Food colouring in corn syrup. Watch as they rotate it 5 times one way and then 5 times back.

This is an example of the strange things that happen in fluids with low Reynold’s number. Reynold’s number is a ratio of the inertial forces and the viscous forces in the fluid. When the viscosity is high and the inertial forces are low fluids behave very differently to the way we are used to. Remember that next time you are trying to swim in honey.