This exhibit demonstrates that the perceived size and distance of an object are intimately related, hence its inclusion in the Dimension, Scale, and Space section. The visitor looks through a small hole (eliminating stereo vision and a different- points-of-view angle) at two disks. A knob can be turned which will move one of the disks closer or farther from the peephole. The visitor tries to guess when the disks are the same distance from the peephole and then confirms the guess by looking through a side window. One of the disks is smaller than the other and it is therefore always placed closer to the peephole.