- Also called:
- Coriolis effect
- Key People:
- Gaspard-Gustave de Coriolis
- On the Web:
- Physics LibreTexts - Coriolis Force (Oct. 29, 2026)
Coriolis force
-
What is the Coriolis force?
The Coriolis force is an inertial force that affects objects moving within a rotating coordinate system. Rather than a true force, it is a pseudoforce that arises from the rotation of the reference frame.
On Earth, the Coriolis effect causes moving objects to be deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection influences various phenomena, such as the rotation of storms, ocean currents, and the trajectories of projectiles. The magnitude of the Coriolis effect depends on the object's velocity, the Earth's angular velocity, and latitude, and is given by (2v\omega \sin\phi), where (v) is the object's velocity, (\omega) is the Earth's angular velocity, and (\phi) is the latitude.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why does the Coriolis force happen on Earth?
The Coriolis force is an inertial force that affects objects moving within a rotating coordinate system. On Earth, this force is due to the planet's eastward rotation and the variation in tangential velocity with latitude.
An object moving along a north-south path will experience an apparent deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection is because an object moving toward the poles is also moving east at a certain speed. As the object moves towards the pole, it passes over ground that is moving progressively slower eastward. Therefore, the object appears to veer to the east.
The Coriolis force is significant in understanding various phenomena, such as the rotation of storms, ocean currents, and even the trajectories of projectiles.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does the Coriolis force affect moving objects, like airplanes or winds?
The Coriolis force is an apparent force that arises due to Earth's rotation and affects the motion of objects moving over its surface. In the Northern Hemisphere, this force deflects moving objects to the right of their intended path, while in the Southern Hemisphere, the deflection is to the left.
This effect influences the direction of winds and the rotation of storms, causing cyclones to rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The Coriolis effect also plays a role in ocean currents, deflecting them about 45° from the wind direction. While the Coriolis force is significant in large-scale systems like weather patterns and ocean currents, its effect on objects like airplanes is less direct.
4 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Which direction does the Coriolis force deflect moving things in the Northern and Southern Hemispheres?
The Coriolis force is an apparent force that arises due to the Earth's rotation and affects objects moving on its surface. In the Northern Hemisphere, this force deflects moving objects to the right, while in the Southern Hemisphere, it deflects them to the left. This deflection influences various phenomena, including the rotation of storms and oceanic currents.
3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does the Coriolis force influence weather patterns, such as hurricanes or trade winds?
The Coriolis force is a pseudo force that arises from the rotation of the Earth and affects moving objects, such as air currents. In the Northern Hemisphere, this force deflects moving objects to the right, while in the Southern Hemisphere, it deflects them to the left.
This deflection influences weather patterns like trade winds, which blow from east to west in the tropics, and hurricanes, causing them to rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The Coriolis force also contributes to the poleward movement of tropical cyclones.
5 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
Why is the Coriolis force considered a 'fictional' or 'apparent' force in physics?
The Coriolis force is considered a "fictional" or "apparent" force because it is an inertial force observed in a rotating frame of reference. It's not a real force in the Newtonian sense but rather a pseudo force that appears due to the rotation of the coordinate system.
An object moving within a rotating system seems to deviate from its path, not because of an actual force, but because the coordinate system is in motion. For instance, a block sliding on a rotating platform moves in a straight line in inertial space, but to an observer on the platform, it appears to curve.
The Coriolis effect is most noticeable when objects move longitudinally. On Earth, objects moving north or south appear to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This is due to Earth's eastward rotation and the variation in tangential velocity with latitude.
2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Coriolis force, in classical mechanics, an inertial force described by the 19th-century French engineer-mathematician Gustave-Gaspard Coriolis in 1835. Coriolis showed that, if the ordinary Newtonian laws of motion of bodies are to be used in a rotating frame of reference, an inertial force—acting to the right of the direction of body motion for counterclockwise rotation of the reference frame or to the left for clockwise rotation—must be included in the equations of motion.
The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system. The object does not actually deviate from its path, but it appears to do so because of the motion of the coordinate system.
The Coriolis effect is most apparent in the path of an object moving longitudinally. On Earth an object that moves along a north-south path, or longitudinal line, will undergo apparent deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. There are two reasons for this phenomenon: first, Earth rotates eastward; and second, the tangential velocity of a point on Earth is a function of latitude (the velocity is essentially zero at the poles and it attains a maximum value at the Equator). Thus, if a cannon were fired northward from a point on the Equator, the projectile would land to the east of its due north path. This variation would occur because the projectile was moving eastward faster at the Equator than was its target farther north. Similarly, if the weapon were fired toward the Equator from the North Pole, the projectile would again land to the right of its true path. In this case, the target area would have moved eastward before the shell reached it because of its greater eastward velocity. An exactly similar displacement occurs if the projectile is fired in any direction.
" height="20" alt="HEW Logo">
The Coriolis deflection is therefore related to the motion of the object, the motion of Earth, and the latitude. For this reason, the magnitude of the effect is given by 2νω sin ϕ, in which ν is the velocity of the object, ω is the angular velocity of Earth, and ϕ is the latitude.
The Coriolis effect has great significance in astrophysics and stellar dynamics, in which it is a controlling factor in the directions of rotation of sunspots. It is also significant in the earth sciences, especially meteorology, physical geology, and oceanography, in that Earth is a rotating frame of reference, and motions over the surface of Earth are subject to acceleration from the force indicated. Thus, the Coriolis force figures prominently in studies of the dynamics of the atmosphere, in which it affects prevailing winds and the rotation of storms, and in the hydrosphere, in which it affects the rotation of the oceanic currents. It is also an important consideration in ballistics, particularly in the launching and orbiting of space vehicles. In modern physics, application of a quantity analogous to Coriolis force appears in electrodynamics wherever instantaneous voltages generated in rotating electrical machinery must be calculated relative to the moving reference frame: this compensation is called the Christoffel voltage.