there is a littlball, it's floating on the surface and the surface of the water goes down cause something pushed the surface of the water down. begin with an a, end with a "r," try it. the air, and there is air in the glass. yeah, there is air in the glass gang. any air in this room? isn't it nice that there is air in the room. what if there is no air in the room? we'll not survive. you would be trouble. have you wondered about that like you're breathing and you really need the air-- in your nighttime, you're breathing all of a sudden you think, "wait a minute, if all the air molecules that are right here all of a sudden goes somewhere else and i go to take a breath and there is nothing there. honey, you're gonna go out, you're gonna check out. aren't you glad the air is all around-- how come the air stays near where your mouth is? because it's being pushed by a pressure and that pressure is due to the weight of air above us. air has any weight? it turns out air has weight, a lot of weight if you talk about a lot of air, okay? what's it called here? one cubic meter of air, it's not like t