in the first sentence, which seems odd, given his efforts to remove the "singularity" from the accompanying picture. One of the things that has suprised me, reading around this article, is how very few prominent cosmologists seem to have taken the "beginning of time" idea literally... not even Gamow! I guess I happened to learn about the big bang when this idea was at a high point in its fortune, a few years after the Penrose-Hawking theorem. The idea seems to be out of fashion at the moment, even though Hawking still supports it. PaddyLeahy 07:48, 9 May 2007 (UTC)

Well, I think "initial" is okay in the beginning, I think it helps distinguish the Big Bang premise that things started hot and dense and then evolved from there (as opposed to being it a hot and dense state today). I find it helps to keep things clear, maybe there's a way to get across the idea without using the word.

My feeling is that many people who work on these things these days are a little bit too enamored with the mighty S-matrix for various reasons, and grow deeply uncomfortable without an asymptotic past. Wheeler took the idea of the beginning of time seriously, and seemed to think that the fact that GR suggested this was a Big Deal^TM. But of course, he's not really of the present generation. Wesino | t | 08:41, 9 May 2007 (UTC)

The funny thing with that discomfort is that it is entirely misplaced. Because the Hubble time is the only relevant scale in the early universe, with a finite absolute past physics still has an asymptotic history simply because of the density of the real numbers between 1 and zero. The logarithmic scale to the "beginning of time" will never reach that beginning. 10^-43 is not zero: it is infinitely far from zero. --ScienceApologist 12:41, 9 May 2007 (UTC)

You know it's getting hairy when physicists start talking about number theory! ;-) Paddy, I didn't mean to contradict your earlier edit. I was a little uncomfortable with "initial" for the same reason as you, but I don't really think "initial state" has to imply "beginning of time". Mostly I think that, in the lead, we should avoid getting into details at the fuzzy edge of the model. In one sense, the Big Bang does take us all the way back to t=0 (because nanoseconds << 13.7 billion years). In another sense, there's tons left to describe after GR (presumably) breaks down. Introducing things concisely and accurately is important and tricky, and we should talk about it, but I think virtually all the possibilities are at least reasonable. I made a change to the first sentence that I think sounds better and also gets rid of "initial". Hope it's an improvement. Gnixon 16:21, 9 May 2007 (UTC)

Just because nanoseconds << 13.7 billion years doesn't mean that you can compare today's timescales to the timescales in the early universe. --ScienceApologist 18:09, 9 May 2007 (UTC)

Well, I think you're taking the usefulness of the Hubble time a little too far. The Big Bang universe is 13.7 billion years old, and that means just what the casual reader thinks it does. The fact that lots of stuff happens within the first fraction of a second doesn't invalidate that statement, even if the interesting physics is spread out over a logarithmic scale. Anyway, I think we're splitting hairs and getting off-topic---I think we basically agree. The article should say that the universe is 13.7 billion years old, and it should also point out that a huge amount of interesting stuff happened at early times because the relevant physical times scale inversely with energy. Regarding "initial," I suggest we just avoid saying anything absolutist up front and then explain the details later on. Gnixon 22:01, 9 May 2007 (UTC)

This is a bit of arguing about angels dancing on pinheads, but the logarithmic nature of lookback time is often obscured in the literature because people believe that their timescales (years) can apply throughout history when they cannot. An eternal and finite universe is simultaneously possible: they need not contradict. Currently, there is no physical mechanism yet which rules out this or any other possibility. --ScienceApologist 22:16, 9 May 2007 (UTC)

ADDED: 6. A few other problems, as very important, cf. [2]

Please help to make this section a bit better!

by wfcKehler@aol.com 84.158.89.2 20:06, 11 May 2007 (UTC)

There's already a section on "problems." I reverted those additions because they didn't fit well in the article. (My edit comment erroneously called them "uncited"; sorry.) It would be useful if a nice way could be found to incorporate them in the previous section. Gnixon 20:18, 11 May 2007 (UTC)

RESPONSE: Thanks! This is partly correctly, please add mentioned completed list for my added section (I can try to put it again better?)

6. A few other problems, cf. [[3]], University Cambridge cited:

Despite the self-consistency and remarkable success of the standard Hot Big Bang model in describing the evolution of the universe back to only one hundredth of a second, a number of unanswered questions remain regarding the initial state of the universe.

The flatness problem Why is the matter density of the universe so close to the unstable critical value between perpetual expansion and recollapse into a Big Crunch?

The horizon problem Why does the universe look the same in all directions when it arises out of causally disconnected regions? This problem is most acute for the very smooth cosmic microwave background radiation.

The density fluctuation problem The perturbations which gravitationally collapsed to form galaxies must have been primordial in origin; from whence did they arise?

The dark matter problem Of what stuff is the Universe predominantly made? Nucleosynthesis calculations suggest that the darrk matter of the Universe does not consist of ordinary matter - neutrons and protons?

The exotic relics problem Phase transitions in the early universe inevitably give rise to topological defects, such as monopoles, and exotic particles. Why don't we see them today?

The thermal state problem Why should the universe begin in thermal equilibrium when there is no mechanism by which it can be maintained at very high temperatures.

The cosmological constant problem Why is the cosmological constant 120 decimal orders of magnitude smaller than naively expected from quantum gravity?

The singularity problem The cosmological singularity at t=0 is an infinite energy density state, so general relativity predicts its own breakdown.

The timescale problem Are independent measurements of the age of the Universe consistent using Hubble's constant and stellar lifetimes?

by wfcKehler@aol.com 84.158.89.2 20:34, 11 May 2007 (UTC)

The fact that it is hosted by Cambridge does not make it a good ref - where are the jstor paper quotes or articles in Ap J? That is the sort of ref that is needed for these types of additions. Sophia 21:52, 11 May 2007 (UTC)

Well, it's not only hosted by Cambridge (as, for example, some undergraduate's homepage), but also seems part of the official pages of their cosmology group. As such, I think it's not an unreasonable citation, although of course a published (review?) article of some sort would be better. The issues pointed out are standard, and as long as they're presented as outstanding problems and not as damning criticisms of the current model, I think they represent the current thinking of cosmologists. Perhaps the label "problem" is a little too strong. For me, the main issue is how to incorporate these points smoothly within the article. Gnixon 22:42, 11 May 2007 (UTC)

ANSWER WITH DEMAND OF REVISION: Ok, may be better to name the main section "other open problems" in order to "incorporate these points smoothly", but not to eliminate them. One incredibly relevant problem is the wellknown fact - computed, and from many other sources confirmed - of really 120 decimal orders of magnitude in difference for the needed Einstein constant as an open question. All other facts are multiply found, partly already indicated within the same article (a bit later on) and mainly already confirmed in WIKI articles like in Non-standard cosmology, Dark matter, dark energy.

See at most [4]:

"Thus, the current standard model of cosmology, the Lambda-CDM model, includes the cosmological constant, which is measured to be on the order of 10^-35s^-2, or 10^-47GeV⁴, or 10^-29g/cm³, or about 10^-120 in reduced Planck units." Let's try it for the last time with the needed smooth incorporation.

wfcK 84.158.88.175 22:57, 11 May 2007 (UTC)

Apologies for not making my point clearer - never edit when tired. For the record I do hold reservations about the BB model for the some of reasons they have given but I do know we won't be able to stabilise the addition unless each point is backed by some meaty link with content. I have been surprised myself how anything not conforming to the BB model has been attacked on wikipedia (note that the Non-standard cosmology article is in the category pseudophysics - there was even a long running attempt last summer to include creationist cosmologies in the article which I saw as an attempt to discredit the non-standard theories by association). So let's take it point by point and see how and where the content will best fit - but I do feel a list on a Cambridge site will not be enough to convince others of their merits. Sophia 05:35, 12 May 2007 (UTC)

I think in some cases there may be an over-reaction by editors who are concerned that Non-standard cosmology or edits like this most recent might be motivated by a religious agenda. I think WP:AGF is key. Gnixon 11:49, 12 May 2007 (UTC)

"Non-standard" is a well recognised term that does not denote "psuedo" in the physics world. The problems stated are active areas of research as these are the "missing links" for the BB. Don't get me wrong - the BB is the best explanation there is but there are still significant areas to be explained so we should be able to include some of this stuff with quality references. Sophia 13:45, 12 May 2007 (UTC)

Ok, this was our last attempt

We have experiend now as true what is written in "An Open Letter to the Scientific Community" [5]. We could not believe it and have logged it for our proposal in BIG BANG:

Links removed

I have removed the following links from the bottom of the page, as I don't think that they are that useful as further reading (which I have repurposed the section to be). If anyone disagrees, then please read Wikipedia:External links and discuss the individual links here before adding them back. If any of them are references to material in the article, then please add them back as footnotes as per the other references.

PBS.org, "From the Big Bang to the End of the universe. The Mysteries of Deep Space Timeline"
"Welcome to the History of the universe". Penny Press Ltd.
Cambridge University Cosmology, "The Hot Big Bang Model". Includes a discussion of the problems with the Big Bang.
Smithsonian Institution, "UNIVERSE! - The Big Bang and what came before".
D'Agnese, Joseph, "The last Big Bang man left standing, physicist Ralph Alpher devised Big Bang Theory of universe". Discover, July 1999.
Felder, Gary, "The Expanding universe".
LaRocco, Chris and Blair Rothstein, "THE BIG BANG: It sure was BIG!!".
Shestople, Paul, ""Big Bang Primer".
Wright, Edward L., "Brief History of the universe".
"Proof of Big Bang Seen by Space Probe, Scientists Say" —National Geographic News
The Sabanci University School of Languages Podcasts: Origin of Elements by Alpay Taralp.
The Big Bang and Cosmic Microwave Background and More Evidence for the Big Bang, episodes of the Astronomy Cast podcast dealing with the Big Bang.

I have also removed the following, on the basis that they don't appear to actually talk about the Big Bang, but about creation/religion in general. I would have no objections to them being used as references (with specific page references) in the "Philosophical and religious interpretations" if they are appropriate there, but otherwise they don't belong in this article.

Leeming, David Adams, and Margaret Adams Leeming, A Dictionary of Creation Myths. Oxford University Press (1995), ISBN 0-19-510275-4.
Pius XII (1952), "Modern Science and the Existence of God," The Catholic Mind 49:182–192.
Ahmad, Mirza Tahir, Revelation, Rationality, Knowledge & Truth Islam International Publications Ltd (1987), ISBN 1-85372-640-0. The Quran and Cosmology

I've re-instated the last two as in-line cites. I think the first was intended to back up the claim that the big bang itself is considered by some as a creation myth... but that claim has been expurgated. PaddyLeahy 23:15, 16 May 2007 (UTC)

Finally, the "Preprints" section:

"Most scientific papers about cosmology are initially released as preprints on arxiv.org. They are generally technical, but sometimes have introductions in plain English. The most relevant archives, which cover experiment and theory, are the astrophysics archive, where papers closely grounded in observations are released, and the general relativity and quantum cosmology archive, which covers more speculative ground. Papers of interest to cosmologists also frequently appear on the high energy phenomenology and high energy theory archives."

Those that work in the area will already know about the ArXiV, so there's not much point linking to it for them. For newcomers, it's not the best place to start reading around the subject - going for the reviews and books would be a much better start. They will doubtless come across it in references in those reviews and books, if they go far enough. So what's the benefit of having it at the end of this article?

Thanks. Mike Peel 19:26, 16 May 2007 (UTC)

While on the topic of citations, one FARC comment is that this article is under-cited in general (e.g. now no cites in the Dark matter section at all). But this article is an introductory summary of such topics, some of which (Dark matter again) are very well referenced on their main article pages. Do we really need to provide cites on this page as well? PaddyLeahy 23:15, 16 May 2007 (UTC)

According to WP:SUMMARY, "There is no need to repeat all specific references for the subtopics in the main "Summary style" article: the "Summary style" article summarizes the content of each of the subtopics, without need to give detailed references for each of them in the main article: these detailed references can be found in the subarticles. The "Summary style" article only contains the main references that apply to that article as a whole." Mike Peel 09:37, 17 May 2007 (UTC)

Logical Nitpicker

In the introduction, there are words to the effect that at (near) time zero "energy was at high temperature and density". Matter yes but energy? I don't think so. What do we mean by the density of energy? I have tried to reword this to reflect the logical inconsistency but have been instantly stomped on by zealots who have apparently bought the article from Wikipedia. Any other opinions? Are we going to continue to say that energy has a temperature? Or are we going to say that matter and energy were constrained within a minute domain where temperature and density tended to infinity? Or am I the Lone Nitpicker? —Preceding unsigned comment added by Captainbeefart (talk • contribs) 13:24, 19 May 2007

Energy density is fine, but energy temperature is wrong (temperature is a form of energy). I've simply removed "and energy" from the sentence; just saying that matter was at a high temperature and density is fine, isn't it? Mike Peel 13:38, 19 May 2007 (UTC)

Temperature is not a form of energy. Temperature is a thermodynamic property. Energy being of high temperature is a bit mushy, but it could allude to electromagnetic radiation of high frequency. I suggest reverting the rewording as it only made matters worse. --Dschwen 14:29, 19 May 2007 (UTC)

"The temperature of a system is defined as simply the average energy of microscopic motions of a single particle in the system." I guess it is more a characterization of the kinetic energy than it is actually energy, but it still boils down to energy.

To a certain extent, having "matter and energy" is a bit of a duplication - after all, E=mc^2 (or rather,

E^{2}=m^{2}c^{4}+p^{2}c^{2}

). How about something like "in which everything (i.e. all matter, including photons) was at an immense temperature and density"? Mike Peel 17:32, 19 May 2007 (UTC)

Photons have a temperature: T = hf/k. --ScienceApologist 14:16, 22 May 2007 (UTC)

It's awkward. Actually its the photon distribution that has the temperature but that's too picky for the lead. Why not cut out matter and energy (after all, "all the matter and energy" is the universe) and just say the universe has the temperature? PaddyLeahy 17:05, 22 May 2007 (UTC)

The tyranny of the distributions! I suppose you're one of those people who hates it when people talk about color temperatures? In any case, temperature itself is an eighteenth century abstraction invented to quantify hot and cold. It was only after statistical mechanics was fully realized that the connection between the Maxwellian, the Planckian, and thermodynamic equilibrium would be realized. These are all, however, statistical mechanics and have nothing to do with individual particles. If you truly believe that higher energy photons are not "hotter" than lower energy photons, then I guess you can complain about distributions. I, however, see no value in holding on to old macroscopic notions when dealing with individual elementary particles. (Who cares to what distribution a particular photon belongs? It still has plenty of measurable properties and follows all the known laws of physics.) In any case, this whole discussion is rather absurd because the CMB is so close to a blackbody, we might as well talk about the temperature of the universe as you suggest. --ScienceApologist 17:15, 22 May 2007 (UTC)

Being picky about these things comes with the territory...I'm marking exams at the moment. But I'd advise, if you want your students to understand thermodynamics, to keep temperature & energy carefully distinct. (And colour temp /= brightness temp /= thermodynamic temp, though all are perfectly legitimate concepts). Aren't we way off topic now? PaddyLeahy 18:55, 22 May 2007 (UTC)

Energy and temperature are indeed distinct just as the period of an orbit squared is distinct from the semi-major axis of the orbit cubed. Way off topic, indeed. --ScienceApologist 20:19, 22 May 2007 (UTC)

In the hope of resolving this, I've changed the sentence to read "Extrapolation of this expansion back in time yields a state in the distant past in which the universe was in a state of immense density and temperature." Are there any problems with this phrasing? Mike Peel 11:33, 27 May 2007 (UTC)

Cosmic egg

ScienceApologist, do you have a reference for the "cosmic egg", especially for it being different from and earlier than the 1931 "primeval atom"? I know it's mentioned at Georges Lemaitre, but without a citation there either. The most detailed account I have access to is Kragh's book, which says that a short Nature letter in 1931 is the origin of the idea of starting at (effectively) a singularity, and Lemaitre used the phrase "primeval atom" in his British Assoc talk, also written up in Nature. (My guess is that "cosmic egg" was used in private only, it would have looked very informal in the context of papers of the time). PaddyLeahy 19:50, 23 May 2007 (UTC)

I have found a number of sources which attribute the "cosmic egg" description to Lemaitre ([7]) but it may also be that "cosmic egg" phrasing may be a bit of historical revisionism. Please help research this more fully. I'll look into my sources a bit more carefully.--ScienceApologist 15:52, 28 May 2007 (UTC)

By the way, the secondary source I list above cites Bernstein, J., Feinberg, G., Eds. (1986), Cosmological Constants: Papers in Modern Cosmology, New York: Columbia University Press as a source as well as Dick Teresi's provactive book. I think that we should definitely look into this more deeply and it may help improve the cosmic egg article as well! -ScienceApologist 16:11, 28 May 2007 (UTC)

Removed paragraphs from article - citations?

I've removed the following paragraphs from the article, as they are uncited and I can't currently find references for them. If anyone else knows of a reference for them, then please add them back along with the reference.

From Hubble's law expansion:

The relation between redshift and distance is more complicated than the simple relation for velocity, for it depends on past behavior of $H$ and thus the detailed content (matter, dark energy etc.) of the model. Also, in practice, the proper distance between two objects at a given time is not measurable, and so the redshift–distance relation also depends on the operational definition of "distance" that is chosen. By coincidence, the redshift–luminosity distance relation for ΛCDM is reasonably linear to high redshift.

From Philosophical and religious interpretations:

Certain theistic branches of Hinduism, such as in Vaishnavism, conceive of a creation event with similarities to the Big Bang. For example in the third book of the Bhagavata Purana (primarily, chapters 10 and 26), describes a primordial state which bursts forth as the Great Vishnu glances over it, transforming into the active state of the sum-total of matter ("prakriti"). Other forms of Hinduism assert a universe without beginning or end.

Buddhism has a concept of universes that have no initial creation event, but instead go through infinitely repeated cycles of expansion, stability, destruction, and quiescence. The Big Bang may be reconciled with this view, since there are ways to conceive an eternal creation and destruction of universes within the paradigm. A number of popular Zen philosophers were intrigued, in particular, by the concept of the oscillatory universe.—Preceding unsigned comment added by Mike Peel (talk • contribs) 16:39, 28 May 2007

Talk:Big Bang/Archive 19

SZ and copernican principle

theoretical underpinnings

Horizons

A couple of issues the in History section -- comments invited

Initial state?

ADDED: 6. A few other problems, as very important, cf. [2]

Ok, this was our last attempt

Other open questions, briefly

The problem cosmological constant

singularity problem

search of "exotic relics"

a probable timescale problem

a thermal state problem

Links removed

Logical Nitpicker

Cosmic egg

Removed paragraphs from article - citations?