1The Science of Hot Air and Buoyancy
To understand how a hot air balloon flies, we have to look at the tiny molecules that make up the air around us. When air is cold, these molecules are packed tightly together, making the air heavy or "dense." However, when the pilot turns on the propane burner, the air inside the balloon heats up to about 120 degrees Celsius (250 degrees Fahrenheit). Heat makes the air molecules move much faster and spread out. Because the heated air is less dense than the cool air outside, it creates an upward force called buoyancy. It is exactly like a piece of wood floating on top of a lake, except the balloon is "floating" on the heavier, cooler air of the atmosphere!
2The World's First Passengers
Long before humans ever stepped into a basket, the very first hot air balloon passengers were actually a collection of farm animals! In 1783, the Montgolfier brothers launched a balloon in Paris, France, carrying a duck, a sheep, and a rooster. Scientists at the time weren't sure if people could survive high up in the sky, so they sent the animals first to see if they would stay healthy. The flight lasted about eight minutes and reached an altitude of roughly 1,500 feet. When the animals landed safely, it proved that the air high above the ground was safe to breathe, paving the way for the first human pilots just a few months later.
3Controlling the Giant Envelope
The giant fabric part of the balloon is called the "envelope," and it is usually made of super-strong nylon reinforced with sturdy tapes. While it looks like a simple balloon, it is actually a clever machine! Since balloons don't have steering wheels, pilots have to find different wind currents at different heights to change direction. To go higher, they blast the burner to add more heat. To go lower, they pull a cord that opens a "parachute valve" at the very top of the envelope. This lets some of the hot air escape, allowing the balloon to become heavier and gently sink back down to the landing site.
