from Richard Feynman. I hope you like them.

Now you may ask, "What is mathematics doing in a physics lecture?" We have several possible excuses: first, of course, mathematics is an important tool, but that would only excuse us for giving the formula in two minutes. On the other hand, in theoretical physics we discover that all our laws can be written in mathematical form; and that this has a certain simplicity and beauty about it. So, ultimately, in order to understand nature it may be necessary to have a deeper understanding of mathematical relationships. But the real reason is that the subject is enjoyable, and although we humans cut nature up in different ways, and we have different courses in different departments, such compartmentalization is really artificial, and we should take our intellectual pleasures where we find them. --* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *The FeynmanLectures on Physics - Vol. 1 (Algebra)

In any thinking process there are moments when everything is going good and you've got wonderful ideas. Teaching is an interruption, and so it's the greatest pain in the neck in the world. And then there are thelongerperiods of time when not much is coming to you. You're not getting any ideas, and if you're doing nothing at all, it drives you nuts! You can't even say, "I'm teaching my class." If you're teaching a class, you can think about the elementary things that you know so very well. These things are kind of fun and delightful. It doesn't do any harm to think of them over again. Is there a better way to present them? The elementary things areeasyto think about; if you can't think of a new thought, no harm done; what you thought about it before is good enough for the class. If you do think of something new, you're rather pleased that you have a new way of looking at it. The questions of the students are often the source of new research. They often ask profound questions that I've thought about at times and then give up on, so to speak, for a while. It wouldn't do any harm to think about them again and see if I can go any further now. The students may not be able to see the things I want to answer, or the subtleties I want to think about, but theyremindme of a problem by asking questions in the neighborhood of that problem. It's not so easy to remindyourselfof these things. So I find that teaching and the students keep life going, and I wouldneveraccept any position in which somebody has invented a happy situation for me where I don't have to teach. Never. --Surely You're Joking, Mr. Feynman (The Dignified Professor)

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Then I had another thought: Physics disgusts me a little bit now, but I used to enjoy physics. Why did I enjoy it? I used to play with it. I used to do whatever I felt like doing - it didn't have to do with whether it was important for the development of nuclear physics, but whether it was interesting and amusing for me to play with. When I was in high school, I'd see water running out of a faucet growing narrower, and wonder if I could figure what determines that curve. I found it was rather easy to do. I didn't have to do it; it wasn't important for the future of science; somebody else had already done it. This didn't make any difference: I'd invent things and play with things. So I got this new attitude. Now that I am burned out and I'll never accomplish anything, I've got this nice position at the university teaching classes which I rather enjoy, and just like I read the Arabian Nights for pleasure, I'm going to play with physics, whenever I want to, without worrying about importance whatsoever. Within a week I was in the cafeteria and some guy, fooling around, throws a plate in the air. As the plate went up in the air I saw it wobble, and I noticed the red medallion of Cornell on the plate going around. It was pretty obvious to me that the medallion went around faster than the wobbling. I had nothing to do, so I start to figure out the motion of the rotating plate. I discovered that when the angle is very slight, the medallion rotates twice as fast as the wobble rate - two to one. It came out of a complicated equation! Then I thought, "Is there some way I can see in a more fundamental way, by looking at the forces or the dynamics, why it's two to one? I don't remember how I did it, but I ultimately worked out what the motion of the mass particles is, and how all the accelerations balance to make it two to one. I still remember going to Hans Bethe and saying, "Hey, Hans! I noticed something interesting. Here the plate goes around so, and the reason it's two to one is ... " and I showed him the accelerations. He says, "Feynman, that's pretty interesting, but what's the importance of it? Why are you doing it?" "Hah!" I say. "There's no importance whatsoever. I'm just doing it for the fun of it." His reaction didn't discourage me; I had made up my mind I was going to enjoy physics and do whatever I liked. I went on to work out equations of wobbles. Then I thought about how electron orbits start to move in relativity. Then there's the Dirac Equation in electrodynamics. And then quantum electrodynamics. And before I knew it (it was a very short time) I was "playing" - working, really - with the same old problem that I loved so much, that I had stopped working on when I went to Los Alamos: my thesis-type problems; all those old-fashioned, wonderful things. It was effortless. It was easy to play with these things. It was like uncorking a bottle: Everything flowed out effortlessly. I almost tried to resist it! There was no importance to what I was doing, but ultimately there was. The diagrams and the whole business that I got the Nobel Prize for came from that piddling around with the wobbling plate. --Surely You're Joking, Mr. Feynman (The Dignified Professor)

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Now that we had got the classical theory right, Wheeler said, "Feynman, you're a young fella - you should give a seminar on this. You need experience in giving talks. Meanwhile, I'll work out the quantum theory part and give a seminar on that later. So it was my first technical talk, and Wheeler made arrangements with Eugene Wigner to put it on the regular seminar schedule. A day or two before the talk I saw Wigner in the hall. "Feynman," he said, "I think that work you're doing with Wheeler is very interesting, so I've invited Russell to the seminar." Henry Norris Russell, the famous, great astronomer of the day, was coming to the lecture! Wigner went on. "I think Professor von Neumann would also be interested. "Johnny von Neumann was the greatest mathematician around. "And Professor Pauli is visiting from Switzerland, so it happens, so I've invited Professor Pauli to come" - Pauli was a very famous physicist - and by this time I'm turning yellow. Finally, Wigner said, "Professor Einstein only rarely comes to our weekly seminars, but your work is so interesting that I've invited him specially, so he's coming too." So I prepared the talk, and when the day came, I went in and did something that young men who have had no experience in giving talks often do - I put too many equations up on the blackboard. You see, a young fella doesn't know how to say, "Of course, that varies inversely, and this goes this way . . . " because everybody listening already knows; they can see it. Buthedoesn't know. He can only make it come out by actually doing the algebra - and therefore the reams of equations. As I was writing these equations all over the blackboard ahead of time, Einstein came in and said pleasantly, "Hello, I'm coming to your seminar. But first, where is the tea?" I told him, and continued writing the equations. Then the time came to give the talk, and here are thesemonster mindsin front of me, waiting! I remember very clearly seeing my hands shaking as they were pulling out my notes from a brown envelope. But then a miracle occurred, as it has occurred again and again in my life, and it's very lucky for me: the moment I start to think about the physics, and have to concentrate on what I'm explaining, nothing else occupies by mind - I'm completely immune to being nervous. So after I started to go, I just didn't know who was in the room. I was only explaining the idea, that's all. --Surely You're Joking, Mr. Feynman (Monster Minds)