Terrell rotation
Encyclopedia
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 independently 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.
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.
Rotation
A rotation is a circular movement of an object around a center of rotation. A three-dimensional object rotates always around an imaginary line called a rotation axis. If the axis is within the body, and passes through its center of mass the body is said to rotate upon itself, or spin. A rotation...
is the distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
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
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
. This behaviour was described independently by both James Terrell and Roger Penrose
Roger Penrose
Sir Roger Penrose OM FRS is an English mathematical physicist and Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute, University of Oxford and Emeritus Fellow of Wadham College...
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, as if rotated.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
American Journal of Physics
The American Journal of Physics is a monthly, peer-reviewed scientific journal published by the American Association of Physics Teachers and the American Institute of Physics. The editor is Jan Tobochnik of Kalamazoo College.-Aims and scope:...
, 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.