Terrell rotation

Terrell rotation is the name of a mathematical and physical effect. Specifically, 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. This behaviour was described by both James Terrell and Roger Penrose in pieces published in 1959.

Due to an early dispute about priority and correct attribution, the effect is also sometimes referred to as the Penrose-Terrell effect, the Terrell-Penrose effect, or just as the Terrell effect.

Further detail

Terrell's paper 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. 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.

For images of passing objects, the apparent contraction of distances between points on the object's transverse surface could then be interpreted as being due to an apparent change in viewing angle, and the image of the object could be interpreted as appearing instead to be "rotated". 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.

Terrell's piece prompted a number of followup papers, mostly in the American Journal of Physics, exploring the consequences of this correction. Terrell's paper pointed out that some existing discussions of special relativity were flawed and "explained" effects that the theory did not actually predict - while his paper did not change the "actual" mathematical structure of special relativity in any way, it did correct a popular misconception regarding the theory's predictions.

References and further reading

* James Terrell, "Invisibility of the Lorentz Contraction": Phys. Rev. 116 1041-1045 (1959).

* Roger Penrose, "The Apparent Shape of a Relativistically Moving Sphere" : Proc. Cambridge Phil. Soc. 55 137-139 (1959)

* Mary L. Boas, “Apparent shape of large objects at relativistic speeds,” : Am. J. Phys. 29 283-286 (1961).

* Eric Sheldon, “The twists and turns of the Terrell Effect,”: Am. J. Phys. 56 199-200 (1988).

* James Terrell, "The Terrell Effect,": Am. J. Phys. 57 9-10 (1989).

* Eric Sheldon, “The Terrell Effect: Eppure si contorce!,”: Am. J. Phys. 57 487 (1989).

* John Robert Burke and Frank J. Strode, “Classroom exercises with the Terrell effect,”: Am. J. Phys. 59 912-915 (1991).

External links

* [http://math.ucr.edu/home/baez/physics/Relativity/SR/penrose.html A webpage explaining the Penrose-Terrell Effect]