So in science class we are learning about air pressure and out teacher did this really cool expirement. He got out a balloon and put it inside of an airtight vacuum thing. Not like the vacuum you use for the carpet but the more sciency one. So basically, he sucked all the air out of the vacuum and something awesome happened - the balloon started expanding! It got really big and we thought it was going to pop. Then he let the air back in and the balloon shrunk back to its normal size. He also did it with a marshmallow, a crushed plastic water bottle, and the coolest one, shaving cream. They all did the same thing and it was pretty sick. They all expanded when the air was sucked out because there was less air pressure pushing on it and so that let whatever the object was, expand. Then when he let the air back in, it shrunk because there was more air pressure forcing it down.