In No Sound Through Empty Space, a plastic jar containing a bell, fan and pinwheel let visitors investigate what happens to sound in a vacuum. When the jar is filled with air, the bell rings and the spinning fan causes the pinwheel to rotate. When the vacuum button is pushed, forcing the air out of the jar, the pinwheel stops spinning (even though the fan is still turning) and the bell’s ring becomes difficult to hear (even though the striker hitting the bell is still visible), vividly demonstrating that sound cannot travel without air.