Feynman: Knowing versus Understanding

I'm sure I'm not alone in realizing this. But when Professor Feynman lectures he also teaches how to think and study. This was natural to him. What a wonderful teacher he was

Love the fact that one of the great minds of the 20th century never lost his thick Brooklyn accent.

"Studying without thinking, is useless. Thinking without studying, is perilous." - Confucius

Feynman was a jewel. A great scientist, a great teacher and a great, great character!

He was a true genius--not only as a physicist, but as a science communicator. He didn't just teach physics...he taught people how to think!

This great man discusses more philosophy, psychology and science in five minutes than all my years at university combined. Remarkable. And it's not a trivial point he's making. This is a very deep insight.

"You can't make imperfections on a perfect thing - you have to have another perfect thing."

"Newton’s ideas about space and time agreed with experiment very well, but in order to get the correct motion of the orbit of Mercury, which was a tiny, tiny difference, the difference in the character of the theory needed was enormous. The reason is that Newton’s laws were so simple and so perfect, and they produced definite results. In order to get something that would produce a slightly different result it had to be completely different. In stating a new law you cannot make imperfections on a perfect thing; you have to have another perfect thing. So the differences in philosophical ideas between Newton’s and Einstein’s theories of gravitation are enormous. ~ What are these philosophies ? They are really tricky ways to compute consequences quickly. A philosophy, which is sometimes called an understanding of the law, is simply a way that a person holds the laws in his mind in order to guess quickly at consequences. Some people have said, and it is true in cases like Maxwell’s equations, ‘Never mind the philosophy, never mind anything of this kind, just guess the equations. The problem is only to compute the answers so that they agree with experiment, and it is not necessary to have a philosophy, or argument, or words, about the equation’. ~ That is good in the sense that if you only guess the equation you are not prejudicing yourself, and you will guess better. On the other hand, maybe the philosophy helps you to guess. It is very hard to say. For those people who insist that the only thing that is important is that the theory agrees with experiment, I would like to imagine a discussion between a Mayan astronomer and his student. The Mayans were able to calculate with great precision predictions, for example, for eclipses and for the position of the moon in the sky, the position of Venus, etc. It was all done by arithmetic. They counted a certain number and subtracted some numbers, and so on. There was no discussion of what the moon was. There was no discussion even of the idea that it went around. They just calculated the time when there would be an eclipse, or when the moon would rise at the full, and so on. ~ Suppose that a young man went to the astronomer and said, ‘I have an idea. Maybe those things are going around, and there are balls of something like rocks out there, and we could calculate how they move in a completely different way from just calculating what time they appear in the sky’. ‘Yes’, says the astronomer, ‘and how accurately can you predict eclipses?’ He says, ‘I haven’t developed the thing very far yet’. Then says the astronomer, ‘Well, we can calculate eclipses more accurately than you can with your model, so you must not pay any attention to your idea because obviously the mathematical scheme is better’. ~ There is a very strong tendency, when someone comes up with an idea and says, ‘Let’s suppose that the world is this way’, for people to say to him, ‘What would you get for the answer to such and such a problem?’ And he says, ‘I haven’t developed it far enough’. And they say, ‘Well, we have already developed it much further, and we can get the answers very accurately’. So it is a problem whether or not to worry about philosophies behind ideas. Another way of working, of course, is to guess new principles. In Einstein’s theory of gravitation he guessed, on top of all the other principles, the principle that corresponded to the idea that the forces are always proportional to the masses. He guessed the principle that if you are in an accelerating car you cannot distinguish that from being in a gravitational field, and by adding that principle to all the other principles, he was able to deduce the correct laws of gravitation. ~ One of the most important things in this ‘guess – compute consequences – compare with experiment’ business is to know when you are right. It is possible to know when you are right way ahead of checking all the consequences. You can recognize truth by its beauty and simplicity. It is always easy when you have made a guess, and done two or three little calculations to make sure that it is not obviously wrong, to know that it is right. When you get it right, it is obvious that it is right – at least if you have any experience – because usually what happens is that more comes out than goes in. Your guess is, in fact, that something is very simple. If you cannot see immediately that it is wrong, and it is simpler than it was before, then it is right. ~ The inexperienced, and crackpots, and people like that, make guesses that are simple, but you can immediately see that they are wrong, so that does not count. Others, the inexperienced students, make guesses that are very complicated, and it sort of looks as if it is all right, but I know it is not true because the truth always turns out to be simpler than you thought. What we need is imagination, but imagination in a terrible strait-jacket. We have to find a new view of the world that has to agree with everything that is known, but disagree in its predictions somewhere, otherwise it is not interesting. And in that disagreement it must agree with nature. ~ If you can find any other view of the world which agrees over the entire range where things have already been observed, but disagrees somewhere else, you have made a great discovery. It is very nearly impossible, but not quite, to find any theory which agrees with experiments over the entire range in which all theories have been checked, and yet gives different consequences in some other range, even a theory whose different consequences do not turn out to agree with nature. A new idea is extremely difficult to think of. It takes a fantastic imagination…" — Richard Feynman, from "The Character of Physical Law"

It warms my heart how he trenchantly recognized these bits of philosophy of science as both fundamentally unscientific and crucially important.

I could listen to him endlessly. Everything he says is so easy to understand. His anecdotes so instructive. He’s always been my favorite Manhattan project physicist. But because of his character not any other reason.

Almost 60 years ago, I was using a similar approach when preparing lessons in high school science. I was inspired by a two volume work of James Conant, a former president of Harvard in which he recounted the search for understanding by empirical methods. Feynman used to claim that, based on empirical methods, we guess the theory. And here in this Feynman lecture, we see that different people guess differently which theory to select. Conant explored the process of selection among theories. Conant was a mentor of Thomas Kuhn. And Kuhn's book, The Structure of Scientific Revolutions, may have been inspired by Conant. A philosopher will see that guessing the theory solves the problem faced by the logical positivists. Theory is not entailed by empirical evidence. There is no compelling link from evidence to theory. We guess theories. Popper's falsifiability has its own problems. It might take a decade, a century or a millennium to falsify a theory. The reply to this is that Popper was not relying on actual attempts to falsify a theory, but on the question: Is the theory CAPABLE of being falsified? If the Big Bang is a scientific theory, then Popper would say there has to be some way to falsify it. If not, the Big Bang Theory is pseudoscience. Feynman was preoccupied by these philosophical questions. Even though they were not the focus of his lectures, one can see that he designed his approach based on his Popperian epistemology of science. How do we know? How can we find out? How certain can we be? Do we really know? Can we really know? Are we fooling ourselves? Do we understand? Will this theory be falsified? If you teach science, have a look at Conant's Harvard Case Histories in Experimental-Science in two volumes. Second hand copies are probably available. Abebooks has volume I at $11.70. Amazon volumes 1+2 at $38. https://www.amazon.com/Harvard-Histories-Experimental-Science-Vols/dp/0674374002 Stanford Encyclopedia of Philosophy. Popper, Positivism, Ian Hacking, Nancy Cartwright https://plato.stanford.edu/ Enjoy!

I don't know who said it or where and when I heard it or even if it's something I just made up myself. But I always remember a quote "facts are not as important as the interpretations of those observing the facts"

I would fucking run to class half an hour before it starts if I had him as my teacher instead of the crap I got to deal with where I am now !

It takes a genius to explain something complicated like this so clearly that practically everybody can understand it

Priceless documentation here. I am eternally grateful for a glimpse into the mind of this great being. 🙏🏾

This is why Feynman was special. The way he explained the most difficult ideas were phenomenal, unlike most in todays day and age making trivial things sound “smart” when in reality it is just common sense.

I love how he still sounds like "he's walking here".

In school and college we're just taught theories and applications. There is no philosophy to teaching something. Feynman had a really neat way of taking you through the same thought process he has. And he doesn't emphasise only the theories but the fact that they hold philosophical value. They can make you think about different things differently. Make you do very different things even though they're the same.

everytime i stumble across these lectures...year after...i stop, pause and am in awe all over again

Anyone who is kind enough, please put subtitle. That would really help.