Michael Atkinson’s experiment, about 40 minutes, works with balance and imbalance in various ways. A stretch of room in which to walk a bit, and a floor on which to lie down should be all you need.
Reaching High
Bob Smith’s experiment, about 50 minutes long, explores what appears as we reach high in a sustained way. Before clicking the play button, find two flat stones, suitable for resting atop your standing feet, and another stone that fits nicely in the hand.