Coriolis force is not a true force at all; instead it is an apparent force. It manifests itself when the observer is in a rotating reference frame, such as the Earth, but the frame is assumed to be at rest, as we often assume with our environment on Earth. For example, consider two children on a merry-go-round. The children are throwing a ball to each other. To us, outside the rotating reference frame, the ball is moving in a straight line, but the children are rotating under the ball. To the children, the ball is being pushed off the straight line path by some unseen force. This fictitious force is the Coriolis force.

Perhaps the most prevalent application of this force is seen in nature. Since the Earth is a rotating reference frame that we often assume is not, the atmosphere experiences the Coriolis force, according...