Talk:Michelson–Morley experiment

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An investigation of the original MM data shows that fringe shifts were observed, indicating speed of light not a constant in all reference frames but only relative to some absolute 3-space! More recent experiments (Jaseja et al, 1964, DeWitte, 1991, Cahill, 2006) have confirmed this. Big News. Watch this space...

The following is a section of the article that is not entirely accurate: Although a small "velocity" was measured, it was far too small to be used as evidence of aether, did not seem to vary in a day/night or seasonal pattern, and was within the range of experimental error that meant the speed might actually be zero. The apparatus behaved as if there were no wind at all—as if the Earth had no motion with reference to a medium.

I have a pdf of the 1887 American Journal of science that the MMX was published in and will be posting it once I get it hosted.

Regardless of if it was experimenter effect, the paper actually does show a small sine wave of observation which reversed at night. (actually the interferometer was spun clockwise at night and counter-clickwise at noon across three days of operation for a total of 6 hours of observations. Obviously this has absolutely no bearing on seasons.

If there are no objections I will be editing this section once I have made the paper available.

Where are the equations for the distances involved?

Previous text stated that Michelson and Morley won Nobel Prize. Info does not appear on official Nobel site here:

http://www.nobel.se/physics/laureates/index.html

Any info?

Michelson won it in 1907. It's on the page you provided. I'm re-adding this information to the article. -Nvf 16:08, 6 August 2006 (UTC)

I wonder that there is not mentioned if Michelson-Morley experiment was originally executed in a vacuum, so it was executed in the air?

Does anyone know if there is any difference in results if the experiment is executed in the air or in a vacuum, so that the interference pattern does not change in either cases when rotating the Michelson interferometer? What about if the air is replaced with the water?

- TS

The original experiment was performed in air. Later versions of the experiment where performed at varying altitudes (to determine whether the aether might be being "dragged" around at the earth's surface), as well as in vacuum pumped tubes (1925); all gave essentially the same results. Chas zzz brown 23:39 Mar 11, 2003 (UTC)

Is the experiment performed so that light beams go through water or other medium, in which speed of light is significantly smaller than in vacuum? What is the result? It is quite clear that if photons (or other information carriers) travel at speed << c in the apparatus, then null result must imply. But if all these lead to null result, M-M experiments with different mediums does not support the Special Theory of Relativity, they contradict it?

- TS

This isn't really the place to discuss this. Talk pages are for improving the encyclopedia, not discussing the subject. A more appropriate forum would be the newsgroup sci.physics.relativity - a newsgroup founded specifically for "Einstein was wrong" discussions. -- Tim Starling 11:49 Mar 12, 2003 (UTC)

Sorry, I didn't notice. But if the name of the game is to improve the encyclopedia, it would be nice if there was a link or explanation of cases where the Michelson-Morley experiment is performed with various mediums (especially water) for light propagation.

- TS

You might find this helpful. -- Tim Starling 13:27 Mar 12, 2003 (UTC)

The article is looking good. However, it should be noted that not all references made to the Aether in modern times refer to something solid enough to influence the speed of light in a wind-like fashion. Modern physics allows for the manipulation of "spacetime" which could be termed as a kind of aether. Light waves have to be travelling through something. Also a reference could be made to the evidence for photons as discrete particles, and the Dual Nature of Light.

What about the possibility that aether is massless and instantly accelerates to the speed of the source of the light waves? Have there been comparisons made with the speeds of light waves from differing sources?

One thing that should be borne in mind is the fact that all matter is made up of fields that themselves are limited to the speed of light. I have a suspicion that the phenomenon of inertia is caused by a simple short time lag in the reactions of these fields caused by temporarily altering their relative shapes. Thus the interchangability of time and space at high velocities.

Comment: According to the Maxwell's equations, light is waving of electromagnetic field around a charge. Thus electromagnetic field can be consider as the medium, or an aether, through which light propagates. Further, the speed of the light is c relative to this field.

--Luke Parrish Sept 21, 2003

Contents

[edit] Swimmer in current

Rewrote:

The effect of the aether wind on light waves would be like the effect of a strong current in a river on a swimmer who is moving at a constant speed back and forth between two points, one upstream, the other downstream. If the second point were directly upstream of the first, the swimmer would be slowed by the current on the way from the first to the second and, similarly, sped up on return. The cumulative round trip effects of the current in the two orientations slightly favors the swimmer travelling at right angles to it. Similarly, the effect of an aether wind on a beam of light would be for the beam to take slightly longer to travel round-trip in the direction parallel to the "wind" than to travel the same round-trip distance at right angles to it.

Sound waves are much closer to the physics of the Michelson-Morely experiment (since they always travel in a constant speed relative to the medium). I rewrote the section to use them instead of a swimmer, since it makes it more obvious why physicists believed there was an ether wind. Jrincayc 17:51, 3 Jan 2005 (UTC)

[edit] Definition of 'Fringe'

May I request an edit please that defines/links fringe in:

Michelson-Morley experiment 1.. 2 The experiment 3.. 4.. 5.. 6..


"Any slight change in the amount of time the beams spent in transit would then be observed as a shift in the positions of the interference fringes. If the aether were stationary relative to the sun, then the Earth's motion would produce a shift of about 0.04 fringes".

I tried a search for the work "fringe" but found definitions out of context (hair style, Edinburgh Festival, fabric edge).

Right. I think what is needed is a minor edit to the "interference" page and a link to that. The interference page, incidentally, has a very pretty diagram of patterns caused by circular waves but does not at present have the one most commonly needed: ordinary inteference in the double-slit context. This kind is the one needed to understand interferometers.
Caroline Thompson 10:21, 6 Jan 2005 (UTC)
A fringe in a Michelson Interferometer is equal to a single wavelength. In this context, it is caused by two coherent light sources of the same wavelength intersecting at different angles of incedence. Across a surface they strike, the waves move between constructive and destructive interference causing bright and dark lines. The distance from the center of one bright line to the center of the next (or dark-to-dark)represents one full wavelength. Path length difference is not required to produce the effect and the two beams can be perfectly in phase. The effect is best understood with the aid of a diagram. I will try to prepare one and update the interference page.--Nemesis75 18:53, 17 January 2006 (UTC)
A new page explaining the concept of a fringe shift is now available.--Nemesis75 23:05, 20 January 2006 (UTC)

[edit] Decay?

According to the article,

lasers and masers amplify light by repeatedly bouncing it back and forth inside a carefully tuned cavity, thereby inducing atoms in the cavity to decay and give off more light.

What does "decay" mean in this context? Fall apart into two atoms and emit radioactive radiation? If so, I must have misunderstood how a laser works. / 82.123.126.111 10:14, 4 August 2005 (UTC)

What it means is that the description is missing a step: the first step is to pump energy into the cavity, raising the electrons of the atoms into a higher-energy state. Interaction with a photon will then cause the electron to decay back to the original state, creating a second photon that is an exact duplicate of the first. --Carnildo 18:12, 4 August 2005 (UTC)


[edit] Kennedy Thorndike Experiment

......In 1932 the Kennedy-Thorndike experiment modified the Michelson-Morley experiment by making the path lengths of the split beam unequal, with one arm being very long. In this version the two ends of the experiment were at different velocities due to the rotation of the earth, so the contraction would not "work out" to exactly cancel the result. Once again, no effect was seen.....

...In this version the two ends of the experiment were at different velocities due to the rotation of the earth..... is wrong.

The interferometer was stationary and not turned. At any given point on the Earth's surface, the magnitude and direction of the wind would vary with time of day and season equally for booth arms and would cause the fringe shift, dependent on arm length difference.

25.8.2005 N. Feist

You are correct, but only due to a "typo". I had confused the name of the experiment, which should be the Michelson-Gale-Pearson experiment. You will note the M-G=P experiment works exactly as I described the K-T experiment as working.

[edit] Disjunct between Special relativity and the Michelson-Morley experiment.

I think it might be useful to note that Einstein himself publicly and specifically denied being inspired or even aware of the Michelson-Morley experiment or it's result, before thinking up his Special RElativity theory. I would add it myself, but I am wary of phrasing it inaccurately or misleadingly. -- 08:30, 9 November 2005 (UTC) 08:31, 9 November 2005 (UTC)Cimon avaro; on a pogostick.

Since there has been no answer to the above comment, I am moving the offending paragraph here. If there is any appropriate information that can be salvaged from it, feel free to reinsert them, but without the assertion that Einstein was inspired by Michelson-Morley.

It had been thought after the Maxwell Equations had predicted the speed of light appeared not to have a reference frame that the speed of light's reference frame must be the aether. So the failure of the Michelson-Morley experiment in proving the existence of an aether made some surprising implications regarding the speed of light itself as it did not appear to be affected by the speed of the earth whereas the Galilean transformation would have predicted that the velocity of the light would have appeared to be less to an earth observer when the light was traveling in the direction of the earth's orbit. This effect was not lost on Albert Einstein who exploited it in his Special Theory of Relativity.

Thank you. -- Cimon avaro; on a pogostick. 22:58, 27 December 2005 (UTC)

In fact there can hardly be any little doubt that Einstein knew about it, as he explained the importance of that experiment for him for the development of SRT at a meeting in Japan. If someone comes up with that reference, the claim can be cited.
But it is in fact not needed, as the MMX was one of the key experiments that Lorentz discussed in his lead-up to SRT; there is no doubt about the historical influence of the MMX on the development of SRT. BTW, Einstein studied Lorentz' papers at the ETHZ. Harald88 23:23, 23 November 2006 (UTC)
I stumbled on someone's ref. myself, maybe someone can look it up:
article on this question published in the August 1982 issue of Physics Today by Prof. Yoshimasa A. Ono. "In Japan, Einstein gave a speech entitled "How I Created the Theory of Relativity" at Kyoto University on 14 December 1922. This was an impromptu speech to students and faculty members, made in response to a request by K. Nishida, professor of philosophy at Kyoto University. Einstein himself made no written notes. The talk was delivered in German and a running translation was given to the audience on the spot by J. Isiwara, who had studied under Arnold Sommerfeld and Einstein from 1912 to 1914 and was a professor of physics at Tohoku University. Isiwara kept careful notes of the lecture, and published his detailed notes (in Japanese) in the monthly Japanese periodical Kaizo in 1923; Ishiwara's notes are the only existing notes of Einstein's talk. ... It is clear that this account of Einstein's throws some light on the current controversy as to whether or not he was aware of the Michelson-Morley experiment when he proposed the special theory of relativity in 1905; the account also offers insight into many other aspects of Einstein's work on relativity. ... [Einstein said:] Soon I came to the conclusion that our idea about the motion of the Earth with respect to the ether is incorrect, if we admit Michelson's null result as a fact. This was the first path which led me to the special theory of relativity. Since then I have come to believe that the motion of the Earth cannot be detected by any optical experiment, though the Earth is revolving around the Sun.[48]
Unverified, Harald88 16:43, 25 November 2006 (UTC)

[edit] Explanation using Classical Wave Theory of Light.

It is possible to explain the null result of the Michelson-Morley experiment fully, by using the Wave Theory of Light in Ether and the Doppler effect that causes change in the Frequency and the Angle of Reflection, when the Mirror is moving in Ether. Can this explanation be added to the existing page? This comments are by first time user daralam@mtnl.net.in 59.183.21.30 00:39, 23 January 2006 (UTC)

-> Could you clarify this or perhaps cite a source? If I understand correctly, since the light source and mirrors are not moving relative to each other (unless sunlight/starlight is used as the source), Doppler effects are not seen. Someone42 07:19, 23 January 2006 (UTC)
-> If experimenter, the light emitter, and receptor are all moving together, then the experimenter will not detect any result of the Doppler effect. The observed results of Doppler Effect which occur in the Ether due to a moving emitter and the moving receptor get cancelled.

The radiated frequency from the moving emitter in Ether, in the direction of movement is higher than the frequency which would be emitted, if the emitter were static in the Ether, due to Doppler Effect. The frequency received by a static receptor in Ether will be same as in Ether, but if it is moving in the direction of light then it will be less than in Ether, due to the Doppler Effect. A moving mirror in direction of light, reflects light at a lesser frequency in Ether than the incident light on it. An observer static in Ether will detect, this but observer moving with the mirror will not. Daralam 23:45, 23 January 2006 (UTC)

To put it another way, co-motion hides the doppler effect even in sound. If an emitter and detector are placed on a carriage moving together at .5 the speed of sound, there would be a doppler shift only to observers stationary or otherwise "moving" wrt the emitter. The detector would still "hear" the same frequency for the same length of time as if the carriage was not moving. The medium is the preferred frame of reference in your mind and feels automatic but doppler is tricky that way. Nemesis75 01:07, 24 January 2006 (UTC)
Here's the equation for Doppler shift in a medium (from Doppler effect): :\frac{f_r}{f_s} = \frac {1 - \mathbf{n} \cdot \mathbf{v}_r / c}{1 - \mathbf{n} \cdot \mathbf{v}_s / c}. As you can see, if v_r (receiver velocity) and v_s (source velocity) are the same, the right side of the equation is equivalent to unity and so f_r = f_s, regardless of what c (speed of propagation in medium) is. Someone42 04:20, 24 January 2006 (UTC)

[edit] helicopter

The bit about the helicopter seems confusing and is probably wrong. A better analogy, or none, might be an improvement.

The cause of confusion was the unrealistic blade tip speed of 50 MPH. In actual fact it is typically about 300 MPH. Therefore, on a helicopter cruising at 150 MPH this results in a maximum relative blade-tip speed of 450 MPH (300 + 150) on the upwind side, versus a minimum relative blade-tip speed of 150 MPH (300 - 150) on the downwind side. (As the latter is still in excess of stall speed, the blade is able to produce balanced lift on both sides of the helicopter through compensation of the speed/lift ratio by cyclic pitch variation).
The few changes I made to the syntax should also help make this analogy more readable. I also think of the air as a good example for the average reader, so please don't remove it as long as the debate on the aether is... on the air in the scientific community!
I just signed the Open letter to the scientific community, posted on the web under cosmologystatement.org by 39 cosmologists, backed by a long list of fellow petitioners, claiming urgent questioning, if not abandon, of the Big Bang theory.
62.202.5.149 20:45, 4 April 2006 (UTC)

In the New Considerations and Interpretations section it sais:

"... one-way anisotropic light formulas as proposed by Nicolas Pashsky could be invalidated by the Ives-Stilwell experiment, because the Nicolas Pashsky formulas do not account for the Transverse Doppler effect."

Could someone please give me a scientific reference proving this statement. Thanks.

[edit] white light?

The article stated that the MM experiment used white light. That seems extremely unlikely to me, especially since they claimed to be able to measure shifts of a tiny fraction of a wavelength. I've deleted the word "white." If someone has a source for this statement, please speak up.--24.52.254.62 19:45, 23 November 2006 (UTC)

Ah, I found the information in their original paper. They used sodium light, not white light.--24.52.254.62 21:10, 23 November 2006 (UTC)

They used both white light for calibration, and sodium light for the experiment. Just read it again and more carefully. Harald88 23:12, 23 November 2006 (UTC)
It sounds like we're in agreement about omitting the word "white," which was clearly misleading.--24.52.254.62 00:41, 24 November 2006 (UTC)
Sorry but I mixed it up, it was just the other way round! If I understood it well, the sodium light was needed for course adjustment as it has a larger coherence length. In any case, white light was used for the experiment. As explained by "Jerry" on sci.physoics.relativity:

[The arms were] Pretty nearly equal, though. Although Michelson and Morley used sodium light for collimating the apparatus, the actual experiment was performed using white light from an argand burner. The colored fringes were much easier to visually monitor; on the other hand, the limited coherence length of white light meant that the path lengths needed to match within microns. Note in Fig. 4 the piece of glass "c" used to compensate for the difference in light paths. http://www.aip.org/history/gap/PDF/michelson.pdf

Thus I will now reinsert "white". Harald88 20:04, 24 November 2006 (UTC)

[edit] Robertson-Mansouri-Sexl test theory

Someone put in a paragraph portraying the Robertson-Mansouri-Sexl test theory as some kind of theory of quantum gravity. I think they're misunderstanding the use of this type of test theory, which is meant to be a framework for analyzing data and searching for deviations from fundamental theories, not as a fundamental physical theory itself. There's a good discussion of this at http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html . There are indeed serious proposals to modify special relativity in ways that might make it more compatible with quantum gravity (e.g., Doubly-special relativity), but I don't think that's what this particular test theory was meant to do. I've taken out the paragraph.--24.52.254.62 20:04, 23 November 2006 (UTC)

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