Before humanity dared venture into the sky, science demanded a proof-of-concept for survival at altitude. On September 19, 1783, Étienne Montgolfier tethered the world's most critical biosensors to a paper-and-silk hot air balloon at Versailles: a sheep named Montauciel, a duck, and a rooster. Natural philosophers of the era genuinely feared the upper atmosphere was devoid of breathable air, toxic to terrestrial life. When the ornate vessel drifted 1,500 feet high and touched down eight minutes later with its barnyard crew entirely unharmed, empirical evidence decisively dismantled the altitude taboo. This whimsical flight was effectively humanity's first aerospace biology experiment, paving the way for crewed flight just two months later and establishing the foundational doctrine of life-support testing that eventually carried humans to orbit.