The Coriolis force is a force which acts upon any moving body in an independently rotating system. The most well known application of the Coriolis force is for the movement or flow of air across the Earth. The effect is named after the French physicist Gaspard de Coriolis (1792-1843), who first analyzed the phenomenon mathematically.
The Earth rotates about its axis from west to east once every 24 hours. Consequently, an object moving above the Earth in a generally northerly or southerly direction, and with a constant speed relative to space, will be deflected in relation to the rotation of the Earth. This deflection is clockwise, or to the right, in the Northern Hemisphere and anticlockwise, or to the left, in the Southern Hemisphere.
Moving air undergoes an apparent deflection from its path, as seen by an observer on the Earth. This apparent deflection is the result of the Coriolis force. The amount of deflection the air makes is directly related to both the speed at which the air is moving and its latitude. Therefore, slowly blowing winds will be deflected only a small amount, while stronger winds will be deflected more. Likewise, winds blowing closer to the poles will be deflected more than winds at the same speed closer to the equator. The Coriolis force is zero right at the equator.
The Coriolis force only acts on large objects like air masses moving considerable distances. Small objects, for example ships at sea, are too small to experience significant deflections in direction due to the Coriolis Force.