Richard Feynman on knowledge versus understanding
from The TeachThought staff
Who is Richard Feynman?
Richard Feynman, born 1918, was a theoretical physicist whose work in quantum mechanics won him the 1965 Nobel Prize in Physics.
According to nobelprize.orgFeynman received his B.A. in 1939 at the Massachusetts Institute of Technology and studied “at Princeton University, where he received his Ph.D. in 1942. “He was a research fellow at Princeton (1940-1941), a professor of theoretical physics at Cornell University (1945-1950), a visiting professor, and then appointed professor of theoretical physics at the California Institute of Technology (1950-1959).”
Feynman’s legendary intellect – often mentioned alongside Isaac Newton and Albert Einstein – extended beyond theory and practice in science. Feynman was also known for his ability to explain complex concepts with clarity and humor. His innovative teaching methods, characterized by wit and deep understanding of fundamental principles, inspire educators around the world. Feynman’s legacy emphasizes the importance of curiosity, imagination, and critical thinking.
The following is an excerpt from a lecture entitled “The Value of Science” delivered in New York in 1955 at a meeting of the National Science Teachers Association.
See also What is the Feynman technique?
“Newton’s ideas about space and time agreed very well with experiment, but to get the correct motion of Mercury’s orbit, which was a small, small difference, the difference in the character of the theory required was enormous. The reason is that Newton’s laws were so simple and so perfect, and they gave certain results. To get something that would give a slightly different result, it had to be completely different. In formulating a new law, you cannot make the imperfections of one perfect thing, there must be another perfect thing, so the differences in philosophical ideas between Newton’s and Einstein’s theories are enormous.
What are these philosophies? These are really hard ways to quickly calculate the consequences. Philosophy, sometimes called the understanding of the law, is simply a way in which one holds the laws in one’s mind in order to quickly guess the consequences. Some people have said, and this is true in cases like Maxwell’s equations, “Never mind the philosophy, never mind anything like that, just know the equations. The problem is just to calculate the answers so that they agree with the experiment, and you don’t need to have a philosophy, or an argument, or words about the equation.”
This is good in the sense that if you just guess the equation, you are not preconceived and will guess better. On the other hand, maybe philosophy helps you guess. It’s very hard to say. For those people who insist that the only important thing is that the theory agrees with the experiment, I would like to imagine a discussion between a Mayan astronomer and his student. The Maya were able to calculate with great precision predictions, for example, about eclipses and about the position of the moon in the sky, the position of Venus, etc. All this is done by arithmetic. They counted a certain number and subtracted some numbers, etc. There was no discussion of what the moon was. There was no discussion of even the idea that he was surrounded. They simply calculated the time when there would be an eclipse, or when the moon would rise on a full moon, etc.
This is good in the sense that if you just guess the equation, you are not preconceived and will guess better. On the other hand, maybe philosophy helps you guess. It’s very hard to say.
Feynman
Suppose a young man went to the astronomer and said, “I have an idea. Maybe these things are spinning around, and there are balls of something like rocks, and we could calculate how they move in a completely different way than simply 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 much yet.” Then the astronomer says, “Well, we can calculate the eclipses more accurately than you can with your model, so you shouldn’t mind your idea, because obviously the mathematical scheme is better.”
There’s a very strong tendency when someone comes up with an idea and says, “Suppose the world is like this,” for people to say, “What would you get for an answer to such and such a problem?” And he says, “I haven’t developed it enough.” And they say, “Well, we’ve already developed it much further and we can get the answers very precisely.”
So it’s a question of whether to worry about the philosophies behind the ideas. Another way of working, of course, is to learn new principles. In Einstein’s theory of gravitation, he guessed, among all other principles, the principle that corresponds to the idea that forces are always proportional to masses. He guessed the principle that if you were in a speeding car, you couldn’t tell that from being in a gravitational field, and by adding this principle to all the other principles, he was able to derive the correct laws of gravity.
One of the most important things in this “guess – calculate consequences – compare with experiment” business is knowing when you’re right. It is possible to know when you are right much sooner, before you have checked all the consequences. You can recognize the truth by its beauty and simplicity. It’s always easy, when you’ve made a guess and done two or three little calculations to make sure it’s not obviously wrong, to know it’s right. When you get it right, it’s obvious that it’s right – at least if you have some experience – because usually what happens is more comes out than comes in. Your assumption is actually that something is very simple. If you can’t immediately see that it’s wrong and that it’s simpler than before, then it’s right.
Inexperienced, cranky, and the like make assumptions that are simple but immediately obvious to be wrong, so it doesn’t count. Others, the inexperienced students, make assumptions that are very complicated and somehow it seems that everything is fine, but I know that it is not true, because the truth always turns out to be simpler than you think. What we need is imagination, but imagination in a terrible straitjacket. We need to find a new view of the world that agrees with everything that is known, but diverges in its predictions somewhere, otherwise it is not interesting. And in this disagreement it must be in accord with nature.
Others, the inexperienced students, make assumptions that are very complicated and somehow it seems that everything is fine, but I know that it is not true, because the truth always turns out to be simpler than you think.
Feyman
If you can find another world view that agrees throughout the range where things have already been observed, but disagrees somewhere else, you’ve made a big discovery. It is very nearly, but not quite, impossible to find a theory which agrees with experiment over the whole range in which all theories have been tested, and yet gives different consequences in some other range, even a theory whose various consequences do not appear to agree with nature. A new idea is extremely difficult to come up with. A fantastic imagination is required…”
Video transcription courtesy of Reddit user Reltpid
