you look through one chain-link fence at another, you sometimes
see a pattern of light and dark lines that shifts as you move.
This pattern, called a moire pattern, appears when two repetitive
patterns overlap. Moire patterns are created whenever one semitransparent
object with a repetitive pattern is placed over another. A slight
motion of one of the objects creates large-scale changes in the
moire pattern. Standing at the table, the visitor can layer and
rotate several different-patterned transparencies to create innumerable
wave interference patterns.