This is a picture of biodegradable hairspray, illuminated by black light, flowing counterclockwise down a standard sink drain. It is believed that the Coriolis force is responsible for the counterclockwise rotation of fluids in sink drains in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere. However, information that contradicts this belief is being presented by various sources. It is being suggested that the rotational motion of the fluids is due to the way the fluid filled the sink and that the Coriolis force is too weak to be a significant factor in causing a very small body of water to rotate in a particular direction. In several experimental trials, where a rubber hose was used to direct the water flow while filling the sink, the direction of drainage was observed to be the same as the direction of filling. This suggests that the micro influences within the sink environment have a greater effect than the Coriolis force on the fluid body.

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Ian Liu
St. Elizabeth Catholic High School, Thornhill, Ontario
1st Prize ( High School/CEGEP )

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