Hot air balloons are an ingenious application of basic scientific principles. The basis of how the balloon works is that warmer air rises in cooler air. This is because hot air is lighter than cool air. The actual balloon, or envelope, has to be large as it takes such a large amount of heated air to lift it off the ground. To help keep the balloon in the air and rising, hot air needs to be propelled upwards into the envelope using a burn­er. Hot air is released fro the top of the balloon to descend. The balloon moves along with the air currents.­