Coriolis Effect
The Coriolis effect (sometimes called the Coriolis force) is the apparent deflection of air masses and fluids caused by Earth's rotation. Named after the French mathematician Gustave-Gaspard Coriolis, (1792-1843), who developed the concept in 1835, the Coriolis force is a pseudoforce (false force) and should properly be termed the Coriolis effect. As a result of the Coriolis effect, there is an apparent deflection of all matter in motion to the right of their path in the Northern Hemisphere, and to the left in the Southern Hemisphere. In the Northern Hemisphere, air is deflected counterclockwise (to right of its established path of motion) as it moves inward toward a low-pressure area (zone of convergence). In the Northern Hemisphere, air is deflected clockwise (again, to the right of its established path of motion) as it moves outward toward a low-pressure area (zone of convergence). These deflections and rotations are reversed in the Southern Hemisphere.
The Coriolis effect is a mechanical principle demonstrating that, on a rotating solid body, an inertial force acts on the body at right angles to its direction of motion. The Coriolis effect is based on the classic laws of motion introduced by English physicist and mathematician Sir Isaac Newton (1642-1727) in his work, Philosophiae Naturalis Principia Mathematica (Mathematical principles of natural philosophy).
Within its rotating coordinate system, the object acted on by the Coriolis effect appears to deflect off of its path of motion. This deflection is not real. It only appears to happen because the coordinate system that establishes a frame of reference for the observer is also rotating. The Coriolis effect is due to the motion of a rotating frame of reference (e.g., Earth's rotation).
For example, if a missile is launched northward from the equator. The missile will land to the right of a directly northward target because, when launched, the missile moving along with the ground at the equator moves faster to the east than its direct northward target. Conversely, if a missile were fired from the North Pole to a directly southward target (a target on a great circle that also passed through the South Pole) will also land to the right of its intended target because during the missile's flight the target area has moved farther to the east faster. In the Southern Hemisphere these deflections are reversed (i.e., objects are deflected to the left).
The Coriolis effect is important to virtually all sciences that relate to Earth and planetary motions. It is critical to the dynamics of the atmosphere including the motions of winds and storms. In oceanography, it helps explains the motions of oceanic currents. Accounting for the Coriolis effect is critical in planning the motions of aircraft and the launch and recovery of spacecraft. In astronomy and astrophysics the Coriolis effect explains the rotation of sunspots.
A popular canard (a popular, widely accepted, but false premise) is that water in sinks and toilet bowls drains away in counterclockwise or clockwise motion depending on whether the drain is located in the northern or Southern Hemisphere. The fact is that the Coriolis effect acts only on fluids over great distances or long lengths of time, but is not great enough to produce these defections. These deflections are caused by other factors (drain shape, initial water velocity, etc.)
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