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.
Robert Nobel Robert Hjalmar Nobel ( ; ] ; August 4, 1829 – August 7, 1896) was the oldest son of Immanuel Nobel and his wife Caroline Andrietta Ahlsell, brother of Ludvig and Alfred Nobel.