The Coriolis Effect: Myths and Misconceptions

If the Coriolis effect makes some objects appear to change direction, why doesn't it have an impact on tornadoes or toilet water?

While the premise makes sense -- that the earth's eastward spin would cause the water in a toilet bowl to spin as well -- in reality, the force and speed at which the water enters and leaves the receptacle is much too great to be influenced by something as miniscule as a single, 360-degree turn over the span of a day. When all is said and done, the Coriolis effect plays no larger role in toilet flushes and baseball games than it does in the revolution of CDs in your stereo. The things that really determine the direction in which water leaves your toilet or sink are the shape of the bowl and the angle at which the liquid initially enters that bowl.

The Coriolis effect may play a small role in the direction of a tornado's spin -- if the circumstances are right. More often than not, however, that direction is determined by the storm system that spawned the twister in the first place. These storm systems, or supercells, result when dry polar air clashes with moist tropical air and creates an updraft as the warmer air quickly rises. As the air flows upward, the increase in wind speed causes a tornado's characteristic rotation.

Likewise, the New York Yankees, the Los Angeles Dodgers and other elite baseball teams can't really credit scientific phenomena for their accomplishments. Things might be different if first base was on the equator and third was at the North Pole. But in the short distance between the pitcher's mound and the batter's box, the Coriolis effect doesn't gain a whole lot of traction. Even the most intimidating closer wouldn't see much difference in the placement of his fastball as a result of the Earth's rotation than he would from a gusty wind.

Slowly Spinning Sinks

As you now know, the Coriolis effect isn't strong enough to influence the way a normal sink drains. Things like gravity and irregularities in the sink's shape can overpower any effects of the Earth's rotation. However, as some perhaps overly curious scientists discovered, if all extraneous factors are eliminated, the Coriolis effect can indeed determine the direction of the water drainage. However, you're unlikely ever to observe this in action: The scientists had to let the water sit still for more than three weeks and then let the sink drain one drip at a time. This allowed outside influences (like currents) to weaken and give the Coriolis effect a chance to do its thing [source: Plait].