Why does water going down a plughole spin in one direction in the Northern hemisphere and in the other direction in the Southern? Which way (if any) does it spin on the equator? Also are there any planets which don’t spin?
It doesn’t. This often asked question is an “urban myth” that derives from a misapplication of the physics phenomenon known as the Coriolis Effect.The Coriolis effect derives from the rotation of the Earth, and does effect a number of important physical systems. Winds blow clockwise around high pressure systems in the northern hemisphere and counterclocwise around high pressure systems in the southern hemisphere as a result of the Coriolis Effect, and the motion of ocean currents are affected by the rotation. However, water going down drains, toilets, or sinks is not effected by the rotation of the earth, rather, the motion of water in such small basins is determined by the friction between the basin and the water, the shape of the basin, and other such factors, but not by the rotation of the earth.