Robert B. Leighton (1919–1997)

My son saw me reading this last month, looked at the page full of differential equations, and remarked, "Some light reading, Dad?" Well, actually, yes! So much here! in an introductory course! That every student at Cal Tech, regardless of major, was required to take these classes is amazing. And if I had Feynman as my instructor, with this as the intro, I think my life would have be quite different. Not that my professor, Dr. V. V. Raman, whose grandfather won a Nobel, was a slouch, but this had meat and my freshman class had basics of simplified mechanics. I changed majors a few times, dropped out, eventually went back and became a mechanical engineer and I've never lost the love of this stuff (and am happy with my life). And this is definitely something I should have read long ago. It's a long read now - Vol 2 is even longer and I expect to stretch it out over next year as I did this one for 2023. The narrative is infectious and you can feel the excitement that Feynman had, and conveyed, for the material.

Feynman is eminently quotable. A sampling:

[on actually measuring positions of planets and how they moved]
This was a tremendous idea—that to find something out, it is better to perform some careful experiments than to carry on deep philosophical arguments.
{This is the idea. Philosphers tend to ask questions with no answers (although some of them think they come up with answers). Science looks for answers to real questions.}

[Universal gravitation]
This phenomenon showed that light does not travel instantaneously, and furnished the first estimate of the speed of light. This was done in 1676.

[on precision of definition]
Perhaps you say, “That’s a terrible thing—I learned that in science we have to define everything precisely.” We cannot define anything precisely! If we attempt to, we get into that paralysis of thought that comes to philosophers, who sit opposite each other, one saying to the other, “You don’t know what you are talking about!” The second one says, “What do you mean by know? What do you mean by talking? What do you mean by you?,” and so on.
{Love it!}

[more on philosophers]
...what is an object? Philosophers are always saying, “Well, just take a chair for example.” The moment they say that, you know that they do not know what they are talking about any more. What is a chair? Well, a chair is a certain thing over there … certain?, how certain? ”
{45 years I've been saying they don't know what they are talking about...}

[on relativity]
Poincaré made the following statement of the principle of relativity: “According to the principle of relativity, the laws of physical phenomena must be the same for a fixed observer as for an observer who has a uniform motion of translation relative to him, so that we have not, nor can we possibly have, any means of discerning whether or not we are carried along in such a motion.”

[on cocktail party philosophers]
When this idea descended upon the world, it caused a great stir among philosophers, particularly the “cocktail-party philosophers,” who say, “Oh, it is very simple: Einstein’s theory says all is relative!” In fact, a surprisingly large number of philosophers, not only those found at cocktail parties (but rather than embarrass them, we shall just call them “cocktail-party philosophers”), will say, “That all is relative is a consequence of Einstein, and it has profound influences on our ideas.””

[on notation]
We could, of course, use any notation we want; do not laugh at notations; invent them, they are powerful. In fact, mathematics is, to a large extent, invention of better notations.… (more)