We live in a world of constant downward gravitational force. We 'weigh' something here on earth (often more than we'd like to but that's beside the point). If we were floating in space we wouldn't weigh anything, and for the split second that the payload in this exhibit is free-falling it experiences weightlessness too. Well the weightless state is interesting... lead weights weigh nothing all of a sudden on a scale, flattened coloured oil droplets go perfectly spherical all of a sudden, and more. Twelve feet is all it takes to get over a half second of weightlessness. Of course much engineering has gone into this one for robustness of the structure, safety, and maintainability. It's a real long distance attractor as well.