Sinistral and dextral are scientific terms that describe chirality (“handedness”) or relative direction in a number of disciplines. The terms are derived from the Latin words for “left” (sinister) and “right” (dexter). Other disciplines have different terms (such as dextro- and laevo-rotary, in chemistry, or clockwise and anticlockwise in physics) or simply use left and right (as in anatomy). Relative direction and chirality are distinct concepts. Relative direction is from the point of view of the observer. A completely symmetrical object has a left and a right side, from the observers point of view, if the top and bottom and direction of observation are defined. Chirality, however, is observer-independent: no matter how one looks at a right-hand screw thread, it remains different from a left-hand screw thread. Therefore, a symmetrical object has sinistral and dextral directions arbitrarily defined by the position of the observer, while an object that has chirality can have sinistral and dextral directions defined by characteristics of the object, no matter the position of the observer.
Posted on: Tue, 30 Dec 2014 23:05:21 +0000
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