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The Handheld Analog Computer That Made the Atomic Bomb

Posted by timothy on from the been-a-good-year-for-the-war-buffs dept.

szczys writes: When the physicists and mathematicians of the Manhattan Project began their work they needed to establish which substance was most likely to sustain vigorous fission. This is not trivial math, and the solution of course is to use an advanced computer. If only they had one available. The best computer of the time was a targeting calculation machine that was out of service while being moved from one installation to another. The unlikely fill-in was a simple yet ingenious analog computer called the FERMIAC. When rolled along a piece of paper it calculated neutron collisions with simple markings — doing its small part to forever change the world without a battery, transistor, or tube.

33 of 45 comments (clear)

  1. That "Made" the Atomic Bomb by xxxJonBoyxxx · · Score: 2

    >> That "Made" the Atomic Bomb

    Should be "that simulated the atomic bomb" instead.

    1. Re:That "Made" the Atomic Bomb by ArmoredDragon · · Score: 4, Informative

      Actually it should be neither. From TFA:

      UPDATE: Commentor [lwatchdr] pointed out that the use of the FERMIAC began after the Manhattan Project had officially ended in 1946. Although many of the same people were involved, this analog computer wasn’t put into use until about a year later.

    2. Re:That "Made" the Atomic Bomb by xxxJonBoyxxx · · Score: 1

      >> Actually it should be neither.

      Well, it DID simulate it. As the community is pointing out, it did its work AFTER the bomb was made, but my correction would make the headline true whether the simulation was before or after.

      Now, as for fixing the submission's harebrained summary, well I'd charge triple for that. :)

    3. Re:That "Made" the Atomic Bomb by MobileTatsu-NJG · · Score: 1

      I wish people on this site would notice how misleading the headlines are whenever there's a topic about patents. "Microsoft patents page turning on a tablet!" "OH noES!! You won't be able to turn pages on digital devices! Let's babble endlessly about prior art that has nothing to do with the specific bit that was actually patented!"

      --

      "I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)

  2. Re:Wooden calculators by glitch! · · Score: 1

    Long ago, I had a nice wooden slide rule. I still have a cheap white plastic one, but it's just not the same. Oh, well. I also have an aluminum E6B flight calculator, which is actually a circular slide rule.

    --
    A dingo ate my sig...
  3. Want to Know More? by turkeydance · · Score: 1

    The Los Alamos Primer ... https://en.wikipedia.org/wiki/...

  4. Really editors? by DougOtto · · Score: 4, Informative

    The whole article is how this device was used to build the bomb.....get to the end and they add a correction. The FERMIAC wasn't used until after the Manhattan project was completed. Basically the whole article is wrong, they said it was wrong, and it got green-lighted here.

    --
    Solving Unix problems since 1989...
    1. Re:Really editors? by Anonymous Coward · · Score: 1

      (KatchooNJ posting Anon because of mod points) True, but the FERMIAC is still interesting tech and I am glad to have now read about it.

    2. Re:Really editors? by gstoddart · · Score: 1

      Honestly, are you expecting some form of "journalism" in which the "editors" are actively involved in proof reading and fact checking?

      Because that has never been part of the job of editors on Slashdot.

      Not even a little.

      --
      Lost at C:>. Found at C.
    3. Re:Really editors? by istartedi · · Score: 1

      Editor: We have the code.
      Commander: Can you authenticate?
      Editor: Yes, the story is authentic.
      Commander: Can you verify?
      Editor: Turning key.
      Commander: WTF? The procedure is authenticate and ver--BOOM!

      --
      For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
    4. Re:Really editors? by LWATCDR · · Score: 1

      I posted the same thing on HAD. This all happened in 1946. While really interesting it is not accurate and I would have loved more details on the FERMIAC.

      --
      See my blog http://ilovecookes.blogspot.com/ for light hearted technical information.
    5. Re:Really editors? by thegarbz · · Score: 1

      Indeed. In August 1945 the Americans bombed the Japanese. The ENIAC was dismantled in 1947 to move to it's new home, and it was during this outage 2 years after the bombings that the FERMIAC was built.

      It contributed to nuclear research, but it definitely did not make the atomic bomb.

    6. Re:Really editors? by Tablizer · · Score: 1

      The ENIAC was built in 1946. So if the FERMIAC came after the first bomb, then what did they use for calculations on the first? The GUESSIAC? PAPERIAC?

      --
      Table-ized A.I.
    7. Re:Really editors? by T.E.D. · · Score: 1

      Not only that, but there were really analog computers (actual human beings with the job of making computations) that were in fact used for the project. Feynman in his first autobiography talks about getting put in charge of them.

    8. Re:Really editors? by TemporalBeing · · Score: 1

      The ENIAC was built in 1946. So if the FERMIAC came after the first bomb, then what did they use for calculations on the first? The GUESSIAC? PAPERIAC?

      Probably a slide-rule which when used correctly is highly accurate to quite a few decimal places, fast, and easy to use. And everyone involved in the Manhattan Project would have known how to use them.

      --
      Truth is like the sun. You can shut it out for a time, but it ain't goin' away. - Elvis Presley (source: imdb.com)
    9. Re:Really editors? by thegarbz · · Score: 1

      Monte Carlo methods can be applied without a computer. They are just painfully slow to do. So yes, PAPERIAC :-)

    10. Re:Really editors? by fnj · · Score: 3, Interesting

      a slide-rule ... is highly accurate to quite a few decimal places

      Bunk. A customary 25 cm slide rule is accurate to 2-3 decimal places - and that is plenty for a great many engineering tasks, such as building bridges and locomotives; hell, even B-29s. There are actually markings for 2 places, and the figure for the 3rd place is interpolated by eye. In 18th century Germany, somebody made a slide rule 2 meters long with a microscope attached to it, which could give 6 places. About the only real physical problems at the time which could even make use of that kind of precision were certain subtle astronomical calculations.

      Circular slide rules are a way to get about three (pi) times the precision for the same linear dimension by winding the scales in a circle. Mostly all they do for "normal" sizes is make the interpolation of the 3rd place a little more precise. A tradeoff is error due to the slop in the axial pivot.

      It should be well known to any high school grad, but I better mention that 3 times the precision is only about half on one decimal place. It's like the way "orders of magnitude" are frequently misspoken. I was reading some bunk about "many" orders of magnitude, where the writer was only talking about a factor of a thousand. A thousand is a large factor, but it's only three orders of magnitude. Ten orders of magnitude encompasses the difference between a large nuclear weapon and a hand grenade.

      Slide rules only give you the mantissa. Everything is normalized to 0-999. You still have to keep track of the 10s exponent in your head or on paper. It was damn good mental exercise. Yeah, I know a thing or two about slide rules since I enrolled in engineering college in 1965.

    11. Re:Really editors? by whit3 · · Score: 1

      The whole article is how this device was used to build the bomb.....get to the end and they add a correction. The FERMIAC wasn't used until after the Manhattan project was completed. Basically the whole article is wrong...

      The artcle described the use of the device in a clever "Monte Carlo" physical modeling scheme for complex geometries of multiple materials. That's how you design reactors, and multistage nuclear bombs (like the Super, or H-bomb, or 'thermonuclear weapon'). Yeah, the first three explosives (Trinity, Hiroshima, Nagasaki) didn't benefit from this particular device. The article isn't wrong, just the clickbait Slashdot title "made the atomic bomb" was an anachronism.

      Teasers are like that, sometimes. The article (and its author) are blameless here.

    12. Re:Really editors? by Tablizer · · Score: 1

      Then MONTIAC. And if you use pencil, it's PONTIAC.

      --
      Table-ized A.I.
    13. Re:Really editors? by mcswell · · Score: 1

      One of the interesting things about a slide rule is that you get appear to get fractionally more significant digits at the 1-end than you do at the 9-end. That is, it's much easier to read off 3 digits at the 1-end than it is at the 9-end. But that doesn't really represent any increase in accuracy at the 1-end, it's just (afaik) an artifact of the way base-10 works. The ratio 1.11/1.10 (3 significant digits), say, is 1.0090909..., while the ratio 0.99/0.98 (2 significant digits) is 1.010204...; the ratio of those two ratios is 0.99889807... That is, a difference of 1 in the 3rd digit of a number near 1.1 is nearly the same as a difference of 1 in the 2nd digit of a number near 0.99.

      A mathematician could probably put that more accurately, but it's sort of intuitively obvious when you look at a slide rule.

  5. Nice article but... by codepigeon · · Score: 1

    This was a nice article, but if you read to the end you will find the update that states this analog device wasn't used until after the manhattan project was over. ... So the summary should probably be updated as well.

  6. Re:MORE SLASHDOT STOOGERY by CaptainDork · · Score: 1

    It's been optimized to appeal to a like audience and stuff.

    --
    It little behooves the best of us to comment on the rest of us.
  7. Re:Special purpose calculator by Anonymous Coward · · Score: 1

    Oddly enough we're moving back to analog methods, in a fashion.

    Modern memory systems, processors, and communication links handle so much data that there is an unavoidable error rate (often dictated by the laws of physics!) that you must factor in to your programs and designs. People are turning back to old analog style methods to deal with noise.

    One of the hallmarks of an analog system is having the accuracy of your result tied to the quality of your parts. Instead of part quality you can substitute in computational power. Take, for example, a video game. On a slow cpu and gpu you can still play the same game, but you have diminished graphic quality (or frame rate. Or both) With a faster computer you have a better looking and smoother game. With analog TVs and radios having higher quality, more consistent parts would let you build a receiver with better picture quality.

    Lossy codecs like JPEG and MP4 are similar. You can reduce the bits-per-whatever to move a similar image or video with less data, and have a lower quality result. You can also affect quality by devoting more computational power at either end. (Accelerated decoding and encoding can yield a better picture with similar or even less data at the expense of needing more computational power or specialized encoding hardware)

    With huge amounts of data and very large sets, if you take a step back, the absolute sea of information has behaviors and patterns that look very "analog" in nature.

  8. Banks of women sitting at adding machines by Anonymous Coward · · Score: 3, Informative

    I thought they used banks of women sitting at adding machines, carrying out algorithms handed to them by Feynman...Fermi would do simple back of the envelope calculations, and Von Neumann would solve the differential equations in his head...

    1. Re:Banks of women sitting at adding machines by tomhath · · Score: 1

      carrying out algorithms handed to them by Feynman

      Feynman was there, he even supervised the team running the ENIAC for a while. But he was a pretty junior contributor at that point. He does mention seeing the room full of women doing calculations in his autobiography.

    2. Re:Banks of women sitting at adding machines by imidan · · Score: 1

      Well, he mentions the room full of women, and he also talks about being in charge of a group that ran problems through some kind of IBM machines:

      And so I was asked to stop working on the stuff I was doing in my group and go down and take over the IBM group, and I tried to avoid the disease. And, although they had done only three problems in nine months, I had a very good group.

                              The real trouble was that no one had ever told these fellows anything. The Army had selected them from all over the country for a thing called Special Engineer Detachment - clever boys from high school who had engineering ability. They sent them up to Los Alamos. They put them in barracks. And they would tell them nothing.

                              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.

      http://calteches.library.calte...

  9. Re:Wooden calculators by rickb928 · · Score: 2

    I still miss my old Pickett aluminum rule. Came with a hard leather case. Magnificent.

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    deleting the extra space after periods so i can stay relevant, yeah.
  10. Square Brackets by rduncan10 · · Score: 1

    I wonder why all the names had square brackets around them: [Fermi], etc. I began to wonder if there was an alternate version of the article that had a different set of names. It was like I image it would be like to read a textbook in North Korea: "Then [Glorious Leader] invented the nuclear bomb." "Later [Glorious Leader] was the first person to walk on the moon".

    1. Re:Square Brackets by joelsherrill · · Score: 1

      I wonder why all the names had square brackets around them: [Fermi], etc. I began to wonder if there was an alternate version of the article that had a different set of names. It was like I image it would be like to read a textbook in North Korea: "Then [Glorious Leader] invented the nuclear bomb." "Later [Glorious Leader] was the first person to walk on the moon".

      Cut and pasted from a wiki?

  11. Misread... by ilsaloving · · Score: 2

    doing its small part to forever change the world without a battery, transistor, or tube.

    Because of the font, I did a double-take cause I initially misread "tube" for "lube". That certainly forever changed my perceptions of nuclear physics research. :)

  12. Slide rule by jfdavis668 · · Score: 1

    When I read the title, I expected the slide rule.

  13. Re:Wooden calculators by fnj · · Score: 1

    The ones I am aware of (and owned) are all either bamboo or aluminum. Bamboo is actually a grass, not a wood.

  14. Re: Wooden calculators by rickb928 · · Score: 1

    N200-ES.

    --
    deleting the extra space after periods so i can stay relevant, yeah.