Out! Time to get out of the tub! I know it's hard but you are now relaxed and clean, nothing else to do here. Let's dry in a hot towel and let all that water drain out of the tub.

What is this strange shape around the plughole? It's nice, actually but how come it forms?

If you ask this question you might often get this answer: This is exactly like the clouds in the sky, this is Coriolis effect, which causes storms to spiral counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.

This explanation sounds very impressive but it is incorrect. It's true that the Coriolis effect plays its part in this vortex in the tub. But more important are the effects of how you get out of the tub, how you pull the plug and how the tub is shapped and positionned. Those little nothings are the main cause for the vortex. You can watch them by adding some drops of food coloring in your bath. You will then be able to follow the movement of water.