Talk:Michelson interferometer

Other Experiments?

For what other purposes of interferometry did Michelson use this particular interferometer? It says they exist but doesn't elaborate, and I can't find details elsewhere. --aciel 18:55, 3 February 2006 (UTC)

It can be used to measure the refractive index of air if one of the lite beams is made to pass through a vacuum whilst the other travels through normal air. It can be used to measure minute expansions or contractions in a material exposed to thermal/magnetic/pressure... changes if the material being tested is attached to one of the mirrors placed after the beam is split. It can be used for determining the wavelength of monochromatic light. — Preceding unsigned comment added by 117.206.42.44 (talk) 07:22, 25 April 2015 (UTC)

Michelson-Morley experiment to disprove aether?

It says

..."Michelson-Morley experiment in which this interferometer was used to prove the non-existence of the luminiferous aether."

but wasn't the M-M exp. meant to proove the opposite (it just didn't work out as planned)? Was it failure seen as sufficient to prove that the aether does not exist? I would doubt that (unfortunately without having further knowledge or reference handy).

-- I agree with this entry, unfortunately i don't have references handy either but i suggest to make some research and correct that part, i'll do it if i have time...

This entry is correct. Amusingly enough, I'm performing this experiment in my Modern Physics Lab even as I type this. The failure of the experiment to work was the death knell for the aether - they didn't expect it to fail, but its failure killed it all the same. Hewhorulestheworld 18:46, 29 August 2006 (UTC)

-- For all intents and purposes, a scientific model or theory requires some form of practical or experimental footing to be accepted as science. The M-M experiment was suppose to provide this experimental backbone to the theory and i believe even predicted to do so by the model (Can someone verify that i am correct in making this last statement). By all intents and purposes, the downfall of the eathirial model of light was due to a combination of the lack of experimental evidence to support it and the success of the quantum model of light at better accounting for such observational phenomena as wave-particle duality (sorry about not providing any sources, but this is a five minute coffee brake contribution, I'll come back and improve this contribution at some point).

-- Make no mistake: the results of the M-M experiment did not simply fail to prove the existence of aether; the results contradicted the necessary predictions which follow from the aether model (unless one were to postulate that every successful interferometetry experiment ever performed was done so while at rest with respect to aether, which is an extremely problematic proposal considering how many such experiments have been performed in various locations traveling at various relative velocities, etc. Such a proposal is also a direct violation of the Copernican principle).

---

Yes, the following sentence is definitely not consistent with historical facts: "Michelson, along with Edward Morley, used this interferometer in the famous Michelson-Morley experiment (1887)[1] to show the constancy of the speed of light across multiple inertial frames, which removed the conceptual need for a luminiferous aether to provide a rest frame for light."

Cf. for instance M. Janssen and J. Stachel, The Optics and Electrodynamics of Moving Bodies, http://www.mpiwg-berlin.mpg.de/Preprints /P265.PDF : [Michelson] took up the challenge to measure the terrestrial effect that Maxwell thought could not be measured." Janssen and Stachel did not yet understand that Michelson's interferometer was indeed not at all suited to measure the motion of earth against space. Recently Shtyrkov managed to measure this motion by means of aberration data from a geostationary satellite. The first one who denied the need for an absolute reference frame was Einstein in 1905. Later, Einstein admitted in principle the need for an ether while he maintained his theory of relativity. As Einstein recalled, he met Michelson only once in 1931 the year Michelson died. Michelson uttered to him he regretted a bit having given rise to Einstein's "monster" theory of relativity, cf. G. Holton (1969) Am. J. Phys. 37, 968.

Eckard Blumschein ____________________ — Preceding unsigned comment added by 94.222.149.82 (talk) 08:00, 5 April 2012 (UTC)

Compensator plate

Doesn't one of the "arms" of the Michelson Interferometer contain a compensator plate to make sure both beams travel through the same amount of glass, removing the dependence of the path length on wavelength? Or is the diagram shown in the article a more general case? --Zapateria 15:21, 2 June 2006 (UTC)

It depends on whether the semi-silvered block is silvered on the front or back. Its easier to stick it on the back, but that means the beam reflected initially has to go through the block twice to be reflected, so the compensator is stuck in the path of the transmitted beam so it has to pass through the body of an equal block an extra two times as well. The current picture is the general case. MilleauRekiir 22:34, 18 October 2006 (UTC)

References to points which do not exist

In the "configuration" part there are references to A,B,M etc. These points are not marked on any of the figures in this article. —Preceding unsigned comment added by 132.68.244.4 (talk) 22:13, 15 June 2010 (UTC)

Does anyone have the missing diagram and can you please post it? Jbeam.scholar (talk) 17:33, 1 July 2011 (UTC)

I believe that I have now correctly re-labeled the diagram that corresponds to the configuration section. I would appreciate someone checking this over. Jbeam.scholar (talk) 18:06, 1 July 2011 (UTC)

The target audience for this article / Disputed section

The recommendation in WP:TECHNICAL is that articles in Wikipedia should be understandable to the widest possible audience.

The general aim of most editors contributing to this article (including myself) seems to have been to make it understandable to moderately knowledgeable high-school/first year undergraduate students. To achieve this aim, technically difficult complications are deliberately ignored provided that the basic gist can be communicated more or less accurately.

Interferometrist placed a "disputed-section" tag on a paragraph in this article dealing with phase shifts in Michelson's apparatus and how, in some arrangements, the central fringe will be dark, and in other circumstances, bright.

When I was making my first edits on this article (an anti-vandalism edit), I had noticed many of the the same deficiencies that Interferometrist noticed. Some of the material which I adapted from other Wikipedia articles was not 100% accurate since the 0 or 180 degree phase shift rule really applies only to near-normal incidence at a dielectric boundary below Brewster's angle, one needs to distinguish between parallel and perpendicular components, a partially transmitting metallic coat absorbs part of the light so that conservation of energy between transmitted and reflected doesn't apply, cube beam splitters are not all alike, but come in different split ratios, may be polarizing or non-polarizing, etc.

I do not believe that it is possible to make this section 100% complete and accurate without intimidating the target audience. However, the description is close enough to the truth as to serve a useful purpose, in that the reader is made aware that the central fringe can be dark or light depending on the configuration.

Perhaps the solution should be to add some sort of caveat that if the reader wants to get a fully accurate description of what is going on, he/she should be directed to some other article. Unfortunately, I don't know what that other Wikipedia article would be.

Stigmatella aurantiaca (talk) 12:59, 7 June 2014 (UTC)

I've added a caveat note and additional references explaining that the situation is actually rather more complex than presented in the text. Stigmatella aurantiaca (talk) 11:32, 9 June 2014 (UTC)

Yes, actually it is so much more complex than presented in the text that the conclusions presented in the text are just wrong, not even correct in any approximate sense. So I'm restoring the tag and would like the entire section to be removed. Very few people ever look at a white light Michelson interferometer and when they do they would not generally see either a centered dark fringe or light fringe. It extremely depends on the coatings used for the beamsplitter (and the two end mirrors, if they are not identical) as well as any residual differential birefringence in the glass plate(s)/prism. And again in this regard, the reference on "Reflection Phase Change" is exactly correct regarding a single dielectric interface, but applies not at all to a beamsplitter consisting of one (or more!) layers of dielectric(s) (or metal!) on a glass plate or within a prism cube. Even in the simplest case of a single dielectric layer on glass (not sufficient to reflect anything near 50% of the light) you have TWO interfaces (as is shown on that page) which both reflect and whose waves need to be added coherently (as implied in the figures) to obtain the net amplitude reflection coefficients (not computed on that page) which will generally have a phase of neither 0 nor 180 degrees and will be wavelength dependent (even ignoring material dispersion). So I am removing that reference as irrelevant and reinstating the "disputed section" until someone else removes the section or figures out a way of writing a conclusion which is true in general. (Actually, I can think of one, but it would be of academic interest only).

The other referenced article "The Effect of Phase Change on Reflection on Optical Measurements" is also perfectly good (well, I didn't read it through but I assume it agrees with what I would compute) but has to do with mirror reflections not beamsplitters. It would be of relevance to the end mirrors (when they are not identical) but only when the phase shift is expressed as a function of wavelength (the paper was just for 633nm) in order to be of relevance to the formation of a white light fringe.Interferometrist (talk) 16:05, 10 June 2014 (UTC)

And by the way, I am also concerned with the target audience and try to make presentations deal more with basics and leave the more esoteric material for later in the article (or not at all). A white light interferometer is already a rather esoteric device so discussion of whether the central fringe is white or dark is already of little general use EVEN if it were so simple. For the target audience, they should learn that a Michelson interferometer IS something you can build at home WITHOUT worrying about passing horse traffic etc.! And they should NOT be lead to believe that they can just expect to run white light into it and get fringes, or they will be extremely disappointed. So I'm going to try to put these things in perspective, again, for the sake of the target audience.Interferometrist (talk) 16:47, 10 June 2014 (UTC)

"Actually, I can think of one, but it would be of academic interest only." Would you be able to present that conclusion here, and maybe we can figure out a way to reword it, splitting it between a summary comprehensible to high school/lower level undergraduate students for the main text, and a detailed note that would be sufficiently accurate to meet your standards? Stigmatella aurantiaca (talk) 17:45, 10 June 2014 (UTC)

Well I'll tell it for your (and others') sake, but I don't think it really belongs in the article for the reasons I mentioned. If the two end mirrors are identical, and there is perfectly balanced material dispersion, then IF the beamsplitter is exactly symmetric, then the central fringe (aka group delay=0) will necessarily be at a peak of intensity (phase delay =0); you'll have a "bright" central fringe. The symmetry condition means that if you flip the beamsplitter over, then it remains unchanged, and that is a difficult and unusual condition. First, it rules out all plate beamsplitters, except for one (but I haven't seen these on sale) where the coating is sandwiched between two identical plates, like a cube beamsplitter. And it WOULD apply to a cube beamsplitter with a single coating, such as a thin aluminum (or silver) layer, but these days those are made with multilayer dielectric stacks. The layers of the stack would have to be symmetric (thus identical when the whole thing is flipped around) which is a very plausible design (but surely never specified in a catalog!). And to meet the dispersion requirement, the two halves of the prism would have to not only be identical in size (which they probably are) but cemented together with the corners matching without an overhang of more than a small amount (which might be standard, I never looked that closely). For instance, transmission through an extra 20 microns of BK7 glass would shift the red from the green fringe peaks by about 1/5 fringe. So what I'm saying is that someone could do this in the lab if it's what they really need to prove, but in ordinary experiments you'd never go to that trouble. Likewise, for the target audience, again, who wants to make a Michelson interferometer at home (or understand its application in >95% of cases) it is illuminated by a laser and this issue doesn't even arise.Interferometrist (talk) 18:58, 10 June 2014 (UTC)

Perhaps the section should state that the explanations that one sees all over the internet (and in elementary textbooks) are oversimplified. There is, I believe, considerable pedagogical value in showing white light fringes and explaining that the central fringe can be light or dark depending on the details of the setup. Use of white light is by no means completely obsolescent. For instance, optical workers testing a partially figured flat will use white light when checking against a master. The white light fringes quickly tell them whether the flat is convex or concave. Stigmatella aurantiaca (talk) 19:21, 10 June 2014 (UTC)

I'll just respond quickly to each of these points; I think the effort and argumentation going into this page is out of proportion. Yes white light interferometry is important, but in almost all applications the phase at the group delay isn't. For instance in a FTS setup it will just be a calibration that's taken out of any actual measurement. There are many oversimplified or just wrong statements on the internet and it isn't so important for them to be pointed out, but rather just kept from creeping into Wikipedia.Interferometrist (talk) 13:03, 11 June 2014 (UTC)

Re accuracy of localization with sodium doublet

"Establishing interferences in sodium light, we found the central part of a series of some seven hundred interferences which are brighter than the adjoining three hundred. With no long search, we could see interferences in white light, although we had provided no screw for moving a mirror with its surface always parallel to a given surface." http://www.jstor.org/stable/20022071?seq=2

In other words, Morley and Miller could identify the central 100 fringes of a series of 700 fringes from the sodium doublet. Stigmatella aurantiaca (talk) 11:53, 11 June 2014 (UTC)

Well yes, we absolutely agree then. My own calculation shows 987 fringes over the visibility cycle due to the doublet, so it goes like (1+cos(2pi x / 987))/2 where x is counted in fringes, so at 50 fringes away the contrast is down to .985 which someone with good eyes might be able to see clearly. A better way is to find where the fringe visibility gets poor on both sides of the white light fringe and center in between them. So that might get you to a few dozen fringes if you're good, as you put in the latest version. OK? Interferometrist (talk) 13:09, 11 June 2014 (UTC)

Agree Stigmatella aurantiaca (talk) 13:13, 11 June 2014 (UTC)

Finickiness of Miller's apparatus

Although Miller's apparatus was dimensionally stable, reproducibly maintaining its settings from day to day, the extremely long path length of the apparatus made it highly sensitive to external disturbances.

For example, Max Born visited Miller's laboratory in 1925/26 and wrote:

I found it [the experimental arrangement] shaky and unreliable; the smallest movement with one's hands or a cough made the interference fringes so fidgety that there was no way to read off their position. After that I didn't believe a word of his experiments.

- from Domenico Giulini, Special Relativity: A First Encounter, 100 Years Since Einstein, p. 34

"A man chopping a stump of wood, several hundred feet away, disturbed the fringes, as also did workmen on a highway three miles distant; the passing of an airplane overhead caused the disappearance of the fringes." - Miller (1933) p. 215

Stigmatella aurantiaca (talk) 12:19, 11 June 2014 (UTC)

I really find this discussion distasteful because it seems to be about how bad you can setup an interferometer. I'm not familiar with Miller so I don't know how much trouble he went to to make his interferometer so sensitive to external vibrations, but I tagged the obviously exagerated accounts you had in the text, because even if possible (which I also dispute) they are not representative of interferometers in use. Since this is about an interferometer topology which had been described as "the most common" you have to consider that 99.9999% of the time it is NOT being used to measure the ether drift and >99% of them have been used after 1930 so why go back to Miller 80 years ago for an account of an interferometer's sensitivity to vibration? That sensitivity was the same then as it is today so you could have well asked me about the Michelson interferometer I had setup (yes, on an optical table, but only because that's the way it's done where I work) recently. Like any interferometer I've ever set up, it functioned as a microphone and the fringes vibrated in response to the radio I had playing (setting on the same optical table). But the fringes were NOT washed out with the radio at conversational levels. The human ear is very sensitive, surely more than any interferometer not designed as a microphone, and I cannot hear a distant thunderstorm (especially indoors) so I find it totally implausible that someone would detect fringe motion due to something I cannot hear, let alone the fringes washing out (peak-to-peak motion approaching one whole fringe) and I want that removed, ok? I likewise find Miller talking about a motorcycle doing that from 1000 feet away rather unlikely but won't make an issue as long as it's not in the main text. If you find this aspect of interferometry (or actually vibration analysis) so interesting then you should concentrate on the MM experiment page, and how that interferometer had particularly long arms which greatly increased its sensitivity to vibration beyond ones used in almost all other applications and then the measures they took to combat external vibrations (successfully). But this is not about optics anymore and not a subject of the article. The article is about optics and should tell you just what the mechanical sensitivity of an interferometer is, namely one fringe shift for lambda/2 mirror motion. Period. Interferometrist (talk) 13:35, 11 June 2014 (UTC)

Lunate cells of Nepenthes khasiana visualized by Scanning White Light Interferometry (SWLI).

I'm awfully sorry that we have been somewhat at cross purposes in our edits. My intention was never to dwell excessively on ancient history, but to point forwards. The short coherence length of white light is not always a disadvantage, as seemingly implied by your edits. Exploitation of the short coherence length of white light allows resolution of the "2 pi ambiguity" in such devices as white light scanners. The only reason I didn't provide a direct link to the white light scanner article was since I didn't have a diagram of a microscope objective incorporating a Michelson interferometer, only a Mirau interferometer. That has been an item long on my "to-do" list.

Modified Michelson interferometer set up as a white light scanner

The flexure of a loaded beam goes as the cube of its length. It is rather difficult to compare the stability of Miller's apparatus, which was in the shape of a 4.3 meter cross with cantilevered arms (remember that it had to be able to rotate), with that of a modern optical bench with multiple support points along its base, but I might guess it was maybe a couple of orders of magnitude less stable than a modern optical bench. The total folded light path in each arm was 32 meters. In addition, Miller performed his Mt. Wilson experiments in a flimsy shed with canvas walls (so as not to impede the supposed aether wind) so he heard (and the apparatus was affected by) virtually every noise- and vibration-making event going around him, and the apparatus was subject to rapid temperature drift. When I multiply out my multiple order-of-magnitude guesstimates, I estimate that it was maybe three orders of magnitude less stable than the arrangement that you recently set up.

I did not intend the paragraph to provide anything more than a short side note into history. As I stated above, my main intention was to point to modern applications of white light interferometry. But the paragraph is now very significantly longer than it was, and the notes have ballooned to six times their original length because of the need to respond to your repeated applications of "dubious" and "citation needed" tags. Stigmatella aurantiaca (talk) 12:36, 12 June 2014 (UTC)

"The short coherence length of white light is not always a disadvantage, as seemingly implied by your edits." My, my. That is absolutely not what I said or implied. I am very interested, in fact involved in broadband interferometry. My point was that it is much more difficult (in a 2-beam interferometer) than narrowband interferometry which is already more difficult than laser interferometry, so you only use the more difficult configuration when there is a particular reason. And I'm sorry you felt a "need" to respond to my tags with obscure historical references because they didn't convince me of anything (besides what Max Born already noted about Miller), and I still expect you to remove the "distant thunderstorm" remark so I don't have to. (Or find an actual citation to that effect). Thanks, Interferometrist (talk) 17:08, 12 June 2014 (UTC)

The thunderstorms reference was from a secondary source, a book that I don't exactly remember the title of, but I can remember where the book stood on the library shelf at the university library. If you want to remove the mention, go ahead, because, as I said before, I no longer work directly across the street from the university and don't feel up to driving across town just to make a point. Life is too short to get annoyed over such matters. Stigmatella aurantiaca (talk) 17:25, 12 June 2014 (UTC)

Listen, I admire your interest in interferometry and all of the useful editing you have done. However some of your content isn't really useful to the (remember?) target audience, and in regards to my request you are missing the point. 1) I do not need your permission to remove incorrect or unsourced material. Rather I was asking for your AGREEMENT so that we could move on. 2) I was wrong to tag with {CN} and I'm glad I didn't waste your time looking for the citation. Because if you had found the citation it would only have told me you were using a bad reference. Just because a point is supported by a "RS" doesn't mean that it goes into WP when you can ascertain that the reported fact is wrong. 3) If you tell me to edit it, then I'm not going to just take out the most absurd statement but will edit it as I'd expect such a page to be for the benefit of the target audience (remember, they looked up "Michelson interferometer" not "History of poorly built interferometers"). I would excise the portion of the paragraph starting with "Lacking modern means" and in fact I would encourage YOU to do just that! 4) The remaining material in the paragraph you could find a better home for (except for the clearly exagerated claims, but you could still include those as quotations from notable people without claiming their truthfulness), if nowhere else then in an historical article.

If I didn't have anything better to do, I'd tell you about many other problems of the paragraph in which the claims do not support the point of the paragraph. At all. For instance, the thing about lack of modern "environmental temperature control" (which I don't use, don't need) isn't a reason for needing a white light fringe, since the temperature never would change THAT fast (unless the guy were too lazy to look at the fringes more than once an hour) and if you were worried about it (or even if you weren't, usually) both arms of the interferometer would be made of the same metal. Temperature changes would lead to fringe DRIFT, and that would have screwed up the result of the M-M experiment (which needed to measure <<1 fringe) LONG before it would cause confusion about which fringe you had been following. Likewise, transient fringe loss caused by a gunshot, say, wouldn't normally be a problem in such an experiment either (as long as the apparatus didn't get shot) since after the transient dies down the fringes would return to where they were a few seconds ago. Again, if that were not the case to within a small fraction of a fringe, then the M-M experiment could not have achieved its precision of a few hundredths of a fringe. So while many of the statements might have some validity taken alone, they do not make for a coherent paragraph about interferometer bandwidth.

And I still have to say that I simply do not believe some of what Miller has written, in addition to you misusing it. I don't know how he is to be considered such an authoritative source concerning non-scientific details of the M-M experiment which was 50 years earlier (was he that old in 1930?). And another thing, the above quote: "chopping a stump of wood, several hundred feet away, disturbed the fringes" is extremely believable, but "disturbing fringes" means that you can see a vibration of the fringes and is much different from the fringes washing out (so that you can't follow them) by a factor of at least 20, which would then require a sound 26dB louder. And "workmen on a highway three miles distant" causing a fringe shift doesn't just sound unlikely (unless they were using dynamite) but one has to ask: how did Miller know it was THOSE workmen causing the fringe shift? Did he survey a larger area than that to determine that nothing else for miles around could have been the cause? Or was he on the phone with them and correlated their movements with fringe shifts? And for that matter, how did someone correlate a distant thunderstorm with the fringe shifts (or actually the claimed fringe wash-out) that was reported? It isn't just these facts that are implausible, but that anyone even would have been able to establish them in the first place. Which makes the telling of such facts a form of bullshitting. Look, I know you're too smart to miss what I'm saying; don't pretend otherwise! And finally, even if all of this were true, does a person wanting to understand the Michelson interferometer and to understand the role of bandwidth, really need to hear all that to understand the technical issues?

Now, having written all that, I have convinced myself to go ahead with the more drastic edit I have suggested. Of course there's nothing stopping you from reverting it, and I'm not planning to get into a revert war. But if you do decide to edit, please consider very carefully the points I have made about the believability of certain exaggerations, the relevance of each claim to the point of the section, and the usefulness of that material to the target audience. Good day, Interferometrist (talk) 21:32, 18 June 2014 (UTC)

I have no intention of getting into an edit war with you. You have your vision of how the article should be, which has legitimate points as well as points with which I disagree. Wikipedia is about compromise between legitimate points of view.

Rapid fluctuations can come from changes of air temperature causing differential refractive index changes in the arms of the interferometer, (A difference of 0.01°C in temperature over 32 meters can result in a shift of 0.55 wavelengths of yellow light.) which would be superimposed on longer-term dimensional changes in the interferometer arms. (When the fringes got too far off center, Miller added or subtracted weights from one of the interferometer arms to bring the fringes back to center.)

Here is a graph by Thomas Roberts of Miller's published sample data. http://arxiv.org/ftp/physics/papers/0608/0608238.pdf

Miller's results, especially, suffered from his insistence on working in as close to an unshielded environment as possible. Shankland (1964) has discovered revealing entries in Miller's notebooks that show how much Miller was affected by temperature effects, beyond what he admitted to in his published writings. Also, I believe that Dayton Miller smoked, and if my memory is correct on this point, it is difficult for me to believe that he didn't have to clear his throat occasionally during an observing run, ruining the fringes...

Replica of Michelson's 1881 interferometer

Remember that the optical tables that you are used to working on to have benefited from a century of advancement in vibration control. I would imagine that you are probably used to working on a table with a honeycomb construction, sitting on an isolation platform, possibly with active damping. You seem unable to appreciate the tremendous difference in technology that exists between today's commercial offerings and the homebrew setups of yesteryear. Despite your various protestations of disbelief, it is clear to me that neither Michelson nor Miller were exaggerating. Michelson's 1881 setup looks particularly absurd to modern eyes. In Berlin, Michelson was completely unable to do any observing until after midnight, and even then, he could only observe at intervals. It wasn't until he moved the apparatus to the Astrophysicalisches Observatorium in Potsdam that he was able to do useful measurements.

I reiterate that I was not so much interested in relating old historical tales as I was in (hopefully) seguing into useful applications of broadband interferometry, something that I never got around to for various reasons. Since you have expressed a degree of expertise in this field, could you perhaps contribute to the Applications section on this? Thanks, Stigmatella aurantiaca (talk) 01:57, 19 June 2014 (UTC)

== Removed: Was Bullshit! ==<<<<<factually correct but maybe not constructive!!??!! come on guys and girls....lets have a bit of consistency here!

The sodium light was used because sodium light has two different wavelengths such that the point to focus (with the pattern of max. intensity) was easier to find. Otherwise at destructive interference points the pattern would have disappeared completely.

Early experimentalists attempting to detect the earth's velocity relative to the supposed luminiferous aether, such as Michelson and Morley (1887) and Miller (1933), used quasi-monochromatic light only for initial alignment and coarse path equalization of the interferometer. Thereafter they switched to white (broadband) light, since using white light interferometry they could measure the point of absolute phase equalization (rather than phase modulo 2π), thus setting the two arms' pathlengths equal. More importantly, in a white light interferometer, any subsequent "fringe jump" (differential pathlength shift of one wavelength) would always be detected.

What is "absolute phase equalization" ?

Gravitational Waves

This is my second attempt to get the gravitational wave detection into the introduction.

This detection is a big deal. All four Wikipedia articles, on the four gravitational wave observatories, mention that they are Michelson interferometers. Both GW151226 and GW150914 were heavily reported in the popular press, and Slate.com (ranks in the top 200 most visited sites in the U.S.) specifically pointed to this article. Google finds 75,700 sites with

"gravitational wave" observation "Michelson" 

(quotes included to force the terms). Finally, the science journal Nature, which ranks #1 in impact, says, “The consequences of this detection are difficult to overstate…”. Forcing laypeople to read down 1,700 words to get to gravitational waves seems to me to reflect an obsolete world view. In fifty years both experiments are going to be seen as equal in importance. Indeed, right now there are a large number of scientists, myself included, that think so. Before removing this, please explain why you believe gravitational wave detection is not more significant than the other seven applications in the article’s list.

Nick Beeson (talk) 18:34, 16 June 2016 (UTC)

No, I'm sorry. The detection of grav. waves IS a big deal. How it's done is important too. But it is only one of thousands of uses for interferometry or the Michelson configuration. The Michelson-Morely experiment was a more important historical experiment and is covered in the lede (perhaps given too much room), whereas you are only highlighting LIGO because it's newsworthy in 2016. Compare for instance the LHC accelerator (that detected the Higgs boson, another recent newsworthy event) which relies on superconducting magnets; the lede in that article mentions particle accelerators but only as part of one sentence. The article on paper doesn't mention every important writing that was done using paper. This article is about the interferometer, not every application. Applications and trivia about it need to be moved down in the page.

Readers are not "forced to" read 1700 words first, they instead are "forced" to go to the article on the subject and not dwell on one concerning a critical piece of technology used in LIGO. I trimmed (not removed) the content you added in the lede, however please feel free to include the additional references I removed in the section on gravitational wave detection where their inclusion might be appropriate (I was too lazy to go through them). Interferometrist (talk)

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what is wrong about michelson-morley experiment??

I explained on my twitter the problem about the michelson-morley experiment ,and I proposed the correct formulas to interpret the results : https://twitter.com/TheDetective_L/status/1090272398040010752