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Re: Why synchronize atomic clocks?

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Tom Roberts wrote:

> On 8/28/17 9:16 AM, Rafael Valls Hidalgo-Gato wrote:
>> GPS atomic clocks are affected by velocity (-7 microsec./day) and
>> gravitational potential (+45 microsec./day) changes, an EXPERIMENTAL FACT
> 
> That is NOT any sort of fact at all, experimental or otherwise; IT IS
> WRONG.
> 
> It is NOT the clocks that are affected, it is the RECEPTION OF SIGNALS
> from the clocks that are affected.
> 
> The on-board Cs133 oscillator ticks at 9,192,631,770 Hz -- that's
> what these words mean. This oscillator IS NOT affected by its
> velocity (relative to anything else) or its gravitational potential
> (relative to anything else), because IT DEFINES WHAT "1 SECOND"
> MEANS IN THE SATELLITE.

ISTM that you are merely performing high-level nitpicking here.  From the 
perspective of an observer who is stationary (or almost stationary by 
comparison) in the ECI frame, the atomic clocks aboard GPS satellites *are* 
affected by their motion relative to the observer (and in a different way by 
their greater distance from Earth’s center of mass).

The principle of relativity states that there is *no* preferred frame of 
reference.  That means that physical reality does not exist only in the rest 
frame: Where observers in different frames disagree about an observation of 
the same object, and the difference in the quantities in their statements 
corresponds to the Lorentz transformation of those quantities, *all* of them 
are correct.  Yet that the rest frame would be the preferred frame against 
which the truth of all statements must be measured is exactly the argument 
that you are using here and have been using before.
 
> Note that the SIGNALS emitted by the satellite and received on the geoid
> are affected by both its velocity relative to the ECI and its
> gravitational potential relative to the geoid. In GPS satellite clocks,
> the divider between the Cs133 oscillator and the clock mechanism has been
> modified so the Doppler shift of the SIGNALS from satellite to a receiver
> at rest on the geoid is canceled by the modification.

AFAIK the clocks have been modified *before* being sent into orbit so that 
_the gravitational time dilation on the ground_ is being canceled instead: 
The clocks have been modified to "tick" slower than normal on the ground, so 
that they would "tick" in orbit as fast as the ground clocks if there were 
no time dilation due to relative motion.

Because by contrast to the height of the satellite orbits, the Doppler shift 
of the signal would depend on the relative velocity between satellite and 
receiver which cannot be known in advance.  In fact, I think that the 
(relativistic) Doppler shift of the GPS signal is completely irrelevant for 
the proper operation of the GPS, and GNSSs in general.

See also: <http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html>
 
-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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Why synchronize atomic clocks? gehan.ameresekere@gmail.com - 2017-08-28 04:36 -0700
  Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-08-28 05:02 -0700
    Re: Why synchronize atomic clocks? Odd Bodkin <bodkinodd@gmail.com> - 2017-08-31 16:03 +0000
      Re: Why synchronize atomic clocks? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-31 21:51 +0200
      Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-01 01:26 -0700
  Re: Why synchronize atomic clocks? Rafael Valls Hidalgo-Gato <rvalls162@gmail.com> - 2017-08-28 07:16 -0700
    Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-08-29 11:45 -0500
      Re: Why synchronize atomic clocks? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-30 00:54 +0200
        Re: Why synchronize atomic clocks? Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-08-29 16:31 -0700
          Re: Why synchronize atomic clocks? The Starmaker <starmaker@ix.netcom.com> - 2017-08-29 19:38 -0700
            Re: Why synchronize atomic clocks? The Starmaker <starmaker@ix.netcom.com> - 2017-08-31 14:34 -0700
              Re: Why synchronize atomic clocks? The Starmaker <starmaker@ix.netcom.com> - 2017-09-01 12:45 -0700
          Re: Why synchronize atomic clocks? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-30 05:47 +0200
        Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-08-31 13:47 -0500
          Re: Why synchronize atomic clocks? Bídníkùm Laterá <bila@wehia.ui> - 2017-08-31 20:12 +0000
          Re: Why synchronize atomic clocks? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-01 04:04 +0200
            Re: Why synchronize atomic clocks? Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-08-31 21:01 -0700
              Re: Why synchronize atomic clocks? Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-09-01 02:12 -0700
                Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-01 04:17 -0700
            Re: Why synchronize atomic clocks? xxein1x1@gmail.com - 2017-08-31 21:34 -0700
              Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-01 11:41 -0500
          Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-01 11:17 -0500
            Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-01 09:43 -0700
            Relativity and physical reality (was: Why synchronize atomic clocks?) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-01 20:10 +0200
              Re: Relativity and physical reality (was: Why synchronize atomic clocks?) Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-09-01 12:30 -0700
                Re: Relativity and physical reality (was: Why synchronize atomic clocks?) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-02 01:29 +0200
                Re: Relativity and physical reality (was: Why synchronize atomic clocks?) Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-09-01 16:52 -0700
                Re: Relativity and physical reality Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-02 02:27 +0200
                Re: Relativity and physical reality Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-09-02 02:22 -0700
              Re: Relativity and physical reality Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-01 19:41 -0500
                Re: Relativity and physical reality mlwozniak@wp.pl - 2017-09-02 01:01 -0700
                Re: Relativity and physical reality Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-02 19:30 +0200
        Re: Why synchronize atomic clocks? Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-09-02 22:23 -0700
          Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-03 02:35 -0700
      Re: Why synchronize atomic clocks? kenseto <setoken@att.net> - 2017-08-30 07:28 -0700
      Re: Why synchronize atomic clocks? Rafael Valls Hidalgo-Gato <rvalls162@gmail.com> - 2017-08-30 09:47 -0700
        Re: Why synchronize atomic clocks? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-31 00:03 +0200
          Re: Why synchronize atomic clocks? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-31 00:22 +0200
        Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-08-30 17:58 -0500
          Re: Why synchronize atomic clocks? Rafael Valls Hidalgo-Gato <rvalls162@gmail.com> - 2017-08-31 13:56 -0700
            Re: Why synchronize atomic clocks? gehan.ameresekere@gmail.com - 2017-08-31 23:17 -0700
              Re: Why synchronize atomic clocks? Rafael Valls Hidalgo-Gato <rvalls162@gmail.com> - 2017-09-01 08:45 -0700
            Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-01 11:54 -0500
              Re: Why synchronize atomic clocks? Gary Harnagel <hitlong@yahoo.com> - 2017-09-01 12:39 -0700
                Re: Why synchronize atomic clocks? Prokaryotic Caspase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2017-09-01 12:51 -0700
              Re: Why synchronize atomic clocks? gehan.ameresekere@gmail.com - 2017-09-04 19:26 -0700
                Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-05 11:06 -0500
                Re: Why synchronize atomic clocks? gehan.ameresekere@gmail.com - 2017-09-05 22:53 -0700
                Re: Why synchronize atomic clocks? Paparios <mrios@ing.puc.cl> - 2017-09-06 05:25 -0700
                Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-06 05:40 -0700
                Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-06 17:22 -0500
      Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-01 01:24 -0700
      Re: Why synchronize atomic clocks? kenseto <setoken@att.net> - 2017-09-06 06:42 -0700
        Re: Why synchronize atomic clocks? mlwozniak@wp.pl - 2017-09-06 07:04 -0700
  Re: Why synchronize atomic clocks? "Dono," <sa_ge@comcast.net> - 2017-08-28 07:49 -0700
  Re: Why synchronize atomic clocks? Ed Lake <detect@newsguy.com> - 2017-08-28 08:12 -0700
    Re: Why synchronize atomic clocks? Ed Lake <detect@newsguy.com> - 2017-08-28 09:11 -0700
      Re: Why synchronize atomic clocks? Odd Bodkin <bodkinodd@gmail.com> - 2017-08-28 11:15 -0500
      Re: Why synchronize atomic clocks? Ed Lake <detect@newsguy.com> - 2017-08-28 09:44 -0700
        Re: Why synchronize atomic clocks? Odd Bodkin <bodkinodd@gmail.com> - 2017-08-28 11:52 -0500
    Re: Why synchronize atomic clocks? gehan.ameresekere@gmail.com - 2017-08-28 23:59 -0700
      Re: Why synchronize atomic clocks? Ed Lake <detect@newsguy.com> - 2017-09-01 14:01 -0700
        Re: Why synchronize atomic clocks? Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2017-09-02 00:20 +0200
          Re: Why synchronize atomic clocks? Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2017-09-02 00:21 +0200
  Re: Why synchronize atomic clocks? Sylvia Else <sylvia@not.at.this.address> - 2017-08-29 17:11 +1000
  Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-08-29 18:38 -0500
    Re: Why synchronize atomic clocks? gehan.ameresekere@gmail.com - 2017-08-31 23:38 -0700
      Re: Why synchronize atomic clocks? Tom Roberts <tjroberts137@sbcglobal.net> - 2017-09-01 20:09 -0500

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