Harry Veeder wrote: > > ----- Original Message ----- From: "Stephen A. Lawrence" > <[email protected]> Date: Friday, September 11, 2009 2:32 pm Subject: > Re: [Vo]:Michelson-Morley Interferometer experiment finally done > correctly? > > >> Which is irrelevant because they have been replicated, with >> variations,many times over. It's a very difficult experiment but >> that doesn't keep people from replicating it, because it's also a >> very important experiment. (Note that the difficulty stems in >> large part from the factthat the effect being tested for is >> *second* *order*. To first order,emission theory, relativity, and >> aether theory all agree, and predict no shift. Consequently a >> sloppily done MMX is of no value, because the looked for effects >> will be swamped in the noise, or, if the apparatus isn't >> sufficiently rigid and there is a systematic flex, the effects will >> be overwhelmed by a false "signal". In general, amateurs need >> notapply -- a version of this done in your basement won't be >> precise enough to prove anything.) > > That may have been true when the experiment was first performed, but > haven't lasers made it much easier to observe a second order effect?
Good question -- they may very well have. Certainly the fringes should be far more visible. However, there is still a major problem with system rigidity; in the classical MMX you need to rotate the whole apparatus without having anything shift or wiggle. The "optical bench" Michelson and Morley used was actually a huge slab of marble (rigid!) floating on a pool of mercury (to allow it to be turned smoothly and easily). This sort of rig is not easy to duplicate, for anyone. Here's an interesting quote from the Wiki article: > Morley was not convinced of his own results, and went on to conduct > additional experiments with Dayton Miller > <http://en.wikipedia.org/wiki/Dayton_Miller>. Miller worked on > increasingly large experiments, culminating in one with a 32 m > (effective) arm length at an installation at the Mount Wilson > observatory <http://en.wikipedia.org/wiki/Mount_Wilson_observatory>. > To avoid the possibility of the aether wind being blocked by solid > walls, he used a special shed with thin walls, mainly of canvas. He > consistently measured a small positive effect that varied with each > rotation of the device, the sidereal day > <http://en.wikipedia.org/wiki/Sidereal_day> and on a yearly basis. His > measurements amounted to only ~10 km/s instead of the ~30 km/s > expected from the earth's orbital motion alone. He remained convinced > this was due to partial entrainment > <http://en.wikipedia.org/wiki/Entrainment_%28physics%29>, though he > did not attempt a detailed explanation. > > Though Kennedy later also carried out an experiment at Mount Wilson, > finding 1/10 the drift measured by Miller, and no seasonal effects, > Miller’s findings were considered important at the time, and were > discussed by Michelson, Lorentz > <http://en.wikipedia.org/wiki/Hendrik_Lorentz> and others at a meeting > reported in 1928 (ref below). There was general agreement that more > experimentation was needed to check Miller’s results. Lorentz > recognised that the results, whatever their cause, did not quite tally > with either his or Einstein’s versions of special relativity > <http://en.wikipedia.org/wiki/Special_relativity>. Einstein was not > present at the meeting and felt the results could be dismissed as > experimental error <http://en.wikipedia.org/wiki/Experimental_error> > (see Shankland ref below). To date, no one has been able to replicate > Miller's results, and modern experiments have accuracies that rule > them out. I have read (someplace) that an analysis of the errors in Miller's apparatus leads to the conclusion that his results were, indeed, within his error bars of being null. So, in modern terms, he didn't get a positive result, after all (it is perhaps telling that Miller himself never attempted to determine how big his error bars should have been -- or maybe that just wasn't done back in those days). It has also been speculated that Miller was suffering from mercury poisoning by the time of his later experiments, which may have interfered with the accuracy of his measurements (a steady hand and a clear head may both fall victim to mercury poisoning). I don't know if there's evidence to support that. Certainly he was performing a very dangerous experiment, whether he realized it or not. It's also true that one should always suspect a result which is near the accuracy limit of the apparatus *and* which was obtained by someone who was heavily invested in the result, and really, really wanted to obtain that particular result. Michelson and Morley, interestingly, apparently really *didn't* want to get the result they got -- their goal had been to support the aether theory, not to demolish it. > Harry >
