Coriolis Effect

The earth's spin influences hurricanes but not toilets
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In the final year of World War I, when the German military pointed its largest artillery at Paris from a distance of 75 miles, the troops adjusted the trajectory for many factors that could be ignored with less powerful guns. In particular, a subtle influence from the rotation of the earth—the Coriolis effect or force—would have shifted all their shots by about half a mile.

Decades earlier a Parisian scientist by the name of Gaspard-Gustave de Coriolis had written down the equations describing that effect as a part of his 1835 paper analyzing machines with rotating parts, such as waterwheels. The Coriolis effect can arise in any situation involving rotation. If you stand anywhere on a counterclockwise-turning carousel, for instance, and throw a ball in any direction, you will see the ball’s trajectory curve to its right. Someone standing next to the carousel will see the ball move in a straight line, but in your rotating frame of reference the ball's direction of motion swings around clockwise. A new force appears to act on the ball. On the spinning earth, we see a similar (but much weaker) force acting on moving objects.

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