Effect

A silver ball bearing is placed on a silver tube. 

After a moments concentration, the ball very slowly descends, into the tube, dropping completely out of sight. 

Then, just as slowly, it rises again until finally it is resting on the top rim of the tube. 

It is immediately handed out to a spectator for examination. 

To their dismay, the ball is too large to fit into the tube, and will only rest on the rim.