Comments about "Terrell rotation" in Wikipedia

This document contains comments about the document "Terrell rotation" in Wikipedia
In the last paragraph I explain my own opinion.



The article starts with the following sentence.
Terrell rotation or Terrell effect is the name of a mathematical and physical effect.
IMO Terrell rotation is neither a mathematical nor a physical effect. IMO it is sollely an observation effect. See also Reflection 1 - Terrell rotation
Terrell rotation is the distortion that a passing object would appear to undergo, according to the special theory of relativity if it were travelling a significant fraction of the speed of light.
IMO Terrell rotation has also nothing to do with Special Relativity See also Reflection 2 - Special Relativity

1. Further detail

Terrell's and Penrose's papers pointed out that although special relativity appeared to describe an "observed contraction" in moving objects, these interpreted "observations" were not to be confused with the theory's literal predictions for the visible appearance of a moving object.
This whole sentence is confusing.
Thanks to the differential timelag effects in signals reaching the observer from the object's different parts, a receding object would appear contracted, an approaching object would appear elongated (even under special relativity) and the geometry of a passing object would appear skewed, as if rotated.
This sentence is correct with two remarks.
  1. I would not mention: even under special relativity.
  2. The geometry of the object when it passes the observer is distorted.
A previously-popular description of special relativity's predictions, in which an observer sees a passing object to be contracted (for instance, from a sphere to a flattened ellipsoid), was wrong
It is important to make a clear distinction between the Terrell Rotation and Special Relativity. Terrell Rotation has to do what one observer sees (observes). No physical changes are involved.
Special Relativity has to do with performing measurements (independent of human activities). Physical changes could be involved.

2. See also

Following is a list with "Comments in Wikipedia" about related subjects

5. References

Reflection 1 - Terrell rotation

Terrell rotation is strictly an observational effect.
Terrell rotation (my understanding) comes in two flavours: Length contraction and Length expansion. The explanation is as follows:

For a demonstration of this effect using Visual Basic see the following link: VB Train operation

Reflection 2 - Special Relativity

It is my understanding that the Terrell rotation has nothing to do with Special Relativity and as such is no demonstration of SR. The length of the moving object is considered fixed.
That does not mean that SR could not be involved and that the length could vary as described by SR. But that is not considered.
See also: Historical Overview Length Contraction and Terrell Rotation


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Created: 31 March 2015

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