Investigate the amount of potential energy given the rubber band vs. the distance traveled by the Wacky Hall Walker. The suspended pearly crystals in Rheoscopic Fluid show current movement continually, without settling out. A Rattleback is a half-ellipsoid object carved so that it will spin in only one direction. The Air Power Soccer Disk runs for about 30 minutes on 4 Alkaline AA batteries. No extra recharging required!