There is nothing quite like watching the ground slowly fall away beneath you as you rise into the sky in a hot air balloon. People dreamed about flying for hundreds of years, and that dream finally came true on November 21, 1783, in France. The Montgolfier brothers sent a hot air balloon into the sky carrying an army officer and a friend of the King. These two men became the first people to fly above the Earth. Their flight lasted about 25 minutes. The balloon climbed more than half a mile into the air and traveled more than five miles.

The Montgolfier balloon looked very different from the balloons we use today. It was made from fine silk and was light blue and gold. Suns and signs of the zodiac were painted on it. The air inside was heated by burning hay and wood. Hot air balloons work because hot air weighs less than cold air, so it rises. When that hot air is trapped inside a balloon, it lifts the balloon and its pilot and passengers. The large part of the balloon that holds the air is called the envelope.

Modern balloon envelopes are made from nylon fabric. Instead of burning hay and wood, today’s balloons use open-flame burners that burn propane. The pilot and passengers stand in a wicker basket hanging below the envelope. Pilots cannot steer balloons the way people steer cars or airplanes. We go where the wind takes us. But winds often blow in different directions at different heights, so a pilot can move the balloon higher or lower to find a wind blowing in the direction he or she wants to travel.

To make the balloon climb, the pilot lights the propane burner and heats the air inside the envelope. The air can reach temperatures as high as 200 degrees. At the top of the envelope is a large vent that the pilot opens and closes with a rope. Opening the vent lets hot air escape. As the air inside the envelope cools, the balloon begins to move back down toward the ground. That simple idea of heating and cooling air is what makes balloon flight possible, just as it did more than 200 years ago.