Who was the French professor that the Robert brothers built the world's first hydrogen balloon for?
Jacques Charles Jacques Alexandre César Charles (November 12, 1746 – April 7, 1823) was a French inventor, scientist, mathematician, and balloonist.
Alexandre Koyré Alexandre Koyré (] ; 29 August 1892 – 28 April 1964), also anglicized as Alexandre or Alexander Koyre, was a French philosopher of Russian origin who wrote on the history and philosophy of science.