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Showing posts from May, 2015

Does water swirl counter-clockwise in the Southern Hemisphere?

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Answer:Yes and no. When applied to toilets and sinks, this is one of those “too good to be true” science factoids, I’m afraid. But it does apply in some situations.


The myth goes that if you flush a toilet in Australia the water swirls down the drain the opposite way than in the northern hemisphere, due the Coriolis effect (an apparent force which describes how objects veer to the left or right when traveling on something that’s rotating — see the link above for a good visualization of this).

If there were no other forces on that water in the sink or toilet, that would be true. The Coriolis effect does actually make hurricanes rotate the opposite direction in the two hemispheres. But for toilets and sinks it’s another story. The toilet myth is easy to dispell — just peek around the rim of the toilet and you’ll see that the water is jetted into the bowl at an angle, which determines the direction the water swirls. Sinks, however, are a little more tricky.

I’ve heard of charlatans who …