by the time this thing gets around to responding to gravity, foop! this thing will be already down there, 'cause i know when i'm pulling things, and i'm pulling something very light, foom! pull something heavy, it lag behind. this thing is being-- gonna lag behind. so the kid says the little ball wins. so you drop the two things-- the beauty of experiment. the kid. what's wrong? you know what that kid say? is that kid saying something like this? on your thoughts, is that kid saying the acceleration is proportional to the amount of mass? check your neighbor. how many say, "no, he ain't saying that"? show of hands. good. he ain't saying that. he's saying this. first of all, i got to ask you guys a question. which number is bigger? how many say, "oh, obviously, this number is bigger"? show of hands. get out of here. get out. out. no. no. this is the bigger number, right? okay. so it turns out that, hey, as the mass gets bigger and bigger, what's the acceleration get? less and less. so it's this way. this is called an inverse relationship. make something

i'm gonna drop this and see if you don't feel all of a sudden the chair, foop! rush up against you a little bit. try it. how many felt it? [laughter] you didn't feel it. you know why you didn't feel it? because the mass of this thing is tiny, tiny. look, here's the idea. here's the force that pulls this down, huh? and here's the force that pulls the earth up. but how about the accelerations of both? the acceleration of this is simply that force divided by its mass, and that turned out to be 10 meters per second per second. we talked about this before. but how about the force that acts on the earth? the mass of the earth is like this. and when you take that force acting on a humungous mass, you get an acceleration like this. see it? [laughter] it's like negligible. and see, you don't sense it. but if the earth was smaller and this more massive-- in fact, what if this was as massive as a whole world and we held it like this and we dropped it. how far will it go, gang? will it go all the way down there? - halfway. - it'll go halfway. right. because if this was a ma