that explains, for example, why these things fall together. let's suppose you asked a little kid, a little kid. "hey, kid, i'm gonna drop these two objects. which one hits the ground first?" now, most kids today-- or we all know. we all know the answers, don't we, gang? what do we say? same same, right? they fall same same, right? how come same same? oh, because the acceleration is the same. well, what's that say? kind of begs the question, doesn't it? but let's suppose you ask a little kid who's very, very bright but ignorant, never seen it before and say, "kid, i'm gonna drop these two objects. "you tell me which one hits the ground first. i'll give you a hershey bar." kid says, "with almonds?" "yeah, with almonds too, all right? you tell me which one hit the ground first." and the kid says, "well, can i feel those things first?" you say, "yeah." the kid takes this. he says, "oh, this pretty heavy piece of metal there." it's aluminum-- so it's kind of heavy. big gravity force acting on that. kid take this. "ooh, this little dinky ball.