Richard Feynman's Story of Particle Physics - 1973 Lecture

we look around us in the world we see matter in an infinite variety of different forms you get solids and liquids in the gas like the air and of different colors of flames and sparks stars rocks and have all these different forms of matter this enormous variety is very puzzling to human beings the scientists have tried from beginning to try to see if all this great variety could really be representing different aspects if in some sense nearly the same thing we announce out that the enormous variety of things can be understood if they were all made out of atoms these atoms don't have such a great variety of different kinds they're just approximately at first it was believed about 92 atoms and the atoms themselves were put in some kind of table of different kinds and the different combinations of the different forms of chemical combinations of relations mixtures of the different kinds of these 92 atoms we could get all the variety of substances and phenomena and so forth that we see after add a few items to the atoms in order to understand everything we have their light which was understood and electrical and magnetic effects and the light and the electric and magnetic effects were understood as being different aspects of the same thing which we call the electromagnetic field the very thing which is carrying the waves by which a radio transmission is able to carry my voice to you now the next question was whether the pattern that was seen in the atoms by Mendeleev for example the relations chemically one atom guna could be again understood and it turned out that the atoms could be understood if they were made of a small nucleus which surrounded by electron and the different atoms of the different kinds were all represented by different numbers of electrons Carbon has six electrons oxygen has eight electrons and so on the business of two steps in a long task to try to represent the different varieties by single things to look deeper and deeper into madame and to find out what it is what I want to report to you tonight is how we're making out in this attempt to understand variety in terms of simple numbers of elements and you'll see that the story is an interesting one because at each time we think we're making progress we find that we have more variety again for example with the 92 elements we thought we were making some progress when we found that they were only differing in the number of electrons that they were on the outside each atom then is represented by a nucleus and electrons going around the electrons from one atom are identical to the electrons through another all the atoms differ by is the number of electron now further studies of electrons until today have never pointed out never shown that there's any structure inside of them at all they seem to be very elementary what we call elementary particles they have very simple properties well simple from our point of view it's a mathematically it's mathematically simple but heartless to understand they have simple properties or let's say well understood well described completely describable property but the little core around which the electrons go the nucleus of the atom turned out not to be so simple first I better tell you what I mean by little before I go any further I forgot the atoms are very small is so small that if an apple was the size of the earth the atoms in the Apple would be about the size of an apple the atom now consists if we magnify it to about the size of a rule we have the electrons go around we'll find in the little core in the middle it's no bigger than a piece of dust the size of the room in that piece of dust is almost all the weight of the atom the electrons are very light and fly around it attracted by electrical interaction for the nucleus now we have a variety the question is how many electrons gather around each nucleus it turns out that the nucleus nuclei contain different amounts of what we call electrical charge some contains six positive charges some contain eight positive charges the ones that contain six positive charges will gather six electrons that will become a carbon at the nuclei that have eight positive charges will gather eight electrons around but all the nuclei of carbon atoms turned out not to be the same some were heavier than others they all both had six charges but they weren't the same way these different weight nuclei were called isotopes so you see we had more different kinds of nuclei than we had different kinds of atoms because each atom had a number of different nuclei so suddenly the variety increased again the nuclei exploded into hundreds of varieties of different weights and different charges but again we were able to make from this variety certain simplicity it turned out that we can understand the nucleus if you imagine that they're made out of two kinds of particles only called a proton and a neutron the proton and a neutron have about the same weight which I'll call it a unit of weight this is just run and the Parton carried a positive charge but the neutron was neutral so we might have a nucleus like containing six protons and six neutrons this would be carbon because the protons carrying the six charges would attract the electrons making six electrons and that makes the atom chemically like carbon the weight of it would be about twelve units or we could have a nucleus with six protons and seven neutrons because it had six protons it would still attract six electrons again it would be chemically carbon but instead of a weight of would be way to 13 having six protons and seven neutrons it's 13 units of way so that the isotopes were explained by different numbers of neutrons and the variety of chemical was explained by the number of protons so the atoms were nothing but numbers numbers of very simple objects so how many practical do we have now we had light which we comes in a particle tool called the photon we have electrons and we have protons and neutrons and that explains all about the nuclear so it seemed again that we had things reduced to a very simple level and I tell you today we have never analyzed light any further every property that it has can be understood from a simple photon that we never found any complication on the outside of the atom in the electron when it comes to a proton or the neutron I had the plot thickens again the problem starts when we try to figure out what holds the protons and neutrons together in a little nucleus instead of letting them fly apart I disregarded some things when I was talking before first of all what holds the galaxies together that's gravitation I left that out when I was listening to the elements of the world we have the law the force of gravitation is what then what holds the electrons to the pro to the nuclei in an atom that's the electrical force I mentioned that before when I talked about light then what holds the protons and neutrons together inside a nucleus that is a mystery that we tried to style out to try to solve and one way to try to solve these things is to find out what kinds of forces there are between particle is to hit them together and see how they bounce away from each other by seeing how they bounce away from each other we find out what kinds of forces what kinds of pushes and pulls that are between how do you do this experiment the way we do an experiment like this is we take a proton we can get a single proton because that's just the atom the nucleus of the atom of hydrogen the lightest color form of hydrogen of hydrogen of weight one there is a hydrogen of weight - which has one proton and one Neutron in it but the most atoms of hydrogen a hydrogen weight one which consists of just one proton that one electron now we push knock the electron off with electrical forces and we have just the proton accelerated may go faster and faster by pulling it electrically but because it's going faster and faster and faster we let it plow in to a piece of matter most of the time it just misses it paired it rips through and leaves a lot of trail of torn up atoms behind and it doesn't hit a nucleus that is it doesn't hit another proton a neutron because the nucleus is so small but once in a while it does and the nuclear collision research is what we have to study what we try to use these rare collisions in which a proton hits a nucleus when the proton hits the nucleus at low energies all it does is not protons or pieces or little groups of protons and neutrons or other partial nuclei out of the nucleus in other words it just splatters the protons and neutrons in order to find more out about it but we have to hit make the experiments at higher energy or we will find out about that is that how the nucleus is put together we want to go further and find out about the proton when we hit the collision a little harder we find that the forces are very complicated there's nothing is so simple as the electrical forces the proton seems to be a more complicated device and we discover new particles are being knocked down as the energy rises we discover that when we hit protons against other protons for example that we get not just two protons out at some angle which is what we might have expected but we also get other particles some of them are called PI on some of the called Sigma's came as ions and so forth we find a great variety of particles coming up many of these particles have to be inferred that is this unstable disintegrates right away in a very very tiny type and so we have to deduce their existence but an any rated very high energy to probably plan that we had before we were near the end the plan that we had of hitting protons against protons of protons against neutrons to find out what their structure was broke there it's like this suppose we wanted to find out how a watch proton is like a watch perhaps how it's made then we hit two watches together at high speed and gear wheels should fly up that would be all right with watches but the trouble is that the walls are batter a little bit different the particle should come out wanted in there the particles are created from the energy of the collision so when we hit a proton a neutron together with the new machines with the hundreds of billions of electron volts that's a unit of energy with well anyway with the highest energies that we could make we make many many particles we make a great variety of particles there may be for example in the particular collision maybe twelve particles cover but the twelve particles weren't in there now the new problem is the decipher what it all means what I mean what I say twelve particles comes out is not that they're just exactly twelve sometimes we hit the two together we get more and sometimes less and at these twelve particles some of them are identical to each other in character but there are different kinds of particles that come out not just twelve different kind but sometimes in rare collisions special kinds coming out sometimes more often and we have it's very hard to tell or what the number of different kinds of particles come out because every day we're discovering new ones it might say in several hundred say four hundred at the present time of different types of objects have been created by colliding neutrons and protons together so again when we thought we were near the end with a simple variety to get the nuclei which had large variety into small number of objects neutrons and protons stuck together with a mysterious force then analyzing this we find indeed that there are just those particles several hundreds again of a great variety of different kinds of things and so the next question is whether this variety can be understood again as all these different types of particles might be perhaps understood as being made of some other thing now we have a theory at the present time well first thing that we did the first thing in order to try and find out oh man this is analogous to what Mendeleev did is to put the different elements in charts to notice if there's certain relationships that some elements appear behave very much like others and that there's some kind of periodicity if you arrange them according to their masses and there was some regularity of the chemical elements so what we do is we arrange them according to their masses and other properties electrical charges carried by these four hundred or other particles different variety of particles we find a number of numbers that we can use which we call quantum numbers in order to describe the various particles and put them in the various put them in to see relations among them in other words to make a kind of Mendeleev chart we're rather successful with making a system a system of pigeon holes in which the particles appear to go they appeared to be in families of various kinds for example of eight in a certain pattern and that pattern of eight is repeated again and again at different spins or different an associate degree to which they're rotating around their axis is called the spirit different masses we find the same pattern of a repeated there's another pattern of ten then it's trying to triangle of masses and this pattern is repeated again and again also we found that the particles can be separated first of all into two mighty classes one is called baryons and the other is called meson we distinguish them this way all the particles are unstable they disintegrate until they get to the one of lowest mass and the one of lowest mass is a proton so if they ultimately disintegrate into a proton that calls a barrier if when they ultimately disintegrate they end up there's nothing but light no proton left over there called lizards so we have this two great classes baryons and mesons and we have pigeon holes baryons and pigeon holes firmeza now we've cooked up a theory we have a little idea turns out that the character of the pigeon holes could be understood if all of these particles both baryons and mesons are made out of little particles called quarks in the native three the baryon should be made of three quarks and the mesons made of a quark and an antiquark I haven't talked about anti particles but an anti particle is one which is exactly the opposite the properties for example if an electron has a negative charge the anti electron which is called a positron has a positive charge and a particle and the antiparticle can annihilate with each other they can come together and simply disappear into energy uniform for example of light or in reverse particle and it's antiparticle beam can be made as a pair from just the kinetic energy of collision of two other particles that's why we get such a big variety of different things made in the collision between energetic particle and another at any rate to get back a meson is made of a quark and an antiquark and the fiery odd is made of three quarks how many different actual products are there only three there's three kinds of quarks which we've given the interesting names of the up quark the down quark and the strange quark I have a little trio of bongo players we like to play drums together by it my two friends and we could we call ourselves the three quarks one guys tall one guy short and so they call them up down and straight I'm strange but that with these three varieties that different kinds of baryons can be understood this way for example you can make a berry out of two up quarks and a down quark or one of two down quarks and a loved quad or one of three strange quads and so on if you think while you find that that doesn't make a very great number to think of while you'll find that there's this ten ways of arranging three quarks together each one of which can be either up-down or strain in fact that 10 is the secret behind the little group of 10 in the pattern that I try to describe before but when we now the next feature that we recognize is that the quarks don't have to just sit next to each other but they can move in different ways in other words the quarks are held together somehow and they vibrate among themselves and in vibrating in different ways they have different energies they have different states of motion then these different states are more in these different states of motion they appear to be these different particles these 400 different well not so many the baryons which it may be to it different variant on systems of three different quarks moving in different kinds of patterns and when you count up what kinds of particles you will get what families of particles you can get from different types of motion you'll find a system of pigeonholes a system of possibility which are just exactly fitted very well by the periodic chart that we had laid out before before we had made up the theory of quote can you characterize these great family analogies are these quarks have to have certain properties of course to get the right properties for the protons and neutrons and so on and I'd like to tell you what one of them is the they carry electrical charge the up quark carries a charge of plus two-thirds the down quark and the strange quark each carry a charge of minus one-third now we have never seen in nature any particles which carry a charge or third of a unit or two-thirds of a unit but we need these charges to get the right answer for example if a proton is made of two up quarks is made of two up quarks and a down quark the each up quark has a charge of plus two-thirds and the down quark has a charge of minus 1/3 so 2 plus 2/3 and 1 minus 1/3 is 4/3 minus 1/3 or 3/3 which is 1 so the proton has a charge of plus 1 Neutron is two down quarks and an up quark it has therefore a charge of minus 1/3 from each down quark that's 2 times minus 1/3 or minus 2/3 and plus 2/3 from the up quark and so it balances out as no charge isn't it clever by putting three objects together each with these 1/3 unit of charges we get integral charges it's very amusing indeed the mysterious thing is that we've never seen any objects with one with one-third charges so it's a matter of imagination the easy way to find out whether there are quarks or not and whether this theory is right if the theory was we would expect that if a quark is for example made of 2 ups and if we hit 2 protons together hard enough we'd knock the quarks out then we find the loose quarks the up quark the down quark if we did we would find a particle in nature which had a charge of 2/3 or minus 1/3 how can you check the electrical charge with the tactical carry it's very easy as it moves along very energetically nearly at the speed of light through matter it tears up the atoms in the neighborhood because of its electrical effects but if the electrical effect of only 1/3 is great it tears up as it turns out the square 1/9 is Munny atoms and thus there is not as strong a track left in some of our instruments by factor of 9 and it would be very easy to notice that we'd get a track that was 9 times a weekend the response that we would get from an ordinary particle like a proton well people have been looking for quarks this way to look for tracks and cloud chambers or sparks and spark chambers or some kind of it effects electrical effects that would show that atoms are torn up by an atom particle going through but a particle of 194 one-third the charge of a two-thirds the charge that is the one ninth or 4/9 the strength of an ordinary particle and it's never been seen so we have a little puzzle because we have an object which the made of quarks is a nice thing to explain the pattern but the experiments don't show that the quarks come apart with the solution and one possibility is the quarks are held together by tremendous forces but if they do that then they're moving around inside these things in very high speed and we know enough about the real theory of relativity to know that the situation can be very simple when they're moving at very high speed there should be pairs of other quarks and antiquarks made in the situation we cannot make a simple model with the periodic properties that they have unless we imagine the quarks are moving around inside relatively slowly if they're moving around relatively slowly they're not held together very strongly and so they should be made to see the experiment would indicate that there are no clocks we can make them but the pattern is so beautifully fitted by the idea that they are quarks that we are standing at the threshold of some sort of paradigm things behave exactly as if they're made out of quarks it's a single exception that they don't come apart a face with such a paradox some people say or whole idea that they may attic quarks not right that the fact that the pattern fits is due to some deeper significance and has to be understood mathematically in similar way there are others who say well it's true the quarks are held together in some way by new kinds of forces that we don't understand they can't really come apart for a reason that we'll discover later and we can philosophize about this all we want but in science we have the advantage and can always do some more experiments to find out more so the next thing that we're going to do and then electron against the proton we don't understand the target but at least we understand the beam so it's a little easier to analyze now by colliding electrons against protons we get a chance to see the behavior of the things that are inside there would be two possibilities for example it may be that the proton is some kind of a smooth like jelly ish stuff on the other hand it may be out made and if internal parts little point-like particles that are moving about now what happens when the electron hits a little hard point-like particle what happens when it's goes past electrical jelly is entirely different and the result the picture of the quarks would be that there would be little hard particles inside where some other pictures may not agree with that well when we balance electrons against protons we find that the proton behaves as if it's made and a little granular particles moving around inside doesn't turn out to look like it's exactly three but we understand the reason for the number not being right these are these particles quarks or maybe the proton is made out of some other particles different than quarks the first thing that we can measure is what we call the spin of these particles the quarks are supposed to have a spin like that of an electron which is called spin 1/2 of a unit and when we scatter the electrons from these particles we can tell by the probability of the electrons being scattered at different angles what the spin is a little part that they're bounced off of and Load spin is 1/2 so we now know that the proton is made out of little parts or perhaps it is at least made out of little parts of spin 1/2 now can we tell what the charges of these things are and the answer is that by scattering electrons we cannot we can just tell something about their momentum distribution the speed distribution that they have inside we cannot tell what charges they carry we can tell though that if the charges were 2/3 and 1/3 and 1/3 as we said before that the total amount of momentum that a proton carries is not correctly given by the quarks in fact it shows that there must be something else inside that the electrons do not bounce off of now electrical electrons bounce off of anything that's charged doesn't bounce off of things that are neutral and so we would conclude if the quark theory is right the quarks have spin ahead but there's something else neutral inside the proton that's not so bad because the question would already narrowly be if you said that the thing was made out of quark what holds the quarks together must be something strong because if the quarks are held together so hard or in such a mysterious manner that when you hit protons together the quacks don't come apart something's holding them together so we have a new particle to hold the quarks together this object we call a gluon horrible word after the glue which is holding the quarks together well anyhow at any rate our experiment shows that if the particles that are inside the proton are quarks there indeed must be something else in addition and then really challenging question is whether the quarks carry charge one-third when they're inside the nucleus and this looking with electrons will in principle measure the charge because the ease with which an electron is bounced back from a particle a quark say depends on the charge on the clock but since we have no independent way to know how many quarks are in there we can't tell we can't tell for any particular direct way whether the charges are indeed given by one-third or two-thirds if we had some other way of bouncing something off a quark that wouldn't depend in a different way on the charge or how many quarks are there it would not depend on the charge but it depend only on how many quarks are there we would have a chance of seeing whether the electrical scattery was indeed given by 1/3 and 2/3 charge it but we do have a way and I'll jump ahead of a story a little bit to tell you there's another particle a neutrino that I'll come back to that we can use to scatter off the quarks and so we planned an experiment in which neutrinos ought to be scattered from protons in a way analogous to the way electrons are scattered from protons and when we find the probabilities of scattering of neutrinos from protons we will be able to tell whether the quarks are really showing their non integral charges there 1 thirds and two thirds charges in the electrical experiment or not this experiment with the neutrinos is set up in the for example several places one place is a National Accelerator Laboratory in Batavia the United States and beam is turned on and probably as I'm talking down to the tree toes are coursing through the apparatus we have to get a large number of collisions and average the collisions that I wish I knew the results at the present time this will make or break the quark picture of the insides of a proton could you tell more about this experiment if you'd like I can tell you a little bit more about how these experiments of bouncing electrons off of protons tell us what the proton looks like when we first when we do this the first experiments it did this just looked at the average proton and it looked like it just a cloud a small cloud the question is whether this cloud is a kind of jelly or is made like a swarm of bees small hard particles moving around now another way to tell whether a thing is made is a way to tell whether a thing is made ever smaller bees would be something like bouncing radar off you know by radar we can tell the speed of an automobile by the way that the waves that bounce back I check changed from the when they're bounced from a moving car so if we shine radar way is at a swarm of bees the waves that come back can show that the particles that there are particles inside moving about and measure their velocities in the same way when we scatter electrons from a proton if we measure the speeds or the momentum of the electrons that are bounce back they reflect the distribution of momenta of pieces inside the proton and so it's this experiment that we've done to determine to watch the distribution of electrons which have been distribution of momentum of electrons that have been bounced back from a proton to determine what the momenta are of the pieces inside and what we've discovered is indeed there are pieces inside and that they're moving about what do you contribute to this research it's very hard to say because a program like this is developed by large numbers of different people over many many years and I've made minor contributions here and there perhaps one that's more relevant to what we've been talking about is I think it was I contributed to the idea that the district that the observations of the distribution of electrons from the scattering from a proton can be interpreted as the moving moving about of hard small particles in other words that we can interpret the experiments of scattering electrons from protons as indicating that the proton is made of small moving particles what kinds of machines do you use for the experiment whether they look like in an ordinary electron microscope the electrons pick up their speed and going through a little gap of about an inch here we need to look at such a tiny object as a proton very much more energetic electrons by several million times and so we need a accelerator to accelerate the electrons to high speed which instead of being an inch long is more like three kilometers so we have this long tube three kilometers at the Stanford University and at the other end there are several big buildings that contain the apparatus which is very enormous for measuring the electrons which is scattered from the proton the machine which is used to generate the neutrinos is also extremely large it consists of a big circle at Batavia in New York it consists of a big circle about six kilometers in circumference in which protons are accelerated the protons hit a target and they make new particles one of the particles I mentioned earlier the four hundred varieties called pi ants and they disintegrate ultimately producing neutrinos and the neutrinos are then used to produce reactions in a further protein further matter further down the beam the targets for the experiment is a gap about three kilometers from the machine that's the hypothesis of the product explain everything about the nature of matter is the quark the smallest building block we find that matter is made out of atoms and atoms made out of electricity and electrons important nuclei and nuclei are made out of protons and neutrons and protons and neutrons are made out of something perhaps quarks maybe we'll find out what a quarks are made out of and we'll have a never-ending search maybe there's no final answer I think that for people who think that it's necessary to have the complete answer to do any research that the purpose is to find the complete answer that that that looks like a complete discouragement but the idea is not to find the complete end necessary to find a complete answer but to find out more and more information it's like exploring if you're exploring a country the fact that when you went through the country and maybe that on the other side you come across a river ocean that you'd have to pass and you couldn't pass doesn't mean that it wouldn't be interesting to explore the new country that you discovered so in the same way the question as to whether this is a never-ending search or that the search will end with the quark is not exactly relevant to our interest in finding out just more about the white matter is constructed is this study could be theoretical but can be used it somehow for our technology practically in all the past discoveries about the properties of matter we found enormous practical applications of our new knowledge the new knowledge of matter meant that we can control matter make it do things that we want to do and you may ask whether we expect to have practical applications from these developments to a man would be a fool to say there are no practical applications because in a few you know this always turns out as soon as you say that in a few years there are but actually I can see none in the other cases when the laws were being unfolded it was almost obvious that they would have some application but in this particular case I can see no particular practical places where much of this will be of great use this is however man's curiosity which leads them on to discover more and more about the world the fact that there are practical applications doesn't stop that or there are are there are and doesn't stop that curiosity and so it's something like the way we study astronomy the exact position of the stars and the galaxies and the universe the size of the universe and these mysterious things have no practical application it's true that astronomy can be used for navigational easty used to be used it's very rarely used now furthermore the amount of astronomy a need to do practical navigation is minimal but the tremendous interest in astronomy shows our interest in the universe we are in to find out what we are what the matter is made out of and so on in this search for the insides of a proton is analogous to the search for the outside galaxies but is the rule of theoreticians in science well it turns out that the problems of to understand nature is very difficult she's very subtle but it takes a lot of imagination to try to imagine what it could be like in such a way that it has to agree exactly with the way she actually behaves we need a kind of imagination in a straitjacket we have to imagine what's there if we imagine something that isn't there it isn't going to do us any good and it's so difficult it's subtle that has turned out there's a kind of division of labor there are people that spend almost all their time thinking about just those problems and those are called theoretical physicists there are those who gather who do a good deal of that times they spend in thinking about these things but also in doing experiments to gather new clues and new tests of the imaginations of either themselves or others those are called experimenters I don't mean to imply that experimenters don't think and don't have imagination this division is only a system of words the experimenters also do a great deal of imagining and their being closer to the actual phenomena very often suggests clues as to how the thing actually might work but some of the more subtle and difficult questions are are analyzed by people who have spend or their entire time on this problem the specialist you might say in thinking about physics and those are theoretical physicists that's what I am that's for example what Einstein was people have called him a mathematician but that was in the day when they didn't know what a physicist was he was a theoretical physicist I should like to mention one other curiosity about the way the quarks have to behave we have discovered a principle when studying atoms that's called the exclusion principle it says that no two electrons can be in the same state then we think we have proved that for spin to have objects there must be a rule that no two can be in the same state nevertheless in making our picture of the quark model we have done we have to make the exact opposite hypothesis that the particles like to be in the same state that they the energies law and the conditions are enhanced when all the particles are in the same state we think we proved that this is impossible but the part of the proof it was assumed that the particles can be separated from other particles now we know experimentally the quarks have not been separated so it's still possible that the things obey this will rule that they like to be in the same state instead of try to avoid being in the same state but this again adds to some of the paradoxes associated with our picture that protons are made out of quarks it's these paradoxes that makes the whole subject very interesting because we're bound to learn something new we learned a paradox in physics of this kite is generated because we have a set of ideas that we think are all necessary and Nature doesn't pay attention to one or two of them and the question is which one the paradoxes are the beginnings of Inklings that were about to make progress in overturning some of my ideas of course I can't tell you which idea we're but over third people are more conservative I've proposed a more complicated picture that the quark because the rule is that no two particles can occupy exactly the same state and yet three quarks tend to do so in some of these particles they propose that maybe the quarks would seem to be the same are really different their theory is that the quark is made there the quarks come in three colors for example there are three kinds of up quarks red blue and white then the quarks that are in a proton has one red one white and one blue so that none of them are in the same condition also in order for this theory to work satisfactorily in to account for everything the glue has to have colored it turns out eight colors so that we've got our theory is usually expanded in this view we have each quark has three varieties up down and strange then each variety has three colors red white and blue so we have nine different quark and eight different gluons the 17 particles and we haven't mentioned the graviton photon and the four leptons that I mentioned earlier so we have to add another six particles up to 23 and though it's far from our subject there are suggestions for other particles too so we perhaps have two dozen particles at this stage so it looks like the work the simplicity is Teddy into variety again even before we're sure that the crux exists yes Timmy on in Susan - Susan

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Keywords: Richard Feynman (Academic), Particle Physics (Field Of Study), Physics (Field Of Study), Quantum Mechanics (Field Of Study), Quantum Theory, Science, Program, Documentary (TV Genre), Lecture, Elementary Particle, Atomic Physics (Field Of Study), Story

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Length: 41min 30sec (2490 seconds)

Published: Tue Apr 07 2015