This is an archive of past discussions about Michelson–Morley experiment. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.
I want to discuss adding to the introduction that the experiment was performed the first time by Michelson in Potsdam 1881 and that it was performed in a refined version 1887 by Michelson and Morley in Cleveland.
The comment in the chapter Experiments: "apparatus was a prototype, and had experimental errors far too large to say anything about the aether wind." can not be stated like that. There were experimental errors in his 1881 paper, but he addressed and discussed these and concluded that there was no movement through the ether:
"This conclusion directly contradicts the explanation of the phenomenon of aberration which has been hitherto generally accepted, and which presupposes that the earth moves through the ether, the latter remaining at rest."
It is important where the experiment was performed (and published) first. — Preceding unsigned comment added by Jadram2011 (talk • contribs) 15:26, 25 April 2011 (UTC)
No one denies that the experiment was first carried out in 1881. But Michelson overlooked some errors, as he himself acknowledged in his 1887-paper. He wrote: "In deducing the formula for the quantity to be measured, the effect of the motion of the earth through the ether on the path of the ray at right angles to this motion was overlooked. The discussion of this oversight and of the entire experiment forms the subject of a very searching analysis by H. A. Lorentz, who finds that this effect can by no means be disregarded. In consequence, the quantity to be measured had in fact but one-half the value supposed, and as it was already barely beyond the limits of errors of experiment, the conclusion drawn from the result of the experiment might well be questioned;" So the 1881-experiment was not conclusive. --D.H (talk) 18:40, 25 April 2011 (UTC)
The Indian journal of science and technology isn't reliable source for that. They publish drivel (check out some of it). IRWolfie- (talk) 09:31, 25 June 2012 (UTC)
"In Ritz's theory there would be no shift, because the net velocity between the light source and detector was zero (they were both mounted on the turntable)"
The net velocity of two points on a rotating turntable can never be zero, as the velocities of the two points are either acting in different directions or have different magnitudes. And if you consider a rotating frame of reference, since this is a ballistic theory of light we are talking about, you have centrifugal forces to contend with instead. Seems to me that a shift would be expected. Scowie (talk) 18:30, 13 January 2012 (UTC)
Reference suggestion
L. S. Swenson, The ethereal aether; a history of the
Michelson-Morley-Miller aether-drift experiments, 1880-1930, U
Tex Press, Austin, 1972. (HCPotter (talk) 08:45, 18 March 2012 (UTC))
I have removed that. We don't just add book titles as references like this in the lead, unless it has something specific to reference.
I also have removed your next section (Light phase) as it is not about the improving or modifying the article — per wp:TPG. Cheers - DVdm (talk) 14:22, 26 March 2012 (UTC)
White or yellow light?
Unfortunately, I can not agree with Stigmatella aurantiaca.
They clearly used yellow sodium light. Citation given by Stigmatella aurantiaca points that white light used to calibrate equality of paths, not for experiment itself.
They must used source of light with known constant wavelength to predict the displacement of the interference fringes. White light (which is spectrum of wide range of wavelengths) is not suitable for this purpose at all. With white light all formulas and calculations become meaningless. Using white light they could detect only that "ether wind" exists, but they couldn't predict and calculate the displacement of the interference fringes.
And Michelson–Morley certainly used wavelength of yellow sodium light in all calculations. For example
If now the whole apparatus be turned through 90°, the difference will be in the opposite direction,
hence the displacement of the interference fringes should be .
Considering only the velocity of the earth in its orbit, this would be .
If, as was the case in the first experiment, waves of yellow light,
the displacement to be expected would be 0.04 of the distance between the interference fringes.
...displacement should be .
The distance D was about eleven meters, or 2×107 wave-lengths of yellow light;
hence the displacement to be expected was 0•4 fringe
If Michelson had used a different color of light (indicating a different wave
length) in each different direction, i.e. red and blue respectively, then a priori this could
have caused a shift of the interference pattern when the apparatus was rotated through
90є. (Figure 11.3) But the same color of light (yellow), and thus the same wavelength,
was used by Michelson in each light pencil, so neither the monochromatic color of the
light nor its wavelength could have caused a fringe shift in Michelson’s experiments.
Two light pencils propagating in space with the same color of light, and thus the
same wavelength, automatically have the same frequency of wave receipt by a relatively
stationary observer such as Michelson…even if they are out-of-phase. Thus, such
identical wavelength and the identical frequency of wave receipt of two out-of-phase
monochromatic light pencils cannot (by themselves) result in a shift of their observed
relative state-of-phase
The mirrors c and d were moved up as close as possible to the plate b, and by means of the screw m the distances between a point on the surface of b and the two mirrors were made approximately equal by a pair of compasses. The lamp being lit, a small hole made in a screen placed before it served as a point of light; and the plate b, which was adjustable in two planes, was moved about till the two images of the point of light, which were reflected by the mirrors, coincided. Then a sodium flame placed at a produced at once the interference bands. These could then be altered in width, position, or direction, by a slight movement of the plate b, and when they were of convenient width and of maximum sharpness, the sodium flame was removed and the lamp again substituted. The screw m was then slowly turned till the bands reappeared. They were then of course colored, except the central band, which was nearly black. The observing telescope had to be focussed on the surface of the mirror d, where the fringes were most distinct The whole apparatus, including the lamp and the telescope, was movable about a vertical axis.
The paths being now approximately equal, the two images of the source of light or of some well-defined object placed in front of the condensing lens, were made to coincide, the telescope was now adjusted for distinct vision of the expected interference bands, and sodium light was substituted for white light, when the interference bands appeared. These were now made as clear as possible by adjusting the mirror e/, then white light was restored, the screw altering the length of path was very slowly moved (one turn of a screw of one hundred threads to the inch altering the path nearly 1000 wavelengths) till the colored interference fringes reappeared in white light. These were now given a convenient width and position, and the apparatus was ready for observation.
Let D, Pl. IX. fig. 1, be a plane-parallel glass plate, silvered so thinly that equal quantities of light are transmitted and reflected. S being a source of light, part of the light passes through D, moves on to the plane mirror II, where it is reflected back to D; here, part is transmitted and lost, part is reflected to the observer at T. The other part of the entering light is reflected at the first surface of D, reflected again by the mirror I, is in part reflected by D, and lost, in part transmitted through D, and proceeds towards T. If distances and angles are suitable, the reunited rays between D and T will produce interference phenomena. If distances are equal, we may obtain interference phenomena in white light. In one of the usual adjustments of distances and angles, parallel fringes are seen when the eye or the telescope is made to give distinct vision of one of the mirrors I or II. The fringes apparently coincide with these surfaces. A central fringe is black; on either side are coloured fringes, less and less distinct till they fade away into uniform illumination. If the path of either ray is shortened, the fringes move rapidly to one side. If we engrave a scale on I or II, we can, after any alteration of one of the paths, restore with great accuracy and ease the former relations by bringing the central dark fringe to its original place on this scale. If the motion of the earth through the aether were the cause of this change of path, we could measure the amount of change by measuring the displacement.
The mirrors, being silvered and polished, were put in place, and the lengths of the two paths were measured with a split rod and then made nearly equal. 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. This we had avoided, in order to have everything about the two arms as symmetrical as possible.
The mercury arc and other monochromatic sources have been tried for the preliminary adjustments but the sodium light is preferred because the middle portion of the interference system can be easily located, which corresponds to equal light paths in the two arms of the interferometer. White light fringes were chosen for the observations because they consist of a small group of fringes having a central, sharply defined black fringe which forms a permanent zero reference mark for all readings.
All citations, except the last, are not about running the experiment, they are about preparation. White light used to make distances equal. The last citation is not about 1881 or 1887 experiments. It's Miller's experiment with strange results
If now the whole apparatus be turned through 90°, the difference will be in the opposite direction, hence the displacement of the interference fringes should be . Considering only the velocity of the earth in its orbit, this would be . If, as was the case in the first experiment, waves of yellow light, the displacement to be expected would be 0.04 of the distance between the interference fringes.
We can not substitute wave lengths in formulas when we are talking about white light.
The length of path of a ray in our apparatus was 3224 centimeters, in which distance there are contained wave lengths of sodium light. The expected effect being doubled by rotation through 90, the displacement of fringes expected on the simple kinematic theory will be . This is 1.5 wave length.
Acetylene light is not monochromatic, and Miller used an efficient acetylene lamp that didn't smoke very much. Sodium light was used for only for initial alignment, and was preferred over true monochromatic sources such as mercury arc because the double sodium lines caused the fringe pattern to become weaker after a hundred or so fringes (whereas a mercury arc's fringes would still be extremely sharp), thus allowing the center to be located more easily. The actual experiments were run with non-monochromatic light. Miller said it best: "White light fringes were chosen FOR THE OBSERVATIONS because they consist of a small group of fringes having a central, sharply defined black fringe which forms a permanent zero reference mark for all readings."
The calculations were done with a number representing yellow sodium light because that wavelength isn't too far off the maximum sensitivity of the human eye and/or the emissions peak of the flame. - Stigmatella aurantiaca (talk) 05:11, 1 May 2012 (UTC)
If human eyes had another sensitivity, the displacement should differs? And predicted velocity of ether wind would be different? :)
Figures are good. Sadly, they are black and white Onedrey (talk) 09:01, 1 May 2012 (UTC)
If I remember correctly, both Kennedy and Illingworth used monochromatic green light, the 546.1nm line of mercury. By 1926 to 1927, the major technical difficulties that forced the early experimenters to use white light were overcome. The most serious of these difficulties was temperature drift. Even in the basement laboratory at Case Western, Michelson and Morley had to contend with dimensional changes which were large even within the space of a single turn. See their table on page 340. Compare their beginning position 16 readings with their end position 16 readings. In the noontime run on July 8, for instance, the drift amounted to about 0.6 fringes within the time of a single turn. They assumed that the drift was linear when they performed their data analysis. Dayton Miller, who performed many of his experiments in a flimsy shed on top of a mountain so as not to block the aether, had even worse drift problems. Furthermore, his giant interferometer was so sensitive to vibration that an accidental cough by a visiting Wolfgang Pauli completely destroyed the fringes for over a minute. Pauli was not impressed, and went away convinced that Miller's results were sheer artifact. The early experimenters needed a "permanent zero reference mark" for their readings. Kennedy and Illingworth, however, performed their experiments in a special constant temperature room at Caltech whose temperature was regulated to hundredths of a degree. Stigmatella aurantiaca (talk) 11:23, 1 May 2012 (UTC)
In regards to your first question, no. Kennedy and Illingworth used a system of calibrated weights to adjust their interferometer to a null reading, i.e. their goal was to achieve equal intensity on both sides of the dividing line. After achieving a null position, they would note the number of weights required to achieve this null. So the measured magnitude of any aether drift would not differ depending on eye sensitivity, only the accuracy of its measurement. Stigmatella aurantiaca (talk) 11:31, 1 May 2012 (UTC)
By loading and unloading weights from one corner of the interferometer, Kennedy and Illingworth could shift the fringes back and forth until they achieved the desired null reading Stigmatella aurantiaca (talk) 12:45, 1 May 2012 (UTC)
Tom Roberts' paper on Miller's results
As Miller's results are pretty widely covered in the article, perhaps Tom Roberts' paper may be interesting as a source for some comments. See [2]. - DVdm (talk) 12:01, 7 May 2012 (UTC)
The article obviously failed on all counts. Here's my assessment of how the article meets the basic GA criteria...
Basic Ratings
Category
Rating
MoS
NPOV
Accuracy
Broad
Stable
Prose
Prose
The prose is what I am having the greatest problem with, as evidenced by my negative review of it. In many places, the prose is quite choppy, with extremely short, one-line sentences (on my 13-inch-screen laptop) in one paragraph and three-lined sentences in the next. In addition, functional elements which are not ideal are used, such as the en-dash or even the hyphen. In yet other examples, unnatural explanations are used (involving parenthetical expressions like this one) where natural explanations could be used. Example (from oldid 491686307), bold indicates problems:
Starting in 1885, Michelson collaborated with Edward Morley, spending considerable time and money to repeat the Fizeau experiment on Fresnel's drag coefficient (finished in 1886)',[1] and to repeat the Michelson experiment (finished in 1887).[2]
At this time Michelson was professor of physics at the Case School of Applied Science, and Morley was professor of chemistry at Western Reserve University, which shared a campus with the Case School on the eastern edge of Cleveland.(transition sentence necessary) Michelson suffered a nervous breakdown in September 1885, from which he recovered in October 1885. Morley ascribed this breakdown to the intense work of Michelson during the preparation of the experiments. In 1886, Michelson and Morley successfully confirmed Fresnel's drag coefficient - (better functional element than "-" necessary) this result was also considered as a confirmation of the stationary aether concept.
This strengthened the hope of finding the aether wind. (abnormally short) Thus, (comma added) Michelson and Morley created an improved version of the Michelson experiment with more than enough accuracy to detect this hypothetical effect. The experiment was performed in several periods of concentrated observations (what are "concentrated observations?") between April and July 1887, in Adelbert Dormitory of WRU (later renamed Pierce Hall, demolished in 1962).[A 1][A 2]
As shown in Fig. 4, the light was repeatedly reflected back and forth along the arms of the interferometer, increasing the path length to 11 m. At this length, the drift would be about 0.4 fringes. To make that easily detectable, the apparatus was assembled in a closed room in the basement of the heavy stone dormitory, eliminating most thermal and vibrational effects. Vibrations were further reduced by building the apparatus on top of a large block of sandstone (Fig. 1), about a foot thick and five feet square (5 square feet?), which was then floated in an annular trough of mercury. They calculated that effects (please restate what these "effects" are) of about 1/100th of a fringe would be detectable.
Figure 5. Fringe pattern produced with a Michelson interferometer using white light. As configured here, the central fringe is white rather than black.
Michelson and Morley, (comma added) and other early experimentalists using interferometric techniques in an attempt to measure the properties of the luminiferous aether, used monochromatic light only for initially setting up their equipment, always switching to white light for the actual measurements. The reason is that measurements were recorded visually. Monochromatic light would result in a uniform fringe pattern. Lacking modern means of environmental temperature control, the fringes showed continual drift even though the interferometer might be set up in a basement. Since the fringes would occasionally disappear due to vibrations by passing horse traffic, distant thunderstorms and the like, it would be easy to "get lost" when the fringes returned to visibility. The advantages of white light, which produced a distinctive colored fringe pattern, far outweighed the difficulties of aligning the apparatus due to its low coherence length. As Dayton Miller wrote, "White light fringes were chosen for the observations because they consist of a small group of fringes having a central, sharply defined black fringe which forms a permanent zero reference mark for all readings."[A 3][B 1] (this paragraph is in the wrong place)
The mercury pool allowed the device to be easily turned, so that given a single steady push it would slowly rotate through the entire range of possible angles to the "aether wind", while measurements were continuously observed by looking through the eyepiece. Even over a period of minutes, it was presumed that some sort of effect would be noticed, since one of the arms would inevitably turn into the direction of the wind and the other away.
It was expected that the effect would be graphable as a sine wave with two peaks and two troughs per rotation of the device. This is because during each full rotation, each arm would be parallel to the wind twice (facing into and away from the wind giving identical readings) and perpendicular to the wind twice. Additionally, due to the Earth's rotation, the (aether) wind would be expected to show periodic changes in direction and magnitude during the course of a sidereal day.
These prose issues are representative of what is wrong with the entire article - erratic sentence structure and poor word choice. For example, the lead says that the experiment was "aimed at..." While this is technically correct, the experiment sounds more like a catapult than the Michelson-Morley experiment with such phrasing. This, in addition to "measurements were observed." Measurements are made, not observed.
I would not let this good article nomination pass now, it has far too many issues. However, I am a new user - anyone else can pass it at any time if they have not contributed substantially to it and are more experienced than I am in making such judgement calls. Additionally, the article appears to be rated as a "C"-class by multiple WikiProjects, further corroborating my conclusion. Wer900talkessay on the definition of consensus01:56, 24 May 2012 (UTC)
The physics and relativity project ratings date from 2008 and 2009, respectively. D.H, the main science contributor to this article over the last two years and an accomplished physicist with multiple publications, is not a native English-speaker. My role in the last few months has mostly been to rework his text without removing all of the unique flavor of his language. Apparently you would wish that I had homogenized his text into completely standard English. I have far too much respect for D.H to have wished to do that. Stigmatella aurantiaca (talk) 10:22, 24 May 2012 (UTC)
I can indeed be judgmental of somebody who is so careless that he does not check the date of project ratings, or who spells "judgmental" "judgemental" the way that you just did. The page ratings were automatically reset to zero around the end of last month because of our extensive edits. From that fresh start, they have been mostly 4s and 5s. I have reason to believe that these multiple votes reflect the quality of our work better than your one single vote. Stigmatella aurantiaca (talk) 23:27, 24 May 2012 (UTC)
Animation yes or no?
D.H – I exchanged thoughts with RJH on the peer review page. He rather likes the animation, while my own feeling is that it's maybe a bit gimmicky. So the deciding vote is yours: Keep or remove? Thanks! Stigmatella aurantiaca (talk) 02:17, 6 July 2012 (UTC)
I first misunderstood the image. But now I see that it is correct, thanks for the nice work. --D.H (talk) 11:34, 6 July 2012 (UTC)
Problematical assertions
I had never really paid much attention to this paragraph before, but now that I've been doing an extensive copyedit of the article, I'm embarrassed that I hadn't deleted it before.
The Sagnac experiment placed a modified Michelson apparatus on a constantly rotating turntable; the main modification was that the light trajectory encloses an area. With this modified apparatus, any ballistic theories such as Ritz's could be tested directly, as the light going one way around the device would have a different length to travel than light going the other way (the eyepiece and mirrors would be moving toward/away from the light). In Ritz's theory there would be no shift, because the net velocity between the light source and detector was zero (they were both mounted on the turntable). However in this case an effect was seen, thereby eliminating any simple ballistic theory. This fringe-shift effect is used today in laser gyroscopes.
The above paragraph dates more or less from December 2004, and it is full of misunderstandings.
A Sagnac interferometer is not a modified Michelson apparatus. Among other things, it is a common path interferometer, whereas Michelson's is a double path interferometer. There is some degree of truth however, in that if one arranges the light path in Michelson's apparatus to enclose an area, it will be sensitive to rotation.
The original authors of this paragraph did not understand that there are multiple emission theories. Tolman's variant of emission theory will give a null result in Sagnac's experiment. But the Ritz and the Stewart theories will not. They will give the wrong result, not a null result.
Going into detail about the distinctions between different emission theories would give undue weight to a footnote in science history. It is something for the Emission theory article, not the MMX article. I feel it is simplest just to delete this paragraph, not even try to correct it.
The following assertions, which also date from approximately December 2004, also bother me:
In recent times experiments similar to the Michelson–Morley experiment have become commonplace. Lasers and masers amplify light by repeatedly bouncing it back and forth inside a carefully tuned cavity, thereby inducing high-energy atoms in the cavity to give off more light. The result is an effective path length of kilometers. The light emitted in one cavity can be used to start the same cascade in another set at right angles, thereby creating an interferometer of extreme accuracy.
The above does not strike me as a particularly good description of how lasers and masers work, yet nobody has tried to change their wording in nearly eight years. And what in heck does it mean when it states, "The light emitted in one cavity can be used to start the same cascade in another set at right angles, thereby creating an interferometer of extreme accuracy"? Stigmatella aurantiaca (talk) 07:03, 28 July 2012 (UTC)
Well it seems, the longer something was placed in the article, the less it was checked for accuracy. It's good that you look at those details. Also this stuff about the first laser experiments can be improved, there are plenty of good sources (indeed, the first experiment was made by Essen, which isn't even mentioned in the article).... --D.H (talk) 08:25, 28 July 2012 (UTC)
Small Problem with initial section "Measuring aether"
The following paragraph raises a question:
Earth orbits around the Sun at a speed of around 30 km/s (18.75 mi/s) or over 108,000 km/hr (67,500 mi/hr). The Sun itself is travelling about the Galactic Center at an even greater speed, and there are other motions at higher levels of the structure of the universe. Since the Earth is in motion, two main possibilities were considered: (1) The aether is stationary and only partially dragged by Earth (proposed by Augustin-Jean Fresnel in 1818), or (2) the aether is completely dragged by Earth and thus shares its motion at Earth's surface (proposed by George Gabriel Stokes in 1844). In addition, James Clerk Maxwell (1865) recognized the electromagnetic nature of light and developed what are now called Maxwell's equations, but these equations were still interpreted as describing the motion of waves through an aether, whose state of motion was unknown. Eventually, Fresnel's idea of an (almost) stationary aether was preferred because it appeared to be confirmed by the Fizeau experiment (1851) and the aberration of light.
The paragraph does not explain why these two possibilities in the emboldened sentence were considered. It simply gives the reason to be "since the earth was in motion".
I feel that an additional sentence is needed explaining the link between the motion of the earth and the dragging of the aether. Accidentprone104 (talk) 16:50, 30 November 2012 (UTC)
This is an archive of past discussions about Michelson–Morley experiment. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.
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