The Coriolis effect is often thought of as a mystical power that controls the movements of everything on Earth. It is a deflection of moving objects when they are viewed in a rotating reference frame.
In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right.
Coriolis Force is the invisible force that appears to deflect the wind. The Coriolis force applies to movement on rotating objects. It is determined by the mass of the object and the object's rate of rotation. The Coriolis force is perpendicular to the object's axis. The Earth spins on its axis from east to west. The Coriolis force, therefore, acts in a north-south direction. The Coriolis force is zero at the Equator.
Though the Coriolis force is useful in mathematical equations, there is actually no physical force involved. Instead, it is just the ground moving at a different speed than an object in the air.
The classic example used to understand this phenomenon is to imagine the Earth flattened out like a spinning merry-go-round. If someone was to sit in the center of the merry-go-round and attempt to throw a ball directly to a friend sitting on the outside edge of the ride, the ball would always seem to turn away from the friend just before he could catch it. In this example, the ball is really moving in a straight line and only appears to sway off course because the friend on the outside edge is moving faster than the person in the middle (he moves faster since he has a greater distance to travel to make one rotation in the same amount of time as the person in the center). Similarly, on Earth, the equator spins much faster than the North and South Poles (the Earth’s axis of rotation).
Now, if that same pair of friends could play a game of catch across the whole globe, with one person standing at the equator and the other standing at the North Pole, then the ball would deflect just as it did on the merry-go-round. That’s because the distance is far enough for the Coriolis effect to have an impact.
The Coriolis effect can’t, however, influence movements on smaller scales, such as the pitch of a baseball or the way water flushes in the toilet. That’s because other forms of energy in the immediate environment overpower the relatively weak Coriolis force.