[Mike Butcher]

Mike Butcher asked the Naked Scientists:
   
Can you confirm (and explain) that water goes around in an anti-clockwise direction down the plug-hole in the Northern Hemisphere and clockwise in the Southern hemisphere?

What do you think?

[Madidus_Scientia]

It is true, but only of very controlled experiments. you can't just fill your sink up then unplug it and watch it, its called the coriolis effect and is only a very insignificant force in terms of deciding the direction of the water spiralling, any motion in the fluid before you pulled the plug would mostly determine it. To actually observe the effect you need a very large shallow dish of uniform shape, leave it for a long time so that any of the initial motion in the fluid has pretty much all stopped, and would have to be at constant temperature to stop any convection currents occuring, and then let it drain through a very small hole (you'd have to unplug from the bottom, putting your hand in the fluid and pulling a plug out would obviously give the fluid motion again).

Then the effect can be observed, it would spiral counterclockwise in the northern hemisphere, clockwise in the southern.

[Chemistry4me]

There was this: http://www.thenakedscientists.com/forum/index.php?topic=18951.0
Also a poll that I cannot find at the moment.

[thedoc]

Listen to the answer to this question on our podcast.