Named after Gustave Coriolis, a nineteenth-century mathematician, the Coriolis effect is caused by Earth's rotation. As wind and ocean currents move across Earth's surface, the planet itself is rotating from west to east. As a result, the currents appear to travel along a curved path instead of a straight one. Wind and water currents traveling from the equator toward the poles bend eastward, while currents traveling from the poles toward the equator bend westward. The Coriolis effect explains why hurricanes spin counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.