Water vortex

HOW

1. Turn the crank slowly and set the rotor in slow rotary motion.
2. Gradually increase the speed.

WHY

The rotating rotor sets the dyed water particles next to it in motion. These in turn move neighbouring ones. Eventually, all the liquid reacts to the rotating rotor and a vortex is created. By watching the ball, you can find out what happens to an object that gets close to the vortex.