Does water drain in different directions in the Northern and Southern hemispheres?

There's a commonly cited idea that water in a drain swirls in opposite directions in the Northern and Southern hemispheres. But is there any truth to it? When you pull the plug from a bathtub, does the water circle one way in New York and the other way in Sydney?

Although the idea is based on a real scientific principle, you probably won't see it play out in a small drain in your house, experts told Live Science.

The Coriolis effect

The idea that water spins in opposite directions in the Northern and Southern hemispheres stems from a phenomenon known as the Coriolis effect. When something, including air or water, moves across Earth as it rotates on its axis, that substance appears to curve because the ground beneath it is rotating at different speeds in different places. Points close to the equator move faster than points near the poles because they have a bigger circle to travel in the same 24 hours.

Over the immense distances covered by weather systems and ocean currents, that small deflection can accumulate and become important. The key words here are ...