We all know that draining water rotates in one direction in the Northern Hemisphere and the other direction in the Southern Hemisphere, right?

WRONG!

This may seems true particularly because this story is supposedly backed by a scientific explanation: It's due to the Coriolis effect.

Make no mistake, my Steemian friend... the Coriolis effect is a real thing. It has a role in bigger events like hurricanes (counterclockwise-rotating storms in the Northern Hemisphere and clockwise in the Southern Hemisphere) but doesn't affect our sinks that much.

It seems weird that something somehow responsible for hurricanes isn't strong enough to rotate the draining water in your bathtub but that's not the right way to approach this. It's the opposite! Coriolis acceleration is very very weak. At mid-latitudes it's about one ten-millionth the acceleration of gravity. For that reason it needs a very long distance to produce an observable curvature to the motion. Great wind velocities and the distances involved in such events do the work. A faucet and a sink don't.

The draining water we watch at home rotates in one determined direction due to accidental twists given by the starting flow, small asymmetry of the shape of the drain, residual currents in the bathtub, etc.
_{Source: Scientific American; Images by Pixabay}

See you tomorrow for more "Useless information"

RMach