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Math Hardware

Know How To Use a Slide Rule? 388

high_rolla writes "How many of you have actually used a slide rule? The slide rule was a simple yet powerful and important tool for engineers and scientists before the days of calculators (let alone PCs). In fact, several people I know still prefer to use them. In the interest of preserving this icon we have created a virtual slide rule for you to play with." Wikipedia lists seven other online simulations.
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Know How To Use a Slide Rule?

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  • Of course (Score:4, Interesting)

    by Kozar_The_Malignant ( 738483 ) on Friday September 28, 2007 @12:51PM (#20784153)
    I did college physics, organic and physical chemistry with my trusty Pickett aluminum log-log slide rule. You needed one for real geek cred in those days.
  • back in the day (Score:2, Interesting)

    by OffTheLip ( 636691 ) on Friday September 28, 2007 @12:51PM (#20784157)
    When I took HS Chemistry a slide rule was required. The instructor spent a bit of time explaining how to use it and we were quizzed later. While it lacked the precession of modern calculators we managed to solve complex problems. My dad earned an engineering degree back in the 50's using only a slide rule.
  • Buy your own! (Score:3, Interesting)

    by PlatyPaul ( 690601 ) on Friday September 28, 2007 @12:52PM (#20784169) Homepage Journal
    In case you'd like to work with the real thing, take a look here [] for some info on places to buy slide rules these days.

    My mother recently bought one in a wave of nostalgia. I can certainly understand the physical appeal - the soft susurration of the pieces gliding against each other, the comforting grip of the leather carrying case, the art of perfectly lining up the dashes to the limits of human precision. If computers were that tactilely slick, nerds might rule the world.
  • Um No. (Score:4, Interesting)

    by VonSkippy ( 892467 ) on Friday September 28, 2007 @12:57PM (#20784269) Homepage
    I also don't know how to use a Flintlock rifle, trap/clean/spit roast a hare, catch a fish with my bare hands, hitch a wagon to a horse, or build/make/use a butter churn.

    Since I live in the 21st century, I don't really lose sleep over those things.
  • Of course (Score:5, Interesting)

    by Brett Buck ( 811747 ) on Friday September 28, 2007 @01:07PM (#20784433)
    I use a slide rule DAILY. It's an extremely useful and (if you know what you are doing) both accurate and fast. For many engineering problems 3 or 4 sig. figs. is plenty enough. The advantages are well-known - the most important being the elimination of "false precision" that you can get with a mindless calculation with a 10-sig-fig calculator.

        They are also just good things to have around. A good slide rule (Aristo, Nestler, Faber-Castell, etc) is just such a fantastically well-made device that you really need to see it to appreciate. The precision is something you don't see these days. Even a lowly Pickett is nicely made.

  • by ZERO1ZERO ( 948669 ) on Friday September 28, 2007 @01:28PM (#20784743)
    I've read the site 10 times now - I still don't get how it works. Can someone explain it please. I'm not even sure I can even comprehend the instuctions. It seems to repeat it self - put the number on C over the number on D to be multiplied. Great done that - where's my answer.
  • I feel bad (Score:5, Interesting)

    by planckscale ( 579258 ) on Friday September 28, 2007 @01:28PM (#20784747) Journal
    My dad gave me his when I was a teen and said that he had used it for many years in college and the aerospace industry (Hughes). He gave it to me as a memento, and although he didn't keep it stuffed in his ass in Vietnam, it did carry a pretty significant sentimental value. It's lost; and although I did try to use it on several occasions, I only go so far as multiplication. It was a nice ivory color and had a leather carrying case. That thing probably helped launch 20 communication satellites.

  • Re:Of course (Score:4, Interesting)

    by rubycodez ( 864176 ) on Friday September 28, 2007 @01:38PM (#20784907)
    but with a slide rule you can see a range of answers around the result for varying the factors. that process is extremely slow on a digital calculator. plus a slide rule forces you to think of the proper magnitude of the answer, with calculator people trust without thinking and "missed decimal point" or just fat-finger error gets believed more readily.
  • by Skuld-Chan ( 302449 ) on Friday September 28, 2007 @01:42PM (#20784987)
    I've always though about what would happen if the end of civilization were to occur and all your electronic gadgets (which require electricity) failed to work.

    If you wanted to rebuild society - what would you use? Yes - things like sliderules. Think of it is a method of survival, rather than - we have better why would you bother to learn how to use sliderules.

    One of the reasons I thought it was fun to learn morse code back in the day when I got my amateur radio license. Morse code happens to be the most fundamental mode you can use to communicate over the airwaves. If you had nothing, and needed to build a radio from scratch you could build a set to do morse code in an evening or two - where as something to do PSK/GMSK, FM/AM, SSB etc would take quite a bit longer.
  • Re:Of course (Score:5, Interesting)

    by Kadin2048 ( 468275 ) * <slashdot,kadin&xoxy,net> on Friday September 28, 2007 @01:47PM (#20785067) Homepage Journal
    A whole lot of engineers calculated a lot of transfer orbits (not just Earth-Mars) with slide rules. In some ways they can be a lot safer than using a calculator, since they don't give you a false sense of precision.

    E.g., divide 52 by 7 on a calculator, and it will spit out 7.428571428571, a completely correct although ridiculous answer when dealing with real-world quantities, since it blows away the precision of the input numbers. Slide rules require you to constantly consider the number of decimal places that you want, and encourage you to only write down the correct number of digits (so you might do the same result and put down 7.4).

    Personally, I think some of the best engineering ever accomplished by man has been conducted mostly by slide rules. I wouldn't go so far as to say that we've necessarily regressed since then -- computers are great, don't get me wrong -- but it's not right to simply write off slide rules. They had very distinct benefits and I think students would be well suited if they were kept around as a pedagogical tool.
  • Re:Of course (Score:3, Interesting)

    by budgenator ( 254554 ) on Friday September 28, 2007 @02:21PM (#20785623) Journal
    The thing about a slide-rule is it makes you think about the answers, so your less likely to forget to convert the acceleration of your ship, from furlongs per fortnight squared to meters per second ^2, like a certain space agency did a while back when they assumed the math was correct because the numbers came out of a computer. Slide ruler have an inherent requirment for the operator to do sanity checking, using a calculator or a computer usually means the operator doesn't even realize when the wrong keys produced outrageous results.
  • by OrangeTide ( 124937 ) on Friday September 28, 2007 @03:52PM (#20786971) Homepage Journal
    You ever take a calculator apart? They are way more complicated inside.

    What's sad is a good 4 function calculator costs 1/10th a slide rule does.
  • Re:Of course (Score:4, Interesting)

    by lgw ( 121541 ) on Friday September 28, 2007 @03:56PM (#20787029) Journal

    well, let's just say that you wouldn't want to have to calculate an Earth-Mars transfer orbit with a slide rule
    Why not - the Earth-Moon transfer orbits were calculated with slide rules originally. I didn't see any Lunar orbiters smack into the moon in the 60s! History proves that slide rules are better for astrogation.
  • by jdray ( 645332 ) on Friday September 28, 2007 @05:21PM (#20788179) Homepage Journal
    When I was in the Air Force (many years ago), I was a Loadmaster on C-130 cargo planes. Every aircraft had a sliderule as standard equipment, and we had to know how to use it to calculate load balances for the cargo, even though we used electronic calculators. The idea was that if our batteries died, we had to have a fallback. When the numbers you're dividing are seven digits for the numerator and four digits for the denominator, and your precision is 0.1, long division on a scrap of paper isn't reliable.
  • Oh yeah! Well... (Score:3, Interesting)

    by bynary ( 827120 ) on Friday September 28, 2007 @05:31PM (#20788295) Homepage grandpa just gave me the slide rule he used in school and it has a genuine "Made in Occupied Japan" sticker on the case. I can't remember the brand or model, but it's in a nice case and really is a beautiful thing. It is machined which is, according to the manual, much better than the painted ones. Just my two cents...
  • by fotbr ( 855184 ) on Friday September 28, 2007 @05:57PM (#20788553) Journal
    I'm a young'n, being in my mid 20s.

    Dad was an engineer. I learned how to use a slide rule for basic math in first grade, just because "it was neat" -- after all, if dad the engineer uses one, it must be cool.

    One of my math classes "required" a TI-82 (Jr. High), since some of the problems were of the "push these buttons in this order to graph this equation" type. After that, most kids went out and bought the latest and greatest TI graphing calculators. I was given a TI-86 when they were first released, as "the calculator that will do anything you need it to through college" by my parents. It was neat for a while, some of the games were cool, and programming in assembly for it was kinda fun - at least much more so than paying attention in Early American Literature. But I didn't use it for my math classes. I was the nerd in the back of the room using dad's old slide rule while everyone else was punching buttons on their calculators.

    I continued using a slide rule for most problems until my senior year in college, when I switched over to a TI-89 because I was extremely lazy and it made the statistics class much easier (it did all the work anywhere where we weren't required to "show our work").

    I still have it, and still use it out in the shop on occasion. My TI-86, TI-89, and HP-48G+ sit gathering dust.
  • Observations (Score:2, Interesting)

    by fishbowl ( 7759 ) on Friday September 28, 2007 @06:26PM (#20788913)
    Everyone in my school had to learn to use a slide rule.

    The main thing I notice about slide rules versus calculators, is that in many computations, the user is required to be aware of certain techniques, often involving logarithmic properties. And in many calculations, you see a *range* around a solution, not just a number popping up like on a calculator.

    Slide rule users tend to have a natural ability to estimate the magnitude of a solution, and do not find sigfigs and scientific notation (with a single digit mantissa) to be an unusual idea.

    One nonobvious consequence of electronic calculators has been to push the understanding of log properties from early grade school arithmetic, into at least middle school territory, and I know for a fact that many College Algebra students today have difficulty with logarithms. In the slide rule era, there was *no way* a student would get out of grade school math without naturally being very comfortable with logarithms, and how to relate multiplcation to the sum of logs.
  • by hedronist ( 233240 ) * on Friday September 28, 2007 @07:59PM (#20789815)
    Circular slide rules were very popular with pilots because of their compactness. Some of them had specially marked scales for doing Time, Speed, and Distance problems.

In less than a century, computers will be making substantial progress on ... the overriding problem of war and peace. -- James Slagle