Crystals, Radioactivity and a Pentafoil
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-15- In 1938 the Germans occupied Austria and Lise Meitner (1878-1968),
the research associate of Otto Hahn (1879-1968) for over thirty years and a Jewish Austrian citizen, was forced to flee.
She succeeded to escape to Sweden. Shortly afterwards Hahn and Strassen observed the first experimental nuclear fission, but hesitated to formulate it as such. In January 1939, Meitner did.
-20- In the early spring of 2002 we visited the Harz mountains for a walking holiday.
We found the medieval towns of Quedlinburg and Wernigerode to be very attractive. The Rammelsberg mine, near the ancient imperial city of Goslar, appeared to be no longer productive, after an exploitation period of more than ten centuries. The corresponding stamp shows a leadsulphide (PbS) cristal in the form of a cuboctahedron, which mathematically can be obtained by cutting off the eight corners of an ordinary cube by planes through the midpoints of the incident edges. The zincsulphide (ZnS) cristal below is a truncated tetrahedron. If we would cut off more, by choosing truncation planes through the midpoints of the edges, an octahedron would result.
-30- The Carl Zeiss optical works in Jena flourished under the leadership of the mathematical physicist Ernst Abbe (1840-1905), one of the first social employers in modern history. After Zeiss' death, in 1888, he changed the organization of the factory into a foundation, with profit sharing, participation, pensions and more.
-30-
The simplest nontrivial knots are the trefoil knots; the stamp to the right presents a colorful picture of a pentafoil and links to a beautiful animation by Eugene Starostin describing an equilibrium of thin plies arising in molecular biology. On the stamp a graph theorist will recognize the self-complementary cyclic graph C5. The graph isomorphism confirming this self-complementarity corresponds to a scalar multiplication x-->2x within the field Z5. Note that 22 = -1, mod 5, indeed.
- Yet another stamp depicting a nested sequence of regular pentagons related to the golden ratio.
- In 1935, together with his wife and scientific partner Irène, Frédéric Joliot won the Nobel Prize in chemistry, for the discovery of artificial radioactivity. He also presided the Nobel Peace Prize Committee and was awarded the Stalin Peace Prize, in 1951. Click on the peace dove to view his laureate mother-in-law, Marie Curie.