Dave Johnson built this mesmerizing hand cranked machine for rare earth magnets for his father’s 75th birthday. At about the 1:15 mark you’ll witness the remarkable behavior of the ball magnets as they are fed in a continuous loop through the innards of the machine.

This machine manipulates small spherical rare earth magnets, slicing one at a time from the end of a long chain, moving it around a bit, then dropping it back to re-connect at the tail end of the chain.

It also demonstrates a little snippet of science called eddy currents. Watch how slowly the magnet falls through the aluminum tube compared to falling through air: the falling magnet generates an electrical current in the tube, and that current in turn generates a magnetic field that opposes the movement of the magnet, slowing it down dramatically.