Although normally dedicated to the peaceful pursuit of nature’s secrets, scientists have often seen politics and war intrude on their work. In the summer and fall of 1783, the invention of the hot air balloon gripped the people of Paris with what one scientist called “Ballomania,” as crowds gathered in the tens of thousands to watch humans take flight for the first time. The “Aerostatique Machines” especially captivated the American scientist and diplomat Benjamin Franklin, in Paris to negotiate a treaty with the French. After witnessing one of the miraculous flights, Franklin almost instantly thought of the military applications of such an invention. “This Method of filling the Balloon with hot Air is cheap and expeditious,” he wrote to a scientific colleague, “and it is suppos’d may be sufficient for certain purposes, such as elevating an Engineer to take a View of an Enemy’s Army, [and] conveying Intelligence into, or out of a besieged Town, giving Signals to distant Places, or the like.” 1