Two young men recently tested to see if water really swirls in opposite directions (as in a toilet) in the northern and southern hemispheres of the earth.
Derek in Sydney, Australia, and Dustin in Huntsville, Alabama, performed the same directional water swirl experiment on two videos (below).
Derek and Dustin advised viewers to watch their videos at the same time to see the experiment work.
The water swirled counter-clockwise in Alabama, while it flowed clockwise in Australia in what is called the "Coriolis effect."
The Friendly Atheist, who flagged the online demonstration, explains:
The Coriolis effect is caused by the rotation of the Earth and the inertia of the mass experiencing the effect. Because the Earth completes only one rotation per day, the Coriolis force is quite small, and its effects generally become noticeable only for motions occurring over large distances and long periods of time, such as large-scale movement of air in the atmosphere or water in the ocean.