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.
Joseph Liouville Joseph Liouville FRS FRSE FAS ( ; ] ; 24 March 1809 – 8 September 1882) was a French mathematician.