Size and Distance

This exhibit demonstrates that the perceived size and distance of an object are intimately related. The visitor looks through a small hole (thus eliminating stereo vision and restricting the observer to one point of view) at two disks. A knob can be turned which will move one of the disks closer to 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 that the other and it is therefore always placed closer to the peephole.