(Lansing State Journal, May 6, 1992)
Question submitted by Dereck Daschke.
It's a myth that water going down the drain will swirl in different directions in the Northern or Southern Hemispheres.
People often talk about the Coriolis force, a result of the Earth's rotation. Anything moving horizontally over the surface of the Earth will be slightly deflected from a straight course by this force. The direction of deflection is different in the Northern and Southern Hemispheres.
The Coriolis force, though, isn't the only one acting on water going down a drain; the shape or tilt of the tub, air currents and even how the plug is pulled affect water motion more than the Coriolis force.
So, bathtubs in Australia don't necessarily drain in the opposite direction.
Science Theatre would like to thank S. Snyder and Dr. P. Parker for contributing to this article.