Feynman the Explainer

I love stories about Feynman — probably because I love his style and try to emulate it — and Surely You’re Joking, Mr. Feynman! (Adventures of a Curious Character) remains one of my favorite books of all time.

Richard Feynman and The Connection Machine, by W. Daniel Hillis for Physics Today1, is a new story for me though:

In the meantime, we were having a lot of trouble explaining to people what we were doing with cellular automata. Eyes tended to glaze over when we started talking about state transition diagrams and finite state machines. Finally Feynman told us to explain it like this,

“We have noticed in nature that the behavior of a fluid depends very little on the nature of the individual particles in that fluid. For example, the flow of sand is very similar to the flow of water or the flow of a pile of ball bearings. We have therefore taken advantage of this fact to invent a type of imaginary particle that is especially simple for us to simulate. This particle is a perfect ball bearing that can move at a single speed in one of six directions. The flow of these particles on a large enough scale is very similar to the flow of natural fluids.”

This was a typical Richard Feynman explanation. On the one hand, it infuriated the experts who had worked on the problem because it neglected to even mention all of the clever problems that they had solved. On the other hand, it delighted the listeners since they could walk away from it with a real understanding of the phenomenon and how it was connected to physical reality.

We tried to take advantage of Richard’s talent for clarity by getting him to critique the technical presentations that we made in our product introductions. Before the commercial announcement of the Connection Machine CM-1 and all of our future products, Richard would give a sentence-by-sentence critique of the planned presentation. “Don’t say ‘reflected acoustic wave.’ Say [echo].” Or, “Forget all that ‘local minima’ stuff. Just say there’s a bubble caught in the crystal and you have to shake it out.” Nothing made him angrier than making something simple sound complicated.

Getting Richard to give advice like that was sometimes tricky. He pretended not to like working on any problem that was outside his claimed area of expertise. Often, at Thinking Machines when he was asked for advice he would gruffly refuse with “That’s not my department.” I could never figure out just what his department was, but it did not matter anyway, since he spent most of his time working on those “not-my-department” problems. Sometimes he really would give up, but more often than not he would come back a few days after his refusal and remark, “I’ve been thinking about what you asked the other day and it seems to me…” This worked best if you were careful not to expect it.

I do not mean to imply that Richard was hesitant to do the “dirty work.” In fact, he was always volunteering for it. Many a visitor at Thinking Machines was shocked to see that we had a Nobel Laureate soldering circuit boards or painting walls. But what Richard hated, or at least pretended to hate, was being asked to give advice. So why were people always asking him for it? Because even when Richard didn’t understand, he always seemed to understand better than the rest of us. And whatever he understood, he could make others understand as well. Richard made people feel like a child does, when a grown-up first treats him as an adult. He was never afraid of telling the truth, and however foolish your question was, he never made you feel like a fool.

  1. Phys. Today 42(2), 78 (1989) 

What Keeps a Train on the Track?

At first, it may seem very simply and obvious: the flange keeps the wheel on the track, right?

Nope, that’s not the answer!

To understand why, let’s first get some background on how train wheels are made:


The primary take away from the above video is that train wheels are big and come together with a joined axle — that is, they don’t have a differential. If you don’t know what a differential is, or want to be impressed by an awesome video from 1937, take a look-see as this:

That still doesn’t explain what keeps a train on the track though. If you haven’t been able to figure it out yet, Feynman will explain:

…and that’s called rail adhesion.

via Kottke

No Stupid Questions

Chauncey has left Seattle for an adventure at seminary. Thus far, I approve of his classes:

From teamchauncey.wordpress.com:

One of my professors said something yesterday that stuck with me. He said, “There are some people who say there are no stupid questions…we know this is patently untrue. However, the stupid question is not asked from ignorance on grounds of seeking understanding. The stupid question is that which is asked to make oneself seem intelligent.” We then made an informal agreement as a class to avoid such questions.

Asking questions is important; and I don’t think there should be shame or embarrassment in asking questions. If something is unclear, I think you have a duty to get understanding about it. This has been a hard thing for me to learn — and I’m still learning it. But I love asking questions and I try to make a lot of what I do about asking questions, there are very few better ways to learn.

One of the stories that has inspired me is Richard Feynman’s experience at Los Alamos. When I’m talking to young engineers, or really anybody, about asking questions, I like to recall this story. Feynman is overseeing some work at Los Alamos, helping design nuclear weapons and such:

I sat down and I told them all about neutrons, how they worked, da da, ta ta ta, there are too many neutrons together, you’ve got to keep the material apart, cadmium absorbs, and slow neutrons are more effective than fast neutrons, and yak yak — all of which was elementary stuff at Los Alamos, but they had never heard of any of it, so I appeared to be a tremendous genius to them.

The result was that they decided to set up little groups to make their own calculations to learn how to do it. They started to redesign plants, and the designers of the plants were there, the construction designers, and engineers, and chemical engineers for the new plant that was going to handle the separated material.

They told me to come back in a few months, so I came back when the engineers had finished the design of the plant. Now it was for me to look at the plant.

How do you look at a plant that isn’t built yet? I don’t know. Lieutenant Zumwalt, who was always coming around with me because I had to have an escort everywhere, takes me into this room where there are these two engineers and a loooooong table covered with a stack of blueprints representing the various floors of the proposed plant.

I took mechanical drawing when I was in school, but I am not good at reading blueprints. So they unroll the stack of blueprints and start to explain it to me, thinking I am a genius. Now, one of the things they had to avoid in the plant was accumulation. They had problems like when there’s an evaporator working, which is trying to accumulate the stuff, if the valve gets stuck or something like that and too much stuff accumulates, it’ll explode. So they explained to me that this plant is designed so that if any one valve gets stuck nothing will happen. It needs at least two valves everywhere.

Then they explain how it works. The carbon tetrachloride comes in here, the uranium nitrate from here comes in here, it goes up and down, it goes up through the floor, comes up through the pipes, coming up from the second floor, bluuuuurp — going through the stack of blueprints, down-up-down-up, talking very fast, explaining the very, very complicated chemical plant.

I’m completely dazed. Worse, I don’t know what the symbols on the blueprint mean! There is some kind of a thing that at first I think is a window. It’s a square with a little cross in the middle, all over the damn place. I think it’s a window, but no, it can’t be a window, because it isn’t always at the edge. I want to ask them what it is.

You must have been in a situation like this when you didn’t ask them right away. Right away it would have been OK. But now they’ve been talking a little bit too long. You hesitated too long. If you ask them now they’ll say, “What are you wasting my time all this time for?”

What am I going to do? I get an idea. Maybe it’s a valve. I take my finger and I put it down on one of the mysterious little crosses in the middle of one of the blueprints on page three, and I say, “What happens if this valve gets stuck?” — figuring they’re going to say, “That’s not a valve, sir, that’s a window.”

So one looks at the other and says, “Well, if that valve gets stuck –” and he goes up and down on the blueprint, up and down, the other guy goes up and down, back and forth, back and forth, and they both look at each other. They turn around to me and they open their mouths like astonished fish and say, “You’re absolutely right, sir.”

So they rolled up the blueprints and away they went and we walked out. And Mr. Zumwalt, who had been following me all the way through, said, “You’re a genius. I got the idea you were a genius when you went through the plant once and you could tell them about evaporator C-21 in building 90-207 the next morning,” he says, “but what you have just done is so fantastic I want to know how, how do you do that?”

I told him you try to find out whether it’s a valve or not.

Feynman clearly is wanting to know what that thing is! And so he asks, although in a definitively roundabout way. But he asks the question. And so should you.

Surely You’re Joking

These past few days have been mostly a blur. Studying late in to the night, getting a quick bit of sleep, and then waking up to take whatever final I might have. Only to repeat the same schedule, irrespective of the time. This has lead to some serious issues for my biological clock, thusly I really don’t have a natural idea of what day or what time it is.

And so it was just past midnight, in my somewhat futile attempt to study physics that I decided to go look up a book I’ve been meaning to read for some time now: Surely You’re Joking, Mr. Feynman!

I read the first few pages and then returned to my studies. However, I decided to take the book with me so that I could finish it off at a later point.

Well, 3am rolls around. I’ve been laying in bed for a good while now, to no avail. I pick up from where I left off.

It’s now just past 4. I’ve been reading for an hour straight. This is simply one of the best books I’ve ever read. I really wish I could have met him.

The little lady came back again and said, “Mr. Feynman, Mrs. Eisenhart would like to see you.”
“OK, OK!” and I go over to Mrs. Eisenhart, who’s pouring tea.
“Would you like to have some coffee or tea, Mr. Feynman?”
“Mrs. So-and-so says you wanted to talk to me.”
“Heh-heh-heh-heh-heh. Would you like to have coffee, or tea, Mr. Feynman?”
“Tea,” I said, “thank you.”
A few moments later Mrs. Eisenhart’s daughter and a schoolmate came over, and we were introduced to each other. The whole idea of this “heh-heh-heh” was: Mrs. Eisenhart didn’t want to talk to me, she wanted me over there getting tea when her daughter and friend came over, so they would have someone to talk to. That’s the way it worked. By that time I knew what to do when I heard “Heh-heh-heh-heh-heh.” I didn’t say, “What do you mean, ‘Heh-heh-heh-heh-heh’?”; I knew the “heh-heh-heh” meant “error,” and I’d better get it straightened out.

In writing this post, I stumbled upon http://www.gorgorat.com/, which appears to have the complete text of the book online. I would still recommend checking it out from the library though.