Taylor J. Smith wrote:
> Stephen A. Lawrence wrote: > > ... time dilation isn't really just a simple number. > > Hi All, 6-8-09 > > Here are some thoughts on time dilation. > > Jack Smith ... > "It is usually stated that this dilation of the proper > time of a body in motion has been proven by experiments... Total nonsense, of course. You can't *PROVE* a theory. You can only DISPROVE it. The meson data is consistent with the predictions made using SR, and so can be viewed as supporting it. Other interpretations are certainly possible, however, and this experiment, alone, certainly doesn't *prove* that time dilation occurs; to claim so is to step way outside the bounds of correct interpretation of the results. (This experiment *does* disprove the null hypothesis, which is that there's nothing at all "funny" going on with the meson half-lives.) The "failure to prove the theory" is true of any individual experiment, of course -- you can always find another theory which is also not disproved by a particular experiment. The trick, if you want to replace SR with something else, is to find a theory which is not disproved by *any* of the experiments which have been performed (and replicated). That's harder than you might think. Jack quoted: > GPS Evidence Against the Relativity Principle, by Thomas > E. Phipps, Jr.; Infinite Energy, Issue 67; May 2006; > p. 22 and following. > > ``The Global Positioning System (GPS) compensates the > running rates of its atomic clocks for their orbital motion > by speeding them up so as to cancel the relativistic time > dilatation. Such compensated clocks, when in orbit, run > in step with each other and with an earth-surface Master > Clock ... > > The relativity principle ... demands ... the clocks of two > ... observers [to be] each running slower than the other. This last quote is total nonsense. I haven't looked at the original paper in IE and certainly won't bother to, based on this quote from it. SR, alone, predicts a clock moving a circle will run more slowly than an unaccelerated clock. GR adds to that the prediction that, all else being equal, a clock higher in a gravity well will run more quickly than one lower in the well; the two effects obviously compensate in this case but not completely. Simple as that; there's no prediction, anywhere, that each clock will run slower than the other (which is a flat contradiction, of course). The GPS compensation is based on a GR model of the situation, which incorporates SR automatically (GR is a proper superset of SR and includes all of SR within its substantially more complex model). (In fact in GR the orbiting clock is following a geodesic, the one on the ground is not, and the "curved" path of the orbiting clock is only curved from a 3-d point of view...) > > Jack writes: > > Somewhere I think I read that Domina Eberle Spencer has the > Hafele-Keating airplane data and has concluded that it > was faked. > I've read a deconstruction of the experiment; here are my impressions. The data wasn't faked, they really did the experiment, and they really did gather the data, and it was not inconsistent with relativity being correct. However, the data was so poor that the null hypothesis was about as good a fit as the conclusion that relativity was at work; in other words, nothing was actually proved or disproved and the experiment did little or nothing to support any particular theory. The problem was that the clocks weren't accurate enough and suffered from too many glitches. Apparently such clocks don't typically run at "exactly" real time, and what's worse, the rate at which an individual cesium clock actually runs *varies* from time to time. Each clock will typically be stable for "a while" and then its "rate" will jump; how long it's stable for, and how big and what direction the jump is in, are unpredictable. You need quite a lot of clocks to really compensate for this annoying behavior -- more than were on the airplane. (I think they carried 6 clocks, but I'm not sure; maybe it was more. Incidentally the fact that they carried more than one is an immediate tipoff that there's something funky about those clocks!) The big red flag was that they did *not* release the raw data for a long, long time after the paper was published. The solution would have been to fly many more clocks. But, as so often happens, they didn't have the resources to do the experiment "right" and when they did it with what resources they had, the result was ambiguous. At that point, either they could have admitted that the result was ambiguous and that the whole thing had been a colossal waste of the resources they did have, or they could have published anyway and tried to pretend the result was significant. Like so many researches before them (and, no doubt, after them) they chose to put the interpretation on the data which they expected to be "correct" and publish anyway. Because the data supported the current view of how things "should" work nobody challenged it, of course. SR had already been validated in many indirect ways, so the "direct" validation was a major yawner as far as the scientific and engineering community was concerned. This kind of mess, uncommon in physics, is actually extremely common in the social sciences, where animal experiments are used to show all kinds of things, sometimes with very low reliability. Rats are expensive, so researchers economize on rat numbers. And then some die, some escape, some measurements are unclear and must be discarded, and in the end there just weren't enough rats, and what's the researcher to do? Publish, or perish? Well... In the case of the HK experiment, there's so little doubt as to the result which would obtain with a correctly done experiment that nobody's bothered to try to replicate it, AFAIK. (Note that if physics researchers in general were in much doubt about the results there would have been replications, whether or not the original experiment was dubious!)
