Tuesday, April 6, 2010

Did you ever wonder: "Clockwise"

From Wikipedia:

"Technically, the terms clockwise and counterclockwise can only be applied to a rotational motion once a side of the rotational plane is specified, from which the rotation is observed. For example, the daily rotation of the Earth is counterclockwise when viewed from the North Pole, and clockwise when viewed from the South Pole.

Clocks traditionally follow this sense of rotation because of the clock's predecessor: the sundial. Clocks with hands were first built in the Northern Hemisphere (see main article), and they were made to work like sundials. In order for a horizontal sundial to work (in the Northern Hemisphere), it must be placed looking southward. Then, when the Sun moves in the sky (east to south to west), the shadow cast on the opposite side of the sundial moves with the same sense of rotation (west to north to east). That's why hours were drawn in sundials in that manner, and that's why modern clocks have their numbers set in the same way.

(The reason for the clockwise orientation of most screws is that supination of the arm, which is used by a right-handed person to turn a screw clockwise, is generally stronger than pronation.)"

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