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.
Jean Becquerel Jean Becquerel (5 February 1878 – 4 July 1953) was a French physicist, and son of Antoine-Henri Becquerel. He worked on the optical and magnetic properties of crystals, discovering the rotation of the plane of polarisation by a magnetic field. He also published a textbook on relativity. In 1909, he became the fourth in his family to occupy the physics chair at the Muséum National d'Histoire Naturelle, following in the footsteps of his father, his grandfather A. E. Becquerel and his great-grandfather Antoine César Becquerel.