Talk:Redshift: Difference between revisions

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Old talk: from Red Shift, up to April, 2004, up to August 2005 ---

Come on guys, I've re-instated the Woolf Effect. The article is about causes of redshift. The Wolf Effect is real, Wolf's paper has been peer reviewed, and the mechanism confirmed in the laboratory. To remove it based on the person who included it, or to suggest that a fact based on a reference to a valid peer reviewed article is "nonscientific meanderings", does surprise me. Surely standard cosmology is not that insecure? --Iantresman 00:03, 7 September 2005 (UTC)[reply]

I've re-instated the Wolf Effect again. Joshuaschroeder mentions that he "removed effect that is not like other redshifts". But the page is about DIFFERENT mechanisms for producing redshift, so yes, it is different. You could have removed the item "3. Gravitational effects" for exactly the same reason. --Iantresman 14:38, 7 September 2005 (UTC)[reply]

Sorry, Ian, but you've missed the point on this one. A redshift is defined at the top of the page. This effect does not result in the same shift of spectrum but also results in distortion. One could also include Compton scattering as a way to change light's frequency, but that's not a redshift. Likewise this effect whether it is true or not does not admit redshifts as defined in the article. Joshuaschroeder 19:09, 7 September 2005 (UTC)[reply]

I've double double checked this, you are correct that the Wolf Effect may result in distortion. But if you check the paper Correlation-induced spectral changes by Emil Wolf and Daniel F V James, they mention that "under certain circumstances the changes in the spectrum of light scattered on random media may imitate the Doppler effect", that is without distortion.

That's also beside the point. In "certain" circumstances (read "special" there or "contrived") you can get Compton Scattering to mimic the Doppler Effect. And if you allined all your scatterings in the same way you could do it without distortion too. That's not a reason for including the Compton Effect as a cause of redshift. It isn't. A cause of redshift has to be free of these extra conditions. We aren't in the business here of explaining all the ways one can distort light's frequency. A redshift is very strictly defined. Joshuaschroeder 20:30, 7 September 2005 (UTC)[reply]

I also contact Emil Wolf himself, and he email back to say that "it is virtually impossible to distinguish between the cosmological redshift and a noncosmological one because shifts in the spectral lines can be the same in both cases. However, there are quite a few laboratory experiments which show the correctness of my prediction".

Fine. He predicts that you can under "certain" circumstances imitate a Doppler Effect. That's not a redshift: that's an imitation of a redshift. I might be able to build a machine that could mimic the Doppler Effect, but that would not be a redshift, it would be an imitation of a redshift. Joshuaschroeder 20:30, 7 September 2005 (UTC)[reply]

In other words, any Doppler redshift may contain an intrinsic Wolf Effect redshift, and there is currently no way to dinstinguish between the two. More information on request via email --Iantresman 20:16, 7 September 2005 (UTC)[reply]

"Any" Doppler redshift may contain some manufactured photons that were created by a God who stole energy from them en-route too. That's beyond the scope of this article. The effect is correctly removed. Joshuaschroeder 20:30, 7 September 2005 (UTC)[reply]

I've re-instated the Wolf Effect again. It is a valid mechanism for generating redshift. Period. That you have decided that this is a page on a "certain version of redshift" is not implicit in the generic title "redshift". If you feel that the text requires further qualification, then feel free to explain that further on on the article.

If the Compton Effect can also generate a redshift then I shall do some more research, and include it too. This is an inclusive page, not an exclusive one.

For the benefit of others who may not see the text that you consider contentious, I have included it below:

--Iantresman 21:31, 7 September 2005 (UTC)[reply]

I tried to compromise by creating a page for the Wolf Effect. I have to say that I basically agree – probably to no-one's suprise – with Joshuaschroeder here. To be a genuine redshift, the frequency must be multiplied by z+1 for all wavelengths. In the case of the Wolf effect, that is certainly not true for arbitrarily short (hard) wavelengths or arbitrarily long ones: it could only hold for a band. That being said, of course it is a priori possible that the Wolf effect could be confused for a Doppler shift in quasars. –Joke137 02:00, 8 September 2005 (UTC)[reply]

(Nit: I think you meant Wikipedia:Neutral point of view) Art LaPella 05:34, 14 September 2005 (UTC). Thanks, corrected. --Iantresman 09:10, 14 September 2005 (UTC)[reply]

1. Redshift that shifts all frequencies is a special kind of redshift, so this page appears to EXCLUDE other kinds of redshift.

This is a matter of definition. I disagree. –Joke137 03:38, 14 September 2005 (UTC)[reply]

Exactly, Redshift is the generic term and consequently has an ambiguous defiinition depending on who is using the term. Specific types of redshift are qualified as Doppler redshift, as graviational redshift, and as cosmological redshift, etc. It does surprise me that some of these terms were removed from the article, making it even more confusing for someone trying to find out what these types of redshift mean. --Iantresman 09:10, 14 September 2005 (UTC)[reply]

2. If the Wolf Effect is a special kinds of redshift that deserves its own page, then so does Doppler redshift, Cosmological redshift, and Gravitational redshift.

I would agree with that, except that these three phenomena are all connected by the principle of relativity: they are all the same effect in general relativity, or at least related closely enough that it is impossible to practically distinguish between them. –Joke137 03:38, 14 September 2005 (UTC)[reply]

They certainly deserve their own pages. Sorry to be picky, but the astronomical context sometimes gives some clues on how to distinguish them; this however is not meant to imply support for including the Wolf Effect. Serjeant 14:35, 8 November 2005 (UTC)[reply]

3. The Wolf Effect will also produce a full-spectrum redshift, with no characteristic signature, that is IDENTICAL to a Doppler redshift.

No, it can't. See my comments above. –Joke137 03:38, 14 September 2005 (UTC)[reply]

See the paper "Correlation-induced spectral changes" by Emil Wolf and Daniel F V James, in Rep. Prog. Phys. 59 (1996) 771–818, where they write: "Suppose now that the anisotropy in the correlation function g(R; T) is strong in one particular direction [..] This expression shows that the relative frequency shift is independent of the central frequency [omega]_0 of the incident light and thus imitates the Doppler effect.". In other words the Wolf Effect may produce a redshift that is IDENTICAL to the Doppler redshift.

4. As it stands, this page is biased against any redshift mechanism that does not support Big Bang cosmology. Some of this information appears to have been censored:

--Iantresman 13:45, 12 September 2005 (UTC)[reply]

It's best not to cry conspiracy. The reason that you want to include alternative explanations for redshifting is because you, Ian, want to see one be correct. It's an agenda called POV-pushing here at Wikipedia and it is not allowed. To be honest about redshifts we need to include honest reporting. There are no ways to use the alternative mechanisms as diagnostics in astronomy or physics. When and if such a thing were to occur, we would certainly include it in the article. Joshuaschroeder 13:43, 14 September 2005 (UTC)[reply]

1. This is not a page about certain redshift mechanisms that can be used as diagnostics in astronomy or physics. This is a page about redshift. That's what the titles says. Some redshift mechanisms can be used for one purpose, others for another. It is important to mention this. To exclude some redshift mechanism because they do not fit your idea of usefulness is also POV-ing.

2. I found "compton scattering" mention in over 1600 articles in the Astrophysics Data System (ADS), over 4000 articles if you include Physics and arXiv e-prints.

3. Your removal of the terms "Doppler Redshift", "Gravitational redshift", "Intrinsic redshift" and "Cosmological redshift" means that people searching for these terms will no longer find this page.

4. The Wolf Effect WILL produce a redshift that is IDENTICAL to a Doppler redshift. See my reference above.

5. The CREIL effect WILL also produce a redshift, though it has a characteristic spectrum, characteristic of a Quasar.

6. The article should be INCLUSIVE with qualifications if necessary, rather than EXCLUSIVE and censoring.

--Iantresman 16:11, 14 September 2005 (UTC)[reply]

I've returned to this article after an absence of a few months and re-read it. My goodness, you folks have been busy! Perhaps unsurprisingly, I would side with Joshuaschroeder and Joke137 that the Wolf effect should not be mentioned as a primary cause of redshift, given that we're also considering excluding e.g. Compton scattering and other wavelength-dependent effects (that is, wavelength-dependent except in some very limited and specific physical situations). This isn't to say that there shouldn't be links to these effects from this article, but rather they shouldn't be listed as primary causes alongside gravitational redshift et cetera.

The comparison with the featured Italian article is interesting; it is similar to ours, but no mention is made of interpretations outside the scientific consensus. Can anyone comment on the effect that moving such material to other pages has had on other articles? Indicentally, you can get a hilariously clunky automatic translation of the Italian article from Google. Serjeant 14:28, 8 November 2005 (UTC)[reply]

Can anyone explain why, while the image is thousands of years old, the red shift today isn't due to expansion today? I am looking at this knowing about the tests where the wavefront arrived faster than the speed of light, but information arrives at exactly the speed of light. Hackwrench 17:03, 30 October 2005 (UTC)[reply]

Are you asking about how to apply comoving coordinates? Or are you trying to reconcile group velocity vs. phase velocity? Either way, the consistency of the interpretation comes from the formulation of geodesics in the Einstein field equations. Let me know if that helps. Joshuaschroeder 07:56, 31 October 2005 (UTC)[reply]

I am trying to resolve whether the light expands the space or the space stretches the light (current article statement). It is similar to the question of whether mass curves space or curved space creates mass. If light expands space then the amount of redshift can correspond to the amount of light travelling between two objects, as opposed to how long the light has been traveling. The current article expresses degree of redshift as a function of successive stretching of light.

The gravity article talks of electomagnetic repulsion. It seems to me that redshift might be a result of that repulsion. Hackwrench 17:05, 31 October 2005 (UTC)[reply]

Light does not "expand" space as space expands due to the details of the FRW metric -- light is not required for them to work. Joshuaschroeder 18:49, 31 October 2005 (UTC)[reply]

From what I can tell from the Friedmann-Lemaître-Robertson-Walker article, it doesn't give any reason for the expansion, it simply models it. In fact, it is simply the core model upon which extensions have to be bolted on for it to even begin to descrbe the universe. So it, in itself would not discount the possibility of light being the cause for the expansion. Hackwrench 03:29, 1 November 2005 (UTC)[reply]

The derivation of Friedmann cosmology comes from the cosmological principle, the copernican principle, and the universiality of physical laws coupled with general relativity. To derive the cause of the expansion one need only invoke these three ideas and the scale factor is automatically derived. Expansion is the most general form a universe described with those assumptions can take. However, ss to what "causes" the expansion, there are nominal explanations provided by cosmic inflation. Joshuaschroeder 10:25, 1 November 2005 (UTC)[reply]

But none of those seem to rule out light as the reason for expansion either. Hackwrench 03:20, 2 November 2005 (UTC)[reply]

I don't understand what "rule out light as the reason" is supposed to mean. An empty universe expands the same way a universe with light expands according to the theoretical models. Joshuaschroeder 12:59, 2 November 2005 (UTC)[reply]

My understanding of the models is that they describe the expansion but aren't complex enough to encompass the concepts of "a universe with or without light"

Indeed they are. An empty universe (without radiation or matter) is called Milne Universe.

I hadn't looked at the Wikipedia article cosmic inflation when I made my last post, and I am uncertain what you mean by your use of the word nominal. The article hints at potential expansion causes but doesn't go into any depth. Hackwrench 17:43, 2 November 2005 (UTC)[reply]

No, the details of how the expansion comes from inflation are rather thorny, but it is there. The idea is simply that the inflaton field causes inflation and establishes the scale factor and we are expanding based on Newton's First Law of dynamics. Joshuaschroeder 18:32, 2 November 2005 (UTC)[reply]

Google search on "inflation field" within en.wikipedia.org currently turns up only one hit, an outdated version of Non-standard cosmologies

Try what I actually wrote [1] Joshuaschroeder 01:58, 3 November 2005 (UTC)[reply]

When light expands energy is transferred. If that energy isn't transferred to the expansion of space, where does that energy go? Hackwrench 18:29, 5 November 2005 (UTC)[reply]

Energy is not conserved in GR, only energy density in a coordinate sense. Therefore even though an individual light wave has lost energy in its travels, it has the same energy density in comoving coordinates. It is comoving coordinates that matter in cosmology. Physical coordinates are only applicable to local phenomena. Joshuaschroeder 20:21, 5 November 2005 (UTC)[reply]

I devised an equation which is now posted on my website, because since 1958 I have not believed the Expanding Universe or Big Bang theories. It is an ordinary statistical decay equation of the kind used to describe radioisotope decay.

It took until 1982 to develop it, through considerable experience and education, so it was not developed lightly. It is on the first page at http://www.eskimo.com/~mikel137/index.htm#home , toward the bottom. It is the ordinary partial differential wave equation with the insertion of a diffusion term which uses the Planck action quantum as the diffusion constant.

The resulting lifetime seems to agree with the observed red shift, and is in addition, within the range of half-life decay times measured for several radioisotopes, as well as being described with an essentially identical decay process.

The equation seems good enough to present it as a candidate for an intrinsic photon decay process in the Wikipedia entry on Red Shift. But a Wikipedia article must meet standards of brevity and clarity with which I am not familiar, and my writing is, uh, difficult. - Michael Lewis

Difficult writing can be improved by other Wikipedians. But the main Wikipedia standard you seem unaware of is described at this link: Wikipedia:No original research. I'm also skeptical at times of mainstream tax-supported science - in particular, the "social sciences" might better be described as a political correctness cult. But Wikipedia is intended to reflect prevailing opinions, not to change them. Has your theory been published anywhere other than your own website, or is it you against the world? Sometimes one guy is right and the world is wrong, but there are other places to promote such things. Art LaPella 15:57, 25 September 2005 (UTC)[reply]

(Reply to Art LaPella) Thank you for the reference to the "No original research" standard. I did not know of that. Since it is my own work, it's not appropriate to Wikipedia, which is reasonable. Perhaps someone else will refer to it someday but it's not empirical yet. The equation or one like it would have been written during the twenties or thirties or soon after the war if things had been different. The document, which includes the equation I wrote, has a Library of Congress Copyright Number (it is a CD file document) and is hosted also at

http://members.chello.nl/~n.benschop/indx-red.htm ... http://groups.msn.com/HubbleRedShiftbyPhotonDecay ... and the local site referred to above http://www.eskimo.com/~mikel137/index.htm#home .

Whether the equation this author proposed is correct and in the best possible form or not, a photon decay equation which describes the red shift is certainly possible. Thus, it should be written well by competent mathematicians, put into the public domain, and comparison made over time with the dominant Doppler velocity shift.

- Michael Lewis

There is an exception of sorts:

It does not refer to original research that is published or available elsewhere (although such research may be excluded if editors consider the source to be disreputable or inappropriate).

Hackwrench 17:03, 30 October 2005 (UTC)[reply]

What are the values of z over the distance of the universe? After the first section z is never mentioned again.

z=0 is today. z=infinity is the fiducial singularity of the Big Bang. The farthest z that can be seen is the z=1100 CMB. Joshuaschroeder 20:20, 5 November 2005 (UTC)[reply]

Since they are in use, why don't we mention and qualify the terms:

• Doppler redshift [2]
• Cosmological redshift [3]
• Gravitational redshift [4]

--Iantresman 15:02, 6 November 2005 (UTC)[reply]

We can mention them. We already define them in the article. Joshuaschroeder 16:32, 6 November 2005 (UTC)[reply]

• Joshuaschroeder, The title of the article says "Redshift", not "Actually observed Redshift". The statement noted that it was theoretical, and I see no reason not to keep it.
• Presumably we should remove "cosmological redshift", since it has not been demonstrated in the laboratory, and we don't know whether it has been observed either.

--Iantresman 18:21, 8 November 2005 (UTC)[reply]

No one said "demonstrated in the laboratory". This article should not be a dumpster for any huckster's fanciful suggestions. Joshuaschroeder 20:17, 8 November 2005 (UTC)[reply]

I see that you have marginalised other redshift causes even more, by moving them to the bottom of the article. Consequently I have put in a Wikipedia:Requests_for_arbitration. If it is accepted, there will be an opportunity to say more. --Iantresman 23:46, 8 November 2005 (UTC)[reply]

Request for arbitration is quite serious - are you sure there are no other avenues? Enochlau 00:59, 9 November 2005 (UTC)[reply]

Yes, I do regret having to go down this path, but feel it is a last resort. As mentioned on the Wikipedia:Requests_for_arbitration page, we have had discussions, and I feel that there are infringements of Wikipedia policy that are fairly serious. --Iantresman 09:50, 9 November 2005 (UTC)[reply]

I do not think we should go down this route. The underlying question is, should the wikipedia present the view of the overwhelming majority of the scientific community, and not give voice to minority opinions that do not follow the accepted consensus? Or should the wikipedia give equal weight to all options, however their standing in the community? I think the casual, non-expert reader of any encyclopedia would expect nothing less than text generally accepted as authoritative, unless they were specifically looking up something that was known to be a minority view and which would be flagged as such.

I don't know for sure, but I suspect that there are at least three professsional or professionally-trained astronomers (including me) contributing to this article, all of whom appear to prefer moving these alternative explanations to the bottom or even to a page of their own.Serjeant 16:27, 9 November 2005 (UTC)[reply]

On the one hand, you are quite correct, and I understand your perspective from an astronomical point of view. On the other, there are professional scientists in physics and optics (I have rerferenced at least three), who would disagree with astronomers marginalising their point of view. I have no problem with Doppler redshift, Cosmological redshift, and gravitational redshift, all having their own pages. But as a launching point for redshift in general, popularity and relevance to astronomy is not as important as explaining redshift as a general phenomenon which applies to more fields than just astronomy. --Iantresman 18:03, 9 November 2005 (UTC)[reply]

The fact remains that these effects are the only effects that are frequency independent. Any physicist can tell that the Wolf effect cannot be frequency independent – how could it affect radio waves and cosmic rays in the same way? – and thus is not a true redshift. It may be frequency independent in some band, which could cause it to mimic a redshift in certain circumstances. I suspect that if you asked the authors of the paper you cite, they would agree.

The Wolf Effect may produce full-spectrum, frequency independent, redshift. I have provided three peer-revieweed papers that back me up. I have emails from at least three authors confirming my understanding. And "may produce" does not mean theoretically contrived either. And since this is a page on Redshift, it should also include frequency dependent redshift. --Iantresman 18:50, 9 November 2005 (UTC)[reply]

Nowhere in the papers you showed us did it indicate that the same effect would be seen for gamma rays and radio waves. Emails are irrelevent original research. Joshuaschroeder 19:12, 9 November 2005 (UTC)[reply]

Speaking of which, a topic which has generated some interest recently as a possibile explanation for the Type Ia supernova data is photon–axion mixing, similar to the neutrino mixing that has recently been discovered. While I don't think many cosmologists buy it, it ought to be mentioned, perhaps on the dark energy or tired light pages. –Joke137 18:32, 9 November 2005 (UTC)[reply]

Yes, this definitely should go on the dark energy page. Joshuaschroeder 18:43, 9 November 2005 (UTC)[reply]

I hope you don't mind me interjecting some comments on this discussion, since it involves some of my work from a few years ago:

1. The term "redshift" is not used just by astronomers. it refers to any process which increases the wavelength of light, or more broadly, any wave. Thus to include only effects which cosmologists think important would leave an article that is incomplete and misleading, to say the least. Further, the Doppler effect and the gravitational field can also produce blueshifts, depending on the relative motion or gravitational potential of the source and observer. Both of these effects also will change the widths of lines (so that the ratio of line width to wavelength is fixed).

2. The "Wolf Effect": Emil Wolf is a very highly respected optical physicist, who in 1986 discovered an interesting optical effect which can cause the shift of spectral lines, due to the correlation properties of a random light source. The effect tends to increase the wavelength rather than to decrease it (i.e. redshifts are more prevalent). Numerous experiments have confirmed the veracity of his predictions. In certain circumstances, specifically the scattering of light from random, highly anisotropic media, the shift in the of the spectrum of the scattered light mimics the Doppler effect in that the wavelength difference divided by the original wavelength is independent of wavelength (i.e. Δλ/λ is constant for different spectral lines.) Like the Doppler effect, it can produce red and blue shifts; in theory, since the spectral shift depends entirely on geometrical factors, it holds for *any* wavelength. A variety of applications of this effect have been studied, including synthetic aperture imaging, cryptography, optical frequency standards and a possible role in interpreting the spectral shifts in cosmology.

3. Although to date there has been no observational evidence to confirm or deny its relevance to astronomy, there are some of predictions which might lend themselves to experimental tests. The authors who investigated this (me included) had in mind the explanation of "anomalous" spectral shift. There is observational evidence (NGC 4319 + Mk 205 for example) to suggest there may be a small population of AGNs where something rather odd is going on: we wanted to find out if the excess redshift of these AGN might be due to some unexpected optical effect, and if we could produce some prediction which might lend itself to observational tests (e.g. relationships between the spectral shift and line asymmetry parameters or the jet columnation angle). I am not aware of anyone having undertaking any observations of this, but I have moved into another area of science and have not been keeping up on the literature. Dfvjames 22:41, 9 November 2005 (UTC)dfvjames[reply]

I notice that Joshuaschroeder has removed my information on "neutrino redshift" without any discussion. As a test suggested by a professional scientist in a peer reviewed article, and of direct relevance to redshift, I don't understand why it was taken out? I had written:

--Iantresman 19:07, 9 November 2005 (UTC)[reply]

Actually I told you that you could just put it on the nonstandard cosmologies page. Joshuaschroeder 19:12, 9 November 2005 (UTC)[reply]

In other words, you deleted it without discussion. And then your "told me" (ie. without discussion). I would still like to know why a test between different kinds of redshift does not belong on the redshift page? --Iantresman 19:22, 9 November 2005 (UTC)[reply]

It isn't a test for different kinds of redshift: it is a test to see whether the cosmological redshift is indeed behaving the same way for neutrinos as it is for light. The only reason to do this is in context of those who deny the cosmological redshift in the first place which is why it belongs on the nonstanard cosmology page. Joshuaschroeder 19:27, 9 November 2005 (UTC)[reply]

Your point of view is noted. --Iantresman 20:32, 9 November 2005 (UTC)[reply]