Dongxue is late for the fireworks, and she apologizes to her brother and sister-in-law, who are waiting for her. She tells them to follow her as she explains the mechanics of the balloon. She explains that inertia will move the balloon toward the ground, and part of the gravitational pull will be offset, so that the balloon will be lighter and move faster. When the balloon is inflated, the gravity will rise, and the balloon's weight will be reduced. He explains that the principle of the hot air balloon is that the density of the air is lower than the amount of buoyancy produced by the balloon, so the air will rise and fall. He also explains that when the balloon gets heated, it will become lighter, and when it is expanded, the pressure will rise. He says that he wants to thank everyone for their help this month, and that he is going to the fireworks.