Everyone should learn the slide rule (2021) | Hacker News Reader

Everyone should learn the slide rule (2021)

scottlocklin.wordpress.com

118 pointsleonry61 comments

The article is over-the-top in lots of ways, which is a shame, because slide rules really are worth learning. I love them. Always have. I've designed several for calculations that are specific to my research field.

I would love to get my students using slide rules, but it's difficult to find physical ones for a reasonable price. Virtual slide rules, like those at http://www.antiquark.com/sliderule/sim/, are just not quite the same as a physical thing, which requires force to slide, and good light to see the details.

I miss the days when you could go into any university bookstore and find sliderules in a wide range of prices. Another fond memory is watching my high-school teacher using a broomstick to move the slider on a giant sliderule he had above his blackboard.

What do students miss, using calculators? 1. Concrete notions of the difficulty of measurement, each digit being much harder to obtain than its predecessor. 2. A intuitive feeling for the propagation of uncertainty. 3. The ability to carry the exponents of 10 in their head.

Lacking this sort foundation seems to make it hard for people to connect their calculations, or numbers they read, with reality. This makes it hard to spot errors. It also makes it hard to remember things effectively. For example, I've found that students remember the mantissa of Avogadro's number correctly to 3 digits, but they have no idea on the exponent. The same goes for the speed of light in a vacuum. These errors were rare in the sliderule age, because it was imperative to keep the exponent in your head, as you worked through a calculation.

Try nomograms instead - you can print them on paper, and they have one for just about everything. https://youtube.com/channel/UCOLYtsL4ge6QfaAvBDeG1IA

"a physical thing, which requires force to slide, and good light to see the details"

I wonder if a slide rule could be made with glow-in-the-dark materials, so it could be read even in poor light.

OK, who's going to make the under-the-scale LED lighting, and a motorized slide and then the number gets displayed in digits in an ambient display under the left bottom stationary part? A 2022 Slide Rule -- Modern Retro-Computing?

Use phosphorescence. You could extend its half life if you shield and prevent erosion, but it could cost more.

>I would love to get my students using slide rules, but it's difficult to find physical ones for a reasonable price.

What's your idea of a reasonable price? I know it's going to be a bulk pack.

This sounds like a hobby project challenge. The scales are easy to do with CNC and computers, or laser printers. You need a small bit of routing, or a rabbit plane, to make the groves to hold the slide in. The two ends. The hairline/scale is the trickiest bit because you want a leaf spring making it slide nice, but hold its position.

It might be something the folks at your friendly makerspace find an interesting challenge. I know I would, were I not having eye surgery and a month or two of "don't do anything fun" ahead of me tomorrow.

Best of luck on the surgery, and the recovery. Audiobooks and podcasts might help to pass the time. Take care.

You could also get nicely printed (engraved I think) log paper (in a number of different scale configurations) for much longer. Also from K&E. Like printed Smith charts, though, it has gone the way of the dodo - people that need one just print out a pdf.

> I would love to get my students using slide rules,

"Slide Rule Loaner Program":

https://sliderulemuseum.com/SR_Loaner.htm

You can get a perfectly good slide rule for less than 20 USD on Ebay including shipping. On Finn.no (a similar site in Norway) there are decent slide rules for half that price. A quick search of a random Craigslist, Central New Jersey also finds several in the sub 20 USD range.

Sounds reasonable to me, what did you mean by a reasonable price?

All he’s saying is that they were more widespread and generally available in places like mainstream stores and University bookstores.

Are you really disagreeing with the best possible interpretation of this?

Back in the day, when you asked an engineer, "How much is 2 x 2", he'd whip out his slide rule, and reply confidently: "approximately 3.99"

Mathematician: "3 is prime, 5 is prime, 7 is prime. The result follows by induction."

Physicist: "3 is prime, 5 is prime, 7 is prime, 9 is experimental error..."

Engineer: "3 is prime, 5 is prime, 7 is prime, 9 is prime..."

(Yeah, that old joke.)

I’ve heard the last as “9 is prime enough”.

3 is prime, 5 is prime, 7 is prime, 9 is Grothendieck prime…

The Grothendieck primes are the composites which aren't obviously divisible by 2, 3, and 5. For most people, they start at 51.

Modern "Engineer": "What's prime, a new Javascript type?"

Yep.

I interviewed a few years ago and the screener asked me what I have been doing lately and I said mostly vanilla JS and he wanted to know all about that framework and if I would be able to use react

The tech lead I was working with a few years ago was absolutely certain vanilla js is a framework. To the point he dismissed some candidate for not knowing about it. I guess he was referring to this one http://vanilla-js.com/

Vanilla JS is kinda the neutral element of the framework algebra.

A pity it is too snarky,

I agree with the thesis (it would be very nice to have children/young people to know how to use it) but the tone is too negative.

I am a big fan of teaching children to use an abacus, also.

I read the article hoping to see examples of reasoning that the slide rule instilled.

It reads more like a jealous rant than anything else. He fails to cite why those plans developments were so fast (hint it wasn't the magic of a slide rule.... It was a decade of design and test in products before the one with the name he assigned all credit to)

He also has a sort of confirmation bias here, failing to note things we could not have possibly done without computers. Try a Martian sky crane landing without atmospheric modeling ha ha.

Anyone have a reference for rules of thumb type thinking or other insights that come from slide rules?

Moreover this doc makes it more apparent how much he waxes without real references: https://ntrs.nasa.gov/api/citations/20090007797/downloads/20...

> Routine calculations were made using slide rules. More complex calculations, such as stress analysis, required Friden mechanical calculators.

Fascinating read. No the SR-71 didn't appear out of thin air in a sprint of intensity unheard of on earth to date. Turns out after the U-2 taught us so much we said let's make a higher, faster U-3 and then spent a decade on that concept in a series of designs and tests.

I really wish that this kind of cherry-picked mythos building fact wasn't what made half of what built the perception of good engineering to most of my present and future colleagues.

While this blog post is over the top, I think it is more charitably read as the real-engineer version of "your hobby project or 20 person startup is not a FAANG". Hobby projects or startups are not limited by their ability to scale with massive load spikes or coordinate thousands of code contributors, trendy solutions used by FAANG aren't going to help.

Similarly science students, machinists and most engineers working in the physical world are not NASA performing atmospheric models, they are not limited by their ability to perform arbitrary precision calculations. Giving a student a slide rule may help them build an intuition and deeper understanding than giving them a TI-89 or copy of Mathmatica.

The slide rule and the abacus both bring particular mathematical concepts to the forefront in ways that discussion alone doesn’t do.

A particular famous slide rule is the circular “flight computer” - E6B. Showing and working out why it works to do various flight calculations can be instructive.

I think that circular "computer" appears explicitly (as a photo) in the post. Thanks for the info!

Fluidly thinking of multiplication as addition of exponents is handy, but a slide rule won't do anything for that a few dozen exercises without a calculator couldn't.

Yes, me too. I bought an abacus a while ago and learned to use it, what a joy.

There are also some great documentaries on abacus education in Japan. It's amazing that the top abacus users stop needing an abacus and can do calculations just by imagining an abacus.

> It’s why engineers will do things like build a cantilever beam which requires finite element analysis instead of just building a fucking bridge.

Because bridges never collapsed due to faulty design before finite elements (Please ignore https://en.wikipedia.org/wiki/Quebec_Bridge#Second_design_an... and https://en.wikipedia.org/wiki/Ironworkers_Memorial_Second_Na... and https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940) and you get the picture).

The thing about slide rules and RPN calculators is they are “close to the calculation”. Algebraic calculators are a level too far away. So you don’t find, or notice, bugs as easily.

The same problem applies to GPs navigators and their small phone screens. You don’t actually know where you are the way you did with a big map, so can’t intuit when things go wrong (e.g. you’re in a parking lot or in construction that the mapping app doesn’t know about).

The newer systems are great for people who already understand what’s going on. But when they are the first introduction to calculating or navigating they are actually a negative influence.

Way back in the dark ages of the 1970s when I was an undergrad at a major midwestern university, I blew several hundred dollars for a brand new TI calculator. Alas, it’s use was limited to homework and we were told we could use pencil and paper or we could buy a slide rule. As some here have noted, slide rules helped develop one’s sense of magnitude and estimation. BTW, my old 50 year TI calculator still works.

Can anyone recommend a slide rule?

I recently bought a vernier caliper and prefer it over digital and dial. I feel more connected with the measurements i make, hard to describe but I suspect the idea is similiar to some of the points the author makes about using a manual slide rule.

Few weeks ago I was watching a random video on YouTube published by matthias wendel and noticed the same vernier caliper sitting on the table in the background.

I prefer duplex slide rules (they have scales on both sides), as these give a wider range of calculations you can perform. Two of the models I personally like are the Post 1460 VersaLog, and the K&E 4081-3 Log-Log-Duplex-Decitrig (that one is fun to say). Specifically the older models that are made on mahogany coated with celluloid. Also there are various Pickett slide rules that are painted aluminum, these work really well too (I like the Pickett N-600 as a pocket slide rule).

I also have a Faber-Castell 2/83n, I believe this model is Cliff Stoll's favorite one, however I find it a bit too busy for my aging eyes. It is really pretty to look at though.

Too bad there isn't a big enough market for someone to make high quality replicas of classic slide rules, with modern machining techniques. I'd really like to see some laser etched metal rules.

I came in here to mention vernier calipers, I've gotten instant respect out of more than one machinist when I pulled them out instead of the digital calipers. They're fun to use too.

Here they still make circular slide rules:

https://www.sliderule.tokyo/products/list.php?category_id=30

At $1200 for one of the cheapest ones... I think I'd rather buy used...

That's actually JPY not USD. Just noticed that when you visit the link on mobile, it shows a dollar sign instead of a yen sign.

And if you don't want to order directly from Japan, you can search for search on Amazon, here is one for 20 bucks: https://www.amazon.com/Concise-Ruler-Circular-Slide-100973/d...

There are a ton of used ones, many in near New or old stock condition, on ebay.

K&E Deci-Trig, or a Deci-Lon if you want something with a few more scales than that one. Those both give you the CF / DF "folded" scales, which are handy.

I'd recommend an Aristo 868 if not a Breitling Navitimer.

Locklin's basic point is about the important of thinking about the actual problem, instead of playing with tools further removed from the problem. And I can't agree more.

The same applies to programming, and applies more and more as we get further removed from the essential problem and the underlying system. It used to be common (appalling but common) to see knowledgeable, experienced programmers give up on trying to understand a system, and to start a cycle of just-change-something, recompile, test... Eventually they'd come up with something that would pass the test and declare the bug "fixed" (for now).

Times change. Now we've got stackoverflow and copilot ... so we've got thousands (millions) of kiddies who have little concern for the problem or the system, because they focus on plugging in some code snippet. And the odds of those snippets being inappropriate, or adding further bugs, is overwhelmingly high.

We should all be concentrating on understanding the situation and the problem, not on producing any old answer or on passing a test suite.

In university studying engineering, it wasn't important that I remembered how to manually calculate all the different types of integrals, I had my calculator to do that (thank goodness for the Ti-89 Titanium), I only needed to make sure I understood what an integral represented and why it was useful to me. A human's most powerful tool is abstraction because the brain is a limited resource. The only thing a slide rule would achieve for me is slowing me down, and wasting precious time and resources on something I already understood. The same reason applies to why I don't program in assembly, it would be a waste of my time for what I was trying to achieve even if it did force me to truly understand everything at a most fundamental level.

The Professor Herning YT channel has a bunch of videos on both using slide rules and reviews/comparisons of various ones:

* https://www.youtube.com/c/ProfessorHerning/videos

The "Practical Slide Rule" [0] and "Basic slide rule theory and use" [1] playlists are a good intro:

[0] https://www.youtube.com/playlist?list=PL_qcL_RF-Zyu6ugp3E2nB...

[1] https://www.youtube.com/playlist?list=PL_qcL_RF-ZyvJYtIr9NRX...

I recall a class in metalworking, which started with the teacher handing each student a chunk of metal and a file. The task was to file out an end wrench. The point was to teach the students the feel of metalworking before introducing them to machine tools.

The similar assignment of which I'm aware: "File a 1" cube" to defined tolerances.

The slide-rule cursor --- the usually clear plastic slider with a line from which calculations are read --- is what gave us the word "cursor" in its computer sense --- the line or box indicating the current input point on a computer, or also in a somewhat less well-known use in database applications.

https://www.etymonline.com/word/cursor

https://www.essentialsql.com/database-cursor/

It would probably be better for everyone if we learned to do math/science with the slide rule instead of a super powered HP graphing calculator. I kept my HP48GX from a sophomore in HS through university. I can’t even use a regular calculator efficiently because I’m hardwired to use the stack and RPN’s order of operation. When the 48 gave up the ghost, I bought the new primo one when I went back to school for PhD… mainly for basic calculations. I have the non graphical scientific HP calculator, but I like seeing the stack on the screen

> I like seeing the stack on the screen

So do I. Therefore I bought the DM42 from SwissMicros:

https://www.swissmicros.com/products

I still have a few of the horizontal format HPs but my 41CV died. The Swiss Micros are really tempting but I realize they'd be an utter extravagance for someone who uses the HP-41CX emulator on my iPhone to add and multiply numbers now and then.

I finally took an instrument design course and am fairly confident I can restore life to the 48GX when I open it up. And my Panasonic plasma that’s been dead for 3 years. I will hear that hum again!

https://www.youtube.com/watch?v=ZIQQvxSXLhI

Its a little off-topic, but my dad passed away last year and left behind a collection of about 40 slide rules.

Aside from his personal slide rule from university and his first job (working at ICL in Manchester designing multiplier boards for mainframes) I don't really want the rest of the collection.

Does anyone else want them?

I bought myself a 2nd hand slide rule on uk ebay last year. Price was something like £5-£10 including postage, for a rather battered and 'cheap' example.

I really liked learning about it, seeing how it worked, etc. Such an ingenious idea!

So if nothing else, it might be worth putting them on ebay - there seems to be a market for them.

Anyone have tips on learning to use a side rule?

I recommend Asimov's (yes, that Asimov) book, "An Easy Introduction to the Slide Rule." I was lucky to pick up a physical copy as a young man, but it appears it's available as a PDF online.

What a lovely recommendation. Thank you!

This seems to be a good tutorial.

https://sliderulemuseum.com/SR_Course.htm

The references others have given look pretty decent. It's not hard to do most stuff you likely have any real need to do. The main thing if you're used to calculators is that you have to handle exponents manually (in your head or on paper), your precision is limited, and you'll still need to do addition/subtraction in some other way.

Virtual sliderules may help. See https://www.sliderules.org/;

I have a 3" pocket slide rule that belonged to my grandfather.

I get the idea of there being something valuable to doing stuff manually and that corporeal activities are something that engages us humans potentially more than screens. But the rest of the article - yikes. Clearly written by a boomer that believes himself to be superior just because he grew up using tools that nowadays are mostly unknown. The article is one sided, hyperbolic, unnecessarily combative and if there is a good point in it then it is mostly lost among the author's rants. Bottom line is this: both the slide rule and CAD are tools, corporeal or not, and both serve the purpose of helping us achieve our goals. Instead of a Luddite reaction towards all things digital and a fetishization of a fucking ruler, why not use both according to the current scenario?

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