It's interesting that some people find science so easy and others find it kind of dull and difficult especially kids you know, some of them are just eat it up and I don't know why it is, it's the same perhaps for all subjects For instance lot of people love music and I could never carry a tune and I lose a great deal a pleasure out of that and I think that people lose a lot of pleasure who find the science dull In the case of science, I think that one of the things that make it very difficult is that it takes a lot of imagination It's very hard to imagine all the crazy things that things really are like Nothing's really as it seems, we used to get you know hot and cold and all that hot and cold is the speeds that the atoms are jiggling if they jiggle more it corresponds to hotter and colder is jiggling less So if you have a bunch of atom, like a cup of coffee or something, sitting on a table and the atoms are jiggling a great deal and they bounce against the cup and the cup then gets shaking and the atoms in the cup shake and the bounce against each other and the heat heats the cup and heats everything else and then hot things spread that heat to other by mere contact because the atoms that are jiggling a lot in the hot thing shake the ones that are jiggling only a little bit in the cold thing so that the hot (heat we say) goes into the cold thing, it spreads but what is spreading is just jiggling, an irregular motion, but it is easy to kind of understand. It brings up another thing that's kind of curious: that I say that things jiggle and if you're used to balls bouncing you know they slow up and stop after a while but we have to imagine with the atoms a perfect elasticity they never lose any energy every time they bounce they keep on bouncing all the time they don't lose anything they're perpetually moving And that the things that happen when we say something loses energy if a ball comes down and bounces, it shakes irregularly some of the atoms in the floor and when it comes up again, it leaves some of the atoms moving, they jiggling So as it bounces, it is passing its extra energies, its extra motions to little patches on the floor each time it rebounces and it loses a little heat each time until it settles down, we say as the falling motion stops But what's left is the floor is shaking more than it was before and the atoms in the ball are shaking more than they were before that the organized motion of all these atoms moving the same way falling down and the quiet floor, is now transformed into a ball sitting on the ground But all the motion is still there in the form of energy of motion in the form of the jiggling of the floor which is a little bit warmer (unbelievable!). But anybody who's hammered a great deal on something knows that it's true that if you pound something and hit it a lot you can feel the temperature difference it heats up it heats up simply because you're jiggling it this picture of atoms is a beautiful one that you can keep looking at all kinds of things this way you see a little drop of water a tiny drop and the atoms attract each other they like to be next to each other they want as many partners as they can get Now the guys at the surface have only partners on one side here in the air on the other side so they're trying to get in And you can imagine this team of people, this team in people, all moving very fast all try (to get) to have as many partners as possible and the guys on the edge are very unhappy and nervous and they keep pounding in trying to get in, and that makes a tight ball instead of a flat and that's what you know surface tension when you realize when you see how sometimes a water drop sits like this on a table then you start to imagine why it's like that because everybody is trying to get in to the water and at the same time while all this is happening, other atoms leaving the surface and the water drop is slowly disappearing I find myself trying to imagine all kinds of things all the time and I get a kick out of it like a runner gets a kick out of sweating I GET A KICK of thinking about these things! I can't stop I mean if you may I could talk forever If you could cool off the water so that the jiggling is less and less, it jiggles slower and slower then the atoms get stuck in a place, they like to be with their friend there's force of attraction and they get packed together, they're not rolling over each other, they're in a nice pattern like oranges in a crate in a nice organized pattern, all just jiggling in place but not having enough motion to get loose of their own place and to break the structure down And that what I'm describing is a solid, it's ice, it has a structure If you held the atom in one end in a certain position all the rest are lining up in a position sticking out and it’s solid at the end whereas if you heat that harder then they begin to get loose and roll all over each other and that's the liquid. And if you heat that still harder, then they bounce still harder and they simply bounce apart from each other and they're just individuals, I said atoms, these are really little groups of atoms: molecule which come flying and hit and although they have a tendency to stick, they're moving too fast their hands don't grab so to speak, as they pass and they fly apart again and this is the gas we call steam You can get all kinds of understanding When I was a kid with this "air", I was always interested in I've noticed that when I pumped up my tires on the bicycle you can learn a lot by having a bicycle I'd pump up the tires that the pump would get hot and that also understand we see as the pump handle comes down and the atoms are coming up against it and bouncing off and it's moving in the ones that are coming off have a bigger speed than the ones that are coming in so that as it comes down and each time they collide it speeds them up and so they're hotter when you compress the gas it heats and when you pull the piston back out then the atoms which are coming faster than the piston feel receiving or sort of a give it gives and it comes out with less energy it's like going up against something which is soft and yielding it go boom boom and it loses so as you pull the piston out and the atoms are hit they lose their speed and they cool off and gases are cool when they expand and the fun of it is that all these things which you see or you notice in the world about it the pump heats the gas and the gas cools when it expands or the steam evaporates until you cover the cover and all these things you can understand from these simple pictures and that's kind of a lot of fun to think about I don't want to take this stuff seriously I think we should just have fun imagining it not worry about there's no teacher going to ask you questions at the end otherwise it's a horrible subject the atoms like each other the different degrees oxygen for instance in the air would like to be next to carbon and if they're getting near each other they snap together if they're not too close though they repel and they go apart so they don't know that they could snap together it's just as if you had a ball that was trying to climb a hill and there was a hole it could go into like a volcano hole a deep one it's rolling along it doesn't go down in the deep hole because if it starts to climb the hill and then rolls away again but if you made it go fast enough it'll fall into the hole and so if it's have something like wood in oxygen there's carbon in the wood from a tree and the oxygen comes and hits it carbon but not hot enough it just goes away again the air is always coming nothing's happening if you can get it faster by heating it up somehow somewhere somehow get it started a few of them come fast they go over the top so to speak they come close enough to the carbon and snap in and that gives a lot of jiggly motion which might hit some other atoms making those go faster so they can climb up and bump against other carbon atoms and they jiggle and they make other jiggle, and you get an horrible catastrophe which is one after the other all these things are going faster and faster and snapping in and the whole thing is changing that catastrophe is a fire it's just a way of looking at it and these things are happening they perpetual once it gets started it keeps on going the heat makes the other atoms capable of reaching to make more heat to make other atoms and so on so this terrible snapping is producing a lot of jiggling and if I put with all lack activity of the atoms there and I put a cup of coffee over that mess of wood that's doing this it's going to get a lot of jiggling so that's what the heat of the fire is and then of course uh you see what's happening when you start thinking, just go on and on wonder how did it get started why is it that the wood's been sitting around all this time with the oxygen all this time and it didn't do this earlier or something where did I get this from？ well it came from a tree and the substance of a tree is carbon, where did that come from? that comes from the air it's carbon dioxide from the air people look at trees and they think it comes out of the ground the plants grow out of the ground but if you ask where the substance comes from you find out where do they come from the trees come out of the air? they surely come out of you know they come out of the air the carbon dioxide in the air goes into the tree and it changes it kicking out the oxygen and uh pushing the oxygen away from the carbon and leaving the carbon substance with water water comes out of the ground you see only it had to get in there it came out of the air didn't it it came down from the sky so in fact most of a tree almost all of the tree is out of the ground I'm sorry it's out of the air there's a little bit from the ground some minerals and so forth now of course I told you the oxygen and we… oxygen carbon stick together very tight how is that the tree is so smart to take the carbon dioxide which is carbon and oxygen nicely combined and undo that so easy? Ah! Life! Life has some mysterious force! No! The sun is shining, and this sunlight comes down and knocks this oxygen away from the carbon, so it takes sunlight to get the plant to work! and so the sun, all the time, is doing the work of separating the oxygen away from the carbon the oxygen is some kind of terrible by-product, which it spits back into the air and leaving the carbon and water and stuff to make the substance of the tree and then we take the substance of the tree to get the fireplace and there's all the oxygen made by these trees and all the carbons would much prefer to be close together again and once you let the heat to get it started it continues and make an awful lot of activity while it's going back together again and all those nice light and everything comes out and everything is being undone you're going from carbon and oxygen back to carbon dioxide and the light and heat that's coming out, that's the light and heat of the sun that went in so it's sort of stored sun that is coming out when you burned a log next question: how is the sun so jiggly, so hot? I gotta stop somewhere; I leave you something to imagine most elastic things like steel springs and so on is nothing but this electrical thing pulling back you pull the atoms up a little bit apart when you bend something and then they try to come back together again but rubber bands work on a different principle there there's some long molecules like chains and other little ones that are shaking all the time that are bombarding them these chains and the chains are all kind of kinky and knockabout in shape when you pull open the rubber band the strings get straighter but these strings are being bombarded on the side by these other atoms trying to shorten them by kinking them so it pulls back it's trying to pull back and it's pulling back only because of the heat so if you heat a rubber band it'll pull strong more strongly for instance if you hang a weight with a rubber band put a little match to it it's kind of fun to watch it rise because heats want and there's another thing you can check that this idea is right that is heat that drives a rubber band if you pull the band out just like when we push the piston and the gas if you pull the band out this tightening string hitting those molecules makes them move faster so it's warmer and if you take the band and let it in then the molecules hitting the strings which sort of give as the thing hits it they give in to the soft like and they lose energy when they hit these retiring band, string so it cools and there is a little way you can do this you're not very sensitive it's a small effect and if you take a fairly wide rubber band and put it between your lips and pull it out you'll certainly notice it's hotter and if you then hold it out and let it in you'll notice it's cooler at least you'll notice a certain difference in whether what happens when you expand it and when you contract it and that's i've always found rubber bands fascinating to think that when they're sitting on an old package of papers for a long time holding those papers together it's done by a perpetual pounding pounding pounding and the atoms that get these chains to hold it, try to kink them and try kink them year after year well rubber bands don't last that long but anyhow for a long time trying to hold this whole thing together The world is a dynamic mess of jiggling things if you look at it right And if you magnify, you will hardly see a little thing anymore because everything is jiggling in its own pattern, and there's a lot of little balls It's lucky that we have such a large scale of view of everything that we can see these as "things" without having worry about all these little atoms all the time If you get hold of two magnet and you push them you can feel this pushing between them. Turn around the other way and they slam together Now, what is it, the feeling between those two magnets? what do you mean "what's the feeling between two magnets when you hold them"? well, there's something there, isn't it? I mean that the sensation that they're something there when you push the two magnets together. Listen to my question what is the meaning when you say that there's there's a feeling of course you feel it. Now what do you want to know? What I want to know is what's going on, between these two bits of matter? magnets repel each other Well then, what does that mean or why are they doing that or how are they doing that? I'm not saying... That's a perfectly reasonable question. Of course it's a reasonab... it's an excellent question. Okay? But the problem that you are asking, you see, when you ask why something happens how does a person answers "why something happens?" for example Aunt Minnie is at the hospital. Why? Because she slip. she went out and she slipped on the ice and broke her hip that satisfies people. It satisfies but wouldn't satisfy someone who came from another planet knew nothing about things first you understand "Why when you break your hip you go to the hospital? "How do you get to the hospital when the hip is broken" well because her husband seeing that she had her hip broken called the hospital up and send somebody to get her all that is understood by people now when you explain a "Why" you have to be in some framework that you allow something to be true Otherwise you are perpetually asking why Why did the husband call up the hospital? Because the husband is interested in his wife's welfare. Not always some husbands aren't interested in their wives' welfare when they are drunk and angry So you begin to get very interesting understanding of the world and all its complications in order to… if you try to follow anything up you go deeper and deeper in various directions. for example you could go “why did she slip upon the ice?" Well ice is lippery everybody knows that no problem But you ask "why is ice slippery?" that's kind of curious, ice is extremely slippery it's very interesting You say "How does it work?" you could either say "I'm satisfied that you have answered me ice is slippery, that explains it" or you could go on and say "Why is ice slippery?” and then you're involved with something because there are not many things as slippery as ice It's very hard to get greasy stuff, but that's a sort of wet slimy But a solid that is so slippery? Because it is in the case of ice when you stand on it (they say), momentarily the pressure melts the ice a little bit so you get a sort of instantaneous water surface on which you are slipping Why on ice and not on other things? Because ice expands… water expands when it freezes so the pressure tries to undo the expansion and melts it. It is capable about melting it But other substances contract when they're freezing and when you push them they're just satisfied to be solid why does water expand when it freezes and another substance don't expand when they freeze all right? I'm not answering the question but I am telling you how difficult a "why" question is. You have to know what it is that you are permitted to understand and allow to be understood and known and what it is you're not you'll notice in this example that the more I ask why, it gets interesting after all that's my idea that the deeper thing is the more interesting in it and you can even go further and say "Why did she fall down when she slip?" That has to do with gravity and involves all other planets, and everything else never mind, it goes on and on! Now when you ask for example "Why two magnets repel?" there are many different levels it depends on whether you are a student of physics or an ordinary person who doesn’t know anything or not If you are somebody that doesn't know anything about all I can say is that it is the magnetic force that makes things repel And that you are feeling that force. You see, that is very strange because I don't feel kind of force like that in other circumstances. When you turn them in the other way they attract there's a very analogous force, electrical force which is the same kind of a question and you say that's also very weird but you're not at all disturbed by the fact that when you put your hand on the chair, it pushes you back. But we have find that looking at it that it is the same force as a matter of fact the electrical force (not magnetic exactly in that case) but it is the same electric repulsions that are involved in keeping you finger away from the chair because everything is made out... it is electrical force in minor, microscopic details there are other forces involved, but they are connected to electrical force It turns out that the magnetic and the electric forces with which I wish to explain these things this repulsion in the first place is what ultimately is the deeper thing that we have to start that we can start with to explain many other things that looks like they were... Everybody would just accept them. You know you cannot put your hand through the chair, that's taken for granted. But you can't put your hand through the chair when you look at it more closely: "Why?" it involves these same repulsive forces that appear in magnets The situation is then to have to explain is: "why in the magnet it goes over a bigger distance than ordinarily?" There it has to do with the fact that in iron, all the electrons are spinning in the same direction, they all get lined up and they magnify the effect of the force until it's large enough at a distance that you can feel it but it's a force which is present all the time and very common and is in a basic force or almost I mean I can go a a little further back if I went more technical but in the early level, I just have to tell you that is going to be one of the thing you will have to take as an element in the world the existence of magnetic repulsion or electrical or magnetic attraction I can't explain that attraction in terms of anything else that is familiar to you. For example, if we say that the magnets attracts like if they were connected by rubber bands I would be cheating you because they are not connected by rubber bands; I shouldn't be in trouble you'll soon ask me about the nature of the bands And secondly, if you are curious enough you will ask me "why rubber bands tend to pull back together again?" I would end up explaining that in terms of electrical forces which are the very things I try to use the rubber band to explain so I have cheated very badly you see So I'm not going to be able to give you an answer to "why magnets attract each other" except to tell you that they do and to tell you that's one of the elements in the world among different forces: there are electrical forces, magnetic forces, gravitational forces and others, and those are some of the parts If you are a student, I could go further and tell you that the magnetic forces are related to the electrical forces very intimately that the relationship between the gravity forces and the electrical forces remains unknown and so on. But I really can't do a good job, any job of explaining magnetic forces in terms of something else that you are more familiar with, because I don't understand it in terms of anything else that you are more familiar with. The stuff of fantasizing in looking at the world, imagining things, which really isn't fantasizing because you just try to imagine the way it really is, comes up handy sometimes The other day I was at the dentist, he was getting ready with this electric drill to make holes and I thought I'd better think of something fast or else it's gonna hurt. And then I thought about this little motor going around and what was that make it turn? And what was going on? and what's going on is that there's a dam some distance away here and water going over the dam turns a great big wheel, alright and this wheel is connected with long thin pieces of copper which split up into other pieces of copper and split up and spread all over the city and then they're connected back to another little gadget and makes wheels turn all the wheels in the city are turning, because this thing turns. If this thing stops, all the wheels stop. If it starts again, they all start again. And I think it's kind of a marvelous thing of nature. It's extremely curious that phenomenon I like to think about a lot, because all it is, it's copper and iron. see, sometimes we think it's man-made generator very complicated, the phenomenon is a result of somet special something that we've made. But it's nature doing it, and it's just iron and copper; if you just take a big long loop of copper, and add iron at each end and move the piece of iron here, the other iron move at the other piece. And if you get it down to the NOTHING here just moving piece of iron in a loop a copper and see other piece of iron move you realize what a fantastic mystery nature is! you don't even need the iron you could if you at least get this pump prime primed and started by jiggling copper strands around fast enough knotting them and unknotting them and so forth you can get other copper strands move at the other end, over a long connection. And what is it? It's only copper! And motion! We're so used to circumstances in which these electrical phenomena are all canceled out Everything is sort of neutral: pushing and pulling, it's all very dull. But nature has these wonderful things Magnetic forces and electrical forces when you comb your hair with your comb and you get some strange condition so you put it in front of a piece a paper, that lifts up the paper, the paper jiggles at a distance far away that in fact turns out that that is the thing that's deeper inside of everything than the things we're used to We're used to forces that only act directly, right? you push with your finger, it only acts directly, but then you have to imagine what it is that's pushing with the finger here's this finger is made of little balls of atoms. And it has got another bunch of atoms that are pushing it. At that little space between those atoms. And that pushing is going through that space. And the only thing that happens with the comb and the paper is that the circumstances have a reason which makes it possible to see those forces go through a bigger distance than just the short distance between the atoms What it is they have charges like electrons, that are both the same they repel each other with a force. They are very tiny parts, they are piece of the atoms and they repel each other with a force which is enormous it's inversely as the square of the distance just like gravity is inverse to the square of the distance but gravity is attractive whereas this one is repulsive and for two electrons the gravity is so weak compared to the electricity electricity is so much more enormous than the gravity I can't express because I don’t know the name of the numbers it's one with thirty eight or forty zeros after the one Bigger is electricity! It's so enormous, that if I were all electrons... well, the number is too big! There's also however for electrical thing other kind of charges, positive charges example of protons are positive, they're inside the nucleus of the atoms and the attract electrons Opposite charges attracts, alike charges repel So you have to imagine enormous forces where likes are trying to get away from likes, and unlikes are trying to get near the opposite What would happen if you had a lot of them? they'd be all the likes would collect with unlike, they attract each other and they'd get an intimate mixture of pluses and minuses all on top of each other, very close together You wouldn't have a lot of pluses anywhere, because they repel each other They're all being compensated with minus very close, and you get these little knots of plus and minus the reason that the knots don't get smaller and smaller is because they are particles and there are quantum mechanical effects that we won’t discuss that don’t make they can't get any smaller than a certain size So you get these little lumps which are balls, they are the atoms The atoms are positive and negative charges and they neutralize they cancel their charges as nearly as they can and because of these force are so big, it ends up nowhere, with very little left because they're so big they cancels out, there's always so exactly the same pluses and minuses in any normal material When you comb your hair, it rubs just a little bit extra off just a few extra minuses say here, and somewhere else a few extra pluses But the forces are so big that just the extra ones which make a force that we can see, that seems to get over a long range and that we find mysterious and that we need an explanation for and we try to find an explanation for it in terms of ideas like forces that are inside of rubber bands, or steel bars and twisted things We would like to have some kind of puller, at a distance because we're used to it that we don't get any push until we're touching but the fact is that the reason we don't get any push until we're touching is the same force as you see at a long distance only it's come down to short because the pluses and minuses have cancelled out so well that you don't feel anything until it gets very very close When it gets close enough of course it makes a difference which is plus and which is minus and where they are and they repel each other so it's kind of fun to imagine that this intimate mixture of highly attractive opposites which are so strong that they cancel out the effects and it's only sometimes, when you have an excess of one kind or another that you get this mysterious electrical force And how can I explain the mysterious electrical forces in any other way? Why should I try to explain it in terms of something like jelly or other things which are made? And I understand the other way around in terms of strong, long distance forces which are all canceled out So it's the electrical forces in fact, and the magnetic forces in fact that we have to accept as the base reality in which we are going to explain all the other things. So again it turns out it's hard to understand, you have to do a lot of imagining that the real world has as its base, a force that acts at long distance that we haven't got much experience with that force we have peculiar phenomena here and there, but ordinarily we don't have much experience with that force is simply because that's what requires explanation That's what requires imagination. The long distance force we haven't other picture for And in the example of the generator for instance what happens is that the electrons which are part of an atom they're pushed by the motion of the copper wires wonderful to think that if you push a few here, and they get too close together so they push the others because they repel at a long distance so it's not just like water which repel at a short distance but it's a wonderful fluid which repel at a long distance and the effects therefore can go very quickly through the wire there is a little concentration you go ZINNNG through the wire all over the city at once. And you can use that stuff to make signals, you can push a few electrons here and there by talking in a telephone, at the other end of the line, a long line of copper across the city the electrons respond because of this very rapid interactions over these long distances to what you're saying in this room and they discovered experimentally the existence of these long forces and that this rapid motion action and so forth was a tremendous thing for human beings I think that the discovery of electricity and magnetism and the electromagnetic effects which are finally worked out, the full equations were worked out by Maxwell in 1873 probably the most fundamental transformation, the most remarkable thing in history the biggest change in history I went to a scientific school-MIT, and then fraternity when you first join they try to keep you from being feeling that you're too smart by giving you what looked like simple questions to try to figure out what actually happens and it's like training for imagination you know, it's kind of fun and I'd tell you some of them that I remember I learned them of course once you learn them the next time somebody comes along with this wonderful puzzle you look at them kind of quietly you wait two or three seconds or five seconds to show ways that you were thinking and then you come up with this answer to astonish your friends but the fact was of course that you were trained by your fraternity brothers as to how to answer these things early on one of the questions we used to we got was the problem about the mirror it's an old-fashioned it's an old problem You look in a mirror, and let's say you part your hair in the right side and you look in the mirror and the image has got its hair part on the left side so the image is left to right mixed up it's not top and bottom mixed up because the top of the head of the image is on the top and the bottom of the feet are at the bottom and the question is how does the mirror know to get the left and right mixed up and not the up and down you get a better idea of the problem if you think of lying down and looking at the mirror all right your hair is still on the left side and now the left and right was the up and down Whereas the up and down which look okay was the left and right before and the mirror somehow figured out what you are gonna do when you're looking at it so what to describe in a sort of symmetrical way what the mirror does that it doesn't look lopsided and it takes left and mixes it up with right and doesn't do the same with up and down and after a lot of fiddling you gradually read we can worked out the answer to that one you see if you wave this hand then the hand in the mirror that waves is the right opposite at it The hand on the east is the hand on the east and the hand on the west is the hand on the west, and the hand that head that up is up and the feet that is down is down. Everything is really all right! but what's wrong is if this is north your nose is to the north of the back of your head, but in the image the nose is to the south of the back of the head so what happens really in the image is neither the left and the right mixed nor the top and the bottom, but the front and back had been reversed, you see that is just the nose of the thing is on the wrong side of the head if you want it, all alright? Now ordinarily when we think of the image we think at it as of another person and we think the normal way that another person would get on that condition over there It's a psychological thing We don't think of the idea that the person has been squashed and pushed backward with his nose and his head because that's not what ordinarily happens to people A person gets to look like you looks in the mirror by walking around and facing you and because people when they walk around don't turn their head for their feet we leave that part alone but they get their right and left hand swung about you see when they turn around so we say that it's left and right interchanged but really the symmetrical way is along the axis of the mirror that thing get interchangeable but that's kind of an easy one a harder one and very entertaining was "what keeps a train on the track?" And of course the answer is, as everyone thinks: the flanges on the wheels you know the wheels have some kind of flange on them but that's not the answer. Because flange is just safety devices if the flanges rub against the tracks you hear a terrible squealing they're just in case the real mechanism doesn't work there's another problem with trains that's connected to it now people all know this about their automobile that when you go around the corner the outside wheels have to go further than the inside wheels and if the wheels were connected on a solid shaft you couldn't do that you can't turn the outside wheels further than the inside wheels and so the shaft is broken in the middle with a gear system it's called a differential did you ever see the differential on a railroad train? no you look at those wheels under a freight car and there are the two wheels and there's a solid steel rod going from one wheel to the other there's nothing that one turns the same as the other so now how does it go around the corner, a curve? when the outside wheel has to go further than the inside wheel and the answer is that the wheels are flanged like this I mean not flange they're cones this way that is they're a little fatter closer to the train and a little thinner further out if you look closely you'll see they've got this beveled edge and it's all very simple when they go around the curve, they slide out on the track a bit So that this wheel travels on a fatter pond a bigger diameter and this on a smaller diameter so when they both turn one turn this swings further than the other and that's what keeps it on the track also the same way suppose the train's running along on this thing, on the track and the track's here and here the two wheels are exactly balanced and it's nice and even suppose accidentally it gets a bump or something and slides out this way then this wheel is on a bigger circumference than this one but they're on a solid shaft so when it turns once around it carries this wheel forward relative to the other and steers the train back on the track of course if it gets too far off on the other side it goes back and forth and it stays on the track because the wheels are tapered and the flange is safety well we had a lot of stuff like that that we had to learn you know that would get straightened out before we could become full-fledged members of the fraternity If I'm sitting next to a swimming pool and somebody dives in and she's not too pretty, so I can think of something else I think of the waves and things that have formed in the water and when there's lot's of people that have dived in the pool, there's a very great choppiness of all these waves all over the water, and to think that it's possible, maybe, that in those waves there a clue as to what's happening in the pool, that some sort of insect or something with sufficient cleverness, could sit in the corner of the pool and just be disturbed by the waves, and by the nature of the irregularities and bumping of the waves have figured out who jumped in, where and when and what's happening all over the pool. And that's what we're doing when we're looking at something: the light that comes out is waves just like in the swimming pool, except in 3 dimensions instead of 2 dimensions of the pool and it's going in all directions and we have a 8'th of an inch black hole into which these things go, which is particularly sensitive to parts of the wave that are coming in a particular direction and it's not particularly sensitive when they're coming in at the wrong angle, which we say is from the corner of our eye, and if we want to get more information from the corner of our eye, we swivel this ball about so that the hole moves from place to place. Then, it's quite wonderful that we figure out so easy; that's really because the light waves are easier and the waves in water are a little bit more complicated; it would have been harder for the bug than for us, but it's the same idea, to figure out what the thing is that we're looking at at a distance, and it's really kind-of incredible because when I'm looking at you, someone standing to my left can see somebody who's standing at my right; that is, the light could be going right across this way, the waves are going this way, the waves are going this way, the waves are going this way, it's just a complete network. Now, it's easy to just think of them as arrows passing each other, but that's not the way it is, because all of this is something shaking -it's called the electric field, but we don't have to bother with what it is- it's just like the water height is going up and down. So there's some quantity shaking about here and the combination of motions that's so elaborate and complicated that the result is to produce an influence which makes me see you. At the same time, completely undisturbed by the fact that there are influences that represent the other guy seeing him on this side. So that there's this TREMENDOUS mess of waves all over in space which we call which is the light bouncing around the room and going from one thing to the other, because of course most of the room doesn't have 8'th inch black holes. It's not interested in that light, but the light is there anyway, and it bounces off this, and it bounces off that, and all this is going on, and yet we can sort it out with this instrument. But beside all that, you see, those waves that I was talking about in the water, maybe they're so big - some of them - and then there's slower swashes which are longer, and shorter. Perhaps that animal is making it's study only using waves between this length and that length, so it turns out that the eye is only using waves between this length and that length, except those two lengths are 100,000'th of an inch - 100,000'th of an inch big, and what about the slower swashes? The waves that go more slowly, that have a longer distance from crest to trough. Those represent heat. We feel those, but our eye doesn't see them focused very well, we don't in fact at all. The shorter waves are blue, the longer waves are red. But when it gets longer than that then we call them infrared. And all this is in there at the same time. That's the heat. Pit viper that get down here in the desert, they have a very little thing that they can see longer waves and pick up mice, which are radiating their heat in the longer waves but their body heat by looking at them with this eye, which is the pit of the pit viper. But we can't, we are not able to do that. And then these waves get longer and longer, and all through the same space, all these things are going on at the same time, so that in this space, there's not only my vision of you, but information from Moscow Radio that's being broadcasted at present moment, and the seeing of somebody from Peru. All the radio waves are just the same kind of waves, only they are longer waves. And there's the radar, from the airplane which is looking at the ground to figure out where it is, which is coming to the room at the same time. Plus X-rays, cosmic rays and all of these other things that are the same kind of waves, EXACTLY the same kind of waves, but shorter, faster or longer, slower. It is exactly the same thing. So this big field, this - this area of irregular motions of this electric field, this vibration, contains this tremendous information, and it's ALL REALLY there, that's what gets you. If you don't believe it, then you pick a piece of wire and connect it to a box and in the wire the electrons would be pushed back and forth by this electric field, swashing just at the right speed for the certain kind of long waves, and you turn some knobs on the box to get the swashing just right, and you hear Radio Moscow! Then you know that it was there. How else did it get there? It was there all the time. It is only when you turn on the radio that you notice it. But that all these things are going through the room at the same time which everybody knows, but you gotta stop and think about it to really get the pleasure about the complexity - the INCONCEIVABLE nature of nature. When we were talking about the atoms, one of the trouble we have with the atoms is that they are so tiny and it is so hard to imagine the scale. The atoms are in size compared to an apple is the same scale as an apple is compared to the size of the earth. That's kind of a hard think to take, and you have to go through all these things all the time and people find these numbers inconceivable and I do too And the only thing you do is just change your scale you just think of small balls but you don't try to know exactly how small they are too often or you get kind of a bit nutty, alright? but in astronomy you have the same thing in reverse because the distances to these stars are so enormous You know that light goes so fast, and it only takes few seconds to go to the moon and back or it goes around the earth in seven and a half times in a second and it goes for years... two years, three years before it gets to the nearest other star that there is to us! But all our stars are in nearby galaxies, a big mess of stars which is called a galaxy, a group but our galaxy is (what is it) some hundred thousand light years, like 100 000 years And then there's another patch of stars It takes a million years for the light to get here going at this enormous rate and you just go crazy trying to make too real that distance. You have to do everything in proportion. That's easy say that galaxies are little patches of stars and they're ten times as far apart as they are big So that's an easy picture. But you just go to a different scale, that's easier once in a while you try to come back to earth scale to discuss the galaxies, but it's kind of hard The number of stars we see at night is only about five thousand. but the number of stars in our galaxy, the telescope have shown when you improve the instruments Oh! We look at a galaxy, we look at the stars, all the light that we see, the little tiny influence, spread from the stars over this enormous distance of what three light-years for the nearest stars on! on! on! this light from the star is spreading, the wavefront's getting wider and wider weaker and weaker, weaker and weaker out into all of space and finally the tiny fraction that comes in one square eighth of an inch little black hole and does something to me so I know it's there! Well to know a little bit more about, I'd rather gather a little more of this tiny fraction of the front of light and so I make a big telescope which is a kind of funnel. The light that comes over this big area-200 inches in cross-is very carefully organized so it is all concentrated back so it can go through pupil. Actually it's better to photograph, and nowadays they use photocells which are better instruments but anyway the idea of a telescope is to focus the light from a bigger area into a smaller area so that we see things that are weaker, less light and in that way we find there's a very large number of stars in the galaxy. There's so many that if you try to name them, one in a second, all of the stars in our galaxy I don't mean all the stars in the universe just this galaxy here it takes three thousand years! And yet that's not a very big number Because if those stars were to drop one dollar bill on the earth during a year each star dropping one dollar bill they might take care of the deficit, which is suggested for the budget of the United States! So you see what kind of numbers we have to deal with! Anyway I think that the numbers are problems in astronomy, the size and numbers the best thing to do is to relax and enjoy the tininess of us and the enormity of the rest of the universe Of course, if you're feeling depressed by that, you can always look at it the other way and think how big you are compared to the atoms and the parts of atoms then you're an enormous universe to those atoms so you can sort of stand in the middle and enjoy everything both ways But the great part of astronomy is the imagination that is necessary to guess what kind of structures what kind of things can be happening to produce the light and the effect of the light of the stars that we do see and I could take an example, a historical example many times in science, by using imagination you imagine something which could be according to all the known knowledge and the laws and you don't know whether it is yet or not And that's very interesting, there is a creative imagination you'd like to call it not just imagining thing that are relatively easy, but something different And to take an example of, a star as we understand it ordinary stars like the Sun, which is just a big ball of gas, of hydrogen that's burning up the hydrogen and so forth and it's an enormous mass of gas and it's held together by gravity you don't to always understand gravity as a curved space good enough for the purpose that a force inversely square the distance When the things are closer together, the force is stronger, and it pulls everything together By the way that's why the world is round: because the globe of earth is pulled together as much as possible and if it had a great mountain and an irregularity like a bump so it would be pulled in by gravity and it all gets smooth Rocks aren't strong enough to hold a bump much bigger than a few miles and Mount Everest is our biggest bump But on the moon where the gravity is less, the bumps are higher; the mountains are bigger on the moon. Anyway, to get back to the star, it's all held together by gravity and it's got a nuclear fuel which we've haven't been talking about that's burning up the hydrogen and generating energy which keeps things going And after a while, it would use the fuel a lot people began to think about what would happen then and it would be possible to just be gas sort of hanging around held together by gravity but quiet but another possibility was to think if I push the stuff together closer, the gravity is stronger, would hold it together. Well if you push a little bit together, the pressure increases when you push the gas together, there are more atoms and they pound on it so the pressure is higher but the gravity is stronger and it turns out the pressure wins so it would just come out again if you're pushing a star like that, it oscillates and there are some stars that are oscillating and vibrating and so on but it turns out if you keep on analyzing you push it together very far to the incredible concentration that the whole mass of the sun is down to the size of the earth or smaller then it turns all the nuclear matter all the nuclei of the atoms are all stuck next to each other tight Spaces where the electrons are all squashed out and it comes out when you get to THAT far, the gravity is strong enough to overpower the pressure again even though the pressure has got to be enormous, the gravity has to be even more enormous and the thing will stay steady at a different size and be nothing but a neutron, a nuclear matter, nothing solid, nuclear matter and this possibility was worked out by Oppenheimer and Volkov, it's called a neutron star And people waited to see if there were any such neutron stars for years until recently they found these strange pulsars which emit flashes of radio waves later they found light which can go 30 times a second for instance the fastest ones or maybe 10 times a second or one a second And at first, that's very mysterious; you are used to stars being big and slow how can anything in a star move in a thirtieth of a second? Well these things are very small neutron stars and they’re spinning very fast. For reason not yet understood, they are emitting a beam, a beam of radio waves like a search light in an airport or something those things that go around boop boop boop so we get the flashes tick tick tick, that fast to imagine a star the mass of the sun, doing something, turning so fast 30 times a second another one of these big numbers, hard to conceive imaginary things okay? and the whole idea that there could be a star of such enormous density that a teaspoon would weigh so much of the matter if you put it on the earth surface it is so heavy that that it will just plough right to the center of the earth! and things like that, it took a lot of imagination: it comes out the mathematics and the analysis of all this helps you to make sure you are not making a mistake and it turns out that such a star is possible, and it turned out a little bit later they do exist and that's a good example of how imagination is a useful thing and produces a guessing ahead of time and how we make advances by using it Besides, the very difficult thing of imagining all the things that might be up there to explain the things we see in the case of astronomy, we have a large number of things we see that we have not yet quite clearly got the imagination to see what it is that's producing them Quasars are very powerful sources of light and radio waves from very great distances and we see them because they are so bright. The exact cause of their sources is gradually been recently understood in terms of another nutty concept of imagination: the black hole which is something that comes from following the logic of gravity of Einstein to its ultimate working out the consequences in crazy circumstances Suppose you had an amount of matter so great that the gravity force is so much that even light trying to get out falls back Nothing can go faster that light, and nothing could escape. You couldn't see it! how would you get there? If you have a large amount of matter to start with, it could fall together and get into this condition that no longer could the light come out. So you would have this thing which continues to attract things to it things would go in and nothing would come out. That is called the black hole. and you say well how can a black hole which is absorbing everything make all this energy that we see Is that an explanation of a quasar? Actually, it may well be Because the things that are falling in don't go pluck in but go around, falling in by swirling then as they are falling irregularly and so forth, and in the fast motions that it produces they go down this whirlpool they generate a lot of energy and friction and so forth, and different kind of effects magnetic and electric effects that could make the jets of matter that come out of the quasar and the radio galaxies in ways that are not really understood. We don't have a real picture why there are jets of radio waves, matter emitting radio waves in galaxies there are galaxies which great jets coming out with big clouds of matter on each side which are emitting radio waves so there's some kind of a source in there it sort of gets wound up and shoots these jets of matter out with tremendous energy And it's guessed that maybe it's a black hole somehow or other and the somehow or other is the challenge of the imagination Which has not yet been answered. by anybody, with any great confidence. You ask me if an ordinary person, by studying hard, would get to be able to imagine these things, like I imagine Of course! I was an ordinary person who had studied hard. There are no miracle people. It just happen they got interested in these things and they learned all these stuffs. There are just people There's no talent, special, miracle ability to understand quantum mechanics or a miracle ability to imagine electromagnetic fields that comes without practicing and reading and learning and study so if you say it take an ordinary person who's willing to devote a great deal of time and study and work and thinking and mathematics and time, then he has become a scientist. When I'm actually doing my own things and working in a high, deep and esoteric stuff that I worry about I don't think I can describe very well what it's like First of all, it's like asking a centipede which leg comes after which it happens quickly and I'm not exactly sure what flashes and stuff go in the head But I know it's a crazy mixture of partial equations, partial solving in equations, then having some sort of picture of what is happening that the equation is saying it's happening but they're not that well separated as the words I'm using and it's a kind of a nut nutty thing it's very hard to describe, and I don't know that it does any good to describe And there's something that struck me, it's very curious: I suspect that what goes on in every man's head might be very very different, the actual imagery or semi-imagery which comes and when we are talking to each other at these high and complicated levels and we think we are speaking very well, that we are communicating but what we are really doing is having a some kind of big translation scheme going on for translating what this fellow says into our images, which are very different. I found that out because in the very lowest level I wouldn't go into much details but I got interested in... Well I was doing some experiments and I was trying to figure out something about our time sense and so what I would do is trying to count to a minute actually say I'd count to 48 then it would be one minute so I calibrate myself and I would count a minute in 48 think I was counting seconds but it's close enough and then it turns out if you repeat that you can do very accurately when you get to 48 or 47 or 49, not far off, you're very close to a minute. And I was trying to find out what affected that time sense and whether I could do anything at the same time I was counting and I found that I could do many things I could, there were some things that not For example, I had great difficulty… I was in the university, I had to get my laundry ready, and I was putting the socks out and I had to make a list "how many socks", there were something like 6 or 8 socks and I couldn't count them because the counting machine was being used, and I couldn't count them until I found that I could put them in a pattern and recognize the number and so I learned a way after practicing by which I could count the line of type in a newspaper and see them in groups three, three, three, three, one that's a group of ten, three, three, three, one without saying the numbers just seeing the groupings I could therefore count the line of types I was practicing in the newspaper the same time I was counting internally the seconds so I could do this fantastic trick of saying "forty-eight, that's one minute and there are sixty seven lines of type" you see! It was quite wonderful and I discovered many things I could read while I was.. no, excuse me, yes, I could read perfectly alright while I was counting and get an idea of what it was about But I couldn't speak, I couldn’t say anything. Because of course I was sort of trying to speak to myself, inside, I would say "one, two, three" or sort of in the head. Then I went down to the breakfast, and there was John Tukey was a mathematician at Princeton in the same time and we had many discussions, and I was telling him about these experiments and what I could do and he says "that's absurd!" he says He said "I don't see why you have any difficulty talking whatsoever, And I can't possibly believe that you could read" so I couldn't believe all this but we calibrated him it was 52 for him to get to 60 seconds or whatever I don't remember the numbers now and then he said "alright, what do you want me to say? Mary had a little lamb. I can speak about anything, blah blah blah, blah blah, 52! that's one minute". He was right. And I couldn't possibly do that And he wanted me to read, because he couldn’t possibly believe it. and then we compared note, and it turned out that when he thought of counting what he did inside his head when he counted was he saw a tape with numbers it went "clink, clink clink" the tape would change with numbers printed on it, he could see well since it's sort of an optical system that he was using, and not voice. He could speak as much as he wanted but if he had to read, then he couldn't look at his clock! Whereas for me it was in the other way. And that's where I discovered, at least in this very simple operation of counting the great difference in what goes on in the head when people think they are doing the same thing And so it struck me therefore, if that is already true at the most elementary level That when we learn mathematics and Bessel functions, and the exponential and the electric field and all these things that the imageries and the method by which we are storing it all and the way we think about it could be really, if we get to each other's head, entirely different And in fact, while somebody sometimes has a great deal of difficulty to understanding a point which you see as obvious, and vice versa it's maybe because it's a little hard to translate what you just said into his particular framework and so on Now I'm talking like a psychologist, and you know I know nothing about this! Suppose that little things behaved very differently that anything that was big, anything that you're familiar with because you see as the animal evolves and so on, as brain evolves it gets used to handling the brain is designed for ordinary circumstances but if the gut particles in the deep inner workings where by some other rules and some other characters they behave differently they were very different than anything on a large scale then there would some kind of difficulty in understanding and imagining reality. And that difficulty, we are in. The behavior of things on the small scale is so fantastic! It is so wonderfully different! so marvelously different that ANYTHING that behaves on a large scale. You said "electrons act like wave", no they don't exactly, "they act like particles", no, they don't exactly, "they act like a kind of a fog around the nucleus", no they don't exactly. And if you want to get a clear, sharp picture of an atom, so that you can tell exactly how it's going to behave correctly and have a good image in other words, really good image of reality I don't know how to do it. Because that image has to be mathematic: we have a mathematical expression, a strange mathematics, I don't understand how it is but we can write mathematical expressions and calculate what the thing is going to do without actually being able to picture it It would something like a computer in which you put certain numbers in and you have a formula for what time the car will arrive at different destination and the thing does the arithmetic to figure out what time the car arrives at the different destinations but cannot picture the car. It is just doing the arithmetic So we know how to do the arithmetic, but we cannot picture the car It's not a 100% because for certain approximate situations, certain kind of approximate pictures work that it's simply a fog around the nucleus that when you squeeze it, it repels you it's very good for understanding the stiffness of certain material that it's a wave which does this and that is very good for some other phenomena alright So when you're working with certain particular aspects of the behavior of atoms for instance when I was talking about temperature and so forth, that it's just little balls it's good enough and it gives a very nice picture of temperature but if you ask more specific question and you get down to questions like "how is that when you cool helium down, even to absolute zero where it's not supposed to be any motion it's a perfect fluid and it has no resistance and it flows perfectly, and it isn't freezing" Well if you want to get a picture of atoms as all of that in it, I can't do it But I can explain why the helium behaves as it does, by taking my equations and seeing that the consequences of them is that the helium would behave as it is observed to behave So we know that we have the theory right, but we haven't got the pictures that would go with the theory And it's that because we haven't caught on the right picture or it's because there aren't any right pictures for people who have to make pictures out of things that are familiar to them Well let's suppose it's the last one, that there's no right picture in terms of things that are familiar to them Is it possible then to develop a familiarity with those things that are not familiar on hand, by studying by learning the properties of atoms and quantum mechanics, by practicing with the equations until it becomes a kind of second nature just like it's a second nature to know that two balls came towards each other, they smash into bits You don't say "the two balls when they come toward each other turn blue". You know what they do So the question is whether you can get to know what things do without... better that we do today as the generations develop, will they invent ways of teaching so that the new people will learn tricky ways in looking at things and be so trained, so well trained, that they won't have our troubles, with the atom picturing. There's still a school of thought that cannot believe that the atomic behaviors is so different than large scale behaviors I think that's a deep prejudice, it's a prejudice of being so used to large scale behaviors and they're always seeking to find to waiting for the day that we discover underneath the quantum mechanics there's some mundane, ordinary balls hitting or particles moving and so on I think they're gonna be defeated I think Nature's imagination is so much greater than man's, she's never gonna let us relax!
