LAST TANGO:  On this day in 1972, Eugene Cernan (1934-2017) and Harrison Schmitt (1935-still kicking) took their last moon walk.  They remain the last human beings to set foot on the moon.

(An interesting analogy might be the Ming Dynasty treasure voyages of the 15th century.  During that period, China sent out an impressive expeditionary fleet to Java, Sumatra, India, Ceylon, Persia, Arabia and East Africa.  These voyages were intended to impress the world with China’s immense wealth and power.  And impress they did.  But then the voyages just stopped.  Scholars still debate exactly why.)