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Explanation of why Michelson Morley measurments of speed of light disproved ether

by mark goldman
Tags: ether, michelson-morley, relativity
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soothsayer
#19
Aug30-12, 10:32 AM
P: 398
I believe there was a theory that some of the ether was dragged along by the earth, making the ether "wind" stationary locally, but not away from the Earth, the idea that is we could put this experiment in orbit, it would find the effect that the experiment on the Earth could not. But that idea was as representative as a death knell for the ether theory than the failed experiment.
ZikZak
#20
Aug30-12, 12:46 PM
P: 242
Quote Quote by soothsayer View Post
But that idea was as representative as a death knell for the ether theory than the failed experiment.
That might be reasonable, if the ether-drag theory had been proposed after MM in order to explain it, but it was in fact proposed by George Stokes in 1845, as an alternative to the partial ether drag hypothesis of Fresnel. Fresnel realized in 1818 that some of the ether must be dragged along by matter in order to explain stellar aberration (otherwise the refractive index of the telescope lens should vary along with its velocity through the ether). The problem with that theory being that partial dragging would itself result in a chromatic aberration that was never seen. So Stokes proposed that ALL of the ether was dragged by a ponderable body, but that the velocities of the ponderable body and the ether occupying the same space were different.

The MM experiment was meant to test the amount of ether wind in the laboratory, which would be substantial under Fresnel's theory but could be essentially zero in Stokes's theory as the Earth dragged all of the nearby ether with it. So when it was performed, the interpretation of the results was unclear, because: (a) contrary to what you read in the textbooks, MM did NOT make the test at different times of year and day (the experiment took place over the course of just a few days in July 1887), (b) the amount of data collected was actually quite small, consisting of only about 25 turns of the instrument, and (c) there were so many ether theories around (no such thing as THE ether theory) that the result seemed to confirm some (such as Stokes'), while falsifying others (such as Fresnel's).

Obviously the experiment needed repetition, but that didn't happen for over a decade, because Michaelson's expertise at building interferometers was essentially unique, and he decided to drop the experiment after the first week. So it should not be surprising that the immediate reaction at the time of publication was lukewarm and basically a scientific shrug.
harrylin
#21
Aug31-12, 03:32 AM
P: 3,188
Quote Quote by ZikZak View Post
[..] Obviously the experiment needed repetition, but that didn't happen for over a decade, because Michaelson's expertise at building interferometers was essentially unique, and he decided to drop the experiment after the first week.[..]
I wasn't aware that he did not repeat quickly the experiment. Why do you think that he decided to drop the experiment after the first week? Michelson claimed to the contrary that he was going to repeat it "at intervals of three months". That's puzzling...
- https://en.wikisource.org/wiki/On_th...niferous_Ether
Histspec
#22
Aug31-12, 05:46 AM
P: 89
Quote Quote by harrylin View Post
I wasn't aware that he did not repeat quickly the experiment. Why do you think that he decided to drop the experiment after the first week? Michelson claimed to the contrary that he was going to repeat it "at intervals of three months". That's puzzling...
- https://en.wikisource.org/wiki/On_th...niferous_Ether
Michelson and Morley tried to use their interferometry technique in order to establish a standard of length. Already in June 1887 (before the ether drift measurement) they performed preliminary standard length measurements. Then they performed their ether drift measurements in July, and soon after they continued their length standard measurements, publishing the papers:

Michelson&Morley (1887): "On a method of making the wave-length of sodium light the actual and practical standard of length", Am. J. Sci, 34, 427-430

Michelson&Morley (1889): "On the feasibility of establishing a light-wave as the ultimate standard of length", Am. J. Sci, 38, 181-186

Further information:
Staley, Richard (2009), "Interferometers and their uses", in: "Einstein's generation. The origins of the relativity revolution"
harrylin
#23
Aug31-12, 05:58 AM
P: 3,188
Quote Quote by Histspec View Post
Michelson and Morley tried to use their interferometry technique in order to establish a standard of length. Already in April 1887 (before the ether drift measurement) they performed preliminary standard length measurements. Then they performed their ether drift measurements in July, and soon after they continued their length standard measurements, publishing the papers:

Michelson&Morley (1887): "On a method of making the wave-length of sodium light the actual and practical standard of length", Am. J. Sci, 34, 427-430

Michelson&Morley (1889): "On the feasibility of establishing a light-wave as the ultimate standard of length", Am. J. Sci, 38, 181-186[..]
Thanks, that's very interesting information! It appears that they were too occupied with those efforts.
ZikZak
#24
Aug31-12, 07:19 AM
P: 242
Yeah, MM were never very good theoretical physicists (Morley was actually a chemist), and I think were a bit overwhelmed by all the possible interpretations of the experiment. What they did discover is that they had invented a fantastic means of measuring length, which was an activity both theoretically simple, and enormously useful.
cmmcnamara
#25
Aug31-12, 08:23 AM
P: 122
I've only briefly read on the topic of LET and some quantum theories, so bear with me, but isn't there a similar kind of controversy going on with modern physics as well? Lorentz believed in an invisible expansive field called ether but aren't were currently hypothesizing about something similar regarding the Higg's field? Please shut me up immediately if I have the wrong idea here, but I thought the arguments exhibit similarity.
ZapperZ
#26
Aug31-12, 08:34 AM
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Quote Quote by cmmcnamara View Post
I've only briefly read on the topic of LET and some quantum theories, so bear with me, but isn't there a similar kind of controversy going on with modern physics as well? Lorentz believed in an invisible expansive field called ether but aren't were currently hypothesizing about something similar regarding the Higg's field? Please shut me up immediately if I have the wrong idea here, but I thought the arguments exhibit similarity.
So how is the Higgs field related to the ether? I fail to see the physics where the Higgs field could somehow define an 'absolute' reference frame. Can you tell me how fast we are moving through this field right now?

Zz.
cmmcnamara
#27
Aug31-12, 08:59 AM
P: 122
Sorry I suppose I wasn't very specific. I'm not saying the Higgs field is related in this manner, I was mentioning it because a concept like the ether was once considered a viable theory as the Higgs field also currently is. I'm not vying for the ethers validity whatsoever.
ZapperZ
#28
Aug31-12, 09:19 AM
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Quote Quote by cmmcnamara View Post
Sorry I suppose I wasn't very specific. I'm not saying the Higgs field is related in this manner, I was mentioning it because a concept like the ether was once considered a viable theory as the Higgs field also currently is. I'm not vying for the ethers validity whatsoever.
But then, one can say the same thing with just about ANY field. Would the EM field that permeates all of space as well (as described by QED) be of the "same concept"? Would the self-energy field that endows mass to the electron in a material be of the same concept?

One doesn't need to reach for the Higgs field if one simply want a similar concept.

It all boils down to here that I really can't see having the ether and the Higgs field even being mentioned in the same manner or sentence. They are as different as night and day, besides the obvious fact that one has no experimental evidence, while the other does.

Zz.
Namesinger
#29
Feb6-13, 02:06 PM
P: 2
[QUOTE=Ken Natton;4052923]Iím not sure that, at the time of the [Michelson-Morley] experiment, the conclusion was that the aether did not exist, only that they had failed to detect it as they had expected to. The basic reasons for believing in it remained.

I agree. The MM experiments showed only that no discernible difference in the speed of light exists in any direction in which we can point an interferometer. One can however postulate that aether has resistance only in a direction 90 degrees away from our three standard spacial dimensions. Another post has suggested that for the concept of aether to be coherent, aether must have properties. Aether has the property of conducting electro-magnetic waves: the evidence for this is that EM does indeed have wave characteristics such as interference patterns. Gotta be something there that's waving. no?

If one accepts the possibility of aether as a kind of "river" flowing at right angles through our three dimensions, this in turn opens the door for a variation on Lord Kelvin's vortex theory of atoms, with atoms as a three-dimensional slice of a hyper-dimensional vortex in the aether.
soothsayer
#30
Feb7-13, 12:28 PM
P: 398
I stumbled across Dirac's aether theory which was derived from QFT. If I'm not mistaken, this idea gradually became the foundation of Superfluid Vacuum Theory as it is today. Very interesting.

http://www.fisicateorica.me/reposito...Dirac1951b.pdf
Namesinger
#31
Feb7-13, 03:58 PM
P: 2
Thanks Soothsayer - I wasn't aware of SVT, but it seems pretty relevant. My thought experiment goes like this: take a snapshot of the universe - a representation of three dimensions in two, to free up another dimension for visualization. Print the snapshot on a permeable surface, like a net. Stretch the net a foot or so over the bottom of a (hyperdimensional) swimming pool. Now open a drain in the bottom of the pool, so a vortex forms that intersects the net. Now restore our 2D snapshot back to three, so the "circle" where the vortex intersects the net is actually a sphere, with little rotating bits (subatomic particles) orbiting the center - the nucleus. Flotsam (like a floating leaf) circling the edges of an irrotational vortex (the kind you generally see in nature) has no spin of its own but only spins relative to the center of the vortex. If particles generally can be thought of as 3-dimensional slices of an n-dimensional vortex, I wonder if this local rotation around the edges of the vortex and relative to its center could be a strong analogy (at least) to the Higgs boson? As the local rotation has to do with fluid getting "sucked in" to the vortex - that is, imparting angular momentum to relatively stationary surrounding hyper dimensional fluid (superfluid?) - I wonder if this could correspond to the notion of the Higgs imparting mass to particles? I would be grateful if you (or anyone) can point out for me any inconsistency or errors in this thought experiment!


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