Well, that’ll teach me to make promises about when the next post will be. In totally unrelated news, I hate moving to a new apartment.
Back to the Feynman lectures! The writing is quite beautiful — Feynman is very clear and readable, while still packing a great deal of information into a small space. There’s no way one blog post of reasonable length could cover all of the ground that Feynman does in each chapter. And this chapter is especially densely packed, because this chapter is setup. After some brief introductory remarks — and some philosophical comments on the nature of science that I’ll get to in a later post — Feynman gives the class a killer hook, and then uses that hook to reel the students (and readers) in through a quick introduction to many, many concepts that will come up again later in the text.
Here’s the hook:
“If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis…that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.”
See what I mean about beautiful writing? I can’t condense this stuff. The best I can hope to be is a tour guide — commentary, not CliffsNotes. But this chapter is already a tour, so there’s not much I can do with it, aside from pointing out how beautifully Feynman sets himself up for the material later in the course, and a few historical oddities. He talks about pressure as the averaged-out pushes of atoms on a container — check out this video from the Exploratorium to see what he’s talking about — which sets him up for the kinetic theory of gases several dozen chapters later. When he says that water evaporates because some molecules move faster than others, he’s setting himself up for the Boltzmann velocity distribution 40 chapters later. And when he says we can’t tell the difference between a picture at the molecular level of salt dissolving into water and salt crystallizing out of water, that’s a great setup for entropy later on. But I can’t do an in-depth explanation of any of these things as well as Feynman can, so I’m going to stick to some fun minutiae instead.
Feynman has, in this chapter, what might be the best footnote I’ve ever seen: “One can burn a diamond in air.” No citation, no further comment beyond that. I’d like to think that he burned a diamond for the class, though I doubt it. But of course, I couldn’t just leave that alone — and thanks to the internet, I don’t have to. I give you a burning diamond, courtesy of Theodore Gray:
Feynman also notes that we can’t see individual atoms with a microscope, whether it’s a conventional microscope using visible light or an electron microscope. While it will always be impossible to see atoms using visible light (since atoms are many times smaller than the wavelength of visible light), other kinds of microscopes have gotten much better in the last 50 years, and it is now possible to get images of individual atoms using a scanning tunneling microscope. In the image to the left, every bright spot is a gold atom. This kind of imaging was done for the first time in 1981 — and won a Nobel Prize in 1986 — so Feynman got to see this before he died in 1988.
Finally, Feynman notes that some solids are actually less soluble as the temperature increases. I’ve never heard of this — does anyone know what stuff he might be talking about?
Next chapter: particle physics!