We’ve been flying in hot air balloons since 1783, but how does it work? Well, it’s pretty simple – as air inside the balloon warms up, it expands, making the air inside the balloon less dense than the cooler air around it.

Less dense things float, so the balloon begins to rise. As the air in the balloon cools down, the density of the air inside the balloon begins to match the air outside, and the balloon returns to earth.

With a commercial hot air balloon, it is possible to regulate the temperature of the air balloon, so the pilot can raise and lower the balloon at controlled speeds.

This video shows some footage of a hot air balloon festival where there were 456 balloons; a world record! You can see how the balloons are filled with air before they leave the ground and some of the fires controlling the height of the balloons.