Originally invented in France in the late 1700s, hot-air balloons use air displacement to rise gracefully into the sky. Air displacement is caused by heating a lifting gas such as helium, hydrogen or oxygen underneath a thin material called an envelope. When the balloon is connected to a basket or other container, air displacement allows the basket to carry passengers up to 32 miles into the atmosphere.
Balloons have been used in wars and raced in competitions. Hot-air balloons have helped conduct weather and other experiments, and they routinely provide a beautiful venue for aerial photography and wedding proposals.