Definition
An apparent force, caused by the rotation of the Earth, that deflects moving air and other freely moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It is not a true physical force but an effect observed because the Earth rotates beneath the moving object. Its strength increases with the speed of the object and with latitude, becoming zero at the equator and greatest at the poles.
Plain English
Because the Earth is spinning, anything moving over its surface — like a mass of air — appears to curve sideways instead of traveling in a straight line. In the Northern Hemisphere it curves to the right; in the Southern Hemisphere it curves to the left.
Context Anchor
Seen in aviation weather discussions about wind direction, pressure systems, and large-scale weather movement.
Derivation
Named after the French mathematician Gaspard-Gustave de Coriolis, who described the effect mathematically in 1835 while studying rotating systems. Knowing it is named after a person (not a physical thing) helps reinforce that it is a described effect, not a force you can feel directly.
Why Pilots Care
Must be considered when planning long flights and interpreting large-scale wind systems.
Analogy
If you roll a ball across a spinning playground merry-go-round, the ball may look like it curves to someone riding on it, even though it is really trying to move straight. Earth’s rotation creates a similar apparent curve for moving air.
Grounding Statement
Picture air starting to flow from a high-pressure area toward a low-pressure area in a straight line. While that air is moving, the Earth rotates beneath it, so by the time the air arrives, it appears to have curved — that apparent curve is the Coriolis force at work.
Intuition Check
Coriolis Force is not a cockpit force that pushes the airplane sideways during normal flight. It is an apparent effect of Earth’s rotation, mainly important for understanding large-scale wind and weather movement.
Example Sentence 1
Coriolis force is the reason wind aloft tends to flow parallel to the isobars rather than directly from high to low pressure.
Example Sentence 2
Coriolis force helps shape the jet stream that pilots use to reduce flight time on eastbound routes.