OK, I'm a day late - the Russian space theorist Konstantin Eduardovich Tsiolkovsky was born on September 17, 150 years ago. It merits repeating that the founder of modern space-travel theory was a poor, almost totally deaf rural mathematics teacher who was fired by an imagination that kept him awake nights working out equations and concepts ranging from large hydrogen/oxygen-powered rockets to staging, space stations, and space suits. The world will owe him a debt for all time.
"Earth is the cradle of mankind, but one cannot live in the cradle forever." - Tsiolkovsky
Item I add just to show that I know it: English-speaking readers may look at his surname and assume the "T" is silent, but it's not. The Cyrillic character beginning his name is pronounced "ts."