Talk:Inflation (cosmology)/Archive 2

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Big bang?

Certainly there is substantial evidence of cosmic expansion, but what is the evidence restricting this expansion to only empty space? I mean, to say something is not expanding is like saying that it's not a part of the universe. The Earth is expanding underneath us while we all and everything around us expand as well. Considering its size though, the earth expands quickly in relation to us, so gravity, right? It seems they're trying to make this expansion be relative to some fixed point, but that leads back to a big bang which mathematically has been shown not to work. --Neptunerover (talk) 03:48, 27 December 2009 (UTC)

Oops, I was trying to put this section on the science help reference desk. I did that too now, so this may be redundant. --Neptunerover (talk) 03:59, 27 December 2009 (UTC)

The Horizon Problem

In this section, it says "they move apart from each other faster than the speed of light—thus have never come in to causal contact" I believe this is wrong: that the regions are moving apart faster than the speed of light is not the criterion that determines whether or not they have ever been in causal contact. It is that each is beyond the other's particle horizon. (See the article "Cosmological horizon".) If no-one objects, I shall amend this phrase appropriately. Dendropithecus (talk) 00:57, 8 January 2010 (UTC)

Being beyond the horizon is the same as saying "moving apart faster than the speed of light", just less colloquial.Likebox (talk) 04:14, 8 January 2010 (UTC)

Can you explain? I don't get it! Unfortunately, I'm a mathematician, not a cosmologist, though I am now teaching myself cosmology through Wikipedia's pages.

As I see it, the particle horizon depends not on the objects' current relative velocity but on the history of a photon that left one of them some time in the past, as indicated in the article "Cosmological horizon". Depending on the past form of the amplification function a, I deduce that it's theoretically possible for two objects to be moving apart (at the present time) at less than the speed of light, yet still be beyond each other's particle horizons or, on the other hand, for them now to be moving apart at more than the speed of light yet still be able to receive light from each other's past existence.--Dendropithecus (talk) 13:20, 8 January 2010 (UTC)

As briefly as possible, the argument goes like this:

At time t in co-moving coordinates, the velocity of a photon is c/a(t).

In a short time dt, a photon will travel a co-moving distance dx = c*dt/a(t)

The co-moving distance the photon moves from time t=t0 to t=t1 is the integral, between these limits, of the quantity c*dt/a(t).

--Dendropithecus (talk) 14:41, 8 January 2010 (UTC)

You are right--- it depends on what the phrase "current relative velocity" means. To be beyond the horizon means that particle number one currently observes the velocity of particle number two as "greater than the speed of light". It's sort of a heuristic. The notion of now is defined as the past light cone of one of the particles.

The slowing down of particles in normal cosmology means that if you use global time slices to define a global notion of time, then the current velocity of the particle might now be less than the speed of light.

It helps to keep a physical point of view which is horizon-centric. The particles which are in view are those inside the cosmological horizon, and the particles which are out of view are outside the cosmological horizon (or squashed very close to the surface of the cosmological horizon in a pure classical picture). The reason one should focus on horizons is because of the holographic principle--- this is essentially the right way to view general relativity.

Sorry for the terseness--- if you could clarify what is the confusing point I might be able to address it more directly.Likebox (talk) 18:56, 10 January 2010 (UTC)

Thanks for being so patient with me. I'm a bit tied up at the moment & I've only just found time to look at your comments, for which many thanks. I shall come back to you when I've had more time to think about the points you've made. --Dendropithecus (talk) 00:37, 12 January 2010 (UTC)

Please excuse the delay. There are a still a few points I don't understand, as well as some I believe I do.

It seems you are suggesting an observer-centric viewpoint, which is equivalent to an anthropocentric viewpoint with the proviso that an observer situated anywhere else in our global time-slice would see a similar picture. Is this correct?

I also understand that anything we can see at any instant must have been on our light cone at that instant. Any object (if any), that remained on our evolving light cone while appearing to be receding from us at the speed of light, would have a total red-shift, i.e. the incoming photons would have zero frequency, hence zero energy, hence no photons, so the object would be invisible to us (objects just within this limit being barely visible).

I'm not sure what you mean by "a sort of heuristic" (A learning process?), nor of the term "horizon-centric".

I've heard of the holographic principle but I don't appreciate its significance.

As I understand it, general relativity must be (and is) involved in choosing or designing a model for the expansion of the universe that is consistent with Einstein's field equations. Having chosen such a model, I can't see why, on the large scale, we subsequently need anything other than coordinate geometry.

Am I right in thinking that, when you refer to the cosmological horizon, you mean the limiting outer surface of the non-Euclidean 3-space of what we can see, and is this is equivalent to the (evolving) surface in our instantaneous light cone on which we deduce that co-moving objects would appear be moving away from us at the speed of light?

I am troubled by the fact that my maths consistently show that there can be no co-moving point on our evolving light cone that appears to be moving away from us at (or greater than) the speed of light. I presume there is evidence for the existence of such places? If so, then there must be something wrong, if not with my calculations (possible, but unlikely), then with some assumption(s) or hidden assumption(s) I have made. I should be grateful if you could tell me what!

The main two assumptions I am aware of are that the distance of an object on our light cone is c times the time taken for light to traverse the space between us and the apparent velocity of the object is the rate of change of this distance, as seen by us (the observer).

Another problem is that I've read that the red-shift can be explained by the evolution of the metric. I can't, however, see how the metric could evolve so as to reduce the frequency of light to zero. Wouldn't this imply an amplification factor of zero at the source? --Dendropithecus (talk) 23:27, 19 January 2010 (UTC)

Is it not the case that, in the Lambda-CDM model, in terms of real distance and global time, distant objects are currently accelerating away from us, not slowing down? --Dendropithecus (talk) 02:15, 20 January 2010 (UTC)

(On second thoughts, please ignore that last paragraph.--Dendropithecus (talk) 02:16, 24 January 2010 (UTC))

I should be quite grateful if you could point out any errors in anything I've said. I apologise if I sound adversarial - that's not the intention. I'm just trying to find some resolution to the disparity that appears to exist. --Dendropithecus (talk) 01:25, 24 January 2010 (UTC)

(deindent) I read your comments--- you are OK with most things, except for the horizon business. The way to get intuition about infinite red-shifts is to start with a black hole solution--- there you have a metric which has the form (1-2m/r)dt^2 + spatial. The zero at r=2m in the dt component means that a signal is infinitely redshifted from the r=2m horizon to an observer at r=infinity. This means that time seems to stop at the horizon, in external coordinates, and all things as viewed from the outside freeze at the horizon. There is an infinite redshift at a finite distance.

This effect of infinite redshift is observer dependent--- if you fall through the horizon, you don't see anything peculiar happen. The observers that see infinite redshift are those that are outside the black hole. The mushing up of things near the horizon is an artifact of the mathematics--- you don't have an infinite collection of layers of stuff on the surface of a black hole. The cut-off is quantum mechanical, and the principle which governs how to fix the description of horizons so that they don't pile up layers forever is called the holographic principle. The holographic principle is the only known way to make sense of the external description of a black hole. It cuts out the interior, and tells you that the black hole is described just by the stuff outside the horizon, heuristically (meaning not rigorously) you can imagine that there is a planck-scale thin skin around the black hole, and there is nothing going on inside this skin.

Cosmologically, you should start with the DeSitter solution. It's (1-lamda/3 r^2)dt^2 + spatial. This has a zero at a big cosmological distance R. If you trace light rays from r=0, the light rays that reach r=0 come from r<R. Any r greater than R is not in causal contact. This is the example of a metric which has the properties that you want. The form of the metric is on this page, or on the de Sitter space page.

Now imagine adiabatically starting with de Sitter space, and slowly shrinking lamda. Then the cosmlogical horizon distance R slowly gets bigger, and new objects come into view. If lambda drops to zero, the universe begins expanding according to FRW. This process is heuristic, because where are the new objects which come into view as R gets bigger coming from? If you trace back their paths, they come from beyond the horizon. But it's not clear that this is right holographically, because from your point of view there is nothing outside the horizon, just as there is no black hole interior.

When the cosmological constant is negligible (in the early universe, when the matter density is bigger), lambda-CDM looks just like FRW, so you couldn't tell there is a cosmological constant. Later on, when the density of matter falls, the cosmological constant starts to dominate, and the universe starts to inflate again (meaning to expand exponentially at the much slower e-folding rate of the current cosmological constant). I know that the crossover is happening now-ish, and this is how Weinberg predicted the cosmological constant from the anthropic principle. He said, the cosmological constant is only small because we need to be here to observe it. That means it should by just this small, and not much smaller, so that we should be transitioning from cold-matter dominated to lambda dominated just about now, and this is what we see.Likebox (talk) 06:44, 24 January 2010 (UTC)

Many thanks, L. I have read your comments, but they will take some time to digest, especially the de Sitter space. So far I have only two comments:

The fact that we can't see something doesn't imply it doesn't exist.We know a black hole has an interior because we can detect its gravity, & we can deduce some properties of the contents, although we cannot see them.

I've read somewhere that the (apparent) discontinuity at a black hole's event horizon may be smoothed out by a change of co-ordinates. Are you familiar with this? Meanwhile, I shall check the few texts I have. --Dendropithecus (talk) 02:53, 26 January 2010 (UTC)

Am I right in thinking that there's a school of thought that says that anything outside our current light cone doesn't exist yet, so in a sense it doesn't exist at all or, perhaps, since it cannot influence us, we may assume it doesn't exist? --Dendropithecus (talk) 03:17, 26 January 2010 (UTC)

About the existence of the black hole interior--- yes, there are coordinates the continue into the interior, and an observer that falls in will see the interior. The main result of holography is that there are two ways to describe the infalling observer. One way is from the infalling point of view, where the observer crosses the horizon and then something happens when it gets close to the center. The other way is to describe only the exterior, and then the observer is encoded in a complicated way in the vibrations of the black hole horizon.

What I am telling you used to be speculative in the eighties and early nineties. But there is now a model black hole, the d3 brane in type IIB string theory, where we have a good handle on how to describe the objects which are close to the black hole. They are described by an ordinary quantum field theory in 3+1 dimensions. That's the surface oscillations of the black hole. There are six (N by N matrix valued) scalar fields in the theory which have an immediate interpretation as the shaking of the black hole in the remaining 6 dimensions of space (this is string theory), there is a gauge theory which represents the exchange property of the N micro-black holes that make up the full black hole (when it is classical, there are N microscopic black holes right on top of each other with N large, and the gauge group is SU(N)) and there are Fermions which enforce supersymmetry, which is believed to be required so that there are flat moduli which correspond to the black holes sliding around freely.

These black holes are charged, and they are maximally charged, meaning they have just enough charge so that they neither attract nor repel, the gravitational attraction is balanced by the (analog of) electrostatic repulsion. To describe a less extreme black hole, you set the field theory at temperature T. This description is by now folklore, and it is called the AdS/CFT correspondence. Holography and AdS/CFT provide a general framework for understanding all the different forms of string theory, and this principle and its matematical realizations are, in my opinion, the most significant advance in physics since the discovery of quantum mechanics, if not ever.

The question of whether something exists is philosophical. The stuff outside our light cone is invisible to us even in principle, so the question of whether it should be thought of as real does not normally have observational consequences, so you are free to think as you like. I believe, along with many people, that the holographic description of black holes makes it seem likely that there will be an interior-only description of the universe which will not make reference to anything outside the light cone. However, this leads to some paradoxes related to the finite area of the cosmological horizon. Banks points out that the area of the horizon is the number of states in the universe, and the area is growing, and that seems to suggest that the Hilbert space is growing, but that's impossible in a normal quantum theory. There is no good theory of string theory in De Sitter space quite yet.Likebox (talk) 04:00, 26 January 2010 (UTC)

Thanks again! That really does give me something to think about! I've borrowed a copy of "The Road to Reality" from my local library, which gives me even more to think about. It does, however, quote the Eddington-Finkelstein metric, which an example of the metrics mentioned above. I think this shows that the singularity at the event horizon is just an artefact of the observer-based co-ordinates, which is what I think you have said, only in different words.

Whilst looking at the various mappings and embeddings, I can't help thinking that none of these alters the fact that, whatever exotic space the mapping is embedded in, what we end up with is still just a mapping of our 3 space co-ordinates and 1 of time. In other words, all these are just different ways of looking at the same object. Giving the sheet a small non-zero thickness or supposing it to be formed of sintered granules or knitting (as it may be) doesn't change the fact that, on the larger scales, light must find its way through it at the same constant velocity. Put another way, what I'm saying is that, at scales that are large compared to the granularity of space-time (or the folded extra dimensions), but small compared to the radius of curvature, we can always find an inertial frame in which the metric approximates to that of special relativity.

In the article "de Sitter Space", in the section "Static coordinates", the author has written:

" .. In these coordinates the de Sitter metric takes the form:

"$ds^{2}=-\left(1-{\frac {r^{2}}{\alpha ^{2}}}\right)dt^{2}+\left(1-{\frac {r^{2}}{\alpha ^{2}}}\right)^{-1}dr^{2}+r^{2}d\Omega _{n-2}^{2}.$

"Note that there is a cosmological horizon at $r=\alpha$."

But is this right?

If we keep the terms in $d\Omega _{n-2}$ constant, we can see that, as r approaches $\alpha$, small changes in r correspond to increasingly large changes in t. So, although there is a singularity at r= $\alpha$, this corresponds to an infinite value of time. There is, of course, nothing beyond it, but does it make sense to call a singularity at infinite time a cosmological horizon?.

Must go now. Thanks again for your patience. --Dendropithecus (talk) 23:49, 28 January 2010 (UTC)

(The above has been slightly edited -- Dendropithecus (talk) 03:24, 29 January 2010 (UTC))

The discussion of horizons is relatively old, and well understood. To get a clear picture, you should start with flat 2-d Minkowski space as viewed by an accelerating observer. This observers trajectory in space time is t=sinh(tau) x=cosh(tau), and a natural set of coordinates for this observer are the rindler coordinates: x=r cosh(a) t=r sinh(a). In terms of r,a, the metric on spacetime is -r^2 da^2 + dr^2, which is exactly like the polar coordinate metric in flat Euclidean geometry. The one difference is that the coordinates r,a cover one-quarter of the spacetime, the part which is spacelike separated from the origin, and to the right.

You can see from this example that the zero in the da^2 part of the metric, which leads to infinite redshift from the point of view of the eternally accelerating observer, does not mean that there are no other quadrants in spacetime. From this example, whenever a metric locally looks rindler near a zero of the dt^2 part of the metric, then it can be extended past the horizon by "Rindler continuation". people usually call this "analytic continuation", but it has nothing to do with being analytic--- the metric does not have to be analytic for this to work. Rindler continuation says that whenever you have a metric with a zero in the time component, a horizon, you can continue this metric past the horizon by assuming that each point on the horizon is just locally a version of Rindler space, and has three other quadrants which are invisible.

This process produces maximal extensions of solutions of General Relativity. But the current consensus on what these extended solutions mean is murky. For the deSitter example, the solution continues on forever past the cosmological horizon, if you want it to. It is just not clear that this is the correct thing to do from the point of view of holographic physics. This discussion is not directly relevant to cosmology, the same discussion could be had for black holes, or for accelerated observers.Likebox (talk) 06:33, 29 January 2010 (UTC)

I now see I was wrong to suggest that r =$\alpha$ corresponds to an infinite value of time in the "static coordinates" version of de Sitter. This large clanger, for which I apologise, was the result of my having misinterpreted the meaning of the variable r ! More on that later.

I have some problems with your version of the Rindler coordinates, but perhaps I should come back to you when I've had more time to think about them.

Thanks again for your help.--Dendropithecus (talk) 13:07, 30 January 2010 (UTC)

Earman/Mosterin Nonsense

Earman and Mosterin are philosophers, and their paper is nonsense. The result that deSitter space is unique is supported by perturbation analysis which is so trivial in deSitter space that people don't spend much time on it. The relevant cite is any book on cosmological perturbations, including any modern cosmology textbook.

As far as "fine tuning", it is well known that cosmologists accept that the fine-tuning of initial conditions in the big bang is not ok without inflation, because it sets up the initial conditions so that distant non-connected regions match. With inflation, the conditions become that the inflaton potential should be flat. The second condition is not very restrictive, and is reasonable in many physical models. Earman and Mosterin wrote a bunch of nonsense, which is rejected by all cosmologists. If it is going to be represented here at all, it must be placed side by side with mainstream understanding.Likebox (talk) 05:51, 14 February 2010 (UTC)

If "any book on cosmological perturbations, including any modern cosmology textbook" support your contentions, then it should be effortless for you to include an appropriate citation. Eugene (talk) 19:10, 26 February 2010 (UTC)

Removed non-sense.

Edit: Okay, I'm giving up. I added a detailed explanation here, I added a "statement of purpose" in the end and still Wikipedia moderators are ignoring my edits to the page. I am very disappointed to see some moderators that I cannot even reply to lower the standard of quality of Wikipedia by allowing crackpot material to be inserted in a scientific article.131.215.195.228 (talk) 18:41, 25 May 2010 (UTC)

John Earman hardly qualifies as a crackpot. Eugene (talk) 18:48, 25 May 2010 (UTC)

His statement clearly qualify as such. "I don't believe in a theorem" he does not understand? Moreover, \Omega ~ 1 being a prediction of inflation is exactly part of the solution to the initial conditions problem. The claim quoted in the page that \Omega < 1 being "hard to reconcile with inflation" is a flaw of inflation is illogical. Why wouldn't those claims qualify as crackpot nonsense non-scientific claims? Because he holds a Ph.D.? Well, Kary Mullis claims on HIV are pure crackpot delusions and he is a chemistry Nobel Prize winner. The qualifications (in this case, actually, the lack of them from John Earman who does not have peer-reviewed accepted papers in cosmology journals) do not at any moment disqualify any of the arguments presented below that the claims are not scientific.

It is clear that the claims are not accepted by the scientific community, e.g. of references in which inflation is considered not to be flawed at all but a sensible theory with testable predictions, among several others: Mukhanov V., Physical Foundations of Cosmology; S. Weinberg, Cosmology; D. Lyth & A. Liddle, Primordial Density Perturbation; Padmanabhan, T., Gravitation; S. Dodelson, Modern Cosmology. As another reader already pointed out, basically, any book in cosmology. When WMAP published their results, they compared the data with inflation and found agreement (http://dx.doi.org/10.1086/377228). Inflation is a testable theory and the claims of John Earman that it is "flawed" because he felt offended by the theory are not scientific. A scientific statement is one in which one shows that the theory is flawed because it predicts something which is ruled out experimentally. As such, his claims do not belong in this page or any other science essay or discussion.129.170.84.49 (talk) 19:25, 25 May 2010 (UTC)

If you have RSes that take issue with Earman's specific claims, please add them to the article in refutation of his concerns. Otherwise, you're merely engaged in WP:SYN at best. Eugene (talk) 19:32, 25 May 2010 (UTC)

If we had to accept in every scientific article a crackpot claim and add below or somewhere around it that the claim is crackpot and explain why, we would be doomed. A simple Google search of "Big Bang Theory wrong" produce an enormous amount of similar claims to the ones allowed in these specific sections of this page. I did exactly what you said and added here a clear statement of why the claims written in the page are nonsensical, and the expected approach from an impartial editor would be the remove the content. You asked for a series of references that show that the claims are wrong in the page discussion above, and I gave them to you. Now you came up with an excuse to maintain the propaganda of these claims by saying that I should add why the claims are clearly from a crackpot without any expertise in the subject into the main article so that the propaganda can continue online. I thought this was not an acceptable quality standard for scientific articles in Wikipedia.129.170.84.49 (talk) 20:49, 25 May 2010 (UTC)

As to the "WP:SYN" thing, if you had read what I posted below, in the reference of Mukhanov he *explicitly* states that point a) of the quoted paragraph is wrong. And the statement b) is one that says that a no-hair theorem does not exist and I explicitly showed it to exist below, which also exposes that b) is incorrect. Now, NO ONE is going to publish a paper on a peer-reviewed journal just to combine explicitly these arguments to explain clearly why Earmans assertions are nonsensical, because any grad student in physics can see they are patently wrong. So you will have to conform with the fact that scientists do not spend their time exposing all crackpots of the world. But anyhow, I gave up, no reason will change the mind of anyone trying irrationally to maintain these claims. I can only hope that some Wikipedia moderator with scientific expertise will pay attention to this issue.129.170.84.49 (talk) 20:49, 25 May 2010 (UTC)

I'm sorry but there is little to discuss on the fact that two sections of this Wikipedia article are being removed by me and this action should not be reverted. The sections were:

"CMTU Alternative theory" and "Philosophy of Cosmology".

Let me first address the second. It starts with the following quote:

"(a) results showing that inflation is likely to occur under generic conditions in the universe were not forthcoming (b) cosmic no hair theorems showing that inflation is effective in ironing out generic nonuniformities were not forthcoming (and in our reckoning are probably not true) and (c) in the straightforward version of inflationary cosmology ... the presence of enough inflation... is difficult to reconcile with a low value of Ω0"

For a), please refer to V. Mukhanov, Physical Foundations of Cosmology, Chap. 5. In Sec. 5.1 he explains what the initial condition problems are and translate that into equations of the sizes of particle horizons as functions of redshift, which all depend on the sign of the derivative of the scale factor, which then anyone following the logic can conclude the following, as I quote from the book:

We have seen so far that the same ratio, dot{ai}/dot{a0}, enters both sets of independent initial conditions. The large value of this ratio determines the number of causally disconnected regions and defines the necessary accuracy of the initial velocities. If gravity was always attractive, then ai/a0 is necessarily larger than unity because gravity decelerates an expansion. Therefore, the conclusion ai/a0 ≫ 1 can be avoided only if we assume that during some period of expansion gravity acted as a repulsive force, thus accelerating the expansion. In this case we can have ai/a0 < 1 and the creation of our type of universe from a single causally connected domain may become possible. A period of accelerated expansion is a necessary

condition, but whether is it also sufficient depends on the particular model in which this condition is realized. (V. Mukhanov, Physical Foundations of Cosmology, Cambridge University Press, p.229-230

Regarding b), the "not forthcoming" theorem is known since 1983: R. Wald, Phys. Rev. D 28, 2118–2120 (1983). "I don't believe in a theorem" may be something to be put somewhere up in the blogsphere but certainly not in a scientific essay about a scientific theory. As to c), it makes no sense. \Omega is not small, it is ~ 1, and this is a prediction of inflation. The fact that inflation cannot be reconciled with a small \Omega is the whole point of inflation.

Moreover, in addition to the fact that the claims inserted in this page about such "Philosophy of inflation" are nonsensical, there are several other non-experts like these two out there criticizing inflation or the Big Bang theory, and the insertion of the comment from these two non-experts in this page instead of any one else is a clear sign of propaganda and self-promotion.

Now, to the "CTMU alternative". It started with the quote:

"Thus, conspansive duality relates two complementary views of the universe, one based on the external (relative) states of a set of objects, and one based on the internal structures and dynamics of objects considered as language processors. The former, which depicts the universe as it is usually understood in physics and cosmology, is called ERSU, short for Expanding Rubber Sheet Universe, while the latter is called USRE (ERSU spelled backwards), short for Universe as a Self-Representational Entity"

No equations. Not scientific. Not an alternative model.

It is ONLY an alternative model to inflation if you can calculate the spectral index of CMB with a calculation in quantum field theory. If that is not what you do, it is NOT an alternative. Inflation predicts the shape of the distribution of galaxies in the universe and an alternative *scientific* theory is not a whole bunch of gibberish like the above paragraph but a CLEAR calculation of this function. Since the cited work does not include such a clear mathematical model for the inhomogeneities of the universe it is not an alternative theory, it is not a Cosmological model, it is not science. 131.215.195.228 (talk) 18:41, 25 May 2010 (UTC)

Edit: Now, everyone that has to deal with explaining scientific theories like quantum mechanics, relativity, or cosmological models known that we eventually face crackpots, which is an entirely different category of claims. One thing is if you come up with an alternative model like the ekypirotic model and you submit to a scientific peer-reviewed journal and this is accepted for publication because it contains sound physics and mathematics that can be tested against experiment, even though your model is not the model of choice of most cosmologists. This is not only acceptable, it is extremely important element of scientific research. Another entirely different thing is someone who, not being an expert, not knowing what are the technical difficulties that a theory like inflation solves, comes up with a naive idea that is written in a way to fool non-experts with random use of jargon and that, in the end, is not capable of elaborating a detailed calculation of any observable in the universe that can be compared to an experiment like WMAP or Planck satellite. And we can clearly distinguish this when we see that such claims were not published in scientific peer-reviewed journals. This is the case of the two sections that I removed, and it should be a consensus that an encyclopedic article about science should respect the criteria of what is scientific knowledge and separate that from other things. This is why such sections should not be included in this article. Only peer-reviewed scientific research paper material should be included here. 131.215.195.228 (talk) 18:41, 25 May 2010 (UTC)

1. CMTU get published in intelligent design journals. Eeeeeh.
2. Anyone who doesn't understand that omega~1 is the central prediction of inflation is a crackpot.

Both reverted.--Michael C. Price ^talk 21:54, 25 May 2010 (UTC)

Removal of Philosophy_of_cosmology

{Copied from --> Wikipedia:Editor assistance/Requests#Cosmological Inflation Moxy (talk) 01:41, 26 May 2010 (UTC) } Hi,

I would like to request two sections of the following Wikipedia article to be entirely deleted. The article is

http://en.wikipedia.org/wiki/Cosmological_inflation

the sections are:

1. http://en.wikipedia.org/wiki/Cosmological_inflation#CTMU
2. http://en.wikipedia.org/wiki/Cosmological_inflation#Philosophy_of_cosmology

Brief description of request:

• This article is about a scientific theory. It should contain scientific material.
• The two sections are not of scientific nature. The material was not accepted for publication in a peer-reviewed cosmology journal. The first section is a blog post; the second section was published in a religious newsletter.
• They seem to suggest a controversy which is inexistent in the scientific literature.

Longer explanatory comments:

The section no. 1 (CTMU) consists of a blog posts. It is not a peer-reviewed paper in a journal. It should not be part of an encyclopedic entry on a scientific article. Moreover, it is not comprised of a mathematical model that can be tested against experiment. The theory at hand (inflation), predicts what is called the power spectrum of cosmological perturbations and is consistent with observed anisotropies in the cosmic microwave background and the galaxy distribution observed by Sloan Digital Sky Survey and 2dF (http://dx.doi.org/10.1086/377228 ; for an accessible account to non-experts, see http://map.gsfc.nasa.gov/universe/bb_cosmo_infl.html). An alternative theory to inflation is one that can make these types of predictions, and there are some available in the scientific literature, but we can see from the blog post that it is not a mathematical model to predict cosmological observables. Instead, it is a random combination of jargon that makes little sense.

The same of the above applies to section no. 2. In addition, it was commented in the talk page in detail at least twice, where specific references were given that debunks the paragraph. In fact, the paragraph in question make three claims that: the first one can be seen to be wrong by following a simple textbook reasoning, such as the one of the reference given in the talk section; the second claim is just plain wrong because there are known theorems of the nature the paragraph disputed to exist.

It would be best if this is passed to someone with technical knowledge in Physics and Cosmology.

Thanks 129.170.84.49 (talk) 21:42, 25 May 2010 (UTC)

I'm not particularly familiar with the science involved here so I can't evaluate those arguments that appeal to what-everyone-in-the-biz-already-knows. But I am pretty good at following references and noticing when someone is saying something about a source that just ain't true. CTMU aside, the material on John Earman and Jesús Mosterín is sourced in part with a citation which in turn refers to a book published by the academic publisher Routledge, not a "religious newsletter". Further, the Routledge book itself is only quoting another source, an article that Earman and Mosterin wrote and which was originally published in the peer-reviewed, Univerisity of Chicago published journal Philosophy of Science. It's entirely possible that they are incorrect, and if so it's entirely possible that their specific claims have been addressed. But given the academic positions of both men and the standing of the peer-reviewed academic journal in which their claims were first made, arm-waving denunciations of them as "crackpots" (made, so far, only by Wikipedia editors and not in published work by experts) won't do as a rationale for deleting their material. I'm readding it. Eugene (talk) 03:34, 26 May 2010 (UTC)

Let us put this way: the paper of Earman was not published in a scientific journal peer-reviewed by cosmologists, and should not figure in a page about science. It was instead published in a journal that should not have allowed the paper to be published since the referees could not assess the technical content of it. The academic positions of both men should be a good reason why the material should be excluded, since none of them are cosmologists. At any rate, since it was not published in a scientific journal, we can at best call it a layman's opinion or philosophical prejudice, not a scientific statement. The flaw they argue for is not in the form acceptable for a scientific publication, namely, showing that there is a mathematical inconsistency in the theory or showing that one of the predictions of the theory was ruled out experimentally. Instead, the paragraph quoted tries to convince that the theory is wrong because the authors do not believe in rigorous theorems of General Relativity. Moreover, publishing this content of Earman here makes little sense since there are several other similar claims, some even by a few physicists and astronomers who also hold academic positions, in non-scientific journals and also in some scientific journals. This kind of thing is inevitable. Therefore, it would be best placed in the author's page in Wikipedia, not in the article about the science of inflation, just like other disputes of the Big Bang theory are usually placed in their author's page and not in the Big Bang theory article. The reference of religious newsletter is is still there, ref. 91, which is in fact of the same nature of the ref. that was removed "CTMU". I can add a technical evaluation of the content of this page, and in my professional opinion, the cited work of Earman is incorrect. I understand his claims and they are wrong. What else can we do here? If you don't understand them, then please do not insist in maintaining this material, you are doing a great disservice to education. The addition of the material on an encyclopedic article supports that there is a controversy as to the predictive power or consistency of the theory, which is not true. It is similar to insisting to keep the claims of some renowned person denying that HIV causes AIDS whenever one is to discuss AIDS in a newspaper, talk to the public, or article in encyclopedia. I'm of the opinion that these types of claims do not belong to an encyclopedia. We can address them in a opinion journal like Earman did. And I think that reading the above post should have made clear why the paragraph by Earman is incorrect. I'm the third or forth person to point this out, what else do we need to do here to get this material removed? I can add a ref. that I found, by George Ellis (http://arxiv.org/abs/astro-ph/0602280), who is a physicist, which was written to address among other things the opinions of Earman. Ellis states clearly:

The physical reason for believing in inflation is its explanatory power as regards structure growth in the universe. Inflation predicts the existence of Gaussian scale-free perturbations in the early universe thereby (given the presence of cold dark matter) explaining bottom-up structure formation in a satisfactory way. This theory has been vindicated spectacularly through observations of the CBR and matter power spectra. It is this explanatory power that makes it so acceptable to physicists, even though the underlying physics is neither well-defined nor tested, and its major large-scale observational predictions are untestable. (p.34)

He is not agreeing with the claim that inflation is fundamentally flawed, or that it is hard to make predictions consistent with observations.131.215.7.137 (talk) 06:19, 26 May 2010 (UTC)

Footnote 91 does not cite a "religious newsletter"; it cites an anthology published through the academic publisher Routledge. Your continued inability (or unwillingness) to recognize this point that I can easily verify only increases my unease in defering to your claims in matters I cannot easily check. Eugene (talk) 13:57, 26 May 2010 (UTC)

Yes, it is, it is a unnecessary reference of a book about intelligent design and it is unacceptable in a scientific article. It is unnecessary because only the paper of Earman is being discussed, and still the ID reference is given. If you have any good reason why the material should be kept here, please explain. I have removed the material and I will continue to do so.131.215.7.137 (talk) 15:42, 26 May 2010 (UTC)

From the section under discussion here: "But it is the first point that contains the essential philosophical position—they claim that 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." I doubt one can give a single reference where the power spectrum of CMB is predicted in the Big Bang model without inflation or some other additional scheme. It is known that it is impossible to generate the cosmological perturbations in the Big Bang without inflation because of the horizon problem (c.f. http://dx.doi.org/10.1016/0370-1573(92)90044-Z). The CMB power spectra is a prediction of inflation and it can be tested experimentally. See, e.g. http://dx.doi.org/10.1016/j.physrep.2004.08.022, where they explain how WMAP, Planck satellite and future observations can test this specific prediction of inflation.131.215.7.137 (talk) 06:37, 26 May 2010 (UTC)

I agree with 131.215.7.137 - the section should be removed. The content is gibberish; unclear in main, and where it is clear it is incorrect. --Michael C. Price ^talk 16:20, 26 May 2010 (UTC)

So are we in agreement that the material should be deleted? Because Eugene in lack of any reasoning to maintain the material is now appealing to the claim that 4 editors are interested in keeping the material. I don't see that.131.215.195.228 (talk) 04:04, 27 May 2010 (UTC)

Four different editors have reverted the deletions; that's what I've refered to. The material on the philosophy of inflation is relevant to the subject, encyclopedic, verifiable, notable, etc, etc, etc. False claims about the source material being a "religious newletter" have been mooted completely by tracking the material back to it's original peer-reviewed academic journal. Additional information related to the subsection has been added which derives from Alan Guth's own pen. And a supportive comment by Roger Penrose has also been integrated. There is no unbiased reason for its removal. Eugene (talk) 04:11, 27 May 2010 (UTC)

"Four different editors have reverted the deletions; that's what I've refered to."

That is because I tried to remove the content and there is an automatic feature to prevent that. It was not four people who looked at the discussion page and said "No, the material is relevant".

"The material on the philosophy of inflation is relevant to the subject, encyclopedic, verifiable, notable"

It is not relevant because it is not a scientific statement and it is placed in a scientific article. I think also that it hardly qualifies as a real philosophical discussion since it simply states that theory is incorrect. In science this type of assertion must come from an experiment. It is just a personal opinion of the authors . The material is not encyclopedic because it is not the consensus of the scientific community. As such, it violates the neutrality of scientific articles of Wikipedia. Three editors are here in favor of removing the material: myself, Michael Price and Likebox long before. You added your own words to the section now and that present original research in violation of terms of a Wikipedia scientific article.

"Additional information related to the subsection has been added which derives from Alan Guth's own pen"

And this is where your original research comes in. The quote from Guth is correct. It is because of what physicists call a "naturalness problem" that indicates a place where a theory lacks an explanation but it is not necessarily incorrect. The theory of inflation complements the Big Bang theory without inflation because without it one cannot explain the near scale-free inhomogeneities, or what physical process produced them. In the Big Bang theory without inflation these perturbations are inserted "by hand", and no causal physical process can produce them. Inflation is the standard theory of cosmology nowadays because it can add to the Big Bang theory an explanation of these inhomogeneities. The words of the section in question that sustain the theory cannot be tested are incorrect since the theory has already been tested with WMAP (cf. ref given above) and will continue to be tested in future experiments like Planck satellite. It is inadequate to say that the theory does not add anything to the Big Bang theory, and that was the whole point of Guth: it does add because it solves naturalness problems. Guth's words were distorted and removed from context to support a claim that was not what he was referring to. Then a completely unrelated remark from Roger Penrose who is not saying the theory is flawed was added. He was saying that a test of the theory in high energy experiment to detect whatever the inflaton may be is the ultimate test of the theory. Even if he did say the theory is flawed, that would be inappropriate. Science should not be what Penrose or Guth said, but what can be found by following mathematical reasoning and performing experiments. It is not a good practice when someone cannot follow the reasoning takes quotes of famous physicists out of place to support claims that they themselves never really made.

To conclude, there are three editors strongly in favor of removing it. I believe is more appropriate that you let it be, specially since it looks from your posts that you cannot assess the technical content of the arguments in question.131.215.195.228 (talk) 04:39, 27 May 2010 (UTC)

Hello. I was one of the editors who reverted your deletion, and I definitely did it because I read this discussion and decided that the material is relevant. There is no such thing as a "scientific article" in Wikipedia. Yes, there are articles on scientific topicss, but these are subject to exactly the same standards and policies as any other article - there is no walled garden of "scientific articles" with special privileges to isolate themselves from other domains of discourse. Any sourced and NPOV statement that is relevant to the topic of an article is appropriate, provided it does not give undue weight to a minority position. There are precedents for including overviews of relevant philosophical issues in articles on science topics - see quantum mechanics, artificial life and consciousness for examples. I agree that it is important to get the contents of the section right - make sure it gives due weight, does not use quotes our of context etc. But your argument that the section should be removed simply because it is about philosophy is incorrect. Gandalf61 (talk) 09:37, 27 May 2010 (UTC)

(removing a response because it not constructive to the discussion. Author of the response removing it here...)131.215.195.228 (talk) 03:37, 28 May 2010 (UTC)

Gandalf, I'm sorry I wrote the post before It was inadequate. I was too nervous. If it matters I now respond adequately: the problem is not the philosophy part, it is that to get the content right to me it seems the section should be deleted. The section in question says that the theory of inflation is incorrect because it cannot make testable predictions and it does not add to the Big Bang model. But the theory does make testable predictions, such as the shape of the distribution of galaxies in the sky, which has been verified by SDSS and 2dF, or the shape of the anisotropies of the CMB, as seen by WMAP satellite. It does add to the Big Bang because without inflation it is not possible to get the shapes of these inhomogeneities. See, e.g., the above quote and paper by George Ellis. It is not a problem that the section is entitled "philosophy", it is because it says things that are not true. I don't see how saying that inflation is flawed can qualify as a philosophical discussion. Now, it is true that the claims were made by two isolated individuals that are not experts in the field. But this is inevitable; if we are to collect all the statements that the Big Bang theory is incorrect from non-experts out there this page would be 100 times bigger. And also, I fail to understand why the points of these two gentlemen should be included here as a significant dispute of the theory, albeit nonsensical, and not all these other authors with their respective disputes?131.215.7.137 (talk) 05:09, 28 May 2010 (UTC)

Wow, not only a poor mind reader but a poor article reader too. I've never said that I'm a creationist (I'm not, BTW) and the article currently does not cite the book God and Design. As for your claim that I've taken quotations out of context, I've linked the Penrose journal article used in the section and you are of course free to read it. You're very words, however, indicate that this section is meaningful. As you said, inflation is largely an attempt to address the "naturalness problem" associated with standard big bang cosmology; that is, inflationary theory has a distinct philosophical motivation. Given that reality I see no reason why the article shouldn't address the philosophical issues involved so long as it does so with reference to reliable sources. Eugene (talk) 17:55, 27 May 2010 (UTC)

inflation is largely an attempt to address the "naturalness problem" associated with standard big bang cosmology; that is, inflationary theory has a distinct philosophical motivation.

You can call it "philosophical", but the motivation is to answer questions that cannot be answered in the theory without inflation. I would not call that philosophical, but a physics question. You are using a layman's loose definition of philosophy. It is a physics question when someone wants to find a model that explains the value of the mass of the Higgs boson, for instance. There is nothing philosophical about that, it is what in the physics literature is called a naturalness problem.

Given that reality I see no reason why the article shouldn't address the philosophical issues involved so long as it does so with reference to reliable sources.

Your section is not about philosophy, it is saying that the theory is flawed and is using quotes from famous physicists that you don't understand to support a claim that they were not making. All the physicists you quote do believe inflation can be tested experimentally and do believe that the theory adds to the Big Bang theory. I know them personally and they do believe in that. I don't understand why are you insisting on this issue. What do you have to gain to maintain this material here? It is not increasing the public understanding of science; it is making it worse by suggesting that inflation cannot be tested experimentally and it is unnecessary assumption to the BIg Bang. I had already explained that it is impossible to derive the CMB power spectrum without a mechanism like inflation and that WMAP has tested the theory experimentally. This is also explained in the Wikipedia article in the "Observational status" section. Why do you continue to ignore this fact? When you say that the theory cannot add anything, you did not provide a reference where the power spectrum without inflation was predicted. Yes, you did take the quotes out of context because they are not supporting your claim that the theory cannot be tested. Quite the contrary, in the popular science book of Guth he talks about how to test the theory, doesn't he? 131.215.195.228 (talk) 03:34, 28 May 2010 (UTC)

(deindent) No, it is not true that "inflationary theory has a distinct philosophical motivation". Inflation theory arose from the technical realisation that the equations of GR implied that a supercooled vacuum state would lead to exponential expansion of the universe. That this solved many exant cosmological conudrums was a corrolary, not a motivation. --Michael C. Price ^talk 18:13, 27 May 2010 (UTC)

"the historical motivation for inflation ... arose largely on more philosophical grounds"

Cosmological Inflation and Large-Scale Structure, Andrew R. Liddle & David Hilary Lyth

"Indeed, the primary motivation for the inflationary paradigm was to solve the naturalness problems"

"Pre-Big-Bang Inflation Requires Fine-Tuning", Physics Review D, Michael S. Turner & Erick J. Weinberg

"A principal motivation of any inflationary model is to get rid of the fine tuning of the initial conditions of standard cosmology."

"The fine tuning problem in pre-big-bang inflation", Physics Letters В, Maggiorea, Michele & Riccardo Sturanib

Eugene (talk) 19:40, 27 May 2010 (UTC)

You've got the Guth book. Read it. Guth found out about the horizon problem after his realisation. --Michael C. Price ^talk 20:18, 27 May 2010 (UTC)

Actually, don't bother. Remain ignorant, I don't care any more. This nicely illustrates how ignorant quote farming can destroy content. Stuff you all. --Michael C. Price ^talk 20:22, 27 May 2010 (UTC)

Classy. Eugene (talk) 20:38, 27 May 2010 (UTC)

The section is total crap. The paper first quoted makes it clear that they are talking about pre big bang inflationary theory, but this article begins with the definition that it covers post big bang inflation. Michael is completely right - it is quote farming by someone who is so out of his depth it is not even funny. Sophia ♫ 22:11, 27 May 2010 (UTC)

Thanks for restoring my faith in WP and/or the human race. Section removed. --Michael C. Price ^talk 22:26, 27 May 2010 (UTC)

Well hello Sophia. Never fear sweetie; I haven't misrepresented the sources.

I'm not entirely sure if you're refering to the first article cited in the short list above or the first article cited in the actual article's section on this matter. In any event I'll address them both so you don't lose sleep over it.

The first article cited in the section in question is by Maggiorea & Sturanib. While their paper is certainly titled "The fine tuning problem in pre-big-bang inflation", their relevant comments are directed at "any inflationary model", of which pre-big bang is merely one variety. As for the first article cited in the above list, the one by Turner and Weinberg, their relevant comments are likewise directed at the entire "inflationary paradigm", of which, again, pre-big bang inflation is merely one example. Nice try though. Section back in. Eugene (talk) 22:47, 27 May 2010 (UTC)

Read Guth's book yet, Eugene? Try reading pg 184 (which you've already quoted from) and tell me if he was motivated by the horizon problem before he discovered inflation. --Michael C. Price ^talk 00:19, 28 May 2010 (UTC)

I got so upset with the fact that I found this section in this article that I posted a detailed explanation of why the section was incorrect. (You know, when you see something like that, you get emotional...) I have to admit it was kind of inflammatory. I also admit that I was emotional and I should have said the same content in a way less aggressive. I apologize for that. It was really, really frustrating to see that after I had written my explanation for deletion with some care and deleted the section, editors reverted the deletion "because it was not constructive". At first I thought it was a bot, so I tried it again. Anyway, when it became clear from the above post that real editors were reverting the deletion I got very upset again. It is frustrating because no editor cared to come here read my explanation of why the section was saying 2+2=5 before reverting. I have provided detailed literature debunking each of the points already. This section is certainly not promoting education of inflation to the public. There is no consensus that the section is relevant and several editors are against it and have explained why the section is wrong, this should be a sign of problem. There does not seem to me that anyone presented a substantial explanation of why the section should be kept online. The only thing provided was "the authors are famous". I apologize again for my very agressive words in my previous post. However, I stand by my opinion that the material is not encyclopedic I think the case for deletion has been made above to exhaustion. It is now only to ask help from some admin or something.131.215.195.228 (talk) 02:40, 28 May 2010 (UTC)