From: helbig@asclothestro.multivax.de
In article <1p3imn8.10geog6da220gN%nospam@de-ster.demon.nl>, "J. J.
Lodder" writes:
> Phillip Helbig (undress to reply)
> wrote:
>
> > Not much effort is put into confirming or refuting undisputed results or
> > expectations, but occasionally it does happen. For example, according
> > to theory muons are supposed to be essentially just like electrons but
> > heavier, but there seems to be experimental evidence that that is not
> > the case, presumably because someone decided to look for it.
> >
> > What about even more-basic stuff? For example, over what range (say,
> > multiple or fraction of the peak wavelength) has the Planck black-body
> > radiation law been experimentally verified?
>
> Very well, given that the cosmic black body radiation has been measured
> in great detail to better than a millikelvin.
Yes, but at what frequencies? As the name indicates, the CMB peaks in
the microwave region. It is well measured there, and a good way in
either direction, but towards higher frequencies the intensity drops
sharply. Even ignoring confusion by other sources and so on, I doubt
that it has been measured to any significant accuracy in the
ultraviolet, not to mention the gamma-ray region. (Photons here will be
few and far between.)
Yes, it looks like a perfect black body, no-one has convincingly argued
that it should be otherwise, and so on, but the question remains over
what range has that been verified.
Discussing the CMB is a bit of a red herring, because if one saw
departures from the black-body spectrum, one would suspect some
astrophysical cause. So think of lab measurements of black bodies: over
what range in frequency have they been made and to what precision?
> > Or that radioactive decay
> > really follows an exponential law? Or that the various forms (weak,
> > strong, Einstein) of the equivalence principle hold?
>
> Eotvos also has been verified to grat precision.
That is just the weak equivalence principle.
> You should realise that a lot of that testing is implicit.
> The design of all experiments takes the laws of physics,
> as we know them, for granted.
> If there really is something wrong with those laws
> the experiments would not behave as expected,
> and then people would start to search for causes.
Right, but, say, a tiny deviation from a black-body spectrum at a
frequency where no-one notices it anyway would go unnoticed.
> For example, LIGO takes general and special relativity for granted.
> So there really is no point in wringing yet another verification
> of Michelson-Morley out of it. (and others can do it much better)
> A mention in Guiness book of records as the largest M&M experiment ever
> really isn't worth the trouble.
Right, to some extent. One can actually use LIGO to contrain
alternatives to GR, which implies that one does not assume GR from the
ground up. For example, Bekenstein's TeVeS theory was ruled out by LIGO
(and the follow-up observations), because it predicts significantly
different Shapiro delays for gravitational and electromagnetic
radiation.
> Moreover, confirming the well-known is not without risk.
> If you fail to obtain the 'right' result
> people will not doubt the result,
> they will doubt your competence as an experimentalist.
Maybe, but that is not good science, especially if someone confirms an
unexpected result.
> You can think of the Italian 'speed of neutrinos' experiment
> that found greater than light speeds from CERN to Gran Sasso
> as a particularly sad example.
> 'Everybody' with standing told them that this just cannot be right.
> And indeed it wasn't, and the team leader resigned in disgrace,
IIRC, they didn't actually believe that their neutrinos went faster than
the speed of light, but said that that was the result of their analysis
and solicited better explanations, which they ultimately got.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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