18 July 17

My chemistry tie for today is primarily a reaction to the 1937 birthday of Roald Hoffman, famous in organic chemistry for studying how the geometry of molecules influences the progress of reactions. He won the Nobel Prize in Chemistry in 1981. Also born on this date, in 1635, was Robert Hooke, an English scientist who developed the microscope and also produced "Hooke's Law" that describes the mechanics of oscillating springs. Some molecular model kits use balls for atoms and springs for chemical bonds (because bonds are "stretchy"), so my photos show some models for formaldehyde (methanal) and benzene. The American philosopher of science Thomas Kuhn was born on this date in 1922, and his theory of "scientific revolutions" can easily be stretched to include the paradigm shifts within chemistry when old ideas about simple linear bonding had to be exploded to include rings and "molecular orbitals." Finally we can celebrate the birthday of astronaut and Senator John Glenn (1921-2016), who was helped into orbit in 1962 through the magic of hydrogen-oxygen combustion.