Coriolis

The Coriolis effect is an apparent deflection of moving objects in a rotating reference frame. It is named after French-Swiss mathematician Gaspard-Gustave de Coriolis, who described the phenomenon in 1835 while analyzing motion of fluids in a rotating system. In non-inertial (rotating) frames, the effect appears as a fictitious Coriolis force proportional to the velocity of the moving body, F_cor = -2 m Ω × v, or its acceleration form a_cor = -2 Ω × v. In inertial frames the effect arises from the conservation of angular momentum rather than a real force.

Earth can be treated as a rotating frame, with Ω representing Earth's rotation vector, magnitude 7.2921159×10^-5 rad/s, directed along the axis. The horizontal deflection is described by a_cor = -2 Ω × v. The magnitude depends on latitude φ; the Coriolis parameter f = 2 Ω sin φ. At the equator f ≈ 0; at higher latitudes it increases toward the poles.

Impacts of the Coriolis effect are most visible in geophysical and engineering contexts. It shapes large-scale atmospheric and oceanic flow, influencing wind patterns (such as trade winds and westerlies) and ocean currents, and it is essential in weather forecasting and climate models. It also affects projectile and vehicle trajectories over long distances, and is demonstrated by Foucault pendulums that reveal Earth's rotation. In engineering, Coriolis effects are accounted for in inertial navigation systems and in the design of rotating machinery.

Notes: The Coriolis effect is not a real force in inertial frames; it is a geometric consequence of observing motion from a rotating reference frame. The concept applies to any rotating system and is widely used in geophysics and engineering.