Today’s Blue Peter on CBBC managed to resuscitate a long-standing myth for a new generation of viewers.

A segment of the programme showed presenter Konnie Huq on a trip to the equator in Uganda where she was shown a purported demonstration that water in the northern hemisphere flows out of a basin with a clockwise rotation, in the southern hemisphere the rotation is anticlockwise, while on the equator itself, the water flows straight out of the basin with no rotation at all. In fact, this is a trick performed by mountebanks at tourist spots across the equator in order to drum up trade.

The supposed phenomenon is said to occur because of the superimposition of motion on the rotation of the Earth. It’s called the Coriolis effect. The effect itself is real and can be seen in storm formation in both northern and southern hemispheres, but the rotational force exerted is far too small to have an effect in a short timescale on a small basin of water anywhere on Earth, let alone one placed so close to the equator. The Coriolis force is easily swamped by the tiniest currents in the water, which accomplished fakers can induce in the basin by small movements of the apparatus on the pretext of giving the audience a better view.

Fuller explanations of this fake phenomenon can be found here and here. The second of these links shows a transcript of a conversation between Michael Palin and a Kenyan “demonstrator” on a programme in the “Pole to Pole with Michael Palin” series. So this is not the first time this has happened to a reputable broadcaster – though since in both cases the broadcaster was the BBC it may be the first time a reputable broadcaster has been fooled twice by the same well-known trick.

Edit

Having just checked my sources, I now find that the Coriolis effect causes anticlockwise motion in the northern hemisphere and clockwise motion in the southern. Looks like the charlatans can’t even be bothered to get their facts straight!