Balloons were the first manned vehicle to reach stable flight. For the first time, in 1783, man had flown. In todays world, balloons are often used as weather tools or as leisure-crafts. But how do these straightforward machines fly? Well, the science is pretty simple.

Hot Air Balloons

Hot air balloons are the simplest types of balloons used for human flight. At the start of the flight, both the air inside and outside the balloon are the same. However when the pilot uses the balloon’s heater to heat the air inside the balloon, the air molecules get farther and farther apart. In other words, this means that the air inside the balloon is now less dense than the air outside it. According to Archimedes’ principle, the cooler air exerts an upward buoyant force on the balloon. As proven by the simplest kitchen experiment ever, when vinegar and oil are put into the same cup, they never mix and oil (less dense) will float while vinegar (more dense) will sink to the bottom. The same principle applies to hot air balloons. The less dense air inside the balloon will force the entire structure to go up.