In which direction runs the water down the sink in Australia? A often asked question.

Our friend Alex who is currently in Ecuador reported as follows:

… “did some experiments. One of them was really interesting. Maybe you know the Corriolis Force: due to the rotation of the earth the water in a sink rotates one way as it drains in the Northern hemisphere and the other way in the Southern hemisphere. They showed this there with a sort of movable sink. Directly above the equator the water ran down without any rotation, 3 meters next to the equator there was a rotation, depending on North or South in opposite directions. I saw it, but I am not sure if this wasn’t a hoax.”

Due to this theory, our house has to be built exactly on the equator, although we are currently living in Perth, Western Australia. Because the water in our sinks is always running down without any rotation. We tried some field tests in our sinks and our toilet, but we couldn’t figure out if the water rotates clockwise or counter-clockwise. Dear Alex, we think that you were the witness of a really good hoax.

But I wanted to know exactly what’s the fuss about the Coriolis Force, so I looked it up in google. It’s true that the Coriolis Force is responsible for rotation differences between the Northern and Southern hemispheres. You can see that with major weather and cloud movements, e.g. hurricans and tornados. But the Coriolis Force is not strong enough to influence the rotation in your sink. The rotation is mainly influenced by external factors such as the size and the form of the drain or sink.

So I have to tell you that the water doesn’t run down the sink in a clockwise rotation only because we are in Australia on the Southern hemisphere.

For more details on the Coriolis Force, please visit
http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html http://en.wikipedia.org/wiki/Coriolis_force

The first link describes a similar story as our friend Alex had experienced.