Hendrik Lenstra, University of Leiden: "Escher and the Droste Effect" - April 3, 2007

In 1956 the Dutch graphic artist M. C. Escher made an unusual lithograph with the title "Print Gallery." It shows a young man viewing a print in an exhibition gallery. Among the buidlings depicted on the print, he sees paradoxically the very same gallery that he is standing in. A lot is known about the way in which Escher made his lithograph. It is not nearly as well known that it contains a hidden "Droste effect," or infinite repetition; but this is brought to light by a mathematical analysis of the studies used by Escher. On the basis of this discovery, a team of mathematicians at Leiden produced a series of hallucinating computer animations. These show, among other things, what happens inside the mysterious spot in the middle of the lithograph that Escher left blank.