Talk:Special relativity

message: The transverse Doppler effect (TDE) is one of the novel predictions of special relativity. Assume that a source and a receiver are both approaching each other in uniform inertial motion along paths that do not collide. 
At the beginning, when the observer approaches the light source, the observer sees a blueshift, and later, when the distance with the source increases, he sees a redshift. The transverse Doppler effect describes the situation when the light source and the observer are close to each other. At the moment when the source is geometrically at its closest point to the observer, one may distinguish 
#the light that arrives at the observer,
#the light that is emitted by the source, and
#the light that is at half distance between the source and observer.
The situation of case (1) is shown in Fig. 5-3(a) in the rest frame of the source.  The frequency observed by the observer is blueshifted by the factor  because of the time delation of the observer (as compared with the rest frame of the source). The dotted blue image of the source shown in the figure represents how the observer sees the source in his own rest frame.
The situation of case (2) is shown in Fig. 5-3(b) in the rest frame of the observer. This light is received later when the source is not any more at closest distance, but it appears to the receiver to be at closest distance. The observed frequency of this light is redshifted by the factor  because of the time delation of the source (as compared with the rest frame of the observer). This situation was Einstein's original statement of the TDE  
In the situation of case (3), the light will be received by the observer without any frequency change. 
Whether an experiment reports the TDE as being a redshift or blueshift depends on how the experiment is set up. Consider, for example, the various Mössbauer rotor experiments performed in the 1960s. Some were performed with a rotating source while others were performed with a rotating receiver, as in Fig 5‑3(c) and (d). 
Fig 5‑3(c) and (b) are corresponding scenarios, as are Fig 5‑3(d) and (a).
=====The effect's "novelty" is exaggerated=====
: The "transverse Doppler" phenomenology isn't as novel to SR as you might think. A similar effect seems to show up in almost any theory where the motion of the emitter has at least some influence on how light propagates.  
: Take nasty old ballistic emission theory as an example. If an object moving through the lab throws light at what it believes to be "90 degrees" to its relative motion vector, a lab onlooker will see that ray to be advancing at the same rate as the object, and therefore angled to point slightly forward. If the lab onlooker aims a narrow-angle detector at lab-90 degrees to the path of the object, the light that registers on the detector does not belong to the transverse-aimed ray, but a different ray that was originally aimed slightly to the rear, and is therefore expected to include a recession redshift component.
: As a result, emission theory predicts a similar (actually stronger) redshift to SR's, and pretty much any dragged-light or dragged-aether model that predicts a transverse-aimed ray being deflected forward in the lab frame will predict that the ray seen at 90 degrees in the lab frame will be seen to be redshifted. ErkDemon (talk) 21:38, 27 August 2023 (UTC)
thread_title: Transverse Doppler effect

message: : The "transverse Doppler" phenomenology isn't as novel to SR as you might think. A similar effect seems to show up in almost any theory where the motion of the emitter has at least some influence on how light propagates.  
: Take nasty old ballistic emission theory as an example. If an object moving through the lab throws light at what it believes to be "90 degrees" to its relative motion vector, a lab onlooker will see that ray to be advancing at the same rate as the object, and therefore angled to point slightly forward. If the lab onlooker aims a narrow-angle detector at lab-90 degrees to the path of the object, the light that registers on the detector does not belong to the transverse-aimed ray, but a different ray that was originally aimed slightly to the rear, and is therefore expected to include a recession redshift component.
: As a result, emission theory predicts a similar (actually stronger) redshift to SR's, and pretty much any dragged-light or dragged-aether model that predicts a transverse-aimed ray being deflected forward in the lab frame will predict that the ray seen at 90 degrees in the lab frame will be seen to be redshifted. ErkDemon (talk) 21:38, 27 August 2023 (UTC)
thread_title: The effect's "novelty" is exaggerated

message: Special relativity is occasionally referred by this name, both in educational resources and in research papers. Is it common enough to mention this alternative name in the beginning and to make a redirect? I ask it here so it's not lost in the edit history. Tarnoob (talk) 10:49, 26 July 2023 (UTC)
replies: text: I don't think it is common enough name to be mentioned in the lead. A redirect can certainly be made, but should probably point to Relativistic mechanics instead of this article. Jähmefyysikko (talk) 11:22, 26 July 2023 (UTC)
thread_title:  Einstein's mechanics 

message: I think it would be interesting that a citation and comment of the following article would be inserted: https://doi.org/10.1119/1.10490
It shows that the Lorentz transformations and the existence of an invariant speed can be derived based on the principle of relativity and homogeneity of space–time, isotropy of space–time, group structure, causality condition. 
It is quite an impressive result that there should be a "limit speed" based on these hypotheses onuly. In this presentation, light does not play such an important role in the elaboration of the theory. 88.180.38.188 (talk) 09:26, 7 February 2024 (UTC)
replies: text: Old hat. Already covered in section Special relativity#Relativity without the second postulate. - DVdm (talk) 18:11, 7 February 2024 (UTC)
replies: text: ok noted. There is no reference to the paper by Levy-Leblond, however. 88.180.38.188 (talk) 08:20, 8 February 2024 (UTC)
replies: text:  The current little section is properly sourced from a textbook and another journal article, so there's no need to add another source. - DVdm (talk) 10:46, 8 February 2024 (UTC)
thread_title:  Special relativity postulates