Coriolis Effect

The apparent deflection of motion relative to a rotating reference frame, including Earth.

On Earth, freely moving air and water are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The effect is zero at the equator and increases with latitude and speed.

It strongly influences large-scale winds, currents and pressure systems but is negligible for water rotating in an ordinary sink or for most close-quarters boat manoeuvres, where other forces dominate.