The Spin Down Under / Do Aussies go with the flow - or against it? By Dan Drollette. SPECIAL CORRESPONDENT. Dan Drollette is a freelance writer. CANBERRA, Australia WHEN I MOVED to the land down under, the first thing my family and friends back home in New York asked me was whether the toilets here flush in the opposite direction from the northern hemisphere. They knew that what is called the "Coriolis force" makes cyclones, tornadoes, hurricanes and ocean currents spin counterclockwise north of the equator and clockwise south of it. But did it also act upon liquids as they spiral down the drains of swimming pools, bathtubs and sinks and pour out the mouths of milk cartons and bottles? Asking this question is one of the easiest ways to start an argument in an Aussie pub, I've discovered (the other way is to mention the words "America's Cup"). Physicist Stuart Kohlhaggen, director of Questacon, Australia's national science museum, says the how and why of the Coriolis is one of the most-asked questions. Several Internet sites devote pages to the phenomenon (sometimes with incorrect data about which way things rotate). And an entire episode of the "Simpsons" - in which the cartoon family travels to Australia - revolved around this "force." The story's climax occurs when Homer finds that the toilet and sink in the American Embassy's bathroom is outfitted with elaborate pumps, valves and pipes to make the water drain counterclockwise, "just like home." Overcome with emotion, Homer starts to cry and sing "The Star-Spangled Banner." Colorful as such stories may be, the impact of the Coriolis is exaggerated, says Kohlhaggen. "While the Coriolis effect does exist, it only works for large bodies of air or water, such as continent-size weather systems," he explained recently. "Its effect on smaller bodies is negligible; the minuscule imperfections in the surface of a sink's bowl and the angle of the spigots would have more of an impact." Theoretical physicist John Love of the Australian National University agrees, adding, "The impact of the Coriolis `force' on small systems such as bathtubs is one of the most persistent `scientific' fallacies of today. People continue to believe in it, despite all evidence to the contrary. It's almost as if they think there's a Coriolis fairy." I found there were two parts to understanding this: what the Coriolis effect is, and why it does not act upon smaller objects such as sinks and toilets. Technically speaking, the Coriolis is not even a real force, but a fictitious one resulting from a rotating frame of reference. It's an apparent deviation caused by the inertia of an object traveling above the Earth's surface while the planet spins eastward below; it is fictitious in the sense that if the globe were not spinning, there would be no deviation. This effect was first described by 19th-Century French mathematician Gustave-Gaspard Coriolis, who evidently became interested in the motion of rotating bodies after writing "The Mathematical Theory of the Game of Billiards." To understand why it works, imagine that you are looking down at the globe from above. The Earth would look like an old-fashioned vinyl record player, with the North Pole for the axis. At the center, the record moves so slowly that it appears to stand still, while at the far edge the record is traveling quickly, where it has more distance to cover in each revolution. Similarly, at the equator, the Earth is moving from west to east at 1,040 mph, while at the latitude of Long Island it is moving closer to 700 mph. This difference in speed at different latitudes has several consequences: If you were to take a piece of chalk and try to draw a straight line from the center of the record to its edge while the record is playing, you would instead get a curving line as a result of the record's motion while the pen is traveling. Likewise, if a rocket was fired from the Earth's North Pole to a point on the equator, the shell would land to the right of its intended target, since the target's faster eastward motion would have caused it to move left by the time the shell landed. (For this reason, the Coriolis effect must always be taken into account when launching spacecraft.) The same is true of streams of air as they head south to their "target" - they curve to the right, setting off cells of air that rotate in a counterclockwise fashion. When going in the opposite direction - from equator to North Pole - a rocket (or stream of wind) would again veer to the right of its intended target, this time because the projectile was moving eastward at the equator faster than its bull's-eye to the north. The object carries this eastward momentum with it while in flight. In the southern hemisphere, everything is reversed. Just as a record player appears to spin one way when viewed from above, and in the opposite direction when seen from below, the Earth's west-to-east rotation appears to be counterclockwise from the North Pole and clockwise from the South Pole. As for why the Coriolis "force" does not affect objects such as the liquid in a tub or milk carton, the fluid's surface area is not big enough to feel the difference in the rate of travel between the container's south and north ends. The disturbances introduced just by filling a tub can cause enough currents and eddies to make the water rotate once every few seconds; meanwhile, the Earth is completing only one rotation every 24 hours. As a result, the impact of the eddies caused by filling the tub or jostling the carton is tens of thousands of times stronger than the Coriolis effect. Under controlled laboratory conditions, with a very large, perfectly symmetrical, circular tank, where the water has stood still for a week, and the plug removed in such a way as to avoid causing any disturbances, it is possible to see the Coriolis effect, writes Alistair Fraser, a Pennsylvania State University professor. Fraser, who also runs the Bad Science Web site (www.ems.psu.edu/fraser /BadScience.html), says that anything less than these extraordinary controls causes the Coriolis effect to be obliterated. As for toilets, "the direction of rotation of a draining toilet is determined by the way the water just under the rim is squirted into the bowl when it is flushed." Incidentally, while attending a reception at the American Embassy in Canberra, I scrutinized the bathroom's plumbing fixtures and found that there was no elaborate mechanism to overcome the Coriolis effect. The water in the sink? It drained counterclockwise. Copyright 1997, Newsday Inc. The Spin Down Under / Do Aussies go with the flow - or against it?., pp C03.