Wednesday, June 24, 2015

Feynman 7: New Laws of Nature?

And so we reach the end of Richard Feynman's famous lectures, The Character of Physical Law, a series of lectures he gave at Cornell in 1964. The six previous were:
1. In the six previous lectures, Feynman had given some descriptions of the principles of nature. But what is nature. What is the something that these are principles of? What is the energy that is conserved? What is the something that has these mechanical laws?

First, that something is matter. Feynman embarks then to give a taste of the panoply of particles that had been discovered by 1964. The "standard model" was then in process of development. In fact, I have another book of Feynman's from the 80s I'd like to blog through sometime called QED, in which he presents some of this material from a vantage point twenty years later.

"All ordinary phenomena can be explained by the actions and the motions of particles" (151). And these particles are present everywhere in the universe. The make-up of matter in far away galaxies is exactly the same as the make-up of matter here.

The many particles that have been discovered--electrons, protons, neutrons, photons, neutrinos, mesons, anti-particles, etc--can be grouped into families. Feynman describes the situation in his time as similar to that of Mendeleev when he was putting together the periodic table and scientists were locating elements on it.

He also mentions a problem that I believe continues even today, which I consider to be Kuhnian "naughty data" just calling for an Einstein or Dirac to solve. Why do so many of the equations of quantum mechanics go to infinity unless you trick them?

2. So how do you find "new laws" of nature? Feynman presents the scientific method. He is worth quoting: "If it disagrees with experiment, it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is--if it disagrees with experiment, it is wrong. That is all there is to it" (156).

One interesting feature about the development of twentieth century physics is the fact that studies were sometimes wrong and not immediately recognized to be so. That is encouraging. These individuals who developed relativity and quantum mechanics sometimes presented papers with errors. They weren't like the proofs of geometry. The greatest minds in physics often did not immediately see what was wrong with their experiments or lines of thought. They were, in the end, mere mortals.

Feynman gives a nearly straight line from Karl Popper--"There is always the possibility of proving any definite theory wrong; but notice that we can never prove it right" (157).

3. It is fun to see how Feynman suggests the process begins. First you look in an area where there are problems and unknowns. Then there is a "feeling" around, an intuitive step because you do not know exactly where to look or even perhaps what you are looking for. Let's just say this is not how a lot of people imagine science working.

As the chapter progressed, Feynman makes it clear that he gets regular mail from ignoramic crack pots like me making stupid suggestions in an area about which they are incompetent. Here are some fun quotes from the last part of this chapter:
  • "Such remarks are obvious and are perfectly clear to anybody who is working on this problem. It does not do any good to point this out. The problem is not only what might be wrong but what, precisely, might be substituted in place of it" (161).
  • "So please do not send me any letters truly to tell me how the thing is going to work. I read them--I always read them to make sure that I have not already thought of what is suggested--but it takes too long to answer them, because they are usually in the class of 'try 10:20:30'" (161-62).
  • "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" (171).
He talks about how people tell him to start from first principles. The problem here is that "all the principles that are known are inconsistent with each other" (160-61). It's easy to point out the problems (as I have)--inconsistencies, infinities--but what are you going to substitute in its place? THAT is what is important.

And there are an infinite number of possibilities of these simple types.

4. In the end, Feynman argues, the great discoverers are great guessers. He mentions Newton and Maxwell, the two first greats. Newton's laws were fairly close to the surface. Not so today. Maxwell guessed at the right answers on the basis of a wrong idea. Einstein was driven to resolve paradoxes among existing laws. Quantum mechanics was developed from two completely different starting points.

Here is another key insight of Feynman: "We must keep all the theories in our heads, and every theoretical physicist who is any good knows six or seven different theoretical representations for exactly the same physics. He knows that they are all equivalent, and that nobody is ever going to be able to decide which one is right at that level, but he keeps them in his head, hoping that they will give him different ideas for guessing" (168).

In the end, he does not believe that history repeats itself in physics. The next big discovery will not come in the way it came for Newton or Maxwell or Einstein or Schrödinger. How do you know when it has worked? "Science is only useful if it tells you about some experiment that has not been done" (164). "You can have as much junk in the guess as you like, provided that the consequences can be compared with experiment." "It is not unscientific to make a guess" (165).

When two principles work in a certain area but are inconsistent with each other, how do you find harmony, if you should? "To guess what to keep and what to throw away takes considerable skill. Actually, it is probably merely a matter of luck, but it looks as if it takes considerable skill" (166).

Feynman gives some of his guesses. Here's an interesting one: "I rather suspect that the simple rules of geometry, extended down into infinitely small space, are wrong." In other words, his hunch is that space is not continuous.

5. You can tell that Feynman isn't particularly impressed with a lot of philosophers. However, "the philosophers who are always on the outside making stupid remarks will be able to close in" eventually, as the science gets closer and closer to completeness. Eventually, the unknown of physics will become known, and then the physicists will not be able to "push them away" (173).

The chapter ends with these striking thoughts on the future of physics. "I think it has to end in one way or another" (172). "We are very lucky to live in an age in which we are still making discoveries. It is like the discovery of America--you only discover it once. The age in which we live is the age in which we are discovering the fundamental laws of nature, an that day will never come again."

"There will be a degeneration of ideas, just like the degeneration that great explorers fell is occurring when tourists begin moving in on a territory." "In this age people are experiencing a delight, a tremendous delight that you get when you guess how nature will work in a new situation never seen before." (173).

Why does it work like this? Feynman's feeling is that it is because "nature has a simplicity and therefore a great beauty" (173). Feynman, who of course was a genius the likes of which I have never met, could recognize when he had a breakthrough. "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" (171).

6. The quote at the beginning of the last paragraph is the end of the chapter and the book. Of course, again, these are arguments that have next been extended to God as the great artist and creator, the great designer.

But in my following the flow I have missed what I consider an important point. Many experimental physicists by their very personality as pragmatists may scoff at competing philosophies about what is happening. My post over the previous chapter dipped into some of those debates, which many consider irrelevant.

But Feynman makes it clear that these philosophies can actually be important. These philosophies are "really tricky ways to compute consequences quickly" (169). "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."

But it may be that one of these approaches to the data gives a slightly better way forward with the unknown. Newton's laws of gravitation worked oh so well except for this tiny discrepancy with Mercury. That gave Einstein a window to completely re-conceptualize the matter. And so, if it were to turn out that pilot waves provided a way forward that indeterminacy does not, even though the results are entirely the same otherwise, that would make it a better theory.

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