The Shapiro delay was predicted in 1964 and observed by 1966, and is now a tool used to measure the mass of distant binary pulsars. The Terrell-Penrose rotation was published in 1959, but I can find no evidence for experimental confirmation. Wikipedia lists none, although it does reference a good animation. Everybody believes the math, but what physical proof is there? What would it take to observe something like the animation shows?
$\begingroup$
$\endgroup$
4
-
$\begingroup$ The physical proof is the huge amount of data that supports special relativity in precise detail over a wide array of phenomena. Observations in astronomy, particle physics and high-precision atomic physics are the main lines of evidence. $\endgroup$– Andrew SteaneCommented Sep 10, 2022 at 8:45
-
$\begingroup$ ... The Shapiro effect is different, in that it offered a way to measure an aspect of physics (i.e. general relativity) for which there was little or no observational evidence available, and where even now such timing effects are a central part of the way the physics can be observed and tested quantitatively. $\endgroup$– Andrew SteaneCommented Sep 10, 2022 at 8:52
-
$\begingroup$ ... I think it may be impossible to construct an elegant physical theory which is both consistent with existing data on special relativity and also predicts no Terrell rotation. This is why a direct observation of Terrell rotation would not offer any increase in our understanding of physics (but it would be fun, and fun does have scientific value). $\endgroup$– Andrew SteaneCommented Sep 10, 2022 at 8:55
-
$\begingroup$ Related: resource recommendations for "relativistic vision" physics.stackexchange.com/a/239470/226902 and same question but for length contraction physics.stackexchange.com/q/122469/226902 $\endgroup$– QuilloCommented Feb 8, 2023 at 23:05
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
2
Well, there is aberration of starlight, which is basically the same effect, except the apparently rotating object is the observing apparatus rather than the source.
Because the speed of light is finite, it takes some time for light to travel through a telescope, during which time the telescope has presumably moved transverse to the line of sight.1 As such, the direction to point the telescope to center the star is slightly off from the "abstract spacetime diagram" representation of the pointing.
If you trace the light backward, the original source would only see the telescope aligned perfectly in the radial direction when the telescope is misaligned in the static clocks-and-rulers reference frame.
Note that this was detected in the 18th century.
1 This is caused, for instance, by the Earth's motion around the Sun, which will have a component transverse to the line of sight except in very special conditions. It could be caused by other motion, too, but to detect it you need a time-varying transverse velocity.
-
1$\begingroup$ I believe the Terrell-Penrose rotation is the result of the addition of two effects: One is the finite speed of light, which results in a rotation and is essentially the same as the aberration effect. The second is the combination of the of the Lorentz contraction, and the projection effect, which results in another apparent rotation. This second effect is not present in the aberration of starlight, but explains nearly fifty percent of the Terrell rotation at near light speeds. $\endgroup$ Commented Apr 5, 2013 at 5:30
-
$\begingroup$ For this reason, I do not accept the observation of aberration as observation of the Terrell effect, as it does not involve relativistic relative speeds between observer and object, unlike the Terrell effect. $\endgroup$ Commented Apr 5, 2013 at 5:31
$\begingroup$
$\endgroup$
My current rating is used by the site to not allow commenting, so I write here my relevant thoughts. As I answered in Terrell-Penrose effect and surface reflectance, I repeat part here:
From mentioned in [Wikipedia][1] [paper by R.Penrose][2]:
the light from the trailing part reaches the observer from behind the sphere, which it can do since the sphere is continuously moving out of its way
Therefore rotation is due to finite speed of light/radiation and fast movement of object (significant proportion of that speed). In case of light, movement of observer should produce same effect due to relativity. However, if object is moving in waves' transmitting medium, similar effect can be argued to manifest itself. So similar effect could be tried to be evidenced for e.g. sound waves. I tried web search but did not see any relevant results. Would be glad (as of now) to find any. Maybe no waves except for electromagnetic could be so directional (because of wave-particle duality) ...could not find answer quickly in the web...
