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Author Topic: YourTube Extended Michelson-Morley Experiment  (Read 21108 times)

BEP

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Re: YourTube Extended Michelson-Morley Experiment
« Reply #15 on: October 11, 2009, 09:55:21 PM »
@MH,

Your opinion please...

Why would this torsional stress only show when the axis of the apparatus is aligned between the 2 and 8 o'clock positions and not also when aligned with the 10 and 4 o'clock positions?

The clock positions are not precise but you should get my drift.

As far as the many different commentators (as I've seen across the web) mentioning that a change in spaces between the fringes is required.... All I can say is that should require a change in wavelength or angle of interference. I can't imagine either happening.

Time will tell on this one. Until then it is not scientific to post insults. That is just something scientists normally do.
As for me.... I will continue on this one. My opinion is the distance the beams travel must be made as great as possible, if this is a speed issue. As for mechanical deformations - yes - the most likely reason for almost any basement experimenter - not for me.

My initial try was not in my basement or garage. If the machine used had such 'flexing' it would have been scrapped a long time ago - yes, I checked for flexing before and during. I didn't think a rotating table made of 4" thick high grade tool steel would flex much. It didn't.


 




zerotensor

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Re: YourTube Extended Michelson-Morley Experiment
« Reply #16 on: October 11, 2009, 11:43:59 PM »
Zerotensor is fundamentally right about this one, but I am not so sure about his calculations.

The number of fringe shifts, N, using a monochromatic light source with wavelength, lambda, is given by;
N = L / lambda
where L is the difference between the lengths of the optical paths in the two arms of the interferometer.

Because of the geometry of the MM interferometer setup, this means that a displacement of one of the mirrors along the beam axis by a distance, d, will cause the path length along that arm to change by a factor 2d;  expressed mathematically, L=2d.  In this case, a shift in the interference pattern by N fringes indicates that the mirror has moved a distance d=(N * lambda) / 2 .

Of course, we don't know which elements of the interferometer might be moving here, so the best we can do is say that the difference in path length, L, changes according to,
L=N*lambda.

Inserting lambda = 532 nm, and N=11, we see that the shift in the interference pattern can be explained by a variation in the path length of 5852 nm.  A displacement of one of the mirrors by half this amount along the beam axis is sufficient to explain the observed shift.  Other kinds of displacements of the optical elements, including angular displacements, could also be responsible  for the effect.  Because the maximum displacement of the fringe pattern occurs when the beam splitter is horizontal, it seems likely that movement of the beam splitter is the culprit in this situation.  Taking steps to minimize any stresses on the optical setup by gravity is therefore an important prerequisite to future experiments along this line.

Quote
The slab of aluminum deforms as the apparatus rotates vertically due to varying stresses on the frame because of the changing gravity field relative to the apparatus.  When the apparatus rotates horizontally the gravity field is constant and therefore the stresses on the frame are constant.

While deformation of the aluminum slab might play some role, I think that it is much more likely that movement of the mirrors and/or the beam-splitter are to blame.  The reason the MM experiment and the myriad others which followed it always employ a horizontal setup is to minimize any stresses on the apparatus due to gravity.

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It is outrageous that the German experimenter didn't think of this and it makes his experiment pure junk science.  <snip>

I wouldn't be so hasty.  While the results are probably due to deformations of the instrument under the influence of gravity, we shouldn't rule-out the possibility that a more careful experiment might yield some evidence of an interesting new phenomenon.  The fact that Martin's setup does not exhibit a shift in the horizontal configuration shows that the apparatus is quite stable.  Furthermore, the observation of periodic 24-hour shifts indicates that the interferometer is sensitive enough to observe the earth's rotation.  I applaud the experimenter and encourage him to perform further experiments which will address the possible shortcomings of the apparatus.  This is the way real science is done.  Simply declaring that we should disregard the main idea of the experiment because of possible instrumental flaws (as you do) is more akin to "junk science", if you ask me.

To the experimenter I say, "Good idea-- but there are possible instrumental artifacts which are probably influencing your results.  You should repeat the experiment with an eye to addressing these concerns."

zerotensor

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Re: YourTube Extended Michelson-Morley Experiment
« Reply #17 on: October 12, 2009, 12:05:03 AM »
@MH,

Your opinion please...

Why would this torsional stress only show when the axis of the apparatus is aligned between the 2 and 8 o'clock positions and not also when aligned with the 10 and 4 o'clock positions?

Well, even though I'm not MH, I'll take a stab at that one.  If the beam-splitter moves, even by a micron or two, that could explain the shift.  We see the maximum displacement when the beamsplitter is horizontal, which is where one would expect the most flex under gravity, considering the way the beam splitter is mounted to the frame.

Quote
As far as the many different commentators (as I've seen across the web) mentioning that a change in spaces between the fringes is required.... All I can say is that should require a change in wavelength or angle of interference. I can't imagine either happening.

I agree.  The width and spacing of the individual fringes is actually very complicated to work-out, and depends strongly on the precise alignment and geometry of the setup.  Fortunately, the shift in fringe number is almost totally immune to these considerations, which is one reason why Michelson interferometry is such a useful and robust technique.

MileHigh

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Re: YourTube Extended Michelson-Morley Experiment
« Reply #18 on: October 12, 2009, 05:53:23 PM »
BEP:

Quote
Why would this torsional stress only show when the axis of the apparatus is aligned between the 2 and 8 o'clock positions and not also when aligned with the 10 and 4 o'clock positions?

I don't see that at all.  I see the interference patterns moving back and forth with a slow sinusoidal motion.  This is exactly what you would expect to see as the device rotates vertically about a horizontal axis where the slab of aluminum that forms the optical table acts like a piece of deforming rubber.  That's exactly what is happening - the aluminum is deforming like a piece of rubber.  We should all know that metal is flexible and deformable because we see it every day in our daily lives.

I used strong language and I think that it is justified.  This experiment is pure junk and any first-year physics student with two weeks experience in an optics laboratory would be able to point out this major flaw.  LASER interferometry is used every day to measure very tiny changes in the dimensions of materials - and that is exactly what you are seeing in this experiment.

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My initial try was not in my basement or garage. If the machine used had such 'flexing' it would have been scrapped a long time ago - yes, I checked for flexing before and during. I didn't think a rotating table made of 4" thick high grade tool steel would flex much. It didn't.

The joke about this experiment is that the aluminum slab that forms the optical table is part of the rotating structure itself, and it is absorbing all of the stresses induced in it from the two metal rods bolted to it as the device rotates.  It is being twisted and deformed by the variations in tension and compression in each rod as the device rotates vertically.

All that the experimenter had to do was mount the optical table on top of the rotating structure with a layer of foam insulation or something like that between the rotating structure and the optical table so that none of the stresses associated with the rotation would be transferred to the optical table itself.  Also, perhaps it would require a real optical table that uses a honeycomb metal support structure mated with a hard steel plate with tapped holes in it for bolting optical components in place - a real optical table and not a slab of aluminum.

The fact that the optical table is not isolated from the stresses of the rotating structure is a joke - how could anybody doing an experiment like this make such an incredibly stupid mistake?

My words are harsh but they are justified.

MileHigh
« Last Edit: October 12, 2009, 10:31:32 PM by MileHigh »

MileHigh

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Re: YourTube Extended Michelson-Morley Experiment
« Reply #19 on: October 12, 2009, 10:40:17 PM »
Zerotensor:

I am not going to disagree with you about the calculations.  My gut feel is that as a general principle an interference pattern can move by one bright band, and the overall geometry of the setup may be such that a fraction of a wavelength difference can induce the displacement of one band.  I could be wrong.  Way back when I was in junior college I did the classic "double slit" experiment in my physics class.

Anyway, here is a thought experiment:  Fix the apparatus so the optical table is not deformed when the device rotates about a horizontal axis.  Then there will be no displacement in the bright and dark bands.

MileHigh

pese

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Re: YourTube Extended Michelson-Morley Experiment
« Reply #20 on: October 18, 2009, 10:17:07 AM »
Other constructions
result the same differiencies between MIN an MAX values !!
over days.

Other Construction
(7 JPG's)

http://otto-gb.150m.com/MG/index.html


It will be seach nor if planet constelation or other (possibel) results are to find, that corelate with  them

G.P.