Talk:Relativistic Doppler effect

message: This article makes no sense. Just to start, it could be better explained in what way speed is a "rotation". Nickptar 21:07, 16 Apr 2005 (UTC)
replies: text: I agree that this presentation is weird; it seems to have been made up by someone with a particular background. The standard way of presenting Doppler equations presents the ratio between measured frequencies, as can also be found in the 1905 paper of Einstein -- html link in Special relativity. 
Harald88 22:08, 9 January 2006 (UTC)

text: IMO it looks better although you made several new unwarrented claims. Anyway, thanks for cleaning up the mess, it now has a much better look. Harald88 20:43, 23 January 2006 (UTC)
replies: text:  PS Your simple derivation to illustrate the connection to true Doppler is just what I had in mind to do myself. Thanks again! Harald88 12:14, 24 January 2006 (UTC)
replies: text:  Thanks, Harald, but why did you revert my correction of the centrifugal force article? What they have there now is a complete nonsense (based on someone's misunderstanding of the Principia or something). (Sorry, I don't feel like contributing to their 100-page talk page :) Yevgeny Kats 04:09, 25 January 2006 (UTC)
replies: text:  Sorry, I had not noticed that the intro had already been messed up; I had not reverted far enough (problem with my watchlist). Harald88 11:13, 26 January 2006 (UTC)
thread_title: Untitled

message: Three formulas in the third "Motion in an arbitrary direction" section seem not to agree in all.
namely,
:f_o = \frac{f_s}{\gamma\left(1+\frac{v\cos\theta_o}{c}\right)}~.  (1)
:\cos \theta_o=\frac{\cos \theta_s-\frac{v}{c}}{1-\frac{v}{c} \cos \theta_s} \,.
and
:f_o = \gamma\left(1-\frac{v\cos\theta_s}{c}\right)f_s. (2)
The first and second seem to yield the third but gamma to the power of 3.Like sushi (talk) 10:14, 7 May 2009 (UTC)
thread_title:  Excuse me 

message: The post just before was a simple mistake. Sorry. Gamma is simple gamma.Like sushi (talk) 13:47, 7 May 2009 (UTC)
thread_title:  I'm sorry. It was a mistake 

message: I just edited the wording in the visualization section. I do not have a background in relativistic physics, I just reorganized the information already written. Please proofread my writing for technical accuracy. Also, as I was rewriting, I realized that I would like to see two different animations. The one that already exists shows an observer's velocity increasing against a stationary background. Another could show an emitter's velocity increasing relative to a stationary observer located somewhere on the grid (like the plot at the top of the article). Can someone please generate this plot? Also, the aberation of light doesn't appear anywhere in the article and has no context. Please provide a brief description of what causes the aberation of light. (I think it has to do with the time differnce between emitting and receiving the light, but I'm not sure.) David.hillshafer 21:31, 9 June 2009 (UTC)
thread_title:  Visualization 

message: I am curious about *Diagram 1* from the article page.  This diagram depicts the redshift and blueshift of waves being emitted by a moving source.  To my untrained eye, it looks like this picture does a good job of showing the relative shift in frequencies/wavelengths that would occur and in illustrating the Doppler effect in general terms.  The note says that the source is moving at 0.7c.  At this speed, I am thinking that the relativistic components of the Doppler effect would show up starkly in the picture.  If this is the case, shouldn't waves emitted transverse (and even waves emitted up to some forward angle) appear redshifted in the "stationary" reference frame?  When generating this image, was relativistic time dilation accounted for?  If not, it would seem appropriate to regenerate this image taking all relativistic effects into account (considering that the wave emitter is moving at relativistic speeds and this article is about relativistic effects). Jsnydr (talk) 22:04, 23 October 2009 (UTC)
thread_title:  Discussion on Diagrams 

message: The following reference is mentioned in the Mossbauer spectroscopy article.
Y.-L. Chen, D.-P. Yang (2007). "Recoilless Fraction and Second-Order Doppler Effect". Mössbauer Effect in Lattice Dynamics. John Wiley & Sons. doi:10.1002/9783527611423.ch5. .  
This may report another experimental confirmation of the transverse Doppler effect. 
Perhaps someone with access to the article could confirm this and determine whether the article also has references to other experiments confirming the effect.  —Preceding unsigned comment added by 68.145.187.67 (talk) 21:44, 22 March 2010 (UTC)
thread_title:  Experimental confirmation of transverse Doppler effect 

message: In the section on Transverse Doppler Effect, it says, "If the predictions of special relativity are compared to those of a simple flat nonrelativistic light medium that is STATIONARY in the observer’s frame (“classical theory”), SR’s physical predictions of what an observer sees are always "redder", by the Lorentz factor..."  Really?  Stationary???  The Lorentz factor has no effect if the source is not moving relative to the observer.  What is this supposed to say???  Thank you.— Preceding unsigned comment added by 98.212.132.146 (talk • contribs) 
:Please put new messages at the bottom, provide a header and edit summary, and sign with four tildes (~~~~)? Thanks.
:It means that in SR the transverse Doppler effect predicts a redshift for a source that is instantanously moving transversally w.r.t. the observer. I.o.w. light from a source that is not approaching or receding from the observer, but that is moving w.r.t. the observer, is redshifted. In this case the source is moving w.r.t. to observer, but not approachin or receding: it could be moving in a circle with the observer at the centre, or it could be moving along a straigh line with the observer sitting at the point of shortest distance to the line — that's what "transverse (i.e. lateral)" means. (note: I have removed the unhelpful wikilink to Transversality). DVdm (talk) 11:45, 12 December 2010 (UTC)
thread_title: What is this supposed to say?

message: The majority of this article doesn't list any sources at all.  Here's a summary" by section:
:1 Visualization                                 NO SOURCES
:2 Analogy                                       NO SOURCES
:3 Motion along the line of sight                NO SOURCES
:4 Systematic derivation for inertial observers  1 ref at very end, not clear what it refers to
:5 Transverse Doppler effect                     NO SOURCES
::5.1 Reciprocity                                 NO SOURCES
::5.2 Experimental verification                   2 sources
:6 Motion in an arbitrary direction              NO SOURCES
:7 Accelerated motion                            2 sources (but mostly original research?)
I think it would be better to base the article more firmly on sources.  At present it just seems to be a collection of essays written by various editors describing their personal (and in some cases non-standard) views of the subject.Flau98bert (talk) 14:39, 14 September 2012 (UTC)
thread_title:  Sources?  Original Research? 

message: Re Jordgette's edit and my amendment: actually, the original wording was, if properly interpreted, correct after all.
The classical Doppler effect is given by
:f_o = \frac{f_s}{1+\frac{v\cos\theta_o}{c}}.
The relativistic effect is
:f_o = \frac{f_s}{\gamma\left(1+\frac{v\cos\theta_o}{c}\right)},
and thus, for the transversal case —which is the subject of the section— this reduces to, classically
:f_o=f_s, \,
versus relativistic
:f_o=\frac {f_s}  {\gamma}. \,
So, indeed, in addition to the classical Doppler effect —being null (aka factor 1) in the transversal case—, the received frequency is reduced by the Lorentz factor. Since we're dealing with factors here, the word "addition" was a bit awkward, so I propose we leave it out, specially since the section is about the transverse effect, which is really non-existent classically. Subtle. - DVdm (talk) 13:26, 10 January 2013 (UTC)
thread_title:  In addition to the classical Doppler effect... 

message: Full disclaimer, I am not a physicist, but, under "Motion along the line of sight", shouldn't the last equation (the approximation) be v', not c'? How can there even be a c'?  — Preceding unsigned comment added by 174.98.234.239 (talk) 16:35, 9 September 2013 (UTC)
thread_title:  C' or V' 

message: The text of the article says that we use Lorentz factor to correct the classical Doppler because it comes from the coordinate transformation. However, Lorentz factor itself can be derived from the classical Doppler effect, which differently distorts the observed frequency, depending on whether receiver or transmitter is in motion. This violates the principle of relativity and attempt to correct gives a birth to the Lorentz factor, like here but I am sure that I have also seen some serious Einstein 2006 anniversary article, which does the same thing - derives the Lorentz factor reconciling the frequency shifts. I mean that it is insightful. Can we add this treatment into the article? --Javalenok (talk) 14:21, 22 March 2014 (UTC)
replies: text: Not a wp:reliable source, this. - DVdm (talk) 15:49, 22 March 2014 (UTC)
replies: text: really? The question is not whether this source is reliable or not. It is just an illustration. The question is whether should I dig deeper for this approach or we should forget about inferring the Lorentz factor as simple byproduct of reconciling the Doppler effect with relativity principle? --Javalenok (talk) 10:33, 23 March 2014 (UTC)
thread_title:  Deriving Lorentz factor from the Doppler effect 

message: Just that. The use of the Greek \nu is standard in the physics literature for frequency.  — Preceding unsigned comment added by 68.146.90.105 (talk) 16:31, 29 March 2015 (UTC)
thread_title:  Replace <math>f_s</math> with <math>\nu_s</math>? 

message: In this section in the article:
"Replacing \tau with 1/f and simplifying, we get the required result that gives the relativistic Doppler shift of any moving wave in terms of the stationary frequency, f^\prime:
:f = \gamma \left( 1 - \frac{v}{u^\prime} \right) f^\prime.
Ignoring the relativistic effects by taking v \ll c or c \rightarrow \infty (equivalent to \gamma \rightarrow 1) gives the classical Doppler formula:
:f = \left( 1 - \frac{v}{u^\prime} \right) f^\prime.
For electromagnetic radiation where u^\prime = c the formula becomes
:f = \gamma \left( 1 - \frac{v}{c} \right) f^\prime = \gamma \left( 1 - \beta \right) f^\prime = f^\prime \sqrt{\frac{1-\beta}{1+\beta}}
or in terms of wavelength: 
:\lambda = \lambda^\prime \sqrt{\frac{1+\beta}{1-\beta}},
where \lambda^\prime is the wavelength of the source at the origin O^\prime as the observer in  S^\prime  sees it."
If \lambda is the observed wavelength, then the equation should read \lambda = \lambda^\prime \sqrt{\frac{1-\beta}{1+\beta}},. The equation in terms of frequency should similarly reverse signs.
Sources:
1)http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/reldop2.html 
Hyperphysics clearly lists that f = f^\prime \sqrt{\frac{1+\beta}{1-\beta}}, which of course means  \lambda = \lambda^\prime \sqrt{\frac{1-\beta}{1+\beta}},.
2) http://spiff.rit.edu/classes/phys314/lectures/doppler/doppler.html
This university website states the equation similarly. Just note that the author of that webpage put the  \lambda^\prime  on the LHS of the equation rather than the right.
Unless someone sees some problem in what I am saying, we should correct teh equations. — Preceding unsigned comment added by 130.212.214.227 (talk • contribs) 01:19, 6 August 2015‎ (UTC)
:Please sign all your talk page messages with four tildes (~~~~). Thanks.
: Note that it depends on how v is defined. In the article v is assumed positive when the source is receding from the observer, and negative when approaching—see opening line of section Relativistic Doppler effect#Motion along the line of sight. How ever the variables are defined must result in the fact that observed wavelength should be larger than emitted wavelength when the source is receding from the observer—red shift.
:* This is how Spiff does it, but there obviously is a typo in that "Likewise, one can express the shifted wavelength λ as...". That should probably be "Likewise, one can express the shifted wavelength λ' as..." Earlier in that section they say "perceived frequency f' is higher than the emitted frequency, and the perceived wavelength λ' is shorter than the emitted wavelength." Bad source.
:* Hyperphysics defines v the other way around. By the way, see how unreliable that site is—they don't understand the bug rivet paradox. More silliness from the same site: "Accelerations are outside the realm of special relativity and require general relativity." Bad Source. To be avoided at all cost.But see Special:LinkSearch/*.hyperphysics.phy-astr.gsu.edu.
:* See for instance this source: https://books.google.com/books?id=-uMRwLaNbC8C&pg=PA87 .
: I have explicitly repeated the assumption at the end of the section. Hope this helps. DVdm (talk) 07:19, 6 August 2015 (UTC)
thread_title: Wrong Formula for relativistic Doppler Effects

message: A person reading up on the Relativistic Doppler Effect would presumably be familiar with the "conventional" Doppler effect and should not need such a back-to-basics explanation. Furthermore, this section is unsourced, and is almost certainly original research. 
If you disagree, feel free to restore the section, which I have preserved below if you believe it needs to go back in. Prokaryotic Caspase Homolog (talk) 05:39, 10 October 2018 (UTC)
thread_title:  No point to the Analogy section 

message: You have done a TREMENDOUS job!!! Great! IMO the previous treatment of Motion in arbitraty direction  was not so bad. The author replaced \theta_o with \theta_s , inserting the formula for relativistic aberration. The author demonstated how relativitic aberration formula "ties" angle of emission \theta_s with angle of reception \theta_o. In simple words it looks like that:  TDE redshift appears when \theta_o = \pi/2, i.e the receiver is "looking" through his tube - telescope  at right angle to direction of motion of the source. In this case the source (since it "moves" in the receiver's frame) MUST "to take into account" relativistic aberration and turn laser pointer backward at angle \theta_s, if it wants to send the light pulse at normal to its path and to hit the target, i.e. the receiver's telescope. The TDE blueshift appears when we work in the source's frame, i.e. the source is "at rest" and it doesn't "think" about aberration, so the angle of emission \theta_s = \pi/2. The source emits at right angle towards the path of motion of the receiver, but in this case, due to relativistic aberration of light the receiver MUST turn his telescope forward at angle \theta_o in accordandce with relativistic aberration angle formula, if it "wishes to see" the source. Naturally, for null - shifted TDE the source emits backward and the emitter looks forward at the equal angles, because they share full amount of relative velocity "fifty - fifty" and the both "take the abberration into account" to the same extent . Albert Gartinger (talk) 14:55, 13 October 2018 (UTC)
thread_title:  Assessment 

message: I have removed this animation. I am not sure that the animation is wrong, but the caption most certainly is. It speaks of the "oblate shape" of the sphere, "as seen from our perspective." 
The effects of Terrell rotation mean that the sphere will not appear oblate from our perspective. There is a profound difference between what is measured versus what is seen in special relativity.
Given that the caption's description of the perceived shape of the sphere from our perspective is wrong, I wonder what else about this animation is wrong. Prokaryotic Caspase Homolog (talk) 22:21, 15 October 2018 (UTC)
replies: text: After studying this animation a bit more, the answer is, "Pretty much everything." Prokaryotic Caspase Homolog (talk) 22:54, 15 October 2018 (UTC)
replies: text:  It's all like that, the animation is confusing, I looked at it. In fairness it must be said, that the "rotated Terrell's sphere" is also a bit confusing since it is only a special case. It depends on spatial position of the camera wrt the sphere.  The Terrell's photo was taken at the moment when the sphere had already flown far away. What for? Terrell photographs the image that was radiated at the moment of closest approach.  While this image "flies" to the camera, the sphere moves away. You can change the reference frame and make the camera moving wrt "stationary" sphere. That makes clear that the "rotated sphere" is just a photo taken from the side. For example, you ask me to take your photo, and I photograph one of your ears from the side. Then I publish a scientific paper that Mr. PCH appears rotated on photographs. Very entertaining!  If you take a photo at that moment when the sphere is directly opposite the camera, it will not be rotated, but \gamma times elongated because of the Lorentz contraction of the film, with the both ears clearly visible. There are parallels with transverse Doppler blueshift at points of closest approach. Albert Gartinger (talk) 06:28, 16 October 2018 (UTC)

text:  If an observer thinks that he is "moving" in the sphere's frame, then he is free to choose non - standard synchronization (Reichenbach's) of clocks in his frame (one - way speed of light will be slow "forward" and fast "backward" and the sphere will be measured as "stretched" fully in accordance with that picture as taken by "moving" camera at point of closest approach. Albert Gartinger (talk) 06:42, 16 October 2018 (UTC)
replies: text:  For comparison, most (but not necessarily all) of the animations on the SpaceTimeTravel.org site are correct. I remember writing to the authors of this site about some detail or other about some figure/animation that seemed a bit off. I don't remember what the detail was, and I don't see the figure/animation to jog my memory, so I think that the figure/animation that I had questions about may have been taken off. Anyhow, the geometric distortion seen in the animation that I took off corresponds to those seen in the movie labeled "Movie: Soccer ball - 90% of the speed of light, length contraction omitted This simulation is not relativistically correct!" Prokaryotic Caspase Homolog (talk) 08:41, 16 October 2018 (UTC)
replies: text:   It looks good. I believe that colors are fine. Maybe the grid must be worked out even though it seems convincing. Albert Gartinger (talk) 09:32, 16 October 2018 (UTC)
replies: text:  Thanks! Prokaryotic Caspase Homolog (talk) 12:09, 16 October 2018 (UTC)
thread_title:  Something wrong with this animation 

message: z is the fundamental observable in cosmological distance calculations.
I just finished deleting a few lines showing a calculation of z in terms of relativistic Doppler shift. But the relativistic Doppler shift of special relativity is, strictly speaking, associated with Minkowski spacetime (i.e. flat spacetime). Other contributions to the observed value of z are the cosmological redshift and gravitational redshift. 
This is way too big a subject to cover adequately in this article, and I do not pretend to be any sort of expert in general relativity or cosmology. Best to leave discussion of z to the articles on redshift, Hubble's law, Cosmology etc. which hopefully are being edited by people who know more about the subject than I do. 
Prokaryotic Caspase Homolog (talk) 18:36, 17 October 2018 (UTC)
thread_title:  I'm not sure I want to get into observational evidence for relativistic Doppler shift 

message: With my last edit clarifying the scope of the article, I think that I'm basically finished. It probably needs some tweaks, but I can't think of anything major that I want to add. Hope you like the result. Prokaryotic Caspase Homolog (talk) 20:33, 17 October 2018 (UTC)
replies: text: Congratulations! Of course I like it! Obviously, it has become more systematic and informative. I believe, that in general it is one of the best. You have done a great job! You make amazing charts and diagrams! --Albert Gartinger (talk) 14:56, 18 October 2018 (UTC)
replies: text:  Remember, you helped! Prokaryotic Caspase Homolog (talk) 16:19, 18 October 2018 (UTC)
thread_title:  I guess that I'm pretty much finished with what I wanted to change 

message: Is there an objection to establishing automatic archiving (> 1 year)? Purgy (talk) 07:41, 7 November 2018 (UTC)
thread_title:  Archives? 

message: Neither of two sources mentioned at the end contain this derivation. Morin, David (2008) actually has these formulas but for the case when receiver moves towards the source whereas the article considers receiver moving away and some of the formulas are taken from the part where receiver's reference frame is considered whereas the article claims to use source's reference frame. Two errors are made in the article which compensate each other in order to arrive at the correct formula:
1. The wavefront moves with speed c\,, but at the same time the receiver moves away with speed v during a time t_s = 1/f_s = \lambda_s/c.
Actually this must be during a time t_{r,s} as measured in the frame of the source. The wording is correct (at the same time) but the formula is not. From this "the period of light waves impinging on the receiver, as observed in the frame of the source." is t_{r,s} = t_s/(1-\beta) which is the formula you can see in Morin, David (2008) (though with different sign for beta due to opposite direction)
2. t_{r,s} is measured between two wavefront hits in the source's reference frame. These events are separated in space there. Receiver measures these events in the same point in space (proper time), so the time between wavefronts measured by receiver is smallest, it's t_r = t_{r,s} / \gamma, not t_r = t_{r,s}  \gamma (which, again, you can see in Morin, David (2008), all this on page XI-33 in Remark section)  — Preceding unsigned comment added by Panda34 (talk • contribs) 18:14, 8 April 2019 (UTC)
thread_title:  Relativistic longitudinal Doppler effect derivation is blatantly wrong 

message: https://en.wikipedia.org/w/index.php?diff=882618498&oldid=880179841&title=Relativistic_Doppler_effect
is the narrowest timeline I could focus on to locate the crooked change:
<<< The converse, however, is not true. The analysis of scenarios where both objects are in accelerated motion requires a somewhat more sophisticated analysis. Not understanding this point has led to confusion and misunderstanding. >>>
probably as a biased response to the controversy about the novelly discovered extra-energy-shift between emission and absorption resonant lines concerning Mössbauer spectra for a co-orbiting source and absorber at the rotor rim the way first tackled by Walter Kündig (1960s).
Firstly, does anyone know who is responsible for this addition?
Secondly, please modify the indicated passage in terms of the following list of references where Prof. Kholmetskii et al. have dismantled all such notions of so-called "relativistic solutions" (such as the debunked "synchronization effect") that allegedly clear away "confusion and misunderstanding":
[1]	KHOLMETSKII A. L., MISSEVITCH O. V. and YARMAN T., Phys. Scr., 78 (2008) 035302.
[2]	KHOLMETSKII A. L., YARMAN T., MISSEVITCH O. V. and ROGOZEV B. I., Phys. Scr., 79 (2009) 065007.
[3]	KHOLMETSKII A. L., YARMAN T. and ARIK M., Ann. Phys., 363 (2015) 556.
[4]	YARMAN T, KHOLMETSKII A. L. and ARIK M., Eur. Phys. J. Plus, 130 (2015) 191.
[5]	KHOLMETSKII A. L., YARMAN T. and ARIK M., Ann. Phys., 374 (2016) 247.
[6] YARMAN T, KHOLMETSKII A. L. and ARIK M., et al., Can. J. Phys., 94 (2016) 780.
[7]	KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., Eur. Phys. J. Plus, 133 (2018) 261.
[8]	KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., J. Synchrotron Radiat., 25 (2018) 1703.
[9]	KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., Ann. Phys., 411 (2019) 167912.
[10] KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., Int. J. Mod. Phys. D, 28 (2019) 1950127.
[11] KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., Ann. Phys., 409 (2019) 167931.
[12] KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., Ann. Phys., 418 (2020) 168191.
[13] KHOLMETSKII A. L., YARMAN T., YARMAN O. and ARIK M., J. Synchr. Rad., 28 (2021) 78.
Prof. Dr. Ozan Yarman
--Ozan Yarman  — Preceding undated comment added 14:23, 14 February 2021 (UTC)
thread_title:  Trying to locate who did the following change (monkbot admin "Trappist the monk" said it was not him) 

message: Regarding the sentence, "This implies that the total radiant intensity (summing over all frequencies) is multiplied by the fourth power of the Doppler factor for frequency."
Isn't it the *reciprocal* of the Doppler factor? Doppler factor is fs/fr. If for example the receivers frequency doubles, then the Doppler factor is half, but the radiant intensity increases by 2^4.  — Preceding unsigned comment added by 2603:8000:E500:E39:DD3E:37DE:5C8C:9DBB (talk) 02:36, 5 December 2021 (UTC)
replies: text: Your understanding is correct. On the other hand, I have no idea what is "the Doppler factor for frequency". The sentence should be reworded. Evgeny (talk) 11:42, 5 December 2021 (UTC)
thread_title:  Radiant intensity changes with the reciprocal of Doppler factor 

message: Great work on this article! May I ask if there is a philosophy behind leaving out the amplitude transformation? Einstein published this in 1905 (§7 - see link below) but I cannot find it anywhere in modern literature. If you make an open Google search on “does doppler effect change amplitude”, the first three hits will tell you that it doesn’t. I believe this is true for sound waves, but not in the case of EMR where the amplitude transforms with the same factor as the frequency. You will find a simple derivation of the equation in this preprint https://osf.io/wn3br that may be useful.
Einstein: http://hermes.ffn.ub.es/luisnavarro/nuevo_maletin/Einstein_1905_relativity.pdf MadsVS (talk) 10:31, 5 February 2023 (UTC)
replies: text: Hi people. Since no one is sharing their opinion, I will go ahead and add a section on the Amplitude transformation. Inputs are welcome. MadsVS (talk) 06:45, 27 March 2023 (UTC)
thread_title:  Amplitude transformation is missing?