An impossible figure named after by the British geneticist Lionel Penrose
(1898-1972), father of Roger Penrose. It served
as an inspiration for the staircase in M. C. Escher's
famous print "Ascending and Descending." Although the Penrose stairway cannot
be realized in three dimensions, this impossibility is not immediately perceived
and, in fact, the paradox is not even apparent to many people at a quick
glance. Although Escher and the Penroses made the Stairway famous, it was,
unbeknownst to them, independently discovered and refined years before by
the Swedish artist Oscar Reutersvard.
In the 1960s the Stanford psychologist Roger Shepard created an auditory
analogue of the Stairway.
AND IMPOSSIBLE FIGURES