The first public demonstration of a lighter-than-air machine took place on June 4, 1783, in Annonay, France, when Joseph and Jacques Montgolfier, two brothers who owned a paper mill, sent up an unmanned hot-air balloon. They had observed that smoke tended to rise and that paper bags placed over a fire expanded and also rose, pushed upward by the hot air.
They concluded that if they could only capture what they thought was a unique gas inside an enclosed lightweight bag, this container or bag would rise from the ground. Etienne Montgolfier carried out the first experiment at Avignon, France, in September 1782, proving their theory to be sound. They had rediscovered the theory of buoyancy, which the Greek mathematician and philosopher Archimedes had discovered in the second century B.C.E.