Max von Laue and the discovery of X‐ray diffraction in 1912

From today’s perspective, only a few discoveries are regarded to be as exciting and as ground-breaking as the discovery of X-ray diffraction by crystals. “The undersigned are engaged since 21 April 1912 with experiments about the interference of X-rays passing through crystals,” a one-page report announced the discovery to the Bavarian Academy of Science. It was signed by Walter Friedrich, Paul Knipping and Max Laue (then still without the “von”) and deposited by Arnold Sommerfeld on 4 May 1912 in order to ascertain the discovery before it was officially communicated in the form of an elaborate paper. “The guiding idea was that interferences arise in consequence of the space lattice structure of the crystals, because the lattice constants are ca. 10 times greater than the conjectured wavelengths of the X-rays.” A simple drawing sketched the experimental arrangement. As evidence for the discovery some exposures were attached.1