The coriolis effect is one of the most misunderstood physical phenomena. The coriolis effect is cited as the reason behind the different ways that drains empty. Drains in the northern hemisphere are believed to swirl in one direction, and drains in the southern hemisphere the opposite direction because of the coriolis effect. In actuality, the direction in which a drain swirls has to do with the shape of the drain, and any motion in the water. The coriolis effect is however a real phenomenon. First identified in 1778 by Pierre-Simon Laplace, and later described by Gustave-Gaspard Coriolis in 1835, the coriolis effect is a result of the daily rotation of the Earth. Each day, the Earth spins eastward on it's north-south axis. If you were to stand on the equator, in one day you will travel a distance equal to the Earth's circumference, which is a little over 40 thousand kilometers. In comparison, if you were to stand at a pole, your rotational trip would be negligible. An object that moves from the equator towards a pole will carry an initial eastward velocity that is greater than the eastward velocity of the surface of the Earth at the object's arrival. This means that the object will be deflected slightly from a straight path. This is the coriolis effect and it is too small to be detected at the scale of a kitchen sink. It is detectable at larger scales, and is responsible for one of the most destructive forces of nature - the hurricane. Air masses that flow from the north in the northern hemisphere will gradually deflect to the west, and air flowing from the south will deflect to the east. As these air flows come together, a clockwise rotation in the air mass results. This air rotation sets the stage for a hurricane to form. In warmer months, warm ocean currents fuel the rotation by adding energy to the system, and destructive hurricanes are born. http://physics.suite101.com/article.cfm/thecorioliseffect

tendency for any moving body on or above the earth’s surface, e.g., an ocean current or an artillery round, to drift sideways from its course because of the earth’s rotation. In the Northern Hemisphere the deflection is to the right of the motion; in the Southern Hemisphere it is to the left. The Coriolis deflection of a body moving toward the north or south results from the fact that the earth’s surface is rotating eastward at greater speed near the equator than near the poles, since a point on the equator traces out a larger circle per day than a point on another latitude nearer either pole. A body traveling toward the equator with the slower rotational speed of higher latitudes tends to fall behind or veer to the west relative to the more rapidly rotating earth below it at lower latitudes. Similarly, a body traveling toward either pole veers eastward because it retains the greater eastward rotational speed of the lower latitudes as it passes over the more slowly rotating earth closer to the pole. It is extremely important to account for the Coriolis effect when considering projectile trajectories, terrestrial wind systems, and ocean currents. http://www.bartleby.com/65/co/Coriolis.html Tendency of any moving body, on or starting from surface of earth, to continue in direction in which earth's rotation propels it. Direction in which the body moves because of this tendency combined with direction in which it is aimed determines ultimate course of the body relative to earth's surface. In the northern hemisphere Coriolis effect causes a moving body to veer or try to veer to right of its direction of forward motion; in the southern hemisphere, to left. Magnitude of effect is proportional to velocity of a body's motion. This effect causes cyclonic storm-wind circulation to be counterclockwise in the northern hemisphere and clockwise in the southern hemisphere and determines final course of ocean currents relative to trade winds. http://www.webref.org/geology/c/coriolis_effect.htm The acceleration which a body in motion experiences when observed in a rotating frame. This force acts at right angles to the direction of the angular velocity. Thus a projectile fired due north from any point on the northern hemisphere will land slightly east of its target because the eastward velocity of Earth's surface decreases from the equator to the poles. The Coriolis effect is responsible for large-scale wind patterns in Earth's atmosphere (and for ocean currents). http://nedwww.ipac.caltech.edu/level5/Glossary/Glossary_C.html A force per unit mass that arises solely from the earth's rotation, acting as a deflecting force. It is dependent on the latitude and the speed of the moving object. In the Northern Hemisphere, air is deflected to the right of its path, while in the Southern Hemisphere, air is deflected to the left of its path. It is greatest at the poles, North and South, and almost nonexistent at the equator. http://www.weather.com/glossary/c.html#coriolis The Coriolis effect is an apparent deflection of moving objects from a straight path when they are viewed from a rotating frame of reference. The effect is named after Gaspard-Gustave Coriolis, a French scientist who described it in 1835, though the mathematics appeared in the tidal equations of Pierre-Simon Laplace in 1778. The Coriolis effect is caused by the Coriolis force, which appears in the equation of motion of an object in a rotating frame of reference. Sometimes this force is called a fictitious force (or pseudo force), because it does not appear when the motion is expressed in an inertial frame of reference, in which the motion of an object is explained by the real impressed forces, together with inertia. In a rotating frame, the Coriolis force, which depends on the velocity of the moving object, and centrifugal force, which does not, are needed in the equation to correctly describe the motion. Perhaps the most commonly encountered rotating reference frame is the Earth. Freely moving objects on the surface of the Earth experience a Coriolis force, and appear to veer to the right in the northern hemisphere, and to the left in the southern. Movements of air in the atmosphere and water in the ocean are notable examples of this behavior: rather than flowing directly from areas of high pressure to low pressure, as they would on a non-rotating planet, winds and currents tend to flow to the right (left) of this direction north (south) of the equator. This effect is responsible for the rotation of large cyclones. http://en.wikipedia.org/wiki/Coriolis_effect

Its caused by people farting....