A recent story labeled Weird Science accompanied photos of students. One of the captions read, “Nancy Morris of the South Holland Public Library creates a vortex by spinning two pop bottles during a program on wild science Thursday at the library. The gravity-driven 'tornado' spins clockwise because the experiment was conducted north of the equator."
This is indeed weird science. First, the Coriolis force causes hurricanes and other global phenomena to rotate counter clockwise in the northern hemisphere. Second, the Coriolis force has no effect on something as small as a pop bottle.
A pop bottle vortex, or water in a toilet, or liquids in any other human-made device, are unaffected by global rotation forces. You can find both counterclockwise and clockwise flowing drains in both hemispheres. The Coriolis force is too weak to affect such small amounts of water.
I don’t know if the point was made by the teacher, or by the caption’s author, but it is in error. Teaching kids science is important and to be commended. It is crucial that the lessons be accurate science.
- Costa Dillon, Valparaiso