- Gravitation as an example of physical law
- The relation of physics to math
- Great conservation laws
- Symmetry in physical law
1. Most of the chapter was about the irreversibility of things on a large scale despite the theoretical reversibility of everything on a small scale. So on a small scale, "there does not seem to be any distinction between the past and future" (109). He does mention friction and beta decay as irreversible.
Perhaps the clearest example he gives in the chapter is of mixing together blue and white water. Gradually, they will combine into a whitish blue throughout the whole tank. Nothing in theory would keep it from becoming unmixed again into blue and white corners. We just know it isn't going to happen in a lifetime.
"One of the rules of the world is that the thing goes from an ordered condition to a disordered" (113).
He then hypothesizes an obscure device that might turn because of random air molecules against a vane only allowed to go one way. The illustration didn't work for me but I got the point. Eventually, heat evens out in a system and reaches equilibrium.
2. This sounded exactly like versions of the cosmological argument that I grew up with. He even mentions entropy (121), the famed second law of thermodynamics that Christians often use to argue that the universe had a beginning. Things go from ordered to disordered and the process seems irreversible. That suggests there must have been an orderly beginning.
Feynman doesn't go there. Indeed, like a novel reader, I kept waiting for the denouement. In a universe this vast, it is possible to find a small pocket of random order, but then we would expect complete bluish-white everywhere else. But we don't. So what was the order with which it all began?
3. At another point, Feynman gives us an amazing instance of the anthropic principle of which I had never heard. Apparently, it is easy to suggest how hydrogen atoms might come together to form helium atoms in a primordial soup of hot atoms. But cosmologists hit a snag when it come to the formation of larger atoms like carbon.
Fred Hoyle found a possible way. If one of the electron levels of carbon was at precisely 7.82 million volts, then three helium atoms could stick together just long enough for carbon to form. And so it was. Carbon does have an energy level in its electron orbitals that is 7.82 million volts. If it didn't, there would be no universe other than a random collection of cooling hydrogen and helium atoms (for the most part).
"The most important things in the real world appear to be a kind of complicated accidental result of a lot of laws" (122).
4. He ends the chapter with a concept he calls a "hierarchy of ideas." At the bottom of this hierarchy are the fundamental laws of nature. Then above them are basic principles like heat. Then there are bigger items like surface tension or refractive indices, properties of substances.
Still further up are waves, sun spots, stars. Then things like frogs. Then further up is history, "man," political expediency. Then evil, beauty, hope. It is here that he finally mentions God, although he does not believe that either end is truly closer to God. By implication, both ends point to God.
"The great mass of workers in between, connecting one step to another, are improving all the time our understanding of the world, both from working at the ends and working in the middle, and in that way we are gradually understanding this tremendous world of interconnecting hierarchies" (126).