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Groups > sci.physics.relativity > #659858
| From | Physfitfreak <Physfitfreak@gmail.com> |
|---|---|
| Newsgroups | sci.physics.relativity |
| Subject | Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. |
| Date | 2024-12-27 14:05 -0600 |
| Message-ID | <vkn1ae$1rm89$1@solani.org> (permalink) |
| References | (17 earlier) <QY25P.1046$4s%.357@fx15.ams4> <iDc5P.41335$rwVa.34840@fx16.ams4> <6755835e$0$28076$426a74cc@news.free.fr> <80D5P.65709$3MVa.14896@fx05.ams4> <675744ea$0$416$426a74cc@news.free.fr> |
On 12/9/2024 1:28 PM, J. J. Lodder wrote: >> Den 08.12.2024 12:30, skrev J. J. Lodder: >>> Paul B. Andersen <relativity@paulba.no> wrote: >>> >>>> Den 07.12.2024 22:19, skrev Paul B. Andersen: >>>>> >>>>> But it isn't impossible, if you had extremely precise instruments, >>>>> that you would measure a value slightly different from 299792458 m/s, >>>>> e.g. 299792458.000001 m/s. >>>> >>>> This is indeed "completely, absolutely, and totally wrong". >>>> >>>> I somehow thought that the "real speed" of light in vacuum >>>> measured before 1985 was different from 299792458 m/s. >>> >>> Of course it was. The adopted value was a compromise >>> between the results of different teams. >>> BTW, you are also falling into the 'das ding an sich' trap. >>> >>>> (Which it probably was, but the difference hidden in the error bar) >>>> And since the definition of metre only contain the defined constant c, >>>> i thought "the real speed" of light could be different from c. >>> >>> Yes, that is where you go wrong. >>> >>>> But this is utter nonsense! >>> >>> Beginning to see the light? >>> >>>> Now I can't understand how I could think so. >>>> My brain seems to be slower than it used to be. :-( >>>> >>>> The real speed of light in vacuum is exactly c = 299792458 m/s, >>>> and 1 metre = (1 second/299792458)c, is derived from c, >>>> which means that the measured speed of light in vacuum will >>>> always be c. >>> >>> Correct. >>> Perhaps I can explain the practicalities behind it in another way. >>> If you measure the speed of light accurately >>> you must of course do an error analysis. >>> The result of this that almost all of the error results from >>> the ecessary realisation of the meter standard. (in your laboratory) >>> So the paradoxal result is that you cannot measure the speed of light >>> even when there is a meter standard of some kind. >>> >>> You may call whatever it is that you are doing >>> 'a speed of light measurement', >>> but if you are a competent experimentalist you will understand >>> that what you are really doing is a meter calibraton experiment. >>> Hence the speed of light must be given a defined value, >>> for practical experimental reasons. [1] >>> >>> Jan >> >> This is my way of thinking which made me realise that I was wrong: >> How do we measure the speed of light? >> We measure the time it takes for the light to travel a known distance. >> So we bounce the light off a mirror and measure the round trip time. >> How do we calibrate the distance to the mirror? >> We measure the time it takes for the light to go back and forth >> to the mirror. >> L = (c/299792458)?t/2 where t is round trip time in seconds >> AHA!!! >> >>> >>> [1] Which have not changed. >>> (and will not change in the forseeable future) >>> Meter standards are orders of magnitude less accurate >>> than time standards. (see why this must be?) >>> >> >> No, I don't understand. >> The definition of metre only depends on the two constants >> ??_Cs and c and both have an exact value. >> Is it because the time standard only depend on one constant? >> >> I can however understand that practical calibration of the meter >> is less precise than the calibration of a frequency standard. >> >> ------------------ >> >> I would like your reaction to the following; >> >> In: >> https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9.pdf >> I read: >> https://www.bipm.org/en/cipm-mra >> >> "The CIPM has adopted various secondary representations of >> the second, based on a selected number of spectral lines of atoms, >> ions or molecules. The unperturbed frequencies of these lines can >> be determined with a relative uncertainty not lower than that of >> the realization of the second based on the 133Cs hyperfine transition >> frequency, but some can be reproduced with superior stability." >> >> This is how I interpret this: >> The second is still defined by "the unperturbed ground state >> hyperfine transition frequency of the caesium 133 atom" >> ??_Cs = 9192631770 Hz by definition. >> >> But practical realisations of this frequency standard, >> that is an atomic frequency standard based on Cs133 is >> not immune to perturbation, a magnetic field may affect it. >> >> So there exist more stable frequency standards than Cs, >> and some are extremely more stable. >> But the frequencies of these standards are still defined >> by ??_Cs. 1 hz = ??_Cs/9192631770 >> This is "Calibration of a frequency standard". >> >> The "secondary representations of second" >> don't change the duration of a second >> and the "secondary representations of metre" >> don't change the length of a metre. > > Instead of replying point by point I'll sum up the whole situation. > (as I understand it, and perhaps repeating what I wrote earlier) > > For understanding all this you must realise > that there are two kinds of frequency standards: > microwave ones, typically in the (perhaps many) GHz range, > and > optical ones, typically in the hundreds of THz range. > The GHz ones may serve as absolute frequency standards and as clocks. > The optical ones (like the standard stabilised HeNe laser) > may also serve as (secondary) meter standards. > Standards labs supply lists of 'recommended' optical frequencies. > The optical frequency sources are of course also 'floating' frequency > standards on their own. > > The GHz ones can be calibrated against each other by direct counting. > So their accuracy may equal that of the Cs standard. (by the definition) > The stability of frequency standards can in general be established > by comparing ensembles of them against each other. (so indepently of Cs) > Which kind of standard to use depends on what you need: > relative or absolute accuracy. > > AFAIK about those matters, the idea among metrologists at present > is to leave things as they are, > until a really big step forward can be made. > (hopefully already at the next CGPM) > > Some of the optical frequency standards are far more stable indeed. > (nowadays pushing 10^18, last time I looked) > But their frequencies (in terms of the Cs standard!) > are known to a much lesser accuracy. > (pushing 10^12, again last time I looked) > The use of frequency combs caused a revolution here. (see 2005 Nobel) > > Summary: optical frequency standards can be far more stable, > but their frequencies are (relatively speaking!) poorly known. > > Once you have a calibrated optical frequency standard, [1] > for which you know the frequency in terms of the Cs standard, > you know its wavelength, by the definition of c, > so you can start measuring distances and sizes > in terms of its wavelength, hence in meters. > It has become a secondary meter standard. > > So measuring distances/lengths is inherently much less accurate > than measuring time/frequency. > And, circle closed, this was precisely the reason > for giving c a defined value. > So c really cannot be measured anymore, > not because some crazed guru-followers decreed so, > but because of hard experimental realities and necessities. > > Hope this clears up the questions you had, > > Jan > > [1] This is the ongoing, never-ending, program I mentioned earlier: > finding optical frequency standards, aka secondary meter standards, > to ever greater accuracy and reproducibiliy. > The original <1983 series of measurements, then called 'measuring c', > was just good enough to base the definined value of c on. > Those decades of added precision had to go into better frequency/meter > standards, not into a 'better' value of c. > > PS There are first indications that it may be possible > to harness a gamma ray line from a nuclear transition > in the not to far future, for again greatly increased stability. > Very low frequency, as gammas go, but still in the very far UV. > Challenges, challenges. > So you're saying that speed of light is not c but is in units of c. -- This email has been checked for viruses by Avast antivirus software. www.avast.com
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E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-01 00:28 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. The Starmaker <starmaker@ix.netcom.com> - 2024-11-30 18:53 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. The Starmaker <starmaker@ix.netcom.com> - 2024-12-01 12:44 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-02 00:36 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-02 17:44 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-02 18:07 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-02 11:20 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-02 21:54 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-02 16:39 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-03 02:35 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-02 19:07 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-03 13:50 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-04 09:13 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-03 02:22 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. "Paul.B.Andersen" <relativity@paulba.no> - 2024-12-03 14:15 +0100
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-03 14:01 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-03 18:27 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-03 19:02 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-04 10:10 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-04 12:40 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-04 12:41 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-04 21:17 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-04 13:29 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-04 22:20 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-04 15:56 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. The Starmaker <starmaker@ix.netcom.com> - 2024-12-04 17:15 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-05 11:57 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-05 12:42 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. "Paul B. Andersen" <relativity@paulba.no> - 2024-12-05 15:26 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-05 19:42 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-05 18:29 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-06 03:55 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-06 11:48 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-06 10:48 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-06 11:48 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-07 04:51 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. "Paul B. Andersen" <relativity@paulba.no> - 2024-12-06 14:46 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-06 21:00 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-06 13:27 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-07 01:21 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-06 18:30 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-07 12:03 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-07 16:03 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-07 10:49 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-07 22:35 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-08 05:42 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-08 06:46 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-08 21:35 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-10 09:15 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-10 23:16 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-10 18:37 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-08 21:35 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-07 22:35 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-07 14:50 -0800
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Athel Cornish-Bowden <me@yahoo.com> - 2024-12-08 10:19 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-08 12:56 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Maciej Wozniak <mlwozniak@wp.pl> - 2024-12-08 15:01 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. "Paul B. Andersen" <relativity@paulba.no> - 2024-12-07 22:19 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-07 22:14 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. "Paul B. Andersen" <relativity@paulba.no> - 2024-12-08 09:19 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-08 12:30 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. "Paul B. Andersen" <relativity@paulba.no> - 2024-12-09 15:21 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-09 20:28 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. "Paul B. Andersen" <relativity@paulba.no> - 2024-12-10 11:20 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Physfitfreak <Physfitfreak@gmail.com> - 2024-12-27 14:05 -0600
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-09 22:44 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-09 23:26 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-08 21:17 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-08 23:32 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-08 12:30 +0100
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. tomyee3@gmail.com (ProkaryoticCaspaseHomolog) - 2024-12-07 00:34 +0000
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. Maciej Wozniak <mlwozniak@wp.pl> - 2024-12-08 04:52 +0100
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. hertz778@gmail.com (rhertz) - 2024-12-04 15:44 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. clzb93ynxj@att.net (LaurenceClarkCrossen) - 2024-12-11 05:59 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-11-30 19:10 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-11-30 19:37 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Mikko <mikko.levanto@iki.fi> - 2024-12-01 12:27 +0200
Re: E = 3/4 mc? or E = mc?? The forgotten Hassenohrl 1905 work. nospam@de-ster.demon.nl (J. J. Lodder) - 2024-12-06 11:48 +0100
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. "Paul.B.Andersen" <relativity@paulba.no> - 2024-12-01 12:38 +0100
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Richard Hachel <r.hachel@liscati.fr.invalid> - 2024-12-01 12:19 +0000
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Ross Finlayson <ross.a.finlayson@gmail.com> - 2024-12-01 10:30 -0800
Re: E = 3/4 mc² or E = mc²? The forgotten Hassenohrl 1905 work. Richard Hachel <r.hachel@liscati.fr.invalid> - 2024-12-02 00:56 +0000
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