and hold an extra electron and that one will be out here. and that atom now is called, guess what? lithium. now, it's lithium. lithium, 1, 2, 3, 4, 5, lithium 5 and 1, 2-- what's the atomic number, gang? - 3. - 3. and you keep going right up the periodic table and then you come way up to what is the heaviest element found in large proportions in nature and that happens to be uranium. and uranium has 92 protons and most uranium has 238 nucleons. if i asked you people hey, uranium, honey, 238 nucleons, how many of those nucleons are protons? and you gotta know. you would say... 92. what if i said how many nucleons in the nucleus? you would say?

238. now here's where you need your calculator. how many of those nucleons are neutrons? and you would say... of course, you'd have to subtract, okay? you take this number, take away this number, and you guys say about 146, huh? you'd have 146 neutrons in that nucleus. so we have all the atoms, all the atoms which differ from one another principally by the number of protons in the nucleus, because anything that has three protons will hold three electrons, no matter how many extra neutrons you put in. and chemically, there's no difference between one isotope and another. chemically, it has to do with mostly this atom here, how that is compared to this, the configuration. and so if you have 92 naturally occurring atoms, then you have 92 different patterns of levels of electrons. and you have then 92 different atoms with different properties. that's when we have the elements,

92 through uranium. got such thing? now, atoms: atoms are mostly empty... because this is grossly exaggerated. i've drawn these very, very big compared to what this is. a better thing would be like if i draw the nucleus here, then out across the street the electron would be. the atom is as empty of matter as the solar system is as empty of masses. you know, you got the sun and then you got mercury, venus, mars, keep going out. if you got out in outer space you see the solar system down there and you throw a dart and let's suppose that dart doesn't respond to gravity. and you throw a dart, and you wanna hit either the sun, the earth, venus, mars, pluto... if you wanna hit one, what's your chances, big or small? very small. small, honey, the solar system is mostly emptiness

and only occasionally would there be a direct hit even if you took showers and showers of particles which didn't interact gravitationally now. if they interact gravitationally, they'll come right up and hit you, but no gravity, they go right on by. well guess what, gang? there are neutral particles, thousands and thousands going right through my hand right now, as i talk to you. millions going right through my hand and these neutral particles are from the cosmos, most of them are neutrinos, little teeny, teeny particles with guess how much charge, called neutrino? none, okay? they're smaller than neutrons. and those neutrinos are flooding the universe. and these neutrinos are going right through, guess who? us. you guys, not me, but, no, all of us. these neutrinos are going right through and right out the other side without making a hit. you know why?

do you ever get the feeling some days that, you know, i just don't feel like i feel like i'm nothing? i'm nothing. i think i'm just nothing. do you ever get that feeling? guess what? i got news for you. you are nothing. compared to the something, there's more nothing, because the atoms that make you up are mostly-- talk about being spongy-- and we're all sponges, hon. and most--the little particles make up... take 133 million tons. that's several city blocks. scrunch all those atoms up, 133 million tons, scrunch them up until all these things here cave into one another. you got the size of a pea. so take the size of a pea and spread out a city block, that's how atoms are, most of them. so these things go right through our body without ever making a direct hit. you get, maybe, one direct hit per year on the average, one got me, okay? very, very seldom, okay? you know what? 1987, the supernova--

the supernova in the heavens-- and showered the whole universe with neutrinos. and neutrino flecks were so enormous that about one out of every 248 people, something like that, got one of those neutrinos, caught one and the rest went just right by through us, right through the other side, never, never making a direct hit. why? because the space between the little particles of the atom are enormous compared to the size of the particular nucleons or electrons. kinda neat, huh? so if there's a great big beam of neutrons coming right by, you just walk right through 'em, and they go right through the other side and they'll register just as much on here whether you're on the beam or not. do neutrons have more effects than neutrinos? it turns out-- i should say, a beam of neutrons, you would have more hits with a neutron than with a neutrino, but not too many more. you could walk through a neutron beam without harm, but i guess the counter reading over here would be a little less for neutrons,

but with neutrinos, you get the whole class standing here. hey, let me tell you what it is. it's a piece of lead, if you get a piece of lead, thick enough, then it will stop half the neutrinos. how thick you suppose is that gonna be about, this thick? this thick? this thick? this thick? as thick as the building? as thick as the world? as thick as like the diameter of the solar system? several light-years thick? and guess what the answer is, gang. six light years. eight solid light years. if you get eight years thick of lead, that's how far the sun will go in eight years, light will go in eight years. get that thickness. now put a beam of neutrinos through, half will come out the other side. so enormously, enormously transparent is even lead to such a thing as neutrinos, let alone us, huh? so mostly empty space, gang. hey, if we're empty space,

how about the chairs we're sitting on? begin with e, s. try it. empty space. how about your foot? your foot's mostly empty space. i remember one time i went to a party, and at this party a guy said this. i didn't know physics, honey. he said, you know what, if you keep kicking a wall, you know, the reason your foot doesn't go through is because the atoms are all... but you ever take a couple of combs and go click, click, click, click, click, click? and this dude said if you keep kicking a wall long enough, pretty soon, your foot's gonna get stuck, because the atoms of the foot will line up with the empty spaces of the wall and the feet can't get back out again. i was really impressed about that. wow, and i kind of thought about that. but then later i happened to think, wait a minute, wait a minute. now, if that's true how about when people are walking along the rocks? and there's never been a recorded case of someone...

sunk in the rock. so why is it that we don't sink down through the chairs we're sitting on? why do you go like this? why don't my hand go right on through? like in the science fiction stories. why? why does it stop? how can i make contact with the table, if this is mostly empty space and the table is mostly empty space? how many say that there is no explanation for that? there is an explanation, gang. you know what it is? oh, nobody be knowing. one be knowing. so you guys didn't have a chance to read the book this weekend. check the neighbor-- see if the neighbor knows. why is it you don't fall through your chair? anyone have any ideas? anyone?

trish. do the charges repel each other? yes, electrical charges, right on, wonderful. wonderful. remember, we talked about the atom here, these electrons repelling other electrons? any electrons on your seat? yes, any electrons on your seat? and when these electrons squished closer and closer, what do they do? begin with "r" end with "l". they repel and this is an electrical repulsion, my friend, between you and the chairs upon which you sit. let's put it this way. let's suppose this table-- pretend this table is a magnet. you guys know about magnets repelling. turn around, they attract, yeah. but you know magnets repel. you've all played with magnets. wow, how come that happened? there's no reason for that. come on, we'll talk about it later, yeah? but pretend that this table is a magnet and pretend that my shoe here is a magnet. and i have a force of repulsion, magnetic repulsion between my shoes and the table. can you picture in your mind's eye me walking across the table and not making contact

such that someone could come up and take a piece of paper and slip it right under my shoe? can you imagine that? can you? how many people say no, i can't imagine such a thing? you have to show me. show your hands. hey, but you know what, let me tell you, it turns out that's what happening anyway, but it's not magnetism. begin with "e". electrical. there's an electrical repulsion between you and the seat you sit on. and when you walk along the floor, there's an electrical repulsion that keeps you from oozing right down into the floor. these charges repel each other. in fact, at the atomic level we talk about touch. i'm touching the table, but get right down into the realm of the atoms, what's going on? where's the touch? there's an electron banging into an electron? it turns out they get closer and they get squashed. the electron, that atom gets squashed up a little bit,

and the atom in the hand gets squashed up and there's an enormous repulsion and you look how you, you make that whole thing vibrate. can you guys hear anything? listen. you know what you're doing? i made those sounds... and the atoms of the air... all the way to here. we'll be talking about sound later, huh? physics, okay. but you make vibrations, you make the atoms vibrate. that's what you're doing. you know the notion of touch is sort of like a lot different than the microscopic levels, at the atomic submicroscopic level, i should say. what do atoms look like? let's suppose you took a microscope, you go to the chemistry depart and say give me an atom. someone gives you an atom, you take some tweezers, you put it under the microscope and you look at it and you get, oh, what's it gonna look like? begin with "n" end with thing. nothing, right? now you take another microscope and put it on the top of that microscope, get 40 microscopes,

get on top of a ladder. every microscope--look down, ooh, what do you see? nothing. then someone says what's the atom look like? and you say, got no looks. atom got no looks. how can atom have no looks? it turn out that atom have no looks because it's smaller than the wavelength of light, that which you look at it with, huh? smaller than the wavelength of light. let me show you what i mean. let's suppose we have a tank, a tank of water here. and all i have here is i have like maybe a rock. there's a rock and a tank and over here i have some sort of detector and over here i take a meter stick and i go flip, flip, flip, flip, flip and i make waves and the waves travel. here's the waves like this. when the waves hit the rocks, can you see the rock disturbs the waves? with this detector, which consists of a little thing there with a ping-pong ball

with a little arm that will float up and down, will this detector detect the presence of that rock? will the waves come in differently to this detector if the rock weren't there? yes. can you kind of picture that in your mind, okay? it turns out that rock would disturb the waves. that's because the rock is bigger than the waves. here's the wavelength. look at the size of the rock. let's take the rock out of there. let's suppose now i have some blades of thin, thin grass sticking up there like this. these are very small compared to the wavelength of the waves. now, you... you generate your waves. what's this gonna get? is this gonna see the grass? somebody see the grass. those waves go right on by the grass. the little shoots of grass are smaller than the wavelengths. this time you're gonna pick it up. in the same way little atoms, of which you're made, are smaller than the wavelengths of light, and so light can't pick up the presence of an atom. light's too coarse.

it turns out with a finer, finer wavelength. you can get a wavelength that's very, very fine. very, very fine wave length, you can get an atom. and when i went to school, teacher types told me, we'll never see a photograph of an atom. look in your book and we got one. you guys see that? what page? whoever finds it first, get an "a." - 180. - 180. lee, you already got your "a". who else said 180? you get an "a" too. troy, at the end of the class, you could just miss all exams. not quite. page 180, gang, and there we have it right there. and that photograph, gang, made some history, because there are the individual atoms, the location of all those atoms very clearly shown. that's taken with an electron microscope. now, there's new kinds of microscopes that are called tunneling microscopes. and these microscopes give you a pattern that looks like this. we have a tunneling microscope right up in the physics department.

now what that does, it takes a little needle that scans back forth, back forth, back forth across the surface of metal and where the atoms are sticking up, makes a sorter path for a little electric current and the little electric current is measured because it goes from the needle to the material itself, and all these little bumps show you the position of an atom. so we're really coming a long way. we can actually see where atoms are now, because of what? the advances in technology. so now we know what atoms kind of look like, not so much what they look like but how they fix one to the other. so the guessing game that biologists used to have to do is greatly enhanced now. now they know. now we can do things with atoms. we can change the structure. we can change molecules. we can affect dna, splice genes, enormous things. lee. if all the parts of us that were made up of the atoms don't have an appearance, how come we have colors and appearances? although one atom doesn't have an appearance,

if i keep putting more and more, take one piece of grass, one piece of grass might not show anything here. now i keep putting more and more and more and more altogether, bunch them together, pretty soon this starts to show. so although one won't show you any appearance many, many will, because then they'll be on the order of the wavelength of light. and when you get larger than the wavelength of light, then light will show their presence. another thing, brownian motion. you've guys will be reading about what robert brown did back in 1830. he's looking in a microscope. and in the microscope, he sees little things jiggling. and at first he thought it was something in there alive, those little particles of soot and these little things are jiggling, jiggling, jiggling, and brown thought that maybe he saw atoms, but they weren't atoms. guess what they were, gang. little specks of dust banged into by, guess what. atoms. it's like this. see this styrofoam cup? you guys can all see this.

see this little bb right here, little bb in my hand. i got a whole bunch up in there, see them, i spill them on the table. see those little bbs, you guys can't see those bbs, 'cause you're too far away from them, okay? but can you picture this? can you picture the styrofoam cup on the table and all these bbs, all moving around haphazardly, chaotically and every once in a while the bbs and more bbs hit one side of the cup than the other, what will the cup do? wouldn't the cup start to jiggle? and you guys can see the cup, but you can't see what's making the cup jiggle. you know there's something smaller than you can see is making the cup jiggle. and that's what robert brown saw in his microscope. he saw little particles, big enough to see, jiggle. why jiggling? small enough, there could be more atoms on one side than the other. little bit more neck force on one side of the atom... that thing will jiggle around. so in response to the jiggling atoms, boom, the visible observation: microscopic particles moving, brownian motion. turned out albert einstein explained that and that was one of the first contributions of einstein

to prove the existence of atoms. he showed that the motion of those little particles of dust corresponded exactly to the motion of atoms at various temperatures. i asked you before, atoms big or small and you guys said... very small. small, right? okay, how small? small-small. small-small-small-small-small- small-small. how big is the sun? - big. - how big? very big. big-big-big-big-big-big. okay, let me tell you this, gang. the atom is small-small-small-small, as many times small than us as the sun and average-size stars are bigger than us. so do you want something for your poetry class? guess who stands between the atoms and the stars... in size? - us. - us. that's right, right in between. human beings are as many times bigger than the atom as the stars are many times bigger than us.

so it will kind of give you a little bit of feeling. here's another one. i like things like this. apple, any atoms in an apple? i'm sure there's a few, couple of dozen. come on, honey. this scads, right? about 10 to the 22, huh? many, many atoms in an apple, okay? how many apples would fit in the world? you take the world and made it all hollow and you stuck apples in there, lot of apples or little? about as many apples would fill up the whole world as, as many atoms fill up the apple, so atoms are really... small small-small. some people say, "no such thing as perpetual motion." someone else say, "that's not true." atoms are perpetually moving. they're moving all the time. - who's right? - both. are atoms in perpetual motion? any atoms in this room? - yeah. - [inhales, exhales] yes. i'll be glad there's atoms in this room, right?