Coriolis Force, Page 1 of 4

The coriolis effect is caused by the earth’s rotation. It is sometimes called a “force,” but it’s not really a force at all. It is merely a manifestation of one of Newton’s laws which says that objects move in a straight line, in an “inertial” frame of reference, unless acted upon by a force. An “inertial” frame of reference is closely approximated by motion relative to the stars. The Earth simply rotates under the straight line motion (relative to the stars) of the body in question. What makes this seem complex to us, who live on the Earth, is that we experience our place on the Earth as fixed. So, it is unexpected that a body in motion, without experiencing a force upon it, would move in a curved path. But, remember the Foucault Pendulum that you see at some science museums. The slow rotation of the earth causes the plane of motion of the pendulum to rotate a full cycle in 24 hours.

Here we use the analogy of a ball thrown on a rotating carousel. Two people sit at opposite sides, and one attempts to throw a ball to the other. For the purposes of this illustration, the earth is analogous to the “inertial” reference frame and the carousel is analogous to the rotating reference frame. Note also that this analogy holds best at the North Pole of the Earth.

Advance to next page

Note: Move the mouse over the bottom of the video to view the controller. You can pause and restart the video, and drag the slider along the bottom to control where you are in the video.

Scroll to the top of the screen to read the entire text.

Applications that support learning about the Earth