Question
Why is it that our weather predominantly moves from west to east, when Earth turns to the east, too? It seems to me that the weather should travel across the face of Earth in the opposite direction of its rotation.
Answer
The flow of weather systems is best explained by the Coriolis effect, named for Gustave-Gaspard Coriolis, the French mathematician/civil engineer who first identified the phenomenon of the Coriolis force in 1835. It is best understood by imagining that someone sitting at the center (A) of a moving merry-go-round throws a ball to someone sitting at a point (B) on the rim. By the time the ball reaches B, that person will have moved to position C, and the ball will appear to have curved away. Similarly, to us on our spinning planet, freely moving objects appear to follow a curved path. Thus, Earth’s rotation deflects moving objects (including weather systems) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
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