"hewitt, off, man. leave me alone. "i don't wanna know anything "about little atoms making red sunsets. leave me my sunsets." some people think that if you explain the sunset, you're kinda spoiling it. you know what i'm saying? "i don't wanna know. "i don't know about that little optical tuning forks "and all that scattering and what's left-- i don't wanna know about that stuff." which then tells you--that can tell you why a cloud is white, and tells you why the water is the color it is off of white here, sort of that greenish blue. why? here's my bias, gang. to understand more about these things is to appreciate more about these things. now that's a bias. i could be wrong. and that's individual. i'll give you an example. the person who appreciates music most is a person who understands music, who knows what to listen for. and i think, too, the person who can appreciate the world most is the person who understands most what's going on. what i'm gonna be doing in this course

is not telling you how beautiful the world is. i'm gonna be telling you what to look for. and when you look for things, you'll see that, "hey, that's a beauty," that you would've-- wouldn't have noticed otherwise. so we're talking things like that. and then we're gonna talk a little bit about nuclear physics: fission, fusion, radioactivity. what do you suppose makes the earth hot? volcanoes. where's all that heat coming from? would you believe it's nuclear power? nuclear power under the ground? would you believe it's radioactive decay? you know, if this were a piece of uranium, this piece of uranium will be a little bit warmer than anything else in the room. you know why? it's shooting out these little particles all the time, heating it up. and if i make it very, very enriched with uranium, it's gonna be hotter, hotter, hotter. and guess what we get about from the bottom of the world. so people that are afraid of radioactivity and nuclear power think it's something new

that the human race has just come up with. nuclear power has been around before the sun was here. that's what keeps the sun and the stars hot, and that's even what keeps the earth hot. how come the earth hasn't cooled off by now? because there's radioactive decay happening underneath. now we're gonna be talking about that. and that's particularly relevant here in hawaii, because what--well, we got that hot, hot, hot spot. what makes that hot spot hot? what's fueling it? is it like a carbon and oxygen combining? no. it's at the nuclear level. and most of everything we're gonna talk about is gonna be like physics of the everyday world like that, but we are gonna get far out, and we're gonna talk about the ideas of albert einstein, the ideas of relativity. what time it is on your clock and how you move through space are related. did you guys know that? we're all sitting at rest right now, and our clocks are running. we are advancing into the future at all the same rate.

we're in the same space and we all share the same time. but when i start to move, my watch is running differently than your watch. so long as i'm moving, it doesn't go at the same pace that yours is. now, i'm only moving a little bit. and so the change is only a little bit. so little there's no way that we have no instruments to measure the change for that kind of speed you saw. but if i start goosing that speed up faster and faster and faster, that difference in time becomes more apparent. you heard about the twin paradox, a couple of twins sitting? one twin sitting over here, one sitting in a rocket ship... takes off, goes off... travels at speeds, you know, the speed of light? comes back down, still young, and the other twin over here-- so the one that travels doesn't age as fast as the one that stays behind. is that true or not? begin with a t. true. take a piece of radioactive mineral,

make it whirl round and round and round, now measure it, and the decay rate goes down. stop it, flip, then, same old decay rate. so when you're moving, the rate at which time travels changes. so does that mean if you wanna be young, you should do a lot of marathon and stuff? you notice i keep walking back and forth like this. [laughter] so you should never sit down... never sit down. keep on trucking, honey. that's where it's at. yeah. so if you keep on running marathons-- marathons, you'll never age. oh, really? now i'm kidding a little bit here, okay? the effect is so small that it's completely escaped the notice of the human race except one particular person, and that's a person who was thought to be a mental retard when he was a kid. that's a person who didn't talk till the age of four. that's a person that took algebra in high school and couldn't hack it. come on. some people can hack it, some people can't hack it. it's okay. you don't have to pass algebra. and he couldn't pass his algebra. who am i talking about? in fact, he didn't even get a high school diploma. no.

then he want to take the entrance exams to get into the polytechnic institute, and guess what he did, begin with a f-l-u. he flunked. that's okay. some people pass, some people flunk. don't make a big deal of it. then he met someone, got him-- tried it again, this time, he passed. and he did very, very well in school, it turns out, and we're talking about who? albert einstein. some people's time is a little bit different than other people's time. some of you people sitting in the class right now, it's the wrong time for you to be here. it really is. maybe a little bit down the road, all the stuff we're gonna talk about will more resonate with who you are. sometimes, information comes in at a time when you're not ready for it. it's kind of a shame. and sometimes it comes at just the right time. and information comes in when you're ready for it and you grow, you grow, you grow. it's like watering a plant. you gotta water the plant at the right time. and here we are all in class and we're gonna all learn physics together, and i hope, for all of us, it's what? it's the right-- the right time, huh? this is the time to learn about the physical world.

i want you all to do something between now and next time. we're all gonna look at chapter two. we're gonna be reading about it. we're gonna be reading about motion, moving things, accelerating things, falling things. and we read about that, and next time we'll talk about it and kind of pull it all together. okay? catch you next time. physics. [music]