Talk:Inflation (cosmology)/Archive 3

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Disruptive editing

Editors, please do not give up on this article. Do not despair. Wikipedia's mechanisms for overcoming a disruptive editor are frustrating and inefficient, but one day they will succeed. Please be patient. This article is not going to be of interest to many, and the article is not about a subject which may bring harm to anyone. Nothing bad is going to happen if we need to take a few months to undo the mischief of User:Eugeneacurry. Please do not let User:Eugeneacurry rile you. Remain calm and carry on. At the moment, User:Eugeneacurry is showing contempt for the entire Wikipedia community by refusing to learn from the result of his experience at WP:Administrators'_noticeboard/Edit_warring. Do not be moved by his contempt; it is of no consequence. Please do not call User:Eugeneacurry "stubborn" or anything else. Calling him names is not going to change anything. The outcome, if User:Eugeneacurry persists in opposing the community, is inevitable and gratifying. For the time being, please revert everything by User:Eugeneacurry. I will collect diffs of User:Eugeneacurry editing against consensus. We need those diffs to help an administrator help us. All will be well in the end. PYRRHON  talk   04:02, 28 May 2010 (UTC)

Hopefully there's no need to be so hard on Eugene. Perhaps we can reach a compromise that might actually improve the article. Whilst there is no merit in some of the new material, it raises a topic that should be clarified to save future heated discussion, namely that of the "motivation" for inflation. Guth didn't know about the horizon problem when he invented/discovered inflation, yet many sources state that this is a motivation for inflation. I think this is because the term "motivation" is used in two different senses; one is historical, and one is retrospective. Historically inflation developed from investigations into the magnetic monopole problem, which uncovered the strange, expansive behaviour of space implied by general relativity and which had lain undiscovered for some 60+ years. Retrospectively, though, once invented everyone realised that this solved sooooo many cosmological puzzles that this became the motivation for inflation's widespread and enthusiastic adoption by astrophysicists in general. Remove those retrospective reasons though, and inflation would still be motivated by the original reason; namely it being implied by general relativity in the presence of a false vacuum.

It's unfortunate that many commentators lose sight of the original historical motivation, concluding that inflation is just a concoction to plaster over cosmological lacunae.

If this makes sense, then I suggest:

1. Forget about Earman et al (i.e. remove from article), they just doesn't cut the mustard; they clearly don't understand the technical side of inflation.
2. Stop asking for sources for statements accepted by all experts in the field.
3. Add a "motivations" section.

--Michael C. Price ^talk 13:39, 28 May 2010 (UTC)

Part of my intractability on this matter stems from the simple falsehoods found in the posts of those advocating for the material's deletion. The IP editor said that a book published by an academic publisher (which was only being used as a pass-through source to a peer-reviewed academic journal anyway) was a "religious newsletter"; Sophia said that the comments from the "first article" cited were directed only at one particular kind of inflation (which statement was shown to be incorrect); Georgewilliamherbert said I was the only one advocating for the material's retention even though Gandalf was arguing for the same thing; Michael C. Price has said I'm misrepresenting Guth's position on the horizon problem as a motivation when I've only included a quote indicating that Guth agrees that the horizon problem is not a failure (strictly speaking) of the SBB model.

But I don't want to be a jerk. As I've said, I'm not qualified to evaluate claims of what-everyone-in-the-biz-already-knows. And if the IP really is BFFs with the cosmologists I've cited--and they've said my edits misrepresent them--then I may really be sunk. Still, the material in question is well sourced, particularly attributed when controversial, and notable (I think). I'm going to put a RfC in on this and, if it goes against me, then I'll drop it. I'm posting to the science board and the philosphy one as well--given the topic in question (I.e. philosophical issues regarding a scientific theory) this seems appropriate. Eugene (talk) 15:21, 28 May 2010 (UTC)

Addressing the complaint against me: Eugene misunderstands the problem. Yes, I deleted Eugene's statement that Guth was motivated by the horizon problem: he wasn't, as his bio' shows. --Michael C. Price ^talk 17:40, 28 May 2010 (UTC)

Not to be nit-picky, but I never actual said that Guth was himself motivated by the horizon problem: "Alan Guth has written that, while the 'horizon problem' has been one of the driving forces behind inflationary theorizing, the 'horizon problem is not a failure of the standard big bang theory in the strict sense...'"[1] Eugene (talk) 18:01, 28 May 2010 (UTC)

And where, precisely, does Guth say that "the 'horizon problem' has been one of the driving forces behind inflationary theorizing"? (Note he says, page 180/1, that he was "totally unaware" of it.) --Michael C. Price ^talk 18:21, 28 May 2010 (UTC)

And correcting the charge against me - I said that the first paper quoted (and by that I meant in the section under dispute) was about pre big bang inflation and it is. They obviously try to use this model to explain the observed features of the universe because that is the point of cosmology! Sophia ♫ 19:08, 28 May 2010 (UTC)

Eugene, yes, you are right, I was initially inclined to think that it was a newsletter, but a fact checking shows that it is not, it is a religious book on creationism with collected material. Are you now ready to understand also that the claims you are making are completely inadequate, since simple fact-checking shows that? Experiments on CMB and large scale structure have already tested inflation and more tests are underway, predicting adiabatic initial conditions and the scalar and tensor spectral indices and the non-gaussianites amplitudes cannot be done without inflation and hence the theory does add testable predictions to the Big Bang theory in a very fundamental way. Naturalness problem is one in which it is asked something that goes beyond a given theory, like when it is said that asking for a model that predicts the ratio of the cosmological constant to the Planck mass, or the ratio of the Higgs mass to the Planck mass are both naturalness problems, and these qualify as physics questions -- I can't see a more physical question than that, like asking why is k ~ 0 or \Omega ~ 1 in the universe. These shows that the section we are discussing here is misleading. Because it is misleading in such important ways, I find it hard to think that this section can improve general public understanding of the Big Bang theory. It leads people to think that most professional cosmologists in the world are saying that they believe the universe had an inflationary epoch without being able to test this idea experimentally, somehow forgot what Galileo taught us. Or that there is a controversy in academia wether or not inflation is a theory with testable predictions, which is also untrue. A single paper of WMAP with the measured scalar spectral index < 1 with tests of inflation have more than 4,000 citations in peer-reviewed journals; in total, WMAP all papers have something of the order of 10,000 citations while the Earman paper shows only 29. So even your "notability" argument seems to be against you.131.215.195.228 (talk) 01:34, 29 May 2010 (UTC)

I still think that you're misrepresenting the book; to call it a "religious book" is a bit of a streach given that sections of it were written by Michael Ruse, Martin Rees, and other notable non-theists. But that's neither here nor there since the book is no longer cited in the material in question.

I'm unfamiliar with a lot of the technical verbage you've used in your last reply so I can't speak to those issues (cynically, I wonder if that was the point). But I do find your comparison of the one article with 3000+ others citing it contrasted against the 29 articles which cite Earman's paper to be a powerful one. This does give a clear prima face impression that the inclusion of the Earman paper may be WP:UNDUE. Before I concede though and limp away to lick my wounds, one question: Is the article on the WMAP by Spergel et al. a "normal" physics article, or does it contain a lot of hard data that isn't available elsewhere--effectively making it a reference work? After all, it would hardly be far to compare the number of academic journal articles on the Kennedy assassination which cite some other such article against the number which cite the Zapruder film. Eugene (talk) 03:06, 29 May 2010 (UTC)

The paper I linked above is the one where the result of the experiment after its third year was given, their discovery paper. It presents the final analyzed data and their fits to it using the standard big bang model and using inflation to tell them how the deviations of the temperature from different patches of the sky depends on the size of the patches one uses (this is the information encoded in what is called "power spectrum"). The data itself is freely available from the NASA website. You can read the main article of Wikipedia on inflation where this is explained. To put most of what I said into perspective, follow the citations link above and go to the "PDF from arXiv", it is free; look at their Fig. 2. The "adiabatic initial conditions" from inflation is what tell us that after following the equations of General Relativity, we have those peaks and valleys in the picture.There are seven different solutions to the shape of this picture in the Big Bang theory without inflation; with inflation, there is the one we see in the picture. If they had obtained any one of the other six possibilities, single-field inflation would have been ruled out by experiment.They quote their spectral index which slow-roll inflation predicts to be close and less than 1, and that is what they observe. This results have significantly improved this year: http://arxiv.org/abs/1001.4538 .131.215.195.228 (talk) 04:10, 29 May 2010 (UTC)

Well, you didn't exactly answer my question. But, from what you have said, it seems like the paper you have mentioned is more of a reference work. And, we would expect it to be quoted much more often than an analysis paper. I think I will wait out the RfC. Eugene (talk) 04:18, 29 May 2010 (UTC)

That is because I don't really know how to answer your question and I want to be honest. I think it is what you would call a "normal" physics paper, say like the paper where Rutherford published with his results that showed evidence for the Rutherford model in place of the Thomson model. Or like the paper that discovered the Z boson at CERN. These kind of paper. These types of papers are highly cited because they have made breakthroughs. I don't know if that is "normal" or "reference".131.215.7.137 (talk) 05:10, 29 May 2010 (UTC)

Stopped expansion, what?

What proof do they have that there are regions that are not inflating? How can they say that anything has stopped inflating? They can tell by redshift that there is inflation. To say that parts have stopped inflating goes against all the evidence. --Neptunerover (talk) 02:05, 27 December 2009 (UTC)

Inflation and expansion are two different things. The inflationary period as postulated was very breif and involved remarkably rapid exponential expansion of the universe such that it increased in volume by a factor of at least 10^78 in a tiny fraction of a second. Since then it has gone on expanding but not inflating in an exponential manner. --LiamE (talk) 14:54, 30 January 2010 (UTC)

Thank you greatly for clearing my confusion on that. I was equating the two words. --Neptunerover (talk) 14:58, 30 January 2010 (UTC)

You're welcome. --LiamE (talk) 15:01, 30 January 2010 (UTC)

Looking back over this question I think the first paragraph of the introduction should be rewritten to make the distinction between infaltion and expansion clearer. I think some reference to the very breif time period and vast exponential volumetric increase should both be noted. Anyone fancy having a go? --LiamE (talk) 21:09, 28 May 2010 (UTC)

Maybe? - 2/0 (cont.) 06:56, 29 May 2010 (UTC)

Yep I think that's the sort of intro the article needs. It is easy for editors with prior knowledge of what is being talked about here to miss the need for clear and concise explanation of the theory in the lead. The earlier question by Neptunerover highlighted the previous lead's shortcomings. My only concern now is it is hard for someone with a good scientific grounding let alone a lay man to visualise just how big a 10^78 expansion is and how short a timescale 10^-30ish seconds is but that is not for the lead here. --LiamE (talk) 11:24, 29 May 2010 (UTC)

RfC: Philosophical issues pertaining to cosmological inflation

There is a dispute at inflation (cosmology) as to whether the following section should be included:

Philosophical issues

Inflationary theory has historically been advanced for largely philosophical reasons. Specifically, all inflationary theories attempt to minimize the fine-tuning of initial conditions required by standard big bang cosmology, sometimes called the "naturalness problem". As Andreas Albrecht (a proponent of inflationary theory) has written concerning the theoretical success of the standard big bang model,

"It turns out that most of the cosmological 'problems' that are usually introduced as a motivation for inflation are actually only 'problems' if you take a very special perspective. ... The Flatness and Homogeneity features describe the need to give the SBB [I.e. standard big bang] very special initial conditions in order to match current data. Who cares? If you look at the typical laboratory comparison between theory and experiment, success is usually measured by whether or not theoretical equations of motion correctly describe the evolution of the system. The choice of initial conditions is usually made only in order to facilitate the comparison. By these standards, the SBB does not have any problems. The equations, with suitably chosen initial conditions, do a perfectly good job of describing the evolution of the Universe."

Alan Guth agrees, having written that the "horizon problem is not a failure of the standard big bang theory in the strict sense, since it is neither an internal contradiction nor an inconsistency between observation and theory."

Philosophers of science such as John Earman and Jesús Mosterín have therefore argued that inflationary cosmology is flawed since inflation is no better as a starting point for cosmology than the standard big bang, except in ways that are not accessible to experimental test. Since a scalar inflatonary model of cosmology can only be fixed to match observations by a certain amount of initial fine-tuning, Earman and Mosterin reckon that this type of fine-tuning is no better as an explanation of experimental results than the initial fine-tuning required by the standard big-bang model. Roger Penrose has argued along similar lines, stating that "[t]he case for inflation must come, not from cosmology, but from high energy physics–though ... this case is 'shaky, indeed.'"

The references used in the section are as follows:

There are two issues: (1) Should this material appear in the article, and, if so, (2) should the material be presented as is, in a single section, or should it be distributed throughout the article? Eugene (talk) 15:21, 28 May 2010 (UTC)

• (1) Include, (2) Single Section The material is well sourced, particularly attributed where contentious, and notable. Eugene (talk) 15:21, 28 May 2010 (UTC)

• (1) Exclude, (2) N/A Looks like WP:Bollocks to me. --LiamE (talk) 21:01, 28 May 2010 (UTC)

• (1) Exclude, (2) N/A I believe the material is inaccurate and misleading and should not be included. Inclusion in the middle of the article would just look silly, since the article contains statements all contradictory of the above section (e.g. the article presents the tested predictions of the theory with scientific references but the section claims that the theory makes no predictions that can be tested experimentally). I also believe the section is poor as it is with a collection of quotes out of place to sustain an idea that was not present in the sources given. For example, the given quote from Guth is displaced out of context since even in the book quoted Guth explains how to test the theory on Chap. 14, cf. page 239 and beyond. The "well-sourced" is therefore being used as a disguise to insert incorrect material into the page.131.215.195.228 (talk) 01:44, 29 May 2010 (UTC)

• Exclude per WP:SCIRS. - 2/0

(cont.) 04:45, 29 May 2010 (UTC)

• Exclude. The content that User:Eugeneacurry wants to include does not make the article better. PYRRHON  talk   01:34, 1 June 2010 (UTC)

• (1)Include The philosophical implications of scientific theories are of interest to many, even if others regard such discussions as Bollocks. (2)Keep as separate section DaveApter (talk) 20:51, 7 June 2010 (UTC)

What sizes are we talking about?

If there are any estimates or assumptions on the volume of the universe before and/or after inflation, they should be stated in the article. Currently it gives only the relative increase in size, but no absolute numbers. Or are these completely unknown? -- 77.7.146.3 (talk) 02:47, 28 September 2010 (UTC)

Inflation only gives relative size increases. Consequently the absolute figures are completely unlnown. --Michael C. Price ^talk 03:11, 28 September 2010 (UTC)

Also, the common assumption is that the volume of the universe is infinite both before and after inflation. (and if its not it, it is infinite for all intents and purposes.) The thing that is growing is the scale factor, which does not have a meaning full absolute size.TimothyRias (talk) 05:41, 28 September 2010 (UTC)

A common assumption before inflation? Where did you read that? It only has to be big enough for a "smooth" patch. --Michael C. Price ^talk 08:00, 28 September 2010 (UTC)

A common assumption in the sense that people seldom explicitly assume a finite size, and just work with an infinite universe. (Of course there are notable exceptions to this, for example in chaotic inflation, and even there the universe itself is usually considered infinite just the inflating patch is a finite piece.) It clearly is not a necessary assumption, just one of convenience.TimothyRias (talk) 08:29, 28 September 2010 (UTC)

Hawkings gives the relative expansion in lay man's terms as "smaller than an atom to the size of an orange in less than a trillionth of a second, almost no time at all" (quoting from memory there so dont use that as gospel but its close). I am pretty sure he is talking about the observable universe there, ie everything we can see now was in something thr size of an orange at the end of inflation. The actual universe is bigger and was infact bigger than than the orange, but as yet we dont know by how much. --LiamE (talk) 18:23, 2 October 2010 (UTC)

Is there a Big Bang before inflation or not?

Hi everybody! I am a physicist. I even did my Master's thesis on Cosmology, but that was 35 years ago and I completely changed topics since then so I am not up to date. But still, I have a pretty clear picture of non-inflationist Big Bang scenarios, and I'd like someone to help me clarify what goes on with inflation. So this is how I see the history of the Universe, backwards in time. Please do tell me if this is correct.

Future: As everything else will get diluted, ‘’dark energy‘’, which is same as cosmological constant, takes over and accelerated, exponential, expansion will go on indefinitely, albeit with a very long characteristic time-scale, of the order of tens of billions of years. Technically this should be called "inflation", since it is exactly the same mechanism, really, but extremely slow.

Right now: ‘’dark energy‘’ is roughly of the same order of magnitude as the remainder (‘’dark matter‘’, ordinary matter), and we are in a transition situation. This is an atypical situation. Has it to do with some “anthropic principle” that this is what we see?

Not so long ago: (I mean in terms of the logarithm of the expansion factor: less than one unit of decimal log, since a factor 1/10 in length, 1/1000 in volume and thus 1000 in matter density×c squared would dwarf the ‘’dark energy‘’ density; timewise this is still a large fraction of the time elapsed since the Big Bang): matter dominated expansion, decelerated evolution of the scale factor as time^(2/3). During this era galaxy and stars are born, supernovae enrich the interstellar gas in heavy atoms, etc. Early in this era there was only a hydrogen-helium fully ionized plasma. This lasted about 10 units of decimal log.

Indeed, 10 units of decimal log before, the total energy density of photons exceeded that of everything else. That happened when the typical energy of a photon was only of about one electronvolt. So the physics was not “exotic” at that time. During this “radiation dominated period”, the scale factor behaved as the square root of time.

In the old, non-inflation picture, the only one I knew at the time of my Master's Thesis, going back in time the energy density grew indefinitely higher and higher, in a finite time, hitting a singularity at time 0: the Big Bang. Nothing can prevent this singularity, not even Quantum Mechanics though QM changes the “instantaneous” character of the singularity and makes it more “fuzzy”, but still there is an origin, albeit a bit fuzzy, of time (this is how I understand Hawkings, anyway).

But inflation changes all this. The energy density that was present during the “radiation dominated period” came from reheating at the transition between ‘’false vacuum‘’ and ‘’true vacuum‘’ that marks the end of inflation. Just before the transition, whatever existed before inflation was diluted to almost nothingness, and nothing effective has been transmitted to us (in particular, the magnetic monopoles are now far, far between) except the ‘’false vacuum‘’ energy that was thermalized and caused the reheating. But before that? What is the accepted scenario, the ‘’standard wisdom‘’?

If there is absolutely nothing but ‘’false vacuum‘’, exponential inflation should have lasted indefinitely in the past, as it will last indefinitely in the future (though with an considerably smaller rate) since it would be a pure de Sitter Universe.

But if there is something at all, however enormously diluted by inflation itself, going backwards in time, backward the huge inflation factor, this “something” would have had a huge energy density, up to a point that this energy density becomes comparable to the cosmological constant of the ‘’false vacuum‘’ (just as now the mass density ×c squared is comparable to the much much smaller residual energy density of the ‘’true vacuum‘’ , the present-day cosmological constant). At that point back in time, the exponential growth should no longer be valid, and earlier than that, one should have again a “radiation dominated period” behavior, scale factor as the square root of time, down to an ‘’origin of time‘’, a Big Bang before inflation in a finite time. And moreover, isn't the very rationale for the ‘’false vacuum‘’ to exist the fact that at hugely high temperature, such as what prevailed when the energy density is much higher than its ‘’dark energy‘’ (= cosmological constant) it is stable, and that if it exists at all after diluting this huge energy density to almost nothing through inflation, it is because it takes some time for it to “cascade down” to the ‘’true vacuum‘’ ? Can anyone comment on this, please, and tell me what the ‘’standard wisdom‘’ is regarding what happened before inflation, if there is such a ‘’before‘’?87.88.114.80 (talk) 18:02, 24 November 2010 (UTC) Sorry, I forgot to log in before typing this. I wanted to sign it so I do it now Alfredr (talk) 18:06, 24 November 2010 (UTC)

BTW, Gandalf61: thanks for rewriting my edit to the main article. We do agree, from the local point of view, things are disappearing beyond the horizon, and “moving beyond” is clearer than “falling out of”. I had just made the minimal change. Alfredr (talk) 18:16, 24 November 2010 (UTC)

I think that the standard wisdom is, that pretty much nothing can be said about what happend before inflation. (Or even if there was a "before".) Various models for mechanisms that could cause inflation might say something about how inflation started, but nothing that is generally agree upon. (PS. talk pages are not the place to discuss the topic of the article. They are meant to discuss changes/improvements to the current article.)TimothyRias (talk) 12:22, 25 November 2010 (UTC)

Well, where then should the topic be discussed? From what I saw above, though some talks were about removing irelevant “philosophical” material (thus improving the page), other discussions were about the topic itself. The mechanisms you refer to, don't they usually involve temperatures corresponding to energy densities much higher then the “dark energy”, implying an initial singularity?Alfredr (talk) 13:02, 25 November 2010 (UTC)

As to why not to discuss the topic on the talk page see WP:TALK and WP:NOTFORUM. If you want have a general discussion about inflation Wikipedia is in general not the place to. If you have a question you want answer then there is the WP:Reference Desk. Sometimes, discussions on a talk page do derail, but this something to try to prevent.

As to your question, there are more models for inflation on the market than I care to count. Each with its own mechanism. In general they do not need "high temperature" (although some obviously do). BTW, most cosmologists I know, speak about the big bang as the reheating phase after inflation. TimothyRias (talk) 13:29, 25 November 2010 (UTC)

SOMEBODY DO SOMETHING!

This is one of the worst articles I've come across on Wikipedia. I know there is lots of discussion concerning the quality of this article, but I feel I have to make an additional plea for an experienced and knowledgeable editor to revise it. Especially the "overview" section. At the very least the numerous unaccepted theories described should be presented as alternative. —Preceding unsigned comment added by 71.65.217.167 (talk) 04:06, 28 December 2010 (UTC)

Paul Steinhardt's critique in Scientific American

I'm not qualified to make edits to this page, but it is clear to me that Paul Steinhardt is a competent expert and that he has significant concerns about inflation. The critique seems twofold: 1) The initial conditions for inflation are highly improbable, and 2) perhaps more problematic, inflation implies so many different possible universes that it may not be falsifiable and thus the evidence in support of inflation may not add much, if anything, to our reasons to believe that it accurately reflects reality. See The Inflation Debate in the April 2011 edition of Scientific American. This page needs more balance to reflect the doubts about inflation among scientists. It need not be reflected throughout the entire article, but a criticism section is justified.Natty1803 (talk) 17:18, 10 April 2011 (UTC)

Section: Criticisms of inflationary cosmology

I just removed the following text from the article:

text for discussion

Since its introduction by Alan Guth in 1981, the inflationary paradigm has being very fashionable in the community of cosmologists. It has been hailed as the only game in town and has been presented as established science in the popular science literature and even in cosmology textbooks. Nevertheless, several physicists, mathematicians and philosophers of science have pointed to its shortcomings, unfulfilled promises and lack of serious empirical support. In 1999, John Earman and Jesús Mosterín published a thorough critical review of inflationary cosmology, concluding that “we do not think that there are, as yet, good grounds for admitting any of the models of inflation into the standard core of cosmology”. It has been questioned whether the alleged problems that inflation was called to solve (from the lack of magnetic monopoles to the uniformity and flatness of the observable universe) are not pseudoproblems, as the magnetic monopoles have nothing to do with the big bang model and the acceptance of initial or boundary conditions is standard practice in the construction of physical models. In any case, in order to work, and as pointed out by Roger Penrose from 1986 on, inflation requires extremely specific initial conditions of its own, so that the problem (or pseudoproblem) of initial conditions is not solved: “There is something fundamentally misconceived about trying to explain the uniformity of the early universe as resulting from a thermalization process. […] For, if the thermalization is actually doing anything […] then it represents a definite increasing of the entropy. Thus, the universe would have been even more special before the thermalization than after.” The problem of specific or “fine-tuned” initial conditions would not have been solved; it would have got worse. A recurrent criticism of inflation is that the invoked inflaton field does not correspond to any known physical field, and that its potential energy curve seems to be an ad hoc contrivance to accommodate almost any data we could get. It is significant that Paul J. Steinhardt, one of the founding fathers of inflationary cosmology, has recently become one of its sharpest critics. He calls ‘bad inflation’ a period of accelerated expansion whose outcome conflicts with observations, and ‘good inflation’ one compatible with them: “Not only is bad inflation more likely than good inflation, but no inflation is more likely than either. … Roger Penrose considered all the possible configurations of the inflaton and gravitational fields. Some of these configurations lead to inflation … Other configurations lead to a uniform, flat universe directly –without inflation. Obtaining a flat universe is unlikely overall. Penrose’s shocking a conclusion, though, was that obtaining a flat universe without inflation is much more likely than with inflation –by a factor of 10 to the googol (10 to the 100) power!” References

Criticism sections are in general deprecated, particularly when the sources presented are not particularly important to the topic of this article. A lot of this material is undue weight, weasel worded, and unclear and unencyclopedic in its presentation. Some of it could probably be used in discussion of alternatives and history, though. - 2/0 (cont.) 00:17, 10 May 2011 (UTC)

The removal is unjustified IMO. (& Criticism sections are NOT in general deprecated). -- cheers, Michael C. Price ^talk 09:33, 10 May 2011 (UTC)

I'm fine with not having a specific Criticism section if there was a reference to the critique in the intro which was then fleshed out in the History section. Perhaps something along the lines of the String theory page? Natty1803 (talk) 22:42, 10 May 2011 (UTC)

This is a good approach. Of the sources presented above, I am leery of using the and 1999 earlier for discussing a developing field of science. They may be necessary for fleshing out the History section, but a modern retrospective critique would be preferred. I am not aware of any issues with the Penrose (2004), but as always, we should be careful of generalizing the views of a single source (disclosure: I prefer LQG to String Theory). The Scientific American 2011 looks like on of their periodic 'stirring up controversy without giving proper caveats' articles; it should be usable, but only with attribution to the author and context. I have not checked Steinhardt (2007), but see no obvious reason not to use it. - 2/0 (cont.) 01:53, 11 May 2011 (UTC)

Censorship of serious criticism should not take place

The inflationary scenario is an important but controversial scientific theory. It should not be treated as the dogma of a religious sect. The dogmatic presentation of the article of Wikipedia and the systematic censorship of any serious criticism of this hypothesis is regrettable. Prestigious mathematicians, physicists and philosophers of science have expressed well-articulated criticisms and doubts about the theory of inflation and its empirical credentials. A balanced and fair encyclopedic article on inflation should not just ignore them. It is only natural that the main body of the article is devoted to the point of view of the proponents of the theory, but dissenting academic voices need not be suppressed. Readers have a right to know that certain theories (even important ones) are more speculative than others, and that not everyone is impressed by their empirical support. References to these doubts and criticisms should not be censored and cut out. This way of proceeding is incompatible with the open spirit of Wikipedia and with the free spirit of the scientific method. Pisto 17:15, 23 May 2011 (UTC)

Not sure what you mean by "censorship" or indeed "dogma". Diffs of the alleged censorship are required for a meaningful discussion William M. Connolley (talk) 18:06, 23 May 2011 (UTC)

By "censorship" in this case I mean the automatic deletion and elimination from the text of the article of any reference to opinions doubtful or critical of inflation, even if they are well refereed and have appeared in respectable publications. Not only philosophers of science are dismissed in a cavalier way, but, unbelievably, even the quotes of such eminent cosmologists as Penrose and Steinhardt are cut out. By "dogma" I mean this attitude of suppressing and silencing dissenting views. By the way, who at Wikipedia confers this right to censorship? Pisto (talk) 18:30, 24 May 2011 (UTC) 18:15, 24 May 2011 (UTC)

Could you please provide examples of this perceived censorship? If you mean the recent case, of badly written/essayic piece that was added to the article being moved to the talk page for further discussion (see section immediately preceding this one), well that is not censorship, but good editing. Note, that everybody in that section agreed, that some discussion of criticisms of inflation is warranted in the article. Thus far nobody, has taken up the task of improving/rewritting the removed piece in such a way that it can be readded.TR 08:02, 25 May 2011 (UTC)

I'd be more inclined to tweak it if was back in the article. -- cheers, Michael C. Price ^talk 11:32, 25 May 2011 (UTC)

[Note that, somewhat confusingly, the above comment was made by [2] User:Epistemion and then signed as Pisto. I don't know why William M. Connolley (talk) 18:08, 23 May 2011 (UTC)]

The first sentence is dumb

The article states there is an early expansion of the universe by 10^78 in volume, with no suggestion of what sort of timeframes they are basing this off. Some sort of clarification is in order. If we're talking about billions of years, I would contest this figure, but if the universe's expansionary rate is per something less than per thousands of years, this is moderately realistic. I suggest an update to this article that specifies within which timeframe we are treating the extent of the article of this article. — Preceding unsigned comment added by 134.173.13.55 (talk) 10:14, 27 May 2012 (UTC)

The timeframe is given a couple of sentences further on, at the end of the first paragraph. Inflationary expansion of the early universe was very rapid, happening in a timescale of less than 10^-32 seconds. Gandalf61 (talk) 14:48, 28 May 2012 (UTC)

What?

Citation: "While special relativity constrains objects in the universe from moving faster than the speed of light with respect to each other, there is no such constraint in general relativity. For example, an object which crosses the event horizon and falls into a black hole can be thought of as moving faster than light from the point of view of an outside observer."

A cosmic humbug. Speed of light is preserved in general relativity as well. And if crossing of the event horizon were an equivalent of approaching speed larger than c, then any object just on the horizon would have to be travelling just at the speed of light. As some of them were massive, their energy would be infinite, and therefore would produce infinite gravitation. I remove this nonsense. I hope it is not needed for the rest of the article.

Please, do something with this article it's not the C class, it should be speedy deleted in case somebody takes it for granted. Olaf (talk) 17:51, 4 January 2011 (UTC)

In what sense can an "object which crosses the event horizon and falls into a black hole" be thought of as moving faster than light from the PoV of an external observer? Could somebody elaborate? Michael? (Since you decided to put this back)

This doesn't seem to make sense, since from the PoV of an external observer any object (including light) will take an infinite amount of time to fall across the horizon. In that sense the external observer will think that the object comes to a halt. There might be some otherw ay of viewing this in which it does makes sense, but for the moment I'm not seeing it.TimothyRias (talk) 16:36, 6 January 2011 (UTC)

Heh, perhaps it should say be thought of as moving slower than light from the point of view of an outside observer. -- cheers, Michael C. Price ^talk 00:33, 25 January 2011 (UTC)

This question is kinda old, but in case it happens again, I'll answer. The speed of light limit is preserved in general relativity, as claimed above, but the limit is retained only with respect to observers who can make a measurement of the speed. What the hell does that mean? All observers who can measure an object's speed will report a speed less than or equal to c, and all massless particles will be observed to travel at the same constant speed, c, regardless of the relative motion of the observing observer. But once inside an event horizon, within which external observers cannot make measurements, all bets are off (you can think of it as: once inside an event horizon, an observer can't tell which part of the black hole's interior volume you are occupying, so you might have instantaneously moved from one side to the other and he can't tell the difference, no violation of his physical limits). In order to measure the speed of a particle within an event horizon, the observer must himself go inside the event horizon. Once there, the observer will once again agree that no particle travels faster than c.Law of Entropy (talk) 20:02, 11 May 2012 (UTC)

Amazing to see that despite the talk is going on since some time, the article has not changed, especially at the very beginning. Certainly, nothing in nature can exceed the speed of light, which is, again and again, of vital importance in the realm of general relativity. As for a beam of light entering an event horizon, the speed remains the same (c), but there is a gravitational redshift seen from the outside observer, who will see an ongoing "reddening" and eventually fading of the beam. You may recall the experiment to measure the distance from Earth to Venus, first done by radar, with the expected result from general relativity that, when the beam had to pass the Sun on it's way, the beam took just a bit longer, taking the gravity potential into account. Hence, the beam was not accelerated beyond light speed, but had to follow the gravitational warp formed by the sun. More experiments like this have been conducted at numerous occasions, just to make sure (and get the sought for precision). Certainly, it would not take too much to correct at least this obvious error in the text?! Regards, casey-san87.184.37.83 (talk) 15:13, 24 August 2012 (UTC)

Big Implosion

The problem with inflation is that it violates our known physics. Also expanding space with a force seemingly greater then gravity is an accepted observation however no explanation that fits these physics. So might it be that instead of a big bang (with a limited starting force) that it might have been an implosion. There once was a pre universe unlike ours, there in it suddenly was a point that collapsed, the point quickly became a sphere. At the surface of the sphere it is still hitting the pre-universe and exploding and growing taller, this expanding explosion could still go on, but might be beyond our vision range. As a side effect the universe is still in its big implosion, and thus there must be way more mass away of our observable center, that ongoing explosive surface of the sphere still enlarges and is pulling our universe appart, because now there is more mass beyond our measurable universe then there is mass within it. What caused it to start in the pre-universe is unknown but might have been bigger then a single point, and that's our inflation 'sized' universe start. — Preceding unsigned comment added by 84.107.183.36 (talk) 19:41, 14 December 2012 (UTC)

There's nothing about inflation that "violates our known physics". In any case, this isn't the place to discuss idiosyncratic notions, it's the place to discuss improvements to this article. Waleswatcher (talk) 23:28, 14 December 2012 (UTC)

Your wrong inflation is an expansion rate faster then the speed of light and such reactions cannot be explained, by physics; its rather accepted that something like that happened but its not explainable currently, one has to to introduce unproven physics to make it work. — Preceding unsigned comment added by 84.107.183.36 (talk) 10:04, 15 December 2012 (UTC)

Alternate Theories

Are there any other theorys that explain the expansion of space? For example, is it possible that everything in the universe is uniformly shrinking? If that were so, distant galaxies would appear to be receding as our units of measurement decreased (unknown to us). It would also account for the acceleration of the universe's expansion. The universe would really just be a static size, but as we shrunk, it would appear to grow at an accelerated rate.Broolaf2 (talk) 00:16, 13 January 2010 (UTC)

It would require careful coordination of various physical "constants" if we were shrinking but couldn't notice. And if we can't tell this effect apart from an inflating universe, does it really make a difference?; they would be the same theory. --Michael C. Price ^talk 18:52, 13 January 2010 (UTC)

That makes it sound static. No matter whether inflating or shrinking, it would be the same (static) for an inside observer, but just moving forward in time to get a redshift (maybe). --Neptunerover (talk) 23:40, 19 January 2010 (UTC)

You could just redefine the metre as some fraction of the distance between two suitable co-moving objects. Space, as measured in the new metres, would then always be the same size. This would, however, mean regularly replacing our earthly measuriing instruments. The speed of light would diminish with time, but its frequency would not, unless we also redefined the second. --Dendropithecus (talk) 23:53, 19 January 2010 (UTC)

They don't know what a second is. They might think they know how to measure one, but they don't know what it is. (At least not as far as I can tell). All the cells in our bodies do stuff lightning fast in a second. What's a second to them? How long does a second for us last for them? Is it because of our great mass in comparison to them that our time should be experienced differently? The human measurement of a second should not be universally applied. How many moments are in a moment depends upon how small (or big) you are. The Bible says a day for God is 1000 years for a man. God's a big guy. --Neptunerover (talk) 00:29, 20 January 2010 (UTC)

I've seen work of a dutch physics professor who has explained space itself as a result of gravtiy and information theory its extreme complex, but from his math inertia might be explained too, it was however extreme complex space was seen as a hologram of information from a blackhole surface. — Preceding unsigned comment added by 84.107.183.36 (talk) 10:07, 15 December 2012 (UTC)

Important Reference Missing

There should also be a reference to an article by Brout, Englert, and Gunzig, written in 1978, proposing cosmic inflation that solves the horizon problem: this predates Guth by two years: http://adsabs.harvard.edu/abs/1979GReGr..10....1B — Preceding unsigned comment added by 173.66.64.228 (talk) 05:02, 31 January 2013 (UTC)

Claim not fully supported by reference: Eternal inflation

The article claims that "It has been shown that any inflationary theory with an unbounded potential is eternal", though the cited reference only considers power law potentials. Unless someone finds a source for the stronger claim that all inflationary theories with unbounded potentials imply eternal inflation, this claim should be changed to "It has been shown that many inflationary theories with unbounded potentials are eternal". — Preceding unsigned comment added by 131.152.108.142 (talk) 10:35, 16 February 2012 (UTC)

As no one answered to this question, I added the [Template:Failed verification] until a complete reference has been cited. 131.152.108.142 (talk) 16:59, 21 March 2013 (UTC)

Smallest structures formed by the density fluctuations

Are they clusters of galaxies, galaxies or stars? The article says that

These tiny fluctuations form the primordial seeds for all structure created in the later universe.

which implies you can trace back everything to the inflaton fluctuations - which I doubt. -- cheers, Michael C. Price ^talk 23:27, 30 July 2011 (UTC)

I added a citation. Ultimately, all modern day deviations from a perfect, isotropic, homogenous fluid are due to quantum fluctuations in the early Universe. Of course, no individual star or galaxy or even cluster (maybe not even superclusters) can be traced back to an individual CMB fluctuation, but without these fluctuations, all gravitational interactions would exactly cancel and the Universe would be perfectly homogenous. This is a case where both statements are correct: no we cannot trace an individual star back to quantum fluctuations in the early Universe, but neither would that star exist without these same fluctuations.Law of Entropy (talk) 20:07, 11 May 2012 (UTC)

An addendum: even in principle we can't trace things back to early Universe fluctuations because there have been quantum fluctuations since then that were themselves random. The only safe statement is that all structure in the modern Universe is due to early fluctuations, not absolutely determined by, but seeded by. Law of Entropy (talk) 20:11, 11 May 2012 (UTC)

Besides- what is the speed of sound in a medium that dense? — Preceding unsigned comment added by Lepton01 (talk • contribs) 13:17, 29 December 2012 (UTC)

The speed of sound in a medium where the particles are relativistic is v=c*sqrt(w) where w defines the equation of state, or about 58% of the speed of light. See Ryden "Introduction to Cosmology", eqn 4.57 George Dishman (talk) 08:13, 31 March 2013 (UTC)

Another speed of light issue

Citation:

In a big bang with only the matter and radiation known in the Standard Model, two widely separated regions of the observable universe cannot have equilibrated because they move apart from each other faster than the speed of light

Well, it's Newtonian thinking. If object A is going left at the speed 0.999c, and object B is going right at the speed 0.999c, then in the frame of the object A object B is moving at the speed $s={0.999c+0.999c \over 1+((0.999c)^{2}/c^{2})}=0.999999499c$ (see velocity-addition formula). It's still possible to send a photon from A to B. There may be not enough time for it, but it's not a superluminal travel.
I didn't fixed it, an expert is needed to rebuild the article. — Preceding unsigned comment added by Olaf (talk • contribs) 06:36, 5 January 2011 (UTC)

There is nothing (factually) wrong that quote. In an expanding universe the distance between to regions can become bigger at a rate faster than the speed of light. The distance at which this happens is called the Hubble sphere.TimothyRias (talk) 06:50, 5 January 2011 (UTC)

All right, I was wrong, it is possible if the timespace expands, but according to this paper it doesn't mean that the communication is broken:

We show that we can observe galaxies that have, and always have had, recession velocities greater than the speed of light.

An observer can still receive light from these faster-than-light objects, so the next sentence of the Wikipedia article seems to be wrong:

An expanding universe generally has a cosmological horizon, and like a black hole event horizon, this marks the boundary to the part of the universe that an observer can see

Olaf (talk) 20:21, 24 January 2011 (UTC)

The text is correct. This article has a reasonably understandable treatment of the particle and event horizons Davis & Lineweaver George Dishman (talk) 08:17, 31 March 2013 (UTC)

Merger proposal

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

The result of the discussion was no consensus.

---

The inflaton article has no references but this one has quite a few. Rather than duplicate the citations here on the inflaton article, I propose we move the info there here, and make inflaton a redirect to this article or section of it. Thoughts? Woz2 (talk) 12:03, 11 July 2012 (UTC)

Seems reasonable. Since the article inflaton is so stubby, go ahead! If it (IMHO unlikely) occurs that inflaton deserves its own article, it could be split then again, but for now, that article doesn't need to be independent. Rursus dixit. (^mbork³!) 16:14, 14 July 2012 (UTC)

I think inflaton should stay as a separate article. There are plenty of details, which are not appropriate in this article, but are very appropriate for a separate inflaton article. For example, a discussion of hypthetical candidates for the inflaton field.TR 21:19, 23 July 2012 (UTC)

At least some part of inflaton should be merged or copied into Inflation. The Inflation article begins by talking about the inflaton (in the Few inhomogeneities remain, Reheating and Theoretical status sections) without ever giving the new reader an understanding of what's going on. Someone (not me, I'm a novice) should give a better description of the inflaton than the one-sentence definition in the lead. At least one or two paragraphs, including the "discovery" history.

I would do that and then re-examine the merger question. --RoyGoldsmith (talk) 05:19, 26 July 2012 (UTC)

Oppose merger. Photon is separate from light; graviton is separate from gravity; inflaton should stay separate from inflation (cosmology). —Lowellian (reply) 00:56, 23 September 2012 (UTC)

Oppose. The inflaton is notable as inflation theory itself is notable, so Inflaton should be expanded. The point made by editor RoyGoldsmith is compelling; however, the link to the Inflaton article (which may be overlinked in this article), when clicked on and opened, will suffice to explain what isn't expressly explained in this article. – Paine (Climax!)  08:15, 10 October 2012 (UTC)

Oppose merger per Lowellian and Paine. MathewTownsend (talk) 22:29, 27 December 2012 (UTC)

Oppose merger. And note that it is not "overlinked" since the linking serves to stop drive-by editors from "correcting" the spelling to "inflation". -- cheers, Michael C. Price ^talk 09:19, 29 December 2012 (UTC)

So hey- what about some calculation of the speed of sound in a medium of near infinite density? — Preceding unsigned comment added by Lepton01 (talk • contribs) 13:26, 29 December 2012 (UTC)

Support. Joining Woz2, Rursus and RoyGoldsmith above. They have made the observations that had become obvious to me too. Move everything into Inflation (cosmology). My name is Mercy11 (talk) 01:18, 2 July 2013 (UTC), and I approve this message.

OK, then – formally support: the argument "Photon is separate from light" would have been OK if the amount and character of information would make such separateness reasonable. Maybe such amounts of information will occur in the future? As for now, the inflaton only occurs in the context of inflation, and the character of the available information is IMHO most significant for the design of the articles. Our expectations of what facts will be revealed in the future are just expectations that will or won't be fulfilled. Rursus dixit. (^mbork³!) 10:20, 2 July 2013 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

why is there no mention that the very concept of empty "space" came within the big-bang itself?

The universe didn't "expand" into anything. Space came from within the big bang. Please update this page to be accurate. 24.176.180.116 (talk) 07:20, 18 February 2014 (UTC)

Where does the article claim that space expands into something? Shmuel (Seymour J.) Metz Username:Chatul (talk) 19:18, 18 February 2014 (UTC)

It's kind of implied with the idea of inflation and a vaccuum that space expanded into "something". It's an obvious logical flaw in the model for inflation that there was ever a big bang in the first place. It's not so much the article explicitly states it, so much that it doesn't explicitly state otherwise - allowing preconceived misconceptions of an "Explosive Big Bang" model to continue perpetuating bad knowledge within the world. 24.176.180.116 (talk) 22:23, 18 February 2014 (UTC)

Inflation is distinct from the big bang and takes place after the big bang, I'm not sure where you confusion is coming from. If your thesis is that inflation is flawed because the big bang never occurred, you'll need to provide a good WP:RS for that theory; otherwise it'll be quite properly dismissed as WP:FRINGE. Rolf H Nelson (talk) 05:19, 20 February 2014 (UTC)

No, it is not implied; there is nothing in the text remotely similar to space expanded into "something". Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:48, 20 February 2014 (UTC)

On the contrary, the very reasoning for the extremely rapid "inflation" is based on pressure differences. From a condensed existence and inflated within a vaccuum. In this sense, the "vacuum" represents "something." There was no empty space or vacuum before the universe "began" with the Big Bang as proposed. The only reason movement, and therefore "time and space" would have to exist, is if any particle (already obviously) within the universe had the ability to move (again, obviously) while still within the limits of the universe. Therefore "space" itself would have had to have originated purely within the confines of a whole-universe (seed of the Big Bang) where space didn't already exist. Good questions would be "Just why is there so much Space?" or "What is Space?" or how it's even reasonable to legitimately claim the universe even "began" with any sort of imaginable event when needing the knowledge that without space there would be no movement or measure-of-time, thereby requiring space to exist at the beginning, even though there wouldn't have been space before the beginning. Winnerex (talk) 18:23, 21 February 2014 (UTC)

Winnerex/24.176.180.116, if you can't provide a WP:RS please do not use this Wikipedia talk page as a soapbox for your personal ideas. Rolf H Nelson (talk) 02:05, 23 February 2014 (UTC)

Relative or absolute expansion?

I second the criticism that a relative inflation of 10^78 doesn't mean anything if an initial dimension isn't given.

The Planck length might be implied here, but this is not universally agreed upon as the starting point of the Big Bang theory of cosmology.

If the initial dimensions of the universe was determined to be 10^-78 of a Planck length to begin with, then an inflation of 10^78 would mean that after that tremendous expansion, the size of universe would be just a single Planck length. Relative vs absolute is what exponents are all about. Any mathematician worth his pencil box knows this property of exponentiation better than his own name.

Asserting that spacetime expanded by 10^78 relative to where inflation began is a throwback to Maxwell's aether theory, absolute space, and time. Given rash assumptions such as these, it is small wonder that the conclusion is that the universe expansion was superluminal. This variety of cosmology is about as convincing as the 10^116 discrepancy in the vacuum expectation value. Concepts like these ceased to be viable shortly after 1905. Danshawen (talk) 03:22, 14 March 2014 (UTC)danshawen

Please cite the text that you are referring to; I don't see the assertion in the article or talk page. I agree that the the article should refer to relative inflation in a specified time interval, but don't understand what you mean by the initial dimensions of the universe. Shmuel (Seymour J.) Metz Username:Chatul (talk) 14:41, 14 March 2014 (UTC)

First direct evidence for the theory of cosmic inflation

Headine-1: BICEP2 finds first direct evidence of cosmic inflation

• http://physicsworld.com/cws/article/news/2014/mar/17/bicep2-finds-first-direct-evidence-of-cosmic-inflation

QUOTE: “Cosmic evolution from the Big Bang to today” [Very popular news coverage, everywhere!] — Charles Edwin Shipp (talk) 00:12, 18 March 2014 (UTC) PS: one reference is in the Article here, but this will explode to more in popular media.

Headine-2: Evidence of young universe's growth spurt is discovered

• http://www.latimes.com/science/la-sci-cosmic-inflation-20140318,0,766934.story#axzz2wKJLhbq0

QUOTE: “Researchers focusing on gravitational waves find the first direct evidence for the theory of cosmic inflation, a faster-than-light expansion just after the big bang.” [One person says the work is worthy of the Nobel Prize.] — Charles Edwin Shipp (talk) 15:39, 18 March 2014 (UTC)