Water really does swirl the other way in Australia

Since the discovery of the Coriolis effect in 1835, many great minds have pondered how it might affect one particular facet of life — namely, toilets in Australia.

Because of the rotation of the Earth, the Coriolis effect means that hurricanes and other giant storm systems swirl counter-clockwise in the Northern Hemisphere, and clockwise in the Southern Hemisphere. In theory, the draining water in a toilet bowl (or a bathtub, or any vessel) should do the same.

In reality, the directions of the jets flushing water through the toilet and other factors overpower the much subtler Coriolis effect, especially because the amount of water in the bowl is small.

But if you could carefully eliminate all outside interference and allow a tank of perfectly still water to drain, could you see the Coriolis effect in action? Recently, Derek Muller from Veritasium and Destin Sandlin from Smarter Every Day made this pair of fascinating videos in the US and Australia — and found that if you're careful enough, you can indeed get water to swirl in opposite directions in either hemisphere.

The videos are meant to be watched simultaneously, side-by-side (see instructions for syncing them up correctly here). Unfortunately, it won't work well on most phones and tablets — you're best off using a desktop.