Coriolis force

Does the Coriolis force determine the swirl in the bath?
Max-Horst Mühlpfordt, Halle /Saale, by E-mail

The persistent rumour that water running out of the bath flows in accordance with the laws of the Coriolis force is in fact only a rumour. The influence of the Coriolis force in a normal bath is so small that even a puff of wind can cancel it. It would only be possible to establish the authenticity of the effect of the Coriolis force in a bath 500 times the size of a normal bath. This statement is the result of calculations made by the Australian mathematician, Michael Page, from the Monash University. The Coriolis force is an effect, which is caused by the rotation of the earth. A point on the equator covers a distance of around 40,000 km during a rotation of the earth. Since the diameter of the earth decreases towards the poles, a point nearer the poles has a respectively shorter distance to cover and is therefore slower. A point on the equator is faster in comparison. If some form of matter moves either north- or southwards it will be deflected by these differences in speed - in the northern hemisphere it will move towards the right and in the southern hemisphere towards the left. According to that the swirl above the plug in an over-dimensional bath in the northern hemisphere would turn in a clockwise direction and in the southern hemisphere anti-clockwise. For the domestic bath this is of cause just a theory.

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