Talk:Hay-Schild controversy

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[edit] I don't get it

Hmm. Although I assume the historical reporting is accurate, the explanation of the"modern view" is opaque and seems wrong. If two different calculations give the same result, then a naive interpretation is that the curvature effects are somehow negligable. That is, if one took the curved-space calculations, and expanded them in powers of the curvature, one might expect to get back the "progression of flat spaces" calculation. Right? So one might naively expect that the reason the two different calculations give the same answer is that, under the covers, they are doing the same thing, up to some negligable terms. Thus, it seems there is some fallacy but its not clear from the article quite what that fallacy really is ... linas 00:38, 30 October 2005 (UTC)

* To my mind, the issue was never adequately resolved. The problem is, when viewed from a frame in which the centrifuge is not rotating, there is no relative motion within the experimental apparatus, and so the entire effect should instead be calculable (according to the general principle of relativity) as the effects of an apparent radial gravitational field. Perhaps as a compromise we might try to say that the "SR" explanation applies in the frame in which the centrifuge rotates, and the "gravitational" explanation holds in the frame in which it doesn't. But since this attempt at a resolution doesn't seem to be in print anywhere, I didn't want to add it. And in any case, if we believe Schild's, the two geometries aren't supposed to be reconcilable ErkDemon 02:56, 31 January 2007 (UTC)

* PS, I don't know how to explain the subsequent absence of the Harwell group's EP argument from the literature, except by suggesting that perhaps nobody actually wanted it. By rights, if we conduct an experiment to test SR's time dilation predictions for a centrifuged clock, or a circular particle storage ring, or Hafele-Keating or GPS, then if we are going to analyse the data for agreement with SR, and then present the agreement as significant (a very loaded word), we are really obliged to disclose whether the same results could have been expected outside of SR, and thanks to the Harwell group's EP argument, we know that we should be able to predict these effects without SR by (1) calculating the physical geeforces on the object, (2) invoking the EP to justify treating these as evidence of a real gravitational field, and (3) using Einstein's "general" 1911 gravitational time dilation argument to predict that the centrifuged or circling clock then ticks slower.

The political problem generated by the Harwell paper is that if we accept this argument, it means that the significance of some of the most convincing experimental tests of special relativity have been slightly hyped -- we could predict those results even if we didn't believe that velocity-based time dilation was physically real, and if we didn't accept the basis of SR. Since we've been sitting on this alternative explanation for forty-odd years, its now very difficult to reintroduce it, because meanwhile, some of the more enthusiastic proponents of SR have been teaching that these experiments have no other explanation. To now admit that there was an alternative explanation, but that we found it convenient not to mention it, is awkward.

I think that the modern view is fairly represented by the current version of the sci.physics "clock hypothesis" article[1] (as of Jan 2007). It says that since the centrifuge results agree so well with SR, that we know that SR time dilation is real, and because there's nothing left over to be explained by acceleration effects, we also know that acceleration effects are too small to be detected, and don't have any effect. That's an entirely valid representation of the situation as it is under SR-based physics. What we have to remember, though, is that this explanation doesn't have a wider legitimacy -- if we don't presuppose that SR is correct, we could argue with similar validity that we "know" that acceleration effects have a very noticeable effect, that these experiments validate the acceleration time dilation predictions to a very high degree of accuracy, and that since there is no effect left over for SR to predict, we therefore know that the SR time dilation effect isn't physically real.

It's a judgement call which path we go down, and that decision probably has to be made on wider issues. Unfortunately, we don't usually get the chance to make that assessment ourselves, because we are told that the SR explanation is the only one available, and that experiment proves that the SR arguments are right and that acceleration effects aren't relevant. This is pretty rotten science: it's like a pharmaceutical company finding that their trials can be explained either by the efficacy of their product or by an outside parameter that shows the same statistical correlation to the results, and deciding that since their drug must be good, the outside factor can be set to zero by hand, and that the study therefore unambiguously supports the idea that the drug is good.

If someone tried to pull this sort of statistical stunt in other branches of science I think they'd be crucified. ErkDemon 05:56, 31 January 2007 (UTC)

* PPS: If anyone who's studied those two papers thinks I've misrepresented anything or strayed away from NPOV, please feel free to rewrite the article if you think you can do it better. I've tried to include lots of quotes rather than paraphrase, but there might be issues about perceived selective quoting or about the bits of text in between. I'm generally not authoring or editing articles here any more, so ... whatever. If anyone knows of additional sources for what happened in the community between the publication of the Hay and Schild papers, that would be interesting.ErkDemon 05:56, 31 January 2007 (UTC)