Talk:Redshift/Archive 9

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History of Redshift

The idea of redshift was first recorded in 1783 by John Michell:

"Let us now suppose the particles of light to be attracted in the same manner as all other bodies with which we are acquainted; that is, by forces bearing the same proportion to their vis inertia, of which there can be no reasonable doubt, gravitation being, as far as we know, or have any reason to believe, a universal law of nature. Upon this supposition then, if any one of the fixed stars, whose density was known by the above-mentioned means, should be large enough sensibly to affect the velocity of light issuing from it, we should have the means of knowing its real magnitude [emphasis added]."

See Philosophical Transactions of the Royal Society of London, November 27, 1783.

--Thangalin 14:44, 25 November 2006 (PST)

frequency: ν or f

f for frequency was changed in ν. That may be more common in physics books, but f is also in use. IMO, f is much clearer for non-specialists, while ν is easily confused with v for velocity. Harald88 01:16, 5 August 2006 (UTC)

Agreed, as long as we mention that f = frequency. --Iantresman 10:03, 6 August 2006 (UTC)

Edits to the headings

I've changed History to a level 1 heading (I think this was left as a level 2 heading from a previous edit) and I've also removed the word redshift from some of the headings where it's obvious that we're talking about redshift (eg. History of redshift -> History). I'm leaving a note here since there is one change I'm not so sure about: Quantifying and interpreting redshift: z -> Quantification and interpretation: z. If I've done wrong, please feel free to revert. Cheers, darkliight^[πalk] 14:17, 18 August 2006 (UTC)

Cosmological redshift

The cosmological redshift is not a Doppler effect, but is caused by the stretching of space. It is analagous to the Dopler effect. The redshift caused by motion through space (eg of stars) is a Doppler effect (not just analogous). See Gravitation, by Misner, Thorne & Wheeler.

Sorry I am new to this game and forgot to sign the above. Charlie T, 19 August 06

This is correct, but that's exactly what the article says at this time. --ScienceApologist 09:11, 19 August 2006 (UTC)

Doppler redshift of source

The text notes that "A single photon propagated through a vacuum can redshift in several distinct ways". Doesn't a moving source appears to be a different mechanism since it requires a physical source in addition to said photon, and the redshift occur BEFORE said photon leaves the source surface and enters the hypothetical vacuum? --Iantresman 11:47, 28 August 2006 (UTC)

According to Galilean relativity, there is no "source" nor "observer" needed because you cannot distinguish between a moving source and a moving observer, therefore the source and observer are just place-holders in the equations and are not relevant to the mechanism. The definition of a reference frame abstraction is simply a change in perspective -- something which can occur while the photon is sailing through the vacuum of spacetime. --ScienceApologist 11:59, 28 August 2006 (UTC)

If you can't distinguish between a moving source or observer, then how can you infer a redshift? Perhaps there is a confusion in the text between "mechanism" and "transformation"; the former causes the latter. In practice, a moving sources CAUSES a redshift? --Iantresman 13:29, 28 August 2006 (UTC)

There is physically no way to determine whether a source is moving or whether an observer is moving. Trying to distinguish between the two is artificial to physics -- a weak form of the equivalence principle. The transformation is the mechanism. --ScienceApologist 13:40, 29 August 2006 (UTC)

• So we can't determine whether stars and galaxies are moving away from us? --Iantresman 17:57, 29 August 2006 (UTC)

• Only by triangulation averaging and assuming a stable spacetime metric.--ScienceApologist 19:57, 29 August 2006 (UTC)

• It's just that I thought that the article tells us that we can calculate the radial velocity of an object from its redshift.
• It occurs to me that "mechanism" might be the wrong word. The transformations are surely descriptions. The mechanism for the Doppler shift is surely the velocity of a source or observer; the mechanism of the cosmological redshift is surely the expansion of the universe. The transformation describe the effects? --Iantresman 22:18, 29 August 2006 (UTC)

This seems to be a matter of semantics rather than substance. I had an earlier discussion with User:Serjeant about the difference between cause and description and we never really resolved the issue. Mechanisms and descriptions to me are basically the same since science ultimately only answers the questions of "how" and not "why". --ScienceApologist 00:24, 30 August 2006 (UTC)

• To me, and I should think most other readers, a mechanism should related to a real world analogy. The siren on an ambulance does not change tone due to the mechanism of "frame transformation"; it changes tone because the truck is moving. Likewise, the optical redshift of stars is CAUSED by the mechanism of stars moving. Mathematically and conceptually, this can also be described as a frame transformation. --Iantresman 08:30, 30 August 2006 (UTC)

You say "poh-TAY-toh", I say "poh-TAH-toh". The siren on an ambulance does change tone due to the mechanism of a frame transformation. In fact, such a physical description is more accurate that relying on the nebulous "truck is moving" observation. The CAUSE is the fact that the siren is in a different frame of reference from the observer. A stationary siren with a moving observer would therefore result in the same phenomenon. --ScienceApologist 13:28, 30 August 2006 (UTC)

Redshift transformations

I can find no refernces that describe redshift mechanisms:

1. as a group of only three (or four), that are...
2. due to Galilean, Lorentz, and general relativistic transformations, and...
3. applying only to single photons in a vacuum.

Sure I can find references that describe a redshift as a certain transformation, but nothing which groups all three/four redshifts with all three transformations, and to single photons in a vacuum. This leads me to suggest that:

1. transformations are not synonymous with mechanisms
2. transformations are not necessarily the only type of mechanism
3. that this summary of mechanism is highly selective and contrived.
4. "single photons in a vacuum" is not a necessarirequirement of redshift mechanism.

--Iantresman 10:05, 30 August 2006 (UTC)

I would suggest you read some of the introductory physics and astronomy texts suggested. By the way, the "single photon" application is an idealization, not a requirement. You can read previous discussions about this. --ScienceApologist 13:29, 30 August 2006 (UTC)

• OK, so give me a citation... not to any old textbook, but one which specifically describes redshift in the terms described above. --Iantresman 14:03, 30 August 2006 (UTC)

• You can try any of the textbooks referenced in the article. --ScienceApologist 13:10, 31 August 2006 (UTC)

• And if the "single photon" is an idealisation, then we should say so? --Iantresman 14:05, 30 August 2006 (UTC)

• No, because it is an accurate statement. (Just like saying "in the absence of air resistance, all objects experience the same acceleration due to gravity"). --ScienceApologist 13:10, 31 August 2006 (UTC)

I've tried various textbooks and journals, and can find no citation that describes redshift as it is described in the article, and summarised above. --Iantresman 14:13, 31 August 2006 (UTC)

Look at, for example, Peebles, Principles of Physical Cosmology Chapter 5, where the first three are discussed in detail. Although, he doesn't explicitly call the first a galilean transformation -- since that derivation can be found in almost any introductory physics text book. Salsb 14:51, 31 August 2006 (UTC)

OK, I've had a look in the book and could find:

• Nothing on Redshift mechanisms, (so there does not appear to be a "link" to transformations)
• Nothing on photons in a vacuum
• One mention of photons moving in free space, in relation to tired light (p.225)

So while I have no problems with the transformations per se, there does not appear to be a suggestion that these are mechanisms, nor any of the other points that I summarised above. --Iantresman 15:30, 31 August 2006 (UTC)

I am afraid you haven't read carefully then. The chapter, pages 94-99, specifically discusses doppler effects, and shows you specifically the transformations required to obtain the first two in detail, although you have to do some math to transform them precisely into the form in the table. Furthermore, the discussion and mathematics is specifically in the context of particles in vacuum. Salsb 15:42, 31 August 2006 (UTC)

• OK, I have read through them, and am quite happy with the Doppler redshift being described as a Galilean transformation. But I can find nothing which describes the transformation as being the mechanism.
• It seems to me that motion of the source or observer is the mechanism; the transformation is the description.
• Indeed, all I find elsewhere are references that suggest that the "Doppler effect" is the mechanism,[1] [2]. And the Doppler effect is described as being caused by the motion of the source of observer.
• Again, I can find no references that suggest that the redshift mechanisms are due to any transformation --Iantresman 16:02, 31 August 2006 (UTC)

Mechanistic descriptions are what physics does. There is no distinction in physics between mechanism and description because, to paraphrase Feynmann, physics asks "How?" and not "Why?" For example, the Doppler Effect is described fully by the Galilean transformation which means that the two are synonymous for waveforms. --ScienceApologist 16:10, 31 August 2006 (UTC)

• So why do ALL the citation that I have found, tell me that one of the redshift mechanisms is due to the Doppler effect, and NO-ONE has been able to find a citation supporting the description that one of the redshift mechanisms is due to a Galilean transformation, or any other transformation? Again, I am not disputing that the Doppler redshift is described by a Galilean transformation.
• Even if the description is technically correct, why should the Wiki article on Redshift be the ONLY ARTICLE ON THE PLANET, to describe redshift mechanisms in this way? --Iantresman 17:54, 31 August 2006 (UTC)

We've been through this already. Take it up with dispute resolution if you want. Protracted circular conversations like this should be avoided. --ScienceApologist 17:58, 31 August 2006 (UTC)

It's not circular. I've asked for a citation supporting the description, and no-one can provide one. The only conclusion is that the article statement is not verifiable. --Iantresman 18:47, 31 August 2006 (UTC)

Valid point - it's not hard to understand why it's hard to find such an unphysical description in the literature. Most literature distinguishes between mathematics (transformations) and physics (Doppler effect). Harald88 21:52, 31 August 2006 (UTC)

Untrue. Go ahead and support your claim with a citation that says that transformations are distinct from the Doppler Effect: or more precisely that the mathematical description of such a phenomena is "unphysical". The citations are provided, the naysayers have no evidence to back-up their claims. This discussion is over until the disputants can make a coherent, verifiable case for themselves. --ScienceApologist 14:22, 1 September 2006 (UTC)

Please don't put things on their heads. What is criticized on this Talk page without support from literature has to go. Simple as that. Harald88 22:38, 1 September 2006 (UTC)

• The "disputants" could not be clearer; The statements in the article are not backed up by ANY citations. It is yourself that has no evidence. To DEMOMSTRATE that this is incorrect, all you have to do is provide a veriable quotation that describes redshift mechanisms in terms of transformation.
• I will happily provide some verifiable quotes which unamibiguious describe redshift mechanisms in verifiable terms. --Iantresman 14:48, 1 September 2006 (UTC)

"This discussion is over." What kind of language is that? Just who the f*** do you think you are? Jon 10:11, 4 September 2006 (UTC)

Verifiable quotes on "redshift mechanisms"

No citations have been provide describing redshift mechanisms as frame transformations; this can be remedied by providing a single attributable quote containing the words "redshift", "mechanism" and "transformation" and any of "Galilean", "Lorentz", or "general relativistic".

I offer the following quotes describing redshift mechanisms, as described in the literature (emphases mine):

• "Modern physics knows two experimentally verified mechanisms which produce redshifts that are independent of wavelength... the Doppler effect ... the Gravitational redshift. Besides these empirical and well understood redshift mechanisms, there is the theoretical phenomenon associated with the expansion of space. [...] Thus three redshift mechanisms act in nature." -- Discovery of Cosmic Fractals] (2002) by Yurij Baryshev, Pekka Teerikorpi
• "For historical reasons, small redshifts are often quoted in velocity units: the radial velocity required to produce the observed shift strictly from the Doppler mechanism due to relative motions." -- "The Road to Galaxy Formation" (2002) by William C Keel
• "Attempts to interpret the red shift by a gravitational mechanism ... efforts have been made to interpret the red shift by a Doppler mechanism", The Red Shift: A Different Mechanism (1972) Urbanovich, S. I.

--Iantresman 16:26, 1 September 2006 (UTC)

note for InvictaHOG

About all the fact tags you lefd thruout, don't the links fulfil the need for citations? Or, why must they be in the same page? -lysdexia 20:54, 23 September 2006 (UTC)

No. Otherwise we would not have a referencing system. A person who wants to verify a statement should be directed to either the page of a book or a scientific paper with that conclusion. A link is not sufficient. This may be basic physics knowledge, but most people do not have basic physics knowledge. I'm not sure I understand your second question about the same page. InvictaHOG 21:05, 23 September 2006 (UTC)

I still don't get it.

I'm happy to see that "recession" and "streching" are no longer called "completely different", but it is still not clear to me if they are different at all. To claim that this question is "clearly illustrated" by the Expanding Rubber Sheet Universe smacks of absolute Newtonian space. The statements toward the end of the section make it sound like the two points of view are related by a coordinate transformation and thus mathematically and physically equivalent, but the sentences before that suggest that it can't be recession because that would require relative velocities greater than c. That sounds to me like someone is using Galilean addition of velocities, obviously out of place here. ScienceApologist now brings in a new argument, the cosmological principle, but I still don't see why "real" recessional velocities would have to violate the CP, or indeed if there is any conceivable observation that could distinguish between the two. If I have trouble understanding this distinction, then I'm sure the average reader does, too. Is there any way to make this section more accurate and/or more understandable? Is it really one way or the other, or are they just two ways of looking at the same phenomenon? --Art Carlson 11:35, 6 October 2006 (UTC)

Thanks for pointing this out. Let's try to get an explanation in there that makes sense. Technically speaking, the expansion of space is all that is left if you assume both the Copernican Principle and the Cosmological Principle's claim of an isotropic universe. The easiest proof of this is to consider an equilateral triangle (ABC) with the observer at the apex (A). The redshifts of the two orther vertices (B and C) would be observed, if they were physically receding, to have the same redshift (z) for Hubble's Law to hold. However, if you considered what an observer at B would be observing, even though such an observer is the same distance from A and C, they would measure a redshift of (1+z)=1+v/2c-v^2/2c^2-v^3/4c^3+... for object B while measuring the redshift z for object A which does not correspond to the same redshift. Thus we have a contradiction and the proposition that we can describe a universe with isotropic, linearly increasing redshifts due entirely to physical velocities must be false. Traditionally, in cosmology classes the proof is done in the other direction where you assume an isotropic expansion and prove that the Hubble Law is linear. In a static three-dimensional space where there is no metric expansion it is simply impossible to observe an isotropic recession in all directions for all positions in space. (Caveat: this assumes that the universe is not infinite due to Olbers's paradox. If you have an infinite universe, there is a way to get an isotropic "explosion" of sorts that corresponds to an isotropic recessional velocity in all directions from all perspectives, but this assumes that general relativity is incorrect because such a universe would have a non-converging mass and a curvature that would warp the linear nature of the expansion. There are forms of Milne universes that propose such a Lorentzian (not GR-based) perpsective of an expanding universe. In fact, there is one cranky editor that keeps trying to insist that the Milne universe hasn't been disproven because of this -- even though this would require abandoning GR).

So the question is (assuming that Art Carlson understands my above explanation), how do we illustrate this to the reader? Please help!

--ScienceApologist 12:29, 6 October 2006 (UTC)

By the way, spacetime is absolute and insamuch as any observer in spacetime (save one travelling at the speed of light) can theoretically isolate space-like manifolds in Lorentzian spacetime, the view of "absolute Newtonian space" is not quite so problematic. So long as we remind ourselves that the rubber sheet's rulers are subject to modification depending on our choice of inertial frame, we still end up with the same situation (only with expansions, velocities, and the sizes of objects changed accordingly). --ScienceApologist 12:42, 6 October 2006 (UTC)

I beg to differ. All you have proven is that the equilaterality of a triangle is not an invariant in special relativity. On the contrary, if any observer sees a linear Hubble relationship, then all observers do. Imagine the first observer extrapolates all the motions back in time. He will find one time in which all the observered objects are on top of him. But such an event - simultaneous in time and co-located in spce - must be the same for all observers. But that can only be the case for other observers if they also see a linear Hubble relationship. (But you might have a point about the homogeneity. I'm not certain that all observers can see a uniform density.) --Art Carlson 20:06, 8 October 2006 (UTC)

I don't think so. Length contraction doesn't affect the sides of the triangle, only the rulers that are carried by the objects that are moving. Distances are equal, velocities are unequal, therefore Hubble's Law is contradicted. --ScienceApologist 00:34, 9 October 2006 (UTC)

Think again. I admit that my knowledge of cosmology and general relativity is rudimentary, but we are talking about special relativity here. A measures the distances AB, AC, and BC to be all equal. If you boost from the frame of A to the frame of B, the distance AB, which is parallel to the boost velocity, experiences the full Lorentz contraction, while the distances AC and BC, which are at an angle to the boost velocity, will be contracted less. Therefore, for B, C is farther way than A, which would correspond to a higher redshift. (Besides, it might help if you would look at the problem a different way, such as the one I suggested.) --Art Carlson 08:55, 9 October 2006 (UTC)

So the situation is even worse because B sees C has having a smaller redshift than A (roughly 1/2 in the low-velocity limit). --ScienceApologist 12:15, 9 October 2006 (UTC)

That's all you've got to say? No derivation of your formula? No critique of my argument? No verifiable citation? Looks like we need to throw out the claim that there is "a distinction between redshifts caused by the velocity of the objects and the redshifts associated with the expanding universe". --Art Carlson 07:40, 11 October 2006 (UTC)

Isn't it a case that there is a theoretical distinction, but no practical difference; a redshift is redshift, and there is no distinction between a cosmological, gravitational, Doppler, or (gasp) Wolf shift. I still don't from the article, how I work out from a measured redshift of a distant galaxy, the proportion due to each redshift mechanism... without making some assumptions.

I think I'm getting there, slowly. I still don't like Joshua's equilateral triangles. In addition to the fact that the observers are measuring with different rulers in different directions, the statement "ABC is an equilateral triangle" means "ABC is an equilateral triangle right now", but the three observers do not even agree what "now" means (simultaneity). I can't find any problem with my argument, so I firmly believe if one observer sees a Hubble relationship, then they all do. What I have realized is that the universe will not look the same to all observers in other respects. If an observer in the center of the explosion sees a uniform density of galaxies out to the limits of observation at v = c, then an observer near the edge, although he would still see a Hubble relationship with galaxies out to the limit, he would see an inhomogeneous universe. Looking toward the center of the explosion, he would see a higher density than looking outward. The argument thus goes like this:

Hubble: We see galaxies moving away in all directions.

Simplicio: Then we must be at the center of the universe.

Galileo: No. Calculate what the other worlds would see: also an expansion in all directions!

Einstein (special): But wait, if you take SR into account, the other worlds would observe an inhomogeneity in the universe.

Simplicio: So we are at the center of the universe!

Einstein (general): There is another possibility. With GR, the redshift could be caused by an expansion of space rather than an actual motion. Then everybody sees a uniform universe again.

Chorus of astronomers: Since we firmly believe that we do not have a special place in the universe, we must conclude that the cosmological redshift is the result of an expansion of space rather than recessional velocities.

Simplicio (coda): Well, there's no way you can prove that I'm wrong without traveling to a distant galaxy, so I still believe I'm special.

I know this is not the place to discuss physics in detail. I'm still hoping we can find a way to make the article more accurate and more understandable. I admit I haven't looked up the references, but that is partly because it is not clear from the text which reference will really answer my question - another opportunity to improve the article. --Art Carlson 07:42, 12 October 2006 (UTC)

Art Carlson points out another problem and that is the "Galilean vs. Lorentzian vs. Cosmological" view of velocities due to redshift. While it may seem that we are talking about a Galilean transformation when we discuss a velocity exceeding the speed of light, we are really talking about a general relativistic transformation and a definition of velocity that is rather brutishly (and some would say "non-physically") pulled out of fundametal kinematics. The problem is that the definition of "velocity" is muddled by the metric expansion of space. If we talk about the recession as the change in the proper distance between the two objects compared to the change in the proper time of either object, then the "speed" which is derived exceeds the speed of light. This means that if we took a space-like cut where dt = 0, there would be no chance for any light beam null-geodesic from either event to enter the future light cone of the other event assuming a linear and consistent expansion of space. In this sense, the objects have slipped past the other object's future horizons. We will continue to observe the distant object for all time, but we will never see it as it is "today". This is different from a Lorentzian redshift that exceeds z = 1 because in that case we will, in the future, see such an object as it is "today": at time t = x/c where x is the proper distance between ourselves and the object. --ScienceApologist 12:50, 6 October 2006 (UTC)

• I think there is always going to be a problem explaining it to the reader, because expansion of space is a unique phenomenon for which there is no real analogy. The blowing-up of a balloon demonstrates "stetching", and dots on the rubber do actually move apart. The analogy with "sea floor spreading" and two people standing stationary either side of a rift, is similar. But I see the vague analogy, without being able to dinsguish the important bits, the "stretching" from the "expanion".
• Personally, I believe that if you expand nothing (space) you end up with nothing, since "expanded" space is indistinguishable from unepxanded space. And the distance between objects due to recession is indistinguishable form that due to expansion.
• Having said that, this is all interesting stuff that should be put in the relevant article, which is not Redshift. --Iantresman 13:32, 6 October 2006 (UTC)

Refs

I added a bunch of references. Someone needs to dig up a spectroscopy textbook to reference that section. Other stuff, such as using spectroscopy to study AGN and the rotation of stars, etc... should be easy to find on ADS. I may take a look later if I feel motivated. As for "Effects due to physical optics or radiative transfer", I don't know where to find most of that stuff, but I assume it has been hashed over about a million times on the talkpage, so perhaps it won't be that hard to reference. –Joke 16:12, 6 October 2006 (UTC)

The first two paragraphs

I find the first two paragraphs are a bit confusing:

In physics and astronomy, redshift is a phenomenon in which the visible light from an object is shifted towards the red end of the spectrum.

Ok, so this phenomenon deals with visible light, and causes a shift towards a specific range of wavelengths (red=620–750 nm).

It is an observed increase in the wavelength, which corresponds to a decrease in the frequency of electromagnetic radiation, received by a detector compared to that emitted by the source.

So it's no longer just visible light? And the shift isn't towards red, but rather a general shift towards longer wavelengths?

The corresponding shift to shorter wavelengths is called blueshift.

Ok.

The phenomenon goes by the same name even if it occurs at non-optical wavelengths (e.g. gamma rays, x-rays and ultraviolet).

I have no problem with this, but why state the opposite in the opening sentence?

At wavelengths longer than red (e.g. infrared, microwaves, and radio waves) redshifts shift the radiation away from the red.

Yes, but why this refrence to the colour red, I thought we just agreed that it was a lenghtening of the wavelength?

Well, I'm being a bit silly here, but I actually experienced a moment of confusion when reading these first two paragraphs. In my opinion, refrences to the colour red and visible light are only of historical interest. These were are probably relevant to the original experiments, but surely the term 'redshift' is now considered to apply to all EM radiation regardless of wavelength, and with no actual refrence to a specific colour (red)? O. Prytz 20:59, 10 October 2006 (UTC)

Tried to make it better. What do you think? --ScienceApologist 21:04, 10 October 2006 (UTC)

Ok, yes, it is clearer. But I would actually prefer to substitute the first two paragraphs with something like:

In physics and astronomy, redshift is a phenomenon in which electromagnetic radiation from an object is observed to have an increased wavelength compared to that emitted by the source. The corresponding shift to shorter wavelengths is called blueshift.

Which is totally unambiguous (but not very well written). Hm... on reading the opening paragraphs again I think it's pretty clear as it is now. Let's not change it furtherO. Prytz 21:12, 10 October 2006 (UTC)

The wording dealing with "red" up front was to avoid the confusion by certain editors (less savvy than yourself) who couldn't wrap their heads around why "red" was in the term. We address it up front and then knock down the misconception based on the assumption that the only forms of light that exist are those which are visible to the naked-eye. --ScienceApologist 21:15, 10 October 2006 (UTC)

I have very little problem with the opening paragraphs as they are now. If I were to make one final suggestion it would be to delete the sentence in par. 2 starting with "At wavelengths longer than red[...]". But I have no strong opinions on the matter. O. Prytz 21:20, 10 October 2006 (UTC)

• Some of these "less savvy" editors, as you call them, perhaps realised that for most people who know little of physics, the description "increase in wavelength" was an abstract description that meant nothing to them. By mentioning the colour red in the definition, we at least give the reader something they are familiar with, that also related to the term "redshift".
• As a guide, I would suggest reading the introduction to someone who is not familiar in phsyics. Our target audience is "people", not "physicists" --Iantresman 22:23, 10 October 2006 (UTC)

Redshift mechanisms

• The text reads: "A single photon propagated through a vacuum can redshift in several distinct ways". The wording implies that there might be no redshift, or a different mechanism for (a) multiple photons, or (b) photons that don't travel in a vacuum? And since this is the practical case, it might be worth clarifying. --Iantresman 12:00, 11 October 2006 (UTC)

• Isn't it the case that "redshift in several distinct ways" should be "the redshift can be caused in several distinct ways, because the resulting redshifs are identical? --Iantresman 12:02, 11 October 2006 (UTC)

I think these issues are more semantic than substantive. Indeed, it is correct that there might be no redshift because sometimes there is no redshift. I disagree that the wording implies a different mechanism for multiple photons not in a vacuum: this is just a common turn-of-phrase in physics when you idealize a situation so you can avoid the non-conservative abberations. For example, when describing inertia we need to eliminate friction. When describing conservation of momentum we need to eliminate impulse. When describing redshift mechanisms we need to eliminate geometrical and physical optics. I don't read any difference between the wording "redshift in several different ways" or "redshift can be caused in several different ways". One takes redshift as a verb, the other as a noun. Redshifting happens differently due to different mechanisms. --ScienceApologist 12:16, 11 October 2006 (UTC)

• I understand it is "a common turn-of-phrase in physics". You and I understand its meaning. But I suspect that the majority of readers, who don't have a physcis background, may note the ambiguity... perhaps they will assume that we refer to photons travelling through a vacuum because space is a vacuum!
• You wrote: "When describing redshift mechanisms we need to eliminate geometrical and physical optics."... but you don't say that in the description, which confirms that ambiguity. By explaining this, we could help the reader differentiate between these redshifts. Currently we don't.
• As I noted earlier, you and I are not the best people to judge the explanation... someone who has no background in physics is. --Iantresman 12:42, 11 October 2006 (UTC)

There is a reason that common turns-of-phrase are common: they work. I don't think they are ambiguous. You are stating that you don't think it is ambiguous but are worried that someone else will think it is ambiguous. I'm not convinced of this. Let's wait and see what other people say, then. --ScienceApologist 12:48, 11 October 2006 (UTC)

• Yes, common turns-of-phrase work... for phsyicists.
• And still excludes the explanation for your using this particular turn of phrase: "to eliminate geometrical and physical optics" --Iantresman 14:22, 11 October 2006 (UTC)

It's not just geometrical and physical optics but also radiative transfer, energetic mechanisms beyond coordinate transformations, and scattering. It is far easier to say what the application is rather than what it isn't. --ScienceApologist 14:29, 11 October 2006 (UTC)

So while Doppler-like (z is independent of wavelength) is a requirement of redshift, is it a requirement or characteristic that a redshift involves either a Galilean, Lorentz, or general relativistic transformation? --Iantresman 15:09, 11 October 2006 (UTC)

It's semantics whether you call it a requirement or a characteristic. Characteristics are requirements in math and physics. --ScienceApologist 17:37, 11 October 2006 (UTC)

• So are you saying that a redshift must be due to either Galilean, Lorentz, or general relativistic transformation? (ie. one of these transformations are a requirement that defines redshift)? --Iantresman 18:23, 11 October 2006 (UTC)

We've had this discussion before. Please read the archives. --ScienceApologist 18:34, 11 October 2006 (UTC)

• Yes, I've read the archives, and can't find an answer, so I thought that for the sake of a quick answer, you might oblige. --Iantresman 19:06, 11 October 2006 (UTC)

• Nope, the answer was given to you by FlyingJazz. Contact him if you are interested. --ScienceApologist 21:33, 11 October 2006 (UTC)

Citation request

So the introductory paragraph in "Mechanism" discusses "a single photon in a vacuum",

• But we don't tell the reader why we have mentioned this restriction (you described it quite well above)
• Applies also to multiple photons in a non-vacuum (ie. reality)
• Mentions z independent of wavelenght, but we don't tell the reader its significance

I do not dispute that any of the individual mechanisms described by coordinate transformations can be considered to apply to a single photon in a vacuum, but I contend that this general description of redshift mechanisms is contrived and unique, and requires a citation.

I've restored the request by InvictaHOG for a citation,[3], and would appreciate a quote which involves "redshift mechanism" "single photon" and "vacuum" --Iantresman 11:09, 12 October 2006 (UTC)

I've included a reference. These works all define redshift in terms of the mechanisms listed. --ScienceApologist 12:01, 12 October 2006 (UTC)

• Thanks for that. I have no problems with redshift and the mechanisms or transformations. I have a problem with its association with a "single photon in a vacuum".
• Can you confirm that your citation to Kutner (2003) refers to "Astronomy: A Physical Perspective" by Marc L. Kutner?
• Can you give me a page number that includes a definition of redshift, or discusses mechanisms, in terms of a single photon in a vacuum. For example, I can find only one page each:

• Page 153: mentioning redshift and vacuum.
• Page 150: mentioning redshift and "single photons". --Iantresman 12:17, 12 October 2006 (UTC)

As per Wikipedia:WikiProject Physics/Citation guidelines proposal, the material is easily inferred from the references you are looking at:

For reasons of notation, clarity, consistency, or simplicity it is often necessary to state things in a slightly different way than they are stated in the references, to provide a different derivation, or to provide an original example. This is standard practice in journals, and does not make any claim of novelty. In Wikipedia articles this does not constitute original research and is perfectly permissible – in fact, encouraged – provided that a reader who reads and understands the references can easily see how the material in the Wikipedia article can be inferred.

--ScienceApologist 12:33, 12 October 2006 (UTC)

"it is often necessary to state things in a slightly different way". So please provide a page number where I can find the association of redshift mechanisms with "a single photon in a vacuum", even if it is not in those words. --Iantresman 12:41, 12 October 2006 (UTC)

Just look at the definition of redshifts found in these sources. They all apply to single photons in a vacuum by virtue of their choice of mechanisms. --ScienceApologist 12:50, 12 October 2006 (UTC)

• They also apply to multiple photons in a non-vacuum, so I'd like a quote indicating the necessity to specify a "a single photon in a vacuum". --Iantresman 12:55, 12 October 2006 (UTC)

For reasons of notation, clarity, consistency, or simplicity it is often necessary to state things in a slightly different way than they are stated in the references, to provide a different derivation, or to provide an original example. --ScienceApologist 12:59, 12 October 2006 (UTC)

• As an example, your source (Astronomy: A Physical Perspective", (2003) Marc L. Kutner) says (my emphases):

• "Gravitational redshift The wavelengths of photons change as they pass through a gravitational field." (Page 145)
• "One possible source of redshift is gravitational. We have already seen that photons are redshifted as they leave the surface of any object." (page 366)
• "Cosmological redshift We can also see that the redshift (Hubble's law) fits ... (Fig. 20.8). As the universe expands, the wavelengths of all photons expand by the same proportion that cosmic distances expand." (Page 386)
• "The redshift arises as a result of the increase in wavelengths of all photons moving through an expanding universe." (page 388)

• These quotes demonstrate that "photons" (plural) are not excluded from the defintiion, and there is no reason to state a "single photon" nor state a vacuum. --Iantresman 13:15, 12 October 2006 (UTC)

There is no implied exclusion, only simplicity for the sake of clarity. --ScienceApologist 17:44, 12 October 2006 (UTC)

If it was simply and clear, we wouldn't be having this conversation, and I note that you have not provided any supporing quotes. --Iantresman 19:04, 12 October 2006 (UTC)

I disagree. I say we are having this conversation because you don't like it despite it being verified. --ScienceApologist 21:15, 12 October 2006 (UTC)

Eliminating geometrical and physical optics

You wrote above: "When describing redshift mechanisms we need to eliminate geometrical and physical optics"[4]. I note that you've included the Wolf effect which is consistent with your statement.

• The article on the Wolf effect includes reliable sources stating that the Wolf effect is a redshift mechanism.
• Can you provide a source that indciates that the Wolf effect should be excluded as you stated (I understand that many books might not include it for whatever reason, but this is not the same as excluding it) --Iantresman 19:26, 12 October 2006 (UTC)
• Or how about a source excluding "physical optics" from redshift mechanism? --Iantresman 19:26, 12 October 2006 (UTC)

Absolutely! The basic astronomy sources listed do not include the Wolf Effect and therefore the Wolf Effect is not supposed to be included on this page in such a fashion since it is generally considered part of the other effects section listed below. --ScienceApologist 21:17, 12 October 2006 (UTC)

• Why would you think that astronomers are the arbiters of the Wolf effect?. Optics sources include the Wolf effect, the very first sentence of the article says that redshift is something in physics and astronomy, and the article mention that "redshift has a number of terrestrial uses".
• By the way, here as some astronomy sources that mention the Wolf effect:

• "Gravitation and Cosmology: From the Hubble Radius to the Planck Scale"[5]
• "The Universe: Visions and Perspectives"[6]
• "Measuring the Universe"[7]
• "Towards the Edge of the Universe: A Review of Modern Cosmology"[8] (Page 136)
• "Gravitation and Cosmology: From the Hubble Radius to the Planck Scale"[9] (pp103) --Iantresman 22:23, 12 October 2006 (UTC)

Okay, so we rightly include the Wolf Effect in relation to its relevance to this page. Congratulations on using a search engine, Ian. Now maybe you can explain how the context of each of these sources mirrors the context of the Wolf Effect here in this article. --ScienceApologist 12:44, 13 October 2006 (UTC)

Poor notes

• This note is rather poor: [2] "See Binney and Merrifeld (1998), Carroll and Ostlie (1996), Kutner (2003) for applications in astronomy"
• There is no indication whether all three texts cover the information to which the note refers, or just one of them. There is also no indication where in the book, the information is discussed.
• WP:CITE suggests that "When citing books and articles, provide page numbers where appropriate".
• And there are many citations which give no titles, let alone a page number, including:

• Feynman, Leighton and Sands (1989)
• Misner, Thorne and Wheeler (1973) and Weinberg (1971)
• Peebles (1993)
• Odenwald & Fieberg 1993

• --Iantresman 14:45, 26 October 2006 (UTC)

The book references are at the bottom of the article. You may need to read substantial parts of the books to obtain the information you want to find out about. Wikipedia cannot teach you to be a competent researcher, they can only lead you to the water and then you can drink. --ScienceApologist 17:25, 26 October 2006 (UTC)

• That's new, the reader needs to be a researcher in order to make use of the citations you've added to an article that I though you had researched.
• Citing three books, and telling me that I "may need to read substantial parts" is a joke.
• Peebles (1993) does not even tell me whether I am looking at a book or a paper.
• WP:CITE suggests that "When citing books and articles, provide page numbers where appropriate". --Iantresman 18:03, 26 October 2006 (UTC)

Page numbers are not appropriate as explained above. If you want to know what book it refers to, check the book references at the bottom of the article. --ScienceApologist 19:06, 26 October 2006 (UTC)

• The text says "It is believed that a yet unknown theory of quantum gravity would take over before the density becomes infinite"[51]
• The reference is Peebles (1993), Weinberg (1971), Misner, Thorne and Wheeler (1973).
• I can not find any reference to "quantum gravity" in Peeble's book, and the reader is not going to read through 700+ pages to try and find what your mean.
• The citations need page numbers. --Iantresman 19:49, 26 October 2006 (UTC)

Please see: Wikipedia:Scientific citation guidelines. --ScienceApologist 20:03, 26 October 2006 (UTC)

Your "please see", like your references, tell me nothing. I have no idea what you are trying to point out. --Iantresman 20:18, 26 October 2006 (UTC)

I really can't see the point of this. Are you disputing this statement? Try pages 8 and 77 of Peebles. I don't have Weinberg or MTW handy to look up the page numbers. I don't think Peebles actually mentions quantum gravity, but he does mention that "unknown physics" becomes dominant near the singularity, which is one of the chief points of that sentence and the preceding two. –Joke 20:20, 26 October 2006 (UTC)

• No, I'm not disputing the statements, so it's not a matter of verification. But like a curious reader, I go to the citations to find out more. If the statement tells me that "unknown theory of quantum gravity" is relevant, then I want to go the original source to find out what the author was trying to say about it, in more detail. Peebles is cited, so I want read what he has to say on quantum gravity. I can't find anything.
• Most of the examples in your proposed Wikipedia:Scientific citation guidelines include page numbers. I agree that they are not always necessary. But if you mention the "aldol reaction", I can find the exact page numbers where the books talk about the "aldol reaction".
• So where there is a reference to "reddening", I want to go the place in a book where "reddening" is detailed. Just as if I mention a concept you are unfamiliar, you'd want to find out exactly what the source said... a page number would help you get there. --Iantresman 21:03, 26 October 2006 (UTC)

- Ian asked me for my opinion on this topic on my Talk page, so here it is. I think the citations are lacking. "See Binney and Merrifeld (1998)" doesn't even tell me the title of the book, let alone the page number. I could just as easily say, "See Jones (2001)", and you would have absolutely no idea what I was refering to. After reading WP:CITE and the Scientific Citation Guidelines, they both show references like this: L. Hussein et al. (1999). "Nutritional quality and the presence of anti-nutritional factors in leaf protein concentrates (LPC)". International Journal of Food Sciences and Nutrition 50 (5): 333–343. or Wade, L. G. Organic Chemistry, 6th ed., Prentice Hall, Upper Saddle River, New Jersey, 2005; pp 1056-1066. ISBN 013187151

- While page numbers may not be absolutely necessary, the title of the book or article is. Footnotes 10 and 11 are good examples of acceptable citations in my mind. ABlake 20:27, 30 October 2006 (UTC)

While I agree that page numbers would be helpful for the book references in many cases, as noted above, the citation for the entire book is provided below the footnotes in the "references" section. This is, I admit, a slightly unusual mixture of citation styles but it seems to be accepted by the editors I've talked to about it. It has the advantage of seperating the references which are important sources that must be repeatedly cited throughout the entire article from sources of passing interest, cited for one statement (it also removes the need to repeat references in a redundant further reading section). –Joke 03:46, 31 October 2006 (UTC)

An example (meant to be so) is Wikipedia:Scientific_citation_guidelines.

I think that this article goes in the right direction. But the need for verification as in the footnotes (which may at some places refer to papers that are disqualified as general reference) is rather independent of the service of providing general references for further reading; in particular, there is no reason to call the general reference section "books", and IMO, mention of a book as general reference isn't an excuse for inaccurate referencing of debataed claims. However, the claim in consideration isn't debated, is it? Harald88 07:38, 31 October 2006 (UTC)

Yeah, I agree. When I was adding references to this article, I actually inserted a book reference (number 47) as a footnote. Perhaps "general references" or somesuch would be more appropriate than "book references". I'm doing something like that at cosmic inflation and intend to do so at cosmic microwave background when I get a chance. (Yes, I realize that it is incongruous that the general referencing I wrote for cosmic microwave background at the scientific citation guidelines is much better than that in the actual article.) I think it is usually helpful to provide page numbers for book references, even for claims that are not debated and particularly when things are not easily found in the TOC or index (as Ian pointed out above). –Joke 03:46, 1 November 2006 (UTC)

• I don't mind so much that the references are below the citations, although if you are not aware that this style is being used, you wouldn't think to look below the citations. It's bad enough having to moving to the bottom of an article to look for a footnote, let alone look for a footnote to the footnotes.
• While I agree that page number are not sometimes required for very general citations, the lack of a page number in a named book or paper, makes many of the citations in this article useless. As a reader, if the article talks about "reddening", I want the exactly page number in a book so that I can find out more. --Iantresman 09:33, 31 October 2006 (UTC)

I now see the books in the "Book References" section, but there is no intuitive link to the footnotes section. If I missed the connection, then a lot of others will too. I think there ought to be a line at the beginning of the Notes section that says, "Books cited in the Notes section are further referenced below in the Book References section." That would be clear up the confusion to my satisfaction. ABlake 11:08, 31 October 2006 (UTC)

As I mentioned above:

• The text says "It is believed that a yet unknown theory of quantum gravity would take over before the density becomes infinite"[51]
• The reference is Peebles (1993), Weinberg (1971), Misner, Thorne and Wheeler (1973).
• I can not find any reference to "quantum gravity" in Peeble's book, and the reader is not going to read through 700+ pages to try and find what your mean, nor read Weinberg, nor Misner, to find out more.

The citation is inadequate, as are all references to footnote [2] --Iantresman 12:29, 2 November 2006 (UTC) --Iantresman 12:29, 2 November 2006 (UTC)

I fixed it. If you want, I will add the pages for Weinberg and MTW tomorrow, but it is easy to find in the index. Is this not making a mountain out of a molehill? –Joke 21:39, 5 November 2006 (UTC)

Many thanks. I'm not criticizing for the sake of it. As a featured article, I think we need to provide top quality citations, and I think that means giving people an accurate reference. If I write something in one of the minority scientific articles, an exact reference is expected, to help the reader verify, clarify and find out more information if necessary. --Iantresman 23:13, 5 November 2006 (UTC)

Congratulations

Well done folks on a very clear, comprehensive and well-referenced article! Work pressures mean I've not contributed for some time, but I'm very happy to see the article in such a healthy state.

I won't wade in straight away with new edits; I'd first like to discuss with you two areas that I wonder if the article should cover, or cover differently.

Firstly, the article gives metrics for each of the redshift mechanisms. In fact, these are only examples; the Kerr metric also has gravitational redshift, for example. I like it that the article mentions coordinate transformations, which are a natural way of explaining the Doppler effect (SR or otherwise), but they are less natural for the other redshift mechanisms. Perhaps this could be expanded or rejigged somehow? The physical distinction between redshift from expansion of space and gravitational redshift is the non-constancy of spatial metric elements and temporal metric elements. I wonder if the article should note this distinction, and note in the table that the metrics are examples. Can we simultaneously satisfy both the expert reader and the novice?

Secondly, there are plans to measure the expansion of the Universe in real time, for example with CODEX on the European Extremely Large Telescope. The effect is tiny (dz/dt is about 10^{-10} per year) but if the systematics aren't a killer it could be a very interesting experiment. Perhaps this rates a mention.

Serjeant 12:40, 25 November 2006 (UTC)

We might resolve your first issue by putting a (for example) disclaimer in the table. You might also head on over to metric expansion of space where I had to explain the difference between the equivalence principle and the expansion of space.

The second issue also might be better discussed at the metric expansion of space page. Though it may deserve at least passing mention here.

--ScienceApologist 13:48, 4 December 2006 (UTC)

"The physical distinction between redshift from expansion of space and gravitational redshift is the non-constancy of spatial metric elements and temporal metric elements." This is very true -- Schwartzschild has a timelike Killing vector, so light bouncing back and forth in a station-keeping box won't redshift, while this is not true for the FRW (actually there are some incredibly subtle issues there that confuse my colleagues! -- although about half of those colleagues think I'm the one who's confused.) In any case, Serjeant, I think that this is a really subtle issue that is best not covered by the article -- it really would take a detailed discussion I think that would better belong in a textbook. Sdedeo (tips) 03:48, 29 December 2006 (UTC)

Using the Wolf Effect as an example in physical opitcs/radiative transfer

Since there are other ways to get frequency shifts in physical optics and radiative transfer, it is inappropriate to unduly weight the Wolf Effect. There is no chance that we will link to every alternative redshift mechanism in this section due to WP:NPOV#Undue weight, so I submit that we remove the reference to this singular effect. --ScienceApologist 13:20, 7 December 2006 (UTC)

Congratulations

I pretty much understood it - I think. I've actually seen red and green falling stars about 10 ten years ago. Did I get it? I hope so, because it was written in such clear, plain, language. Once again, thanks so much to all who worked on it (The picture is extra-pretty:) )NinaEliza 00:54, 29 December 2006 (UTC)

Unfortunately, the color of falling stars is likely due to the chemical composition and temperature of the meteor rather than this effect, but I'm glad you liked the article. --ScienceApologist 02:23, 29 December 2006 (UTC)

Congratulations

I'm mostly out of the wikiproject these days, but I'm a professional astronomer (a postdoc right now), and read through the article pretty carefully. It is very well done, and I doubt that Britannica could cover the subject a fraction as well as it is covered here. Not only are some of the usual fallacies avoided, but some important and clever editorial decisions are made (unifying the discussion under reference frame transformations) that really enlighten the subject. I would be more than happy to recommend this article to a student.

Congratulations to everyone who has worked on this article.

Sdedeo (tips) 03:42, 29 December 2006 (UTC)

majorish edit

I just made a somewhat large edit to the breakdown of linearity in the Hubble Law. The previous version we had was a little unfocused and a bit confusing, and I think what I put in is a better direction to take (i.e., focusing on the breakdown of the Hubble law). But people like dark energy, so like the last version I snuck it in anyway. The material about quantum cosmology is not relevant to the discussion, and I took that out as well. Sdedeo (tips) 18:32, 29 December 2006 (UTC)

Plasma Redshift and Tired Light

I think this page would be more complete if it mentioned some theories which challenge the conventional explanation for the observed cosmological redshift - and therefore which challenge the Big Bang Theory. The most prominent one is Ari Brynjolffson's January 2004 "Redshift of photons penetrating a hot plasma" (http://arxiv.org/abs/astro-ph/0401420). I have a partially developed theory, and a long discussion of the implications of any such plasma redshift mechanism (http://astroneu.com). For instance, a theory such as this might explain the heating and acceleration of the solar corona, which is not explained by the best conventional theories, which are based on magnetic waves, rather than the interaction of sunlight on sparse plasmas (http://astroneu.com/plasma-redshift-1/#Cranmer). Other theories include Paul Marmet's neutral hydrogen (and therefore not plasma-based) theory (http://www.newtonphysics.on.ca/HUBBLE/Hubble.html), Lyndon Ashmore's Tired Light theory (http://www.lyndonashmore.com) and Thomas Smid's theory (http://www.plasmaphysics.org.uk/research/redshift.htm) of light pulses being stretched by the electric fields between particles in low density plasmas. I don't understand Ari Brynjolfsson's theory enough to criticise it, and I don't support the other theories, but I think they are worth mentioning.

Alternatively these theories might be mentioned on the Tired Light page, with a more prominent link to that page from the Redshift page. Currently Tired Light is only mentioned via a footnote to the statement: "the consensus among astronomers is that the redshifts they observe are due to some combination of the three established forms of Doppler-like redshifts. Alternative hypotheses are not generally considered plausible." I am not sure if all the other theories would be classed as "tired light" by their authors, but my theory certainly is.

There have been long discussions about tired light in the past, such as in archive 7 of this page.

I think the current page is good in many ways. However, I think the term "cosmological redshift" should be applied to an observed relationship between redshift and apparent distance, rather than to a specific purported mechanism by which the redshift occurs: the theorised expansion of the Universe. This concern could be resolved by replacing "Cosmological redshift" with "Expansion of space" in the table, which would bring the left column into line with the headings which follow. The current redirection of "Cosmological_redshift" to "Hubble's Law" makes me think that the term does refer to an observational concept, rather than a specific mechanism.

I do not accept as a factual statement: "The difference between physical velocity and space expansion is clearly illustrated by the Expanding Rubber Sheet Universe,". Its not at all clear to me what the expansion of space is, if it is not simply things being blown apart - which means "physical velocity" to me. An encyclopedia article shouldn't assume that everyone understands or accepts as an absolute fact that the Universe is expanding or that electromagnetic radiation is quantized and so can be reliably treated as individual "photons". Robin Whittle 04:17, 29 December 2006 (UTC)

• Not a chance in hell. I have spent the last year trying to add information on alternative redshift theories, even generic descriptions such as "intrinsic redshift", "Non-cosmological redshift", and more specifically the "Wolf effect", "Tired light" and others.
• One individual, ScienceApologist has taken it upon himself to ASSUME that the only description of redshift, is that used by cosmologists.
• Despite Wiki policy allowing us to describe all significant views, these alternatives have been systematically removed for all manner of reasons, from absolute denial, to claiming little or no support.
• Worse, there is little will from editors to change this situation, where the mainstream view is ipso facto taken to be both the neutral point of view and the truth. --Iantresman 10:15, 29 December 2006 (UTC)

Just to be clear, I can not think of a single professional astronomer I have met working in the field (and I have met about a thousand) who thinks that the description of redshift as appears in this article is incorrect. Alternative explainations for redshift died out many years ago (the 1960s?) under the mountains of evidence accumulating from vastly different subfields of the science. We cover fringe theories in the relevant articles and speaking as someone in the field it seems that the "alternative" theories are given the proper weight -- i.e., referenced in passing but not treated as in any sense mainstream. Sdedeo (tips) 11:13, 29 December 2006 (UTC)

• You (Robin) will have a hard time establishing notability of a scientific theory that has not been published in a peer-reviewed journal (and even then it is not automatic).
• I agree that the Expanding Rubber Sheet Universe does not "clearly" illustrate anything. (See, however, the recent comment by Sdedeo.)
• In my opinion, the quantization of light is one of those things, like the roundness of the Earth, that is so well supported and so widely accepted, that it is editorially appropriate to refer to it as though it were a fact. In contexts where it might not be understood, of course, there should be a link, probably to Photon.

--Art Carlson 13:03, 29 December 2006 (UTC)

There is a difference, of course, between the quantization of light and the quantization of redshift. --ScienceApologist 13:06, 29 December 2006 (UTC)

In this article I feel it could be better explained that there are other 'fringe theories' out there. Either in the article or more clearly stated in Note 33 (or in the area where Note 33 is referenced). I don't know much about the subject matter but I think the 'fringe theories' are hidden a bit too much in the article. Strawberry Island 16:09, 29 December 2006 (UTC)

The 'fringe theories' are not notable enough for further inclusion in this article as reported by Sdedeo. --ScienceApologist 16:14, 29 December 2006 (UTC)

• Sdedeo, no-one is saying that the description of redshift in this article is incorrect. And no-one is saying that alternative redshift theories are correct either. You are wrong about the alternative redshift theories, as is evidence from the peer reviewed papers that continue to appear on the subject. How many peer reviewed papers do you want? Five? Ten? {http://adsabs.harvard.edu/cgi-bin/nph-abs_connect?db_key=AST&db_key=PHY&db_key=PRE&qform=AST&sim_query=YES&ned_query=YES&aut_logic=OR&obj_logic=OR&author=&object=&start_mon=&start_year=&end_mon=&end_year=&ttl_logic=OR&title=&txt_logic=OR&text=%22intrinsic+redshift%22&nr_to_return=100&start_nr=1&jou_pick=NO&ref_stems=&data_and=ALL&group_and=ALL&start_entry_day=&start_entry_mon=&start_entry_year=&end_entry_day=&end_entry_mon=&end_entry_year=&min_score=&sort=SCORE&data_type=SHORT&aut_syn=YES&ttl_syn=YES&txt_syn=YES&aut_wt=1.0&obj_wt=1.0&ttl_wt=0.3&txt_wt=3.0&aut_wgt=YES&obj_wgt=YES&ttl_wgt=YES&txt_wgt=YES&ttl_sco=YES&txt_sco=YES&version=1}
• That you consider "astronomers" to be the sole arbiters of redshift is highly selective and biased.
• For example, the Wolf effect is described as a redshift in the literature (peer reviewed), by the experts in the field, and textbooks on the subject. I am not aware of any reliable sources that dispute this. --Iantresman 18:31, 29 December 2006 (UTC)

Sorry, I should be clear. The vast, utterly overwhelming consensus on cosmological redshifts is what is currently described in the article. Astronomers, being the professional group that studies these cosmological redshifts, are surely the arbiters of this question and the relevant community to define what is and is not fringe. Meanwhile, the existence of peer-reviewed papers disputing this is really insufficient to challenge that. The Wolf effect is, by vast community consensus in place for many decades, not the cause of cosmological redshifts. You will not find any recent textbook on cosmology or astrophysics from a reputable publishing house that disputes this. Sdedeo (tips) 18:41, 29 December 2006 (UTC)

• Absolutely. But this is not an article solely about "cosmological redshifts". It's an article about "redshift" in general, as indicated by the title, and the introductory paragraph. I have no problem with a separate article called "Cosmological redshift", and even Doppler redshift, just as there is already an article called Gravitational redshift.
• But to suggest that there are only three types of redshift, and no other alternative theories, is demonstrably and verifiably false.
• No-one is suggesting that the Wolf effect is a cause of Cosmological redshift. Reliable sources, the experts, and textbooks describe it as a "redshift" (or new redshift mechanism). A small number of people have also suggested it as a contributing non-cosmological redshift, but not as an alternative to the cosmological redshift. --Iantresman 19:19, 29 December 2006 (UTC)

I see what you are saying. My feeling is that this article should not become a grab bag for every single mechanism that changes the frequency of a photon, and I've added a paragraph to the introduction that I think solves the problem you describe. Sdedeo (tips) 19:55, 29 December 2006 (UTC)

• That's perfect, it makes the acknowledgment, is verifiable, accurate and allows the reader to find out more. --Iantresman 20:38, 29 December 2006 (UTC)
• Is it worth mentioning "Intrinsic redshift" an article which describes some of these theories in more detail? --Iantresman 20:41, 29 December 2006 (UTC)

I see that the mention of the Wolf effect lasted less than 24 hours, being excised by ScienceApologist claiming "more general" usage, when it does no such thing. The text now implies some other mechanisms which may only be described as a redshift, whereas the Wolf effect actually produces a redshift, and other theories might too. Nothing like giving the reader misleading information. Once again, ScienceApologist is the only person on the planet that disputes the Wolf effect as a new redshift mechanism. --Iantresman 16:58, 30 December 2006 (UTC)

I find it hard to see the changes, amidst all the vandalism reversion, which I guess results from the article being featured on Wikipedia's main page for a day.

The theories I mentioned do not pass the notability test, but does that guideline apply to what can be mentioned in an article? My impression of the http://en.wikipedia.org/wiki/WP:NOTE guideline is that it controls whether there should be an article on a topic, with the notability test being applied to the topic.

I am not suggesting that alternative theories be accorded any greater status than that they are not accepted as valid by the mainstream cosmologists. I just think that it would be good to have a list of them at the bottom of the article. While I do not support Halton Arp's theories at all, I think the list should link to Intrinsic Redshift and Redshift Quantization.

The entire edifice of the Big Bang Theory, which is the most prominent alternative to multiple religiously based views of creation, rests on the mechanisms responsible for the observed cosmological redshift. Religion/cosmology is probably the oldest and most over-arching human activity. I think the redshift debate is really important - though most people think everything has been settled.

The fact that mainstream researchers don't recognise problems in the current paradigm does not guarantee that the paradigm will survive. For instance: http://en.wikipedia.org/wiki/Continental_drift#Debate .

Is this Redshift article about the conventional understanding of redshift mechanisms or about the current state of scientific debate about redshift mechanisms? I don't think the matter is settled enough to forget that this is a debate.

A reader wanting conventional 'facts' to solve a problem - such as their homework assignment - wouldn't be interested in unconventional theories, but adding a short section on unconventional theories at the bottom of the page wouldn't cause them any bother.

Maybe the main redshift article should contain a link to a second article "Redshift Debate", where non-conventional theories and the history of the debate are covered. In such a page, the fact that theories are non-conventional and perhaps not written up in peer-reviewed journals would not be a problem. Non-standard Cosmologies is a relevant article, but I think there are enough non-conventional redshift theories to make a good article.

Regarding 'photon' and quantization of electromagnetic radiation: I assume both mean that emr is ejected as a discrete packet from one piece of matter and that this entire packet is absorbed by another piece of matter. The idea that two photons can interfere is not compatible with my understanding of the emr itself being quantized.

The Photon article currently mentions nothing about interference between two different photons. My impression is that the original Dirac theory has been modified to account for interference, such as between two lasers or radio transmitters - but I don't see how that is compatible with quantization of emr itself, which to me is different from quantization of emr's interaction with matter. I can't explain why the apparently diffuse field results in what we observe as discrete, intense, energy deposition - but lack of a full explanation doesn't mean that I think interference between two separate sources disproves the hypothesis of actual quantization of emr.

Thanks ScienceApologist for changing "a photon" to "electromagnetic radiation". Robin Whittle 05:21, 30 December 2006 (UTC)

I don't wish to start a debate on quantization of emr here - I just wanted to explain why I don't accept it. The Photon article lists some references (note 28) for experiments which supposedly demonstrate that it is quantized. I am reading the Thorn et al. paper http://people.whitman.edu/~beckmk/QM/grangier/Thorn_ajp.pdf which seems to contain a good review of this field and some other papers on interference between two photons. These include papers citing Phleegor and Mandel 1967. I can send these to anyone who is interested. Robin Whittle 10:18, 30 December 2006 (UTC)

Of course less notability is required to mention something in a minor article than to mention it in a major article or to give it its own article. In this case, we could consider mentioning the alternative theories in a footnote. I'm thinking of the case that I come here with the idea of taking a look at all the far-fetched redshift theories, just in case there is some gold among the dross. Or maybe I'm only interested in the sociology of fringe theories and want to look into what kind of people so enjoy swimming against the tide. On the other hand, including a link to an external site, even in a footnote, suggests that that site has some educational value. We have not yet established that for these sites, and doing so is probably beyond our mandate. If no one has published their opinion of the theory, not even the anonymous referee of a journal, then we can only report our own opinion, but that is indistinguishable from original research. If we include a list of theories without evaluating them, then we have no rationale not to include a link to every crackpot theory an individual puts on his web site. On the whole, I think it is a better decision to stick to half-way notable theories, even within a footnote.

The fundamental problem is that I see no evidence that the "scientific debate" you talk about actually exists. If the debate takes place completely outside of professional journals, then it is not a scientific debate. I can not see any significant debate in politics or the popular press either.

P.S. It seems to me that your skepticism of the quantization of radiation results from a misunderstanding. Two photons cannot interfere with each other unless they are coherent, but then they are (in some sense at least) one and the same photon. But you are right, this is not the place to debate it, and that fact that you have some questions does not change the fact that photons are so widely accepted that Wikipedia should talk about them in the indicative mood.

--Art Carlson 17:15, 30 December 2006 (UTC)

Please see new section below: "List or separate article for unconventional theories?". I am discussing about emr quantization on the photon talk page. Robin Whittle 12:38, 1 January 2007 (UTC)

List or separate article for unconventional theories?

(Continuing from "Plasma Redshift and Tired Light".) Art, I don't think it is fair to characterise all proponents of non-conventional redshift theories as "people who enjoy swimming against the tide". You are entitled to think such people are misguided, but some such folk are genuinely trying to explain something which they think is wrongly understood at present.

I think I understand the concern about slippery slopes and science articles being loaded down with references to theories which are so vague or ridiculous that they are never going to advance scientific understanding. Likewise I think I understand the desire to only mention scientific work which has appeared in peer reviewed journals.

Here are some concerns I have with the peer review system and some arguments about why at least some unconventional theories should be listed, either in a section at the end, or in a separate page such as "Redshift_ unconventional_theories" which is not so restricted by the goal of protecting the reader from the work of people who choose to communicate directly, rather than via peer-reviewed journals.

I think incomplete theories can make an important contribution to science - as a stepping stone to something better, once some other people work with the good bits and add their own improvements. It is my impression that such theories are unlikely to pass peer review and be published.

Suppose for a moment that the Universe is not expanding and that most of the cosmological redshift is due to interaction with the intergalactic medium, by a mechanism which is currently not recognised - due to the mechanism being inconceivable (that is, it looks impossible and therefore unscientific) within the photon paradigm of electromagnetic radiation. If so, it is vital that new theories, including incomplete ones, be discussed. I think that a WP article can safely point to non-conventional theories, and so enable the reader to look at the scientific process, with all its messiness, in progress. The current narrow focus of this and other articles where extensive deletions have been challenged by people such as Iantresman seems to result from the view that the current paradigm is beyond question, and that the interests of readers could not possibly be served by mentioning theories which are outside this paradigm. (The trouble with paradigms is no-one can see what their own paradigm really is. Only someone with very different ideas can see the limitations of someone else's paradigm.)

I think a paper which suggests this - challenging the current paradigm of cosmology and probably quantum mechanics - is going to have a much harder passage through peer review than a conventional paper devoted to a smaller and more conventional topic.

I understand that Ari Brynjolfsson's paper http://arxiv.org/abs/astro-ph/0401420 languished in peer review for an unreasonably long time before being rejected without satisfactory explanation. Although I don't understand the math sufficiently to evaluate this paper, it seems to be a theory which is perfectly amenable to scientific discussion. It is carefully written, coherent, not too vague, makes definite predictions, and is - as far as I know - based on conventional mathematics and established principles. It may turn out to be completely wrong, but it is not the purpose of peer review to prevent publication of theories which the reviewer considers merely wrong. I think that Ari Brynjolfsson's theory is scientifically testable, and that if the peer review system was working properly, his paper would have appeared in a peer reviewed journal well before 2004.

I don't have enough faith in peer review to feel that we are doing readers a service by excluding mention of every single non-peer reviewed theory. Having a set of links to unconventional theories shouldn't detract from the value of the article, or give the impression those theories are as accepted as the mainstream theories. However, if the list became very long, it could be a drag and cause for the creation of a separate page.

By ignoring the unconventional, textbooks and encyclopedias (which are relied upon by most non-specialists and establish new entrants' conceptual framework) lock in the prevailing paradigm and make most people think that the field is settled and beyond question. This stifles the critical and imaginative thinking which is required for further scientific progress. Of course, not all textbooks and encyclopedias do this, but there is a tendency towards brevity at the expense of a richer exposition of doubts and controversies.

The question of redshift mechanisms in plasma is absolutely crucial to astronomy, cosmology and therefore a great deal of science and philosophy. Since there is no satisfactory conventional explanation (http://astroneu.com/plasma-redshift-1/#Cranmer) for how the sun deposits 1/10000 of its output in the the corona and solar wind, I don't think that conventional theories regarding light and plasma should be regarded as being beyond question.

To not mention any scientific theory which is outside the peer review system tends to restrict WP to portraying the prevailing paradigm - and tending to imply, without formally acknowledging so, that the current paradigm is not worth questioning, and that no-one is questioning it.

Such an approach tends to present WP's science content as "reliable facts, or the best conventional theories can get to them". This ignores the fact that science is an imperfect, human, activity. Anyone interested in how scientists actually work - including wannabe scientists and scientists who have chosen to publish directly in arxiv.org, rather than via peer reviewed journals - would be badly served by such an approach.

An external site doesn't have to contain only peer-reviewed work to be of "educational value". I think that at least some work outside peer-reviewed journals has educational value to at least some readers. Firstly it is of interest to anyone studying the broader topic of people struggling to contribute to science. Secondly there may well be some lasting scientific gold amongst the half-baked or seemingly crazy theories. Thirdly, it enables people to compare sites which they may well decide are loony and genuinely unscientific with sites and papers they (and the prevailing editors) think are of high scientific value.

Broadly speaking, in a user-maintained encyclopedia which involves no physical cost constrains (except due to printer ink and paper to those who chose to print the entire article), I think we can be more helpful to readers by at least including links to theories which are clearly challenging the mainstream paradigms, as long as we indicate this is their status, and don't try to pretend they are any more widely than they are.

So, prevailing editors (ScienceApologist et al.), if you can't handle the idea of a list of links to non-conventional theories on this page, then would you please accept a link at the bottom to a page such as "Redshift_ unconventional_theories" AND not interfere with that page? I am sure Iantresman and like-minded individuals would start such a page with a link to the conventional page with a note that the new page discusses and links to theories which fall outside the framework adopted by editors of the conventional page. Robin Whittle 12:38, 1 January 2007 (UTC)

All editors are welcome to edit all articles of Wikipedia. No article can ever be declared off-limits (see WP:OWN). An article with such a title and suggested content would be deleted per Wikipedia's original research policy and it is also a POV fork which is an editting tactic that is specifically forbidden. So, unfortunately you're stuck editting here, at redshift quantization or at intrinsic redshift. And no, I will not restrict my editting. --ScienceApologist 13:56, 1 January 2007 (UTC)

Dear Robin, I appreciate the care you are taking to explain your point of view (and especially the civil tone), but I think you are missing the kernel of my reservations. How are we, as encyclopedia editors, to decide which theories are worth linking to and which are such garbage that it would be a disservice to our readers to give them any free press? The bar of peer review is really quite low, and any scientist can tell you that a lot of garbage gets past it. All you have to do is find one referee of one journal that is willing to say that your ideas are not obviously flawed and might be interesting to other scientists in one way or another. If a theory has not passed this minimal test, how are we as editors to decide it merits exposure without doing any original research? We have no basis within the policies of Wikipedia to decide that the peer review process for Ari Brynjolfsson's paper was "unreasonably" long, or that the reasons for rejection (which are not a matter of public record anyway) were not "satisfactory". Such objections to including non-notable theories remain regardless of the form in which we present them. I don't think the peer review system is as bad as you do, but it doesn't really matter. We are not here to right the wrongs of the world, just to present the current state of collective knowledge. --Art Carlson 20:50, 1 January 2007 (UTC)

I apologise for suggesting something which violates http://en.wikipedia.org/wiki/WP:OWN. I suggested it because I think it makes sense in the context of a discussion list where it is desired to let two or more individuals or groups discuss something in their own way, without interference from people who have contrary purposes or fundamental beliefs.

Persistent problems can arise from Wikipedia's attempt to get a loose and changing group of self-selected individuals to create and maintain a single article which aims to resembles that which might be created by a single, paid, carefully chosen, leading authority. One approach is to create another system with different policies, such as Wikinfo.org - which "provides a seamless platform for the meshing of encyclopaedic material, original work, creative work and public domain material to further both education and information."

I think the central issues on this Redshift page - and on potentially tens or hundreds of thousands of other pages - are:

1 - WP insistence on peer-reviewed material as the only criteria for notability in science articles.

2 - Whether this notability requirement must be applied to everything which is mentioned in the article, including non-peer-reviewed critiques or alternative perspectives - and if so, whether such mentions should be in the main body of the article, or only in footnotes.

Thanks ScienceApologist for pointing out your view that my suggestion runs foul of http://en.wikipedia.org/wiki/WP:POVFORK - although you state your view as if it was a fact.

However it could be argued that what I am suggesting is an article not so much on "redshift" (according to the limits imposed by WP guidelines), but on redshift theories which are outside the mainstream and due to their lack of publication within the peer review system are not considered as worthy of mention as "science" within WP.

I know this sounds dodgy, but your response raises some important questions about the scope of "science" as you see it, and the scope of articles and elements of articles which you believe you can, and should, delete or edit in ways which are contrary to the wishes of those whose material you alter. For instance, is an article on philosophy of science a "scientific" article for the purpose of applying WP guidelines? I don't think of philosophy as science.

I consider the WP policies on "science" and the way you and others interpret them to be important matters of philosophy of science. If I were to write a philosophical essay on this subject, would there be any objection to it being linked to from a "philosophy of science" WP article?

Writing essays on your own personal opinions are not allowed in Wikipedia per original research limitations. --ScienceApologist 00:43, 2 January 2007 (UTC)

Similarly, discussions on these talk pages can mention all sorts of things which are not peer-reviewed. WP presents the "Discussion" tab ready for anyone to click, but would you consider it to be against WP guidelines to include, within the body of an article (perhaps within a footnote) a specific reference to the talk page (and perhaps a particular date or link to a relevant discussion) for the benefit of readers who are interested in disputes about what theories are excluded from being even mentioned the main article?

Readers may be interested in a lot of things. However, it is not our job as editors to provide them with their hearts' desires, it is our job to write a verifiable and reliable encyclopedia. --ScienceApologist 00:43, 2 January 2007 (UTC)

If a "non-scientific" article discusses or links to a theory, essay, external resource etc. which is somehow deemed to be "scientific" for the purposes of applying WP guidelines, would you argue that all such discussions or links be deleted if the material it refers to has not been peer-reviewed?

Talk pages have considerably more leeway for discussing articles. Articles themselves need to contain information that conforms to verifiability and reliability. --ScienceApologist 00:43, 2 January 2007 (UTC)

Regarding creating two articles to cope with differing points of view, WP:POVFORK states, in part:

There is no consensus whether a "Criticism of .... " article is always a POV fork. At least the "Criticism of ... " article should contain rebuttals if available, and the original article should contain a summary of the "Criticism of ... " article.

If I amended my proposal to include the following, would you consider that it might be admissible under http://en.wikipedia.org/wiki/WP:POVFORK?

1 - The new article be titled "Criticism of conventional Redshift theories". (Though I think "Redshift_ unconventional_theories" is preferable, the longer title would be better if it clearly identifies the new article within WP as a particular form of article.)

2 - The new article should contain rebuttals, or links to rebuttals within WP and without, including to peer-reviewed and non-peer-reviewed sources and to WP articles which do not necessarily concern "science").

3 - That the original "Redshift" article should contain a summary of the new page, in a separately titled section before the references and footnotes, such as "Some of the theories mentioned in this article have been the subject of criticism from sources which fall outside WP guidelines for inclusion in scientific articles such as these. These are discussed in "Criticism of conventional Redshift theories". (I think that is enough of a summary of the new article. It would be impractical to summarise the criticisms themselves.)

I would still object on the grounds I outlined above. --ScienceApologist 00:43, 2 January 2007 (UTC)

Thanks, Art, for your constructive response. The current state of collective knowledge includes some material which exists outside (non-self-published) books and peer-reviewed journals. For instance some people choose to use arxiv.org, to use websites (which can be instantly updated, contain hyperlinks and have many pages) and to contribute via conference proceedings.

For instance a Zero Point Energy FAQ http://van.physics.uiuc.edu/qa/listing.php?id=1256 is currently an external link from http://en.wikipedia.org/wiki/Zero-point_energy . Ned Wright's web pages are cited in footnotes and links in various WP pages, including Tired_light.

I can imagine that a researcher who believes their research was delayed from being made public for a long time, after submitting it to the peer review system, only to have it rejected, would not want to try putting that paper or probably others through another such attempt.

I am well aware that a lot of important scientific communication occurs before the stage of peer-reviewed articles, starting with shooting the breeze at the Monday afternoon tea in the physics department. This does not change the fact that professional scientists publish peer-reviewed articles as soon as an idea has been sufficiently developed to make that possible. Before that, the chatter and fermentation is not notable in the sense of an encyclopedia. -- You have written a lot in this discussion, but you still haven't said what criteria you propose as an alternative to the imperfect tool of peer-review in order to separate the grain from the chaff. --Art Carlson 11:09, 2 January 2007 (UTC)

Perhaps the best place to continue this discussion is http://en.wikipedia.org/wiki/Wikipedia_talk:Fringe_theories, http://en.wikipedia.org/wiki/WP:SCIENCE, http://en.wikipedia.org/wiki/Wikipedia_talk:Notability_(science) where potential guidelines are currently being formulated by some participants in this discussion. Robin Whittle 00:34, 2 January 2007 (UTC)

Yes, WP:SCI and WP:FRINGE are good places to discuss what kinds of sources and material should be in Wikipedia. --ScienceApologist 00:43, 2 January 2007 (UTC)

Oops - I see Ned Wright's pages may be acceptable in http://en.wikipedia.org/wiki/WP:RS because he is writing in a field where his work has been published in peer-reviewed journals. Still, it would have been more professional if he http://www.astro.ucla.edu/~wright/lerner_errors.html and Eric Lerner http://www.bigbangneverhappened.org/wrightreply.html linked to each other's sites.Robin Whittle 00:59, 2 January 2007 (UTC)

ScienceApologist, I wasn't suggesting placing my own essay on WP. I will rephrase my question: In a philosophy of science article, would you delete a discussion of, or a link to, something which you thought was not scientifically notable, due to your view that either the article itself was "scientific" or that the section of the article which linked to or discussed the external resource was "scientific"?

Opinions on reliability of an encyclopedia vary, but I would consider an article which gave even a brief mention of critiques of itself, or of the policies and paradigms within which it was created, to be more reliable. This is a broad principle which applies to science and other fields. A reliable source shouldn't be so short of space or written with an overly obsessive aim of saving readers the bother of reading even a few lines regarding alternative perspectives.

Would you delete a reference at the end of main article to its talk page regarding disputes over the contents of the article ? This is a simple and commonplace mechanism to alert interested readers to the complexities and compromises which were involved in creating the article they are reading. I have placed a 3 line test case in the article:

Non-conventional theories - Some theories which challenge the mainstream understanding and which do not meet Wikipedia scientific notability are mentioned in this article's Discussion page. (See link at top of page.)

You indicate you would object to, or delete, an article of the form "Criticism of . . ." despite it sometimes being acceptable under WP guidelines. You give no reason why this approach is allowable in some cased, but not to science articles. I suggest that this and the question of links to the discussion page regarding non-conventional theories be discussed at: WP:SCIENCE and WP:FRINGE.

—Preceding unsigned comment added by Robin Whittle (talk • contribs) 02:20, 2 January 2007

Talk page link inappropriate and already removed (before I got to it). Vsmith 02:50, 2 January 2007 (UTC)

I often see links to the talk page when there is a Disputed_statement banner at the start of the article. I have been unable to find rules or guidelines governing link from the main article to its talk page or to any other talk page. Can someone point me to them? Robin Whittle 03:44, 3 January 2007 (UTC)

Wikipedia:Avoid self-references#Examples of self-references states that a possible exception to the rule against self-reference is "Use of templates in the article namespace that self-reference because they link to articles in the user, talk, or Wikipedia namespace or that are special articles", which presumably covers the banner Robin Whittle refers to. Notice the quote implies that "link to articles in the ... talk ... namespace" would otherwise be a prohibited self-reference. Also, the rest of that article opposes self-reference regardless of whether a wikilink is involved. In addition to this legalism, I'm unaware of any page that links or mentions its talk page, except through a template. Art LaPella 04:19, 3 January 2007 (UTC)

Thank, Art. I apologise for making this self-reference to the talk page. Robin Whittle 02:17, 6 January 2007 (UTC)

Hello everyone. I'm dipping back into this article talk page for a bit. I would like to congratulate the very vigilant professional scientists who have had a hand in the editing of this article, which is super. The following comment from a non-scientist drew my attention:

To not mention any scientific theory which is outside the peer review system tends to restrict WP to portraying the prevailing paradigm - and tending to imply, without formally acknowledging so, that the current paradigm is not worth questioning, and that no-one is questioning it.

This seems to be the nub of the discussion above, and it's the view of a reasonable and open-minded lay person. However, to me this seems to mis-understand what science is. Scientists (and I speak as one) are whores for ideas. If a new idea is supported by evidence, professionals leap over themselves to claim to have been among the first to appreciate this (witness the cosmological constant bandwagon, which I'm also on). There are a few examples of new great ideas in science being slow to catch on, but there are many, many more examples that don't catch on because they're not very good. Because of this, it's important for encyclopaedia articles on scientific topics to accurately and honestly represent the consensus view. Inevitably there is the risk that good ideas are not presented, but the place for presenting such ideas is in the scientific literature, whether their merits can be tested, not in a public encyclopaedia in which the general reader expects reliable, well-tested information. Software companies don't willingly release buggy software, and encyclopaedias shouldn't release ill-tested information. ScienceApologist, and others, are quite correct in taking every step to do this. Incidentally, there has already been extensive debate on the archived talk pages about various non-consensus, fringe positions. Best wishes,Serjeant 22:23, 19 March 2007 (UTC)

Red shift in one direction = blue shift in opposite direction and vice versa?

If there's a red shift in one direction, does this mean that there will ALWAYS be a blue shift in the opposite direction, and vice versa? JustN5:12 22:13, 23 March 2007 (UTC)

Poorly phrased question. If there is a redshift for an object and it is moving 90 degrees to the line of sight, there will also be a redshift for an object if it is moving 270 degrees to the line of sight (opposite direction). If there is a redshift for an object that is moving 0 degrees to the line of sight, there will be a blueshift for an object moving 180 degrees to the line of sight. --ScienceApologist 23:57, 23 March 2007 (UTC)

Relative Doppler Effect question

Why doesn't the relativistic doppler effect say that, while we see many galaxies moving at high C-ratio speeds relative to us, we do not know what direction they are moving in? That is, if a galaxy is moving at .7C relative to ours, it will show Lorentz contraction, time dilation, and a redshift no matter what the direction. What convinced us that everything moving fast relative to us is moving away? Thanks.

Bruce Wallman Brucewallman 18:13, 1 October 2007 (UTC)

The Hubble law is works out to very far distances and is not due to the doppler effect, per se. The evidence is tied together with our current understanding of physical cosmology. ScienceApologist 18:30, 2 October 2007 (UTC)

Junk Science?

My youth preacher was telling me that this, along with evolution and all the science of origins and what not is junk science. I can go to the evolution page and at least see some mention of this controversy (though it's hardly a fair representation of both sides) but there's not even a mention of the possibility that this isn't true. Why aren't both sides presented? —Preceding unsigned comment added by 74.227.196.57 (talk) 21:47, 22 October 2007 (UTC)

Just calling the consensus view of redshift "junk science" doesn't give me a lot to go on. Did your preacher have any concrete criticisms of the view presented in the article? I think you should keep in mind that this view was developed over decades by hundreds of people devoting their careers to it, and based on a lot of very sophisticated measurements. It is not easy for an outsider to even understand the state of the art, much less debunk it. How many years has your preacher spent studying physics and astronomy? But getting back to the article, even if the view of redshift presented there really is "junk science", we can only put things into the article that are based on reliable sources, and the weight given to any point of view must be in proportion to the prominence of that point of view. Can you give us a source calling the consensus view of redshift "junk science" or challenging it with scientific arguments? Is this source reliable for the information it provides, and does it represent a significant viewpoint within the scientific community or society at large? These are the ground rules we have tried to follow in writing this article. You are welcome to contribute and correct us where we may be wrong, but be aware that you will have to follow the same rules. --Art Carlson 07:53, 23 October 2007 (UTC) (P.S. I am willing to get into the details of the science with you, if you are interested, but this page is is not really the right place to do that. It would be better if you emailed me using this link.)

Dude quit wasting your time on wikipedia. You can't even tell when people are being facetious anymore. —Preceding unsigned comment added by 74.227.196.57 (talk) 16:53, 24 October 2007 (UTC)