Escher’s World: Structure, Symmetry, Sense

In 1959 I heard for the first time about the interesting and original artist Maurits Cornelis Escher. My scientific supervisor A.V. Shubnikov showed me Escher’s book Grafiek en Tekeningen, which was sent to him from Sweden by the well known crystallographer P. Terpstra. Shubnikov also told me about the letter which he sent to Sweden; the letter gave high praise for the artist’s drawing skill. Only recently did I have the chance to read Terpstra’s account of Shubnikov’s letter and Escher’s reaction to it. Here is this letter [1, p. 99]: Groningen, 1 February 1960: Dear Mr. Escher, I sent a copy of your Graphiek en Tekeningen to the Academician A. V. Shubnikov in Moscow (one of the top authorities in the field of crystallography). Today I received a letter from him in which he says, “I find Escher’s prints extremely interesting, because they are an excellent illustration of the theory of antisymmtery. The picture on the cover of the book, for example, shows that antisymmetry rotation points of the second order exist in the given two-dimensional symmetry group.” The print Day and Night made a great impression on me. It can be considered as the imaginary antisymmetrical operation of transformation of our light, left world in[to] the right, dark counter — world of Dirac. I presume you will be pleased to hear this. Yours sincerely, P. Terpstra.