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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)
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)
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)
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. [1] Specifically, all inflationary theories attempt to minimize the fine-tuning of initial conditions required by standard big bang cosmology, [2] sometimes called the "naturalness problem". [3] 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." [4]
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." [5]
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. [6] 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.'" [7]
The references used in the section are as follows:
{{
cite book}}
: Unknown parameter |coauthors=
ignored (|author=
suggested) (
help)
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)
( cont.) 04:45, 29 May 2010 (UTC)
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)
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)
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)
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)
I just removed the following text from the article:
text for discussion
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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”. [1] 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.” [2] 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!” [3] References
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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 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)
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)
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)
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-san 87.184.37.83 ( talk) 15:13, 24 August 2012 (UTC)
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)
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)
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)
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)
Are they clusters of galaxies, galaxies or stars? The article says that
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)
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)
Citation:
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 (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)
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)
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)
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)
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
Headine-1: 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
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)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 | Archive 3 | Archive 4 | Archive 5 |
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)
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)
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)
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. [1] Specifically, all inflationary theories attempt to minimize the fine-tuning of initial conditions required by standard big bang cosmology, [2] sometimes called the "naturalness problem". [3] 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." [4]
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." [5]
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. [6] 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.'" [7]
The references used in the section are as follows:
{{
cite book}}
: Unknown parameter |coauthors=
ignored (|author=
suggested) (
help)
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)
( cont.) 04:45, 29 May 2010 (UTC)
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)
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)
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)
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)
I just removed the following text from the article:
text for discussion
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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”. [1] 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.” [2] 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!” [3] References
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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 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)
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)
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)
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-san 87.184.37.83 ( talk) 15:13, 24 August 2012 (UTC)
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)
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)
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)
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)
Are they clusters of galaxies, galaxies or stars? The article says that
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)
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)
Citation:
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 (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)
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)
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)
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)
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
Headine-1: 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
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)