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Newsgroups: sci.physics.relativity
Subject: Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work.
From: nospam@de-ster.demon.nl (J. J. Lodder)
Reply-To: jjlxa31@xs4all.nl (J. J. Lodder)
Date: Sun, 8 Dec 2024 23:32:09 +0100
References: <674BCF8E.822@ix.netcom.com> <674CCA90.3DD9@ix.netcom.com> <a89d71ab22cb1e3e279a59fe50ab5ebb@www.novabbs.com> <9f1cd556912a273a8946c77614611242@www.novabbs.com> <8a0014e4135992c8ec7bd3f2f1983164@www.novabbs.com> <d906fde3148d43d339b1663f1127216a@www.novabbs.com> <13877dcc9c6a6f2dd8056d8c05f0c661@www.novabbs.com> <a7d26012926823b22e139af8670cbbe7@www.novabbs.com> <df76d88c3e9729de443afca2c0cf99fa@www.novabbs.com> <2c831e6c7e0103c00fcebe8074fec8db@www.novabbs.com> <7d37d6e841cd1936217b21a5847fc507@www.novabbs.com> <7511bb1b9b748c76df265f91eaaa468a@www.novabbs.com> <67503f94$0$12915$426a74cc@news.free.fr> <3c8abe81804e4c5b6ced7aefae766c7d@www.novabbs.com> <6750b8d4$0$29710$426a74cc@news.free.fr> <2Ji4P.2$4s%.1@fx15.ams4> <6751f410$0$518$426a74cc@news.free.fr> <geD4P.802$qW31.662@fx07.ams4> <675357ca$0$28494$426a74cc@news.free.fr> <QY25P.1046$4s%.357@fx15.ams4> <iDc5P.41335$rwVa.34840@fx16.ams4> <981080dc25972ab561cbe765334f1a32@www.novabbs.com>
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ProkaryoticCaspaseHomolog <tomyee3@gmail.com> wrote:

> On Sun, 8 Dec 2024 8:19:33 +0000, Paul B. Andersen wrote:
> 
> > Den 07.12.2024 22:19, skrev Paul B. Andersen:
> >> Den 06.12.2024 21:00, skrev J. J. Lodder:
> >>> Paul B. Andersen <relativity@paulba.no> wrote:
> >>>
> >>
> >> According to:
> >> https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9.pdf
> >> (2019)
> >> The SI definitions are:
> >>
> >> The relevant defining constants:
> >>   ??_Cs = 9192631770 Hz  (hyperfine transition frequency of Cs133)
> >>   c = 299 792 458 m/s (speed of light in vacuum)
> >>
> >> The relevant base units:
> >> Second:
> >>   1 s = 9192631770/??_Cs  1 Hz = ??_Cs/9192631770
> >>
> >> Metre:
> >>   1 metre = (c/299792458)s = (9192631770/299792458)?(c/??_Cs)
> >>
> >> The home page of BIMP:
> >> https://www.bipm.org/en/measurement-units
> >>
> >> Give the exact same definitions, so I assume
> >> that the definitions above are valid now.
> >>
> >>
> >> https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9.pdf
> >
> >>>>
> >>>> If the speed of light is measured _with the meter and second
> >>>> defined above_ it is obviously possible to get a result slightly
> >>>> different from the defined speed of light.
> >>>>
> >>>> So I was not "completely, absolutely, and totally wrong".
> >>>
> >>> You were, and it would seem that you still are.
> >>> You cannot measure the speed of light because it has a defined value.
> >>> If you would think that what you are doing is a speed of light
> >>> measurement you don't understand what you are doing.
> >
> > Yes, I was indeed "absolutely, and totally wrong",
> > but not completely wrong.
> 
> I disagree that you were wrong at all.

So you are not there yet.

Remember that nothing you say, and no definitions you make
can have any effect on reality as it is.
It can only change your way of looking at it,
and your interpretations of what you see.

> 1) The expression "c" has multiple meanings. On the one hand, it is,
>    according to a widely accepted geometric model of spacetime, a
>    constant that expresses the relationship between units of space and
>    units of time. This "c" is given a defined value of 299792458 m/s,
>    and because it has that value by definition, it cannot be measured.
> 2) Another meaning of "c" is the speed of photons in vacuum. Photons
>    are, to the best of our knowledge, massless, and according to the
>    above geometric model of spacetime, all unimpeded massless
>    particles travel at the speed "c" given in definition (1).

All very true, but completely irrelevant
from the point of view of metrology.

Metrology is about how to realise units, and nothing else.
Deep thoughts about the nature of things,
or what words might mean, do not come into it at all.
In particular, the whole theory of relativity is irrelevant
as far the definition of the meter is concerned.
[snip more irrelevancies]

Jan