Groups > sci.physics.relativity > #589437

Re: correct transversal Doppler shift

Newsgroups	sci.physics.relativity
Date	2022-08-06 22:11 -0700
References	<9c63a3d5-022e-430d-a2a6-0fdb6717abd9n@googlegroups.com>
Message-ID	<2df25db2-ece5-4ac3-9409-3603fb02a22bn@googlegroups.com> (permalink)
Subject	Re: correct transversal Doppler shift
From	"erkd...@gmail.com" <erkdemon@gmail.com>

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On Saturday, July 9, 2022 at 12:47:57 PM UTC+1, Alsor wrote:
> The Doppler shift for angle 90 degs at receiver is blue not red: 
> 
> The general formula: 
> 
> d = k(1-v/c cosf); k = 1/sqrt(1-v^2/c^2) 
> 
> for transverse Doppler f = 90, cos90 = 0: 
> 
> d = k = 1/sqrt(1-v^2/c^2); 
> this is a blue shift! 

Hi Alsor!
  This query comes up from time to time. 

Special relativity's transverse prediction in the lab frame //is// actually red.

You are quite correct that the equation on page 56 described a Lorentz blueshift. Well done for spotting that!

However, if you read the text before it, you'll find that in order to make the equation simpler, Einstein is not calculating things by the traditional SR approach of assuming a speed of light fixed in the observer's frame. Instead, he's assuming that the speed of light is fixe din the emitter's frame and the the observer is moving and is therefore time-dilated. If the observer is ageing more slowly, then they shoudlsee things with a Lorentz blueshift.

The reason why Einstein (on page 56) feels entitled to do this the other way round to normal, is that it is a feature of SR that you can do the same calculations with the s.o.l. assumed to be globally fixed in ANY SR-legal inertial frame, and when the propagation effect is multiplied or divided by the appropriate Lorentz correction, the final physical prediction always comes out the same. 

Notice also that the conventional propagation-based Doppler component shown in the top part of the equation is not the Doppler predictions for a speed of light fixed for the observer. that would be 
E'/E = c/(c+v), 
What Einstein uses on p56 is equivalent to 
E'/E = (c-v)/c,  or
E'/E = 1-v/c
, which is the Doppler prediction for a speed of light fixed in the emitter's frame.  

Anyway ... as long as you do all the calculations correctly, you'll get the same final physical predictions regardless of which SR frame you use s a reference for the propagation of light. 

Have a Nice Day.

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Thread

correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-09 04:47 -0700
  Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-07-10 09:05 +0200
    Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-07-11 09:21 +0200
      Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-02 08:52 +0200
        Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-02 00:29 -0700
          Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-03 09:08 +0200
            Re: correct transversal Doppler shift Volney <volney@invalid.invalid> - 2022-08-03 04:33 -0400
              Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-04 08:01 +0200
                Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-04 00:05 -0700
                Re: correct transversal Doppler shift Maciej Wozniak <maluwozniak@gmail.com> - 2022-08-04 00:11 -0700
                Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-04 07:37 -0700
                Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-04 08:04 -0700
                Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-08-04 15:16 +0000
                Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-04 08:21 -0700
                Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-08-04 15:27 +0000
                Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-04 08:59 -0700
                Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-04 09:12 -0700
                Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-05 07:08 +0200
                Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-05 03:29 -0700
                Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-06 10:35 +0200
                Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-06 02:03 -0700
                Re: correct transversal Doppler shift Maciej Wozniak <maluwozniak@gmail.com> - 2022-08-06 02:26 -0700
                Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-06 06:06 -0700
                Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-07 07:18 +0200
                Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-07 03:27 -0700
                Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-08 08:45 +0200
                Re: correct transversal Doppler shift "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2022-08-08 08:51 -0700
                Re: correct transversal Doppler shift Diego Traversa <toed@iavdattg.ev> - 2022-08-08 22:35 +0000
                Re: correct transversal Doppler shift "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2022-08-08 21:01 -0700
                Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-05 03:33 -0700
                Re: correct transversal Doppler shift "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2022-08-05 21:10 -0700
            Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-03 09:59 -0700
            Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-08-03 10:12 -0700
  Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-10 06:43 -0700
    Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-10 16:34 +0000
  Re: correct transversal Doppler shift Tom Roberts <tjroberts137@sbcglobal.net> - 2022-07-13 11:02 -0500
    Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-13 09:28 -0700
      Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-13 09:36 -0700
      Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-13 18:55 +0000
      Re: correct transversal Doppler shift Tom Roberts <tjroberts137@sbcglobal.net> - 2022-07-18 20:55 -0500
        Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-19 08:13 -0700
          Re: correct transversal Doppler shift Tom Roberts <tjroberts137@sbcglobal.net> - 2022-07-20 11:28 -0500
            Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-20 12:03 -0700
            Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-20 13:04 -0700
              Re: correct transversal Doppler shift Tom Roberts <tjroberts137@sbcglobal.net> - 2022-07-21 21:19 -0500
                Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-22 07:28 -0700
                Re: correct transversal Doppler shift Tom Roberts <tjroberts137@sbcglobal.net> - 2022-07-22 12:11 -0500
                Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-22 17:19 +0000
          Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-22 22:44 +0000
            Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-23 04:46 -0700
              Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-23 04:59 -0700
                Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-23 14:34 +0000
              Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-23 12:20 +0000
      Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-07-29 21:27 -0700
        Re: correct transversal Doppler shift Prokaryotic Capase Homolog <prokaryotic.caspase.homolog@gmail.com> - 2022-07-29 21:59 -0700
        Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-30 11:26 +0000
        Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-07-30 05:34 -0700
    Re: correct transversal Doppler shift Richard Hachel <r.hachel@tiscali.fr> - 2022-07-13 18:51 +0000
      Re: correct transversal Doppler shift Tom Roberts <tjroberts137@sbcglobal.net> - 2022-07-20 12:12 -0500
  Re: correct transversal Doppler shift "mitchr...@gmail.com" <mitchrae3323@gmail.com> - 2022-08-04 16:06 -0700
    Re: correct transversal Doppler shift Duan Bonomo <ddfs@dtszpmat.zy> - 2022-08-06 16:15 +0000
      Re: correct transversal Doppler shift Alsor <alsorgzl@gmail.com> - 2022-08-06 11:25 -0700
        Re: correct transversal Doppler shift Thomas Heger <ttt_heg@web.de> - 2022-08-07 07:25 +0200
  Re: correct transversal Doppler shift "erkd...@gmail.com" <erkdemon@gmail.com> - 2022-08-06 22:11 -0700

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