Lesson 6: Richard Feynman and The Manhattan Project

Many of you know what the Manhattan Project was: the American secret project to create the first atomic bombs. What you might not know is that human computers were vital to the completion of this task. Making sure they got atomic physics right required running simulations, and electronic computers like what we're used to now did not exist in the 1940s. So, human beings, then called "computers" because they performed the task of computation, had to perform the calculations for compression waves and neutron propagation by hand.


[Richard P. Feynman's ID Badge at Los Alamos, United States Army, c. 1943]

The solution came by way of Richard Feynman, a physicist better known nowadays for his excellent skills in communicating physics to students. The "Feynman Lectures on Physics" and his presentation on nanotechnology, "There's Plenty of Room at the Bottom", are both excellent examples of this. He was also responsible for the invention of the particle physics tools known as Feynman diagrams, which helped to greatly speed up progress in that field. However, in the 1940s, under cover of deep secrecy, his concerns were in getting the human computers to work together and complete tasks, without having to communicate directly besides the numbers.

Working with Oppenheimer, Feynman got the computers together and gave them the methods they would use to finish the job. As Feynman himself put it:

Then they came to work, and what they had to do was work on IBM machines - punching holes, numbers that they didn't understand. Nobody told them what it was. The thing was going very slowly. I said that the first thing there has to be is that these technical guys know what we're doing. Oppenheimer went and talked to the security and got special permission so I could give a nice lecture about what we were doing, and they were all excited: "We're fighting a war! We see what it is!" They knew what the numbers meant. If the pressure came out higher, that meant there was more energy released, and so on and so on. They knew what they were doing.

Complete transformation! They began to invent ways of doing it better. They improved the scheme. They worked at night. They didn't need supervising in the night; they didn't need anything. They understood everything; they invented several of the programs that we used - and so forth.

So my boys really came through, and all that had to be done was to tell them what it was, that's all. As a result, although it took them nine months to do three problems before, we did nine problems in three months, which is nearly ten times as fast.

But one of the secret ways we did our problems was this: The problems consisted of a bunch of cards that had to go through a cycle. First add, then multiply and so it went through the cycle of machines in this room, slowly, as it went around and around. So we figured a way to put a different colored set of cards through a cycle too, but out of phase. We'd do two or three problems at a time.

What's more, when later they were forced to focus on only one problem at a time, to meet Army deadlines on very short order, Feynman discovered the computers working on multiple decks of cards like this again. At first he was furious, but then he realized they were all actually one set of problems, just re-done in different pieces on multiple sets of cards.

The reason was that manual calculations like these have errors. There were problems with the mechanical machine, or an operator would put wrong numbers in, and the output would be wrong too. This would normally not be a problem, as you could just notice the error and correct it, but as these errors were propagated for a while before anyone would notice what went wrong, the changes would affect cards in the set that were near the position of the error in the first set. So, to get around this, the computers were running the same calculations over again, and finding out where something went wrong with a run, and stopping that run to switch over to the corrected one.

That was the way those guys worked, really hard, very clever, to get speed. There was no other way. If they had to stop to try to fix it, we'd have lost time. We couldn't have got it. That was what they were doing.

Of course, you know what happened while they were doing that. They found an error in the blue deck. And so they had a yellow deck with a little fewer cards; it was going around faster than the blue deck. Just when they are going crazy - because after they get this straightened out, they have to fix the white deck - the boss comes walking in.

"Leave us alone, “ they say. So I left them alone and everything came out. We solved the problem in time and that's the way it was.

After the war, Feynman would go on to invent the Feynman Diagrams, perform his famous lectures, and spoke about a rather interesting sort of future computer, a quantum computer, that could get around a problem he saw in simulation space. Ordinary digital computers can only calculate quantum problems numerically, and the limitations on this require a large amount of computational power to simulate a handful of particles. But what if the computer itself ran on quantum principles? Then, Feynman proposed, you could calculate using a much smaller computer, one approaching the size of the quantum systems you were trying to simulate. His keynote lecture at "The Physics of Computation" MIT Conference in 1981, covered this topic at length.

If you're interested in learning more about physics, and in particular computer physics, I encourage you to look up Feynman's lectures on physics and on computation, many of which are available online in one form or another. They're a very good read, or when available, a good listen too. You'll learn more than you ever expected to.


Microsoft Research Blog, Celebrating Richard Feynman at TEDxCaltech, February 4, 2011, Retrieved from https://www.microsoft.com/en-us/research/blog/celebrating-richard-feynman-at-tedxcaltech/ on May 19, 2017

Richard Feynman, Los Alamos From Below: Reminiscences 1943-1945, University of California at Santa Barbera, 1975, Retrieved from http://calteches.library.caltech.edu/34/3/FeynmanLosAlamos.htm on May 19, 2017

Exercise: Quiz Yourself (Feynman)

After reading the above history (or reviewing again now), ask yourself the following questions about what you read, and make sure you know how to answer correctly.

  1. What was a vital physical phenomenon that Manhattan Project computers had to simulate?

  2. What was the physics tool Feynman is famous for inventing?

  3. What method did Feynman's group use to solve simulations more rapidly?

  4. When the Army insisted they finish a vital problem in a very short time, how did Feynman's team do this effectively?

  5. What lecture did Feynman give to the computers to get them more interested in doing their work?

  6. What was the purpose of the Manhattan Project?

  7. What was the name of Feynman's presentation on nanotechnology?

  8. What purpose did Feynman suggest for quantum computers?