This week the students of Auroville schools did a project on Vacuum lift. The task was to lift the glass jar with the use of balloon and not with the hand. When they first set the balloon on top of the jar, the air pressure outside the jar and the air pressure inside the jar were the same. As they lit a small piece of paper and dropped it inside the jar, heat was created inside it and was pushing its way out of the jar. This hot air pushing out past the balloon caused the balloon to wiggle. However, while hot air was going out, no new air was able to coming in (the balloon works like a one-way valve, letting air out but not in). So now there was less air, less stuff, in the jar. With less stuff taking up space in the jar, the pressure inside the jar was less than it used to be, that is, less than the air pressure outside the jar. Since the pressure outside the jar was greater than the pressure inside the jar, a part of the balloon was sucked into the jar due to vacuum. And now the students were able to lift the jar up by holding the balloon from its top.