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Illustrated Self-Guided Course On How To Use The Slide Rule (sliderulemuseum.com)
363 points by ngram 11 months ago | hide | past | favorite | 98 comments

What a blast from the past. I can draw a direct line from my encountering a slide rule to ending up as a programmer. I owe my career to that device.

I was a nerdy 10 year old kid who liked doing arithmetic in 1970, but didn't know anything particularly advanced. I convinced my parents to get me a slide rule as a Christmas present that year; a basic white Post model 1447 - I know that because I'm looking at it right now. It's been in my desk drawer forever as I could never convince myself to throw it away, even though I've long since lost the sliding cursor.

Anyway, I got the slide rule, had fun with basic multiplication/division, but didn't understand what the S, T, and L scales on the back were for. Sine/Tangent/Logarithm? What are those?

Off to the library, where I picked up a Tutor-Text book [0] on trigonometry, discovered I'd better first learn some algebra, picked up another Tutor-Text book on that, and began a two-year tear teaching myself algebra to integral calculus. Which meant I tested out of a couple years of math in high school, ran out of courses to take, and in my junior year was allowed to walk to the local college to take 2nd year Calc classes.

At that college, they started letting me play with the computers, both an IBM 5100 APL machine over one summer, and hands-on access to the IBM 11/30 clone minicomputer that was the main machine. The math prof pointed me at Knuth's "The Art of Computer Programming", and that began my transition from pure mathematics to computer programming/science instead. I even wrote a MIXAL assembler/MIX simulator for the minicomputer that the college ended up using to teach an assembly language course.

So thank you, Post, Pickett, K&E! And Tutor-Text as well.

[0]: https://gamebooks.org/Series/457/Show

Similar background story, I was 8 in 1970, and my father knew what a slide rule was, and how to use it, so I learned a bit of trig from him before repeatedly checking out a textbook on trig from the public library.

True story: my son took an AP physics class in high school, (LASA) taught by sokeone with a PhD in physics. They had an oversized teaching sliderule hanging from the ceiling, where nobody could use it. It had become decoration, as nobody was left to teach with it.

When I was at the school for a “meet your student’s teachers” night, one of the other parents asked about the side rule. Instructor didn’t know how it worked.

So I explained it.

My wife still has her grandfather’s slide rules from when he was the state engineer in the 50s and 60s.

I remember those large teaching slide-rules, but haven't seen one in decades. Great to know they still exist, if only as mysterious artifacts from the dark ages.

Neither of my parents were mathematically inclined, but they were content to let me forage for information on my own, with lots of trips to the library. Amazing how clear are my 50-year-old memories of 10-year-old me sitting on the floor with a trig book, drawing random triangles on paper, measuring them as carefully as I could with ruler and protractor, and verifying the law of sines and cosines with paper and slide-rule. God, I was such a nerd. Paid off well in the end, though :-)

Now I'm retired, and for fun, I work my way through the problems at Project Euler. Four years in, and only two more problems to go to hit 90% complete! It'll probably take me another year+ to finish them all (hopefully).

We end up doing a lot of back-of-the-envelope calculations for various odds-and-ends. I keep a 4’ long teaching slide-rule next to my desk for this purpose. New employees are befuddled. Everyone else just accepts it as a fact-of-life when asking for my help.

I love your story. Thanks for sharing! I think we could have way more stories like this if we were able to provide more enriching environments for kids and properly nourish their curiosity. I think so many young kids love asking questions and the adults around them get fed up with the questions instead of engaging with them in the process of discovery.

Not to mention schools using grades, signed slips, and other extrinsic motivators to encourage conformity and obedience, all the while extinguishing any intrinsic motivation, like curiosity.

I'm sure the way schools look made a lot of sense in the time of industrialisation and the manual labour of the factory worker, but it's crazy we still shape students by that mould when it's so far removed from the creative pursuits we expect them to go on later in life.

“Signed slips”... our son turned 18 half-way through his senior year of high school. So I explained that he could now sign his own excuses for being tardy, and no actually explanation was required.

“Please excuse <name>, I am tardy.” <signature of name>”

If signed slips are ever needed with my children, I plan on doing what my parents did for me: teach the children to self-sign from day one. Their responsibility, their signature.

> So thank you, Post, Pickett, K&E! And Tutor-Text as well.

I didn't even grow up in this era and I keep buying stuff from eBay purely out of fascination for old ways of doing things. These names on all kinds of things I have horded - architectural templates, drafting machine, cutting mat, compass set, lettering templates, etc.

Thanks for sharing your story!

Thanks for sharing such a wonderful story. Something tells me your career path wouldn’t have changed significantly if you had never touched a slide rule, though :)

Not in quite the same way, but I was inspired by watching Apollo 13 as a kid. I felt like the heroes were the engineers who could do the math and calculate the trajectories and work out the procedure for starting up the LM with low power. I was drawn to the engineering side of software by that. I keep an antique slide rule and some other old engineering instruments on my desk as a reminder of that inspiration.

I went through a very similar evolution, starting with slide rules, at about the same time. You don't mention middle school and high school -- I was very fortunate in having access to Wang and Monroe programmable calculators, and then a PDP-8M.

Still have a few slide rules, includingn Pickett and K&E.

One under-appreciated aspect of a slide rule, is for instantly seeing fraction reductions at a glance. For example, lets say I want to find out what aspect ratio a given screen resolution is at. I can set that resolution as a ratio on the slide rule's C/D scales (i.e., 1680x1050 becomes 1.68 one C, lined up with 1.05 on D. Then I glance over, and see immediately that is 16 x 10 resolution.) If the value goes off the scales, look up to the CF/DF scales.

This is also great when you have a bunch of resistors and capacitors, and you need to build a circuit where the two are at a particular ratio. Set the ratio you want, then you can take whatever resistor you have, and see if you have a cap that is "close enough" to what you need.

Also ratio multiplications, e.g. when increasing the amounts of ingredients in recipes to match a particular amount of something.

So if the primary ingredient is chevre cheese, the recipe calls for 180 grams, but you can only buy it in 250 gram packages, you can set the slide rule to "180 over 250" and then just mechanically read off the proportionally correct amounts of all other ingredients.

Slide rules are indispensable in the kitchen to me and I'm surprised they're not part of standard kitchen equipment like e.g. scales.

Edit: Similarly, if the recipe is expressing ingredients in US units and you would want to know the international amounts, you can set the slide rule to the conversion ratio and again, mechanically read off the correct amounts as you go.

This is one advantage of the customary (English language non-metric) units: the common ones are full of rational factors (1/2, 2/3 etc) — it’s pretty easy to adjust a recipe to the number of people.

Seems to me that you could place tickmarks or colored dots or something, at the E12 values along one scale (where resistors are usually binned) and the E6 values along the other scale (caps are usually sold in E6), and then it'd be an even quicker glance to see where two line up.


Figuring out that 1680/1050 ≈ 16/10 might not be the best example ;)

Yes, I was trying to think of something real quick, so I picked the resolution of my (older) monitor at work because it was simple. You caught me!

> This is also great when you have a bunch of resistors and capacitors

Yes! This is the sort of thing my Dad used them for (see my other comment here for the context)

A few years ago I met Fred Haise Jr and got him to sign one of my Slide Rules. He was so excited to see it, took it from me, and started to show the event host how to use it!

He asked me what I use to lubricate it, and when I said "Pencil graphite" he got even more excited. Apparently a lot of the other astronauts had used fancy light lubrication oils, but he always used a pencil and never had any problems.

He was a lovely man, and it was fabulous to enthuse with him over this wonderful piece of technology.

Powdered graphite is an excellent lubricant that doesn't attract crud. My father had a little squeeze tube of it for locks; it eventually ran out and I haven't seen any more since.

You can find the small tubes at hobby stores, with the supplies for Pinewood Derby cars for Cub Scouts. I went through several tubes during my son's years in Scouts.

You can also get it at hardware stores for lubricating locks.

The versions for lubricating motorcycle cables are finer and less messy than the cheap stuff they sell for locks. If you want to be neater with your slide rule, anyway :)

As someone who grew up in India in the 20th century: slide rules are unfamiliar, but we used log tables (calculators of any kind were prohibited through high school and standardized tests). For those unfamiliar, log tables serve to replace multiplication/division of floating-point numbers with addition/subtraction instead, making scientific computation a lot easier.

The main benefit of introducing this friction, rather than allowing calculators, is that it (a) encourages one to do simple calculations by hand, and (b) gets one in the habit of quickly double checking that log-table-based results fall in the correct ballpark. Calculators induce a sort of mindlessness where glaring orders-of-magnitude errors pass us by since we expect the machine to get it right.

With all that said, I don't know that I would recommend the use of log tables to high schoolers in the 21st century. That effort might be better utilized on more pressing needs e.g. statistical literacy. Many folks (including me) got entirely through STEM-focused high school knowing not even the slightest basics of statistical inference or causality.

I think that learning how to use a log table might cement certain relationships for more advanced students. But I do agree that in general there are probably better uses of one's time than to teach them as a first class citizen.

Another great thing about slide rule days is that results are naturally constrained to 2 or 3 significant digits, so you'd never see nonsense like "The mountain is 10km high, or 32808.4ft" as if the 10km figure was accurate to 6 significant digits.

I still remember the day I found out the "98.6 degrees" human body temperature was just an oversignificant conversion from "about 37 C, or maybe lower."

> I still remember the day I found out the "98.6 degrees" human body temperature was just an oversignificant conversion from "about 37 C, or maybe lower."

Really? According to Wikipedia, the Fahrenheit scale (https://en.wikipedia.org/wiki/Fahrenheit#History) is about 18 years older than the Celsius scale (https://en.wikipedia.org/wiki/Celsius#History), and I'm surprised that human body temperature wasn't included as a calibration. (But of course the fact that I'm surprised by it doesn't mean it isn't true!)

Fahrenheit was initially intended to have 96°F be equal to body temperature (in fact it was one of the three fixed points in the temperature scale, designed to have 64 steps between the freezing point of water at 32°F and human body temperature).

However after the introduction of Celcius, Fahrenheit was redefined slightly (with the freezing and boiling point of water being the fixed "nice" values for the scale -- to match the model used by Celcius) which resulted in human body temperature no longer having such a nice value. This also moved the 0°F value. So while technically Fahrenheit does predate Celcius and it did have a "nice" value for body temperature when invented, it was soon afterwards redefined such that arguably the value is just a conversion from Celcius.

In short, you're both correct. :D

Why did they come up with 96 instead of 100, a nice round number?

Imagine you've just made yourself a thermometer by marking off the 0° and 100° points. Now delineate the 2° intervals, using only the tools you would have had available in the early 18th century.

Now imagine making a thermometer by marking off the 32° and 96° points (64° apart). Now delineate the 2° intervals.

Considering those two tasks, 64 seems a much better number to me (only have to divide unit lengths in half) than 100 (have to divide something by 5).

Great explanation, thanks.

Sounds like the motivation was powers of 2, not 10.

Could've sworn I remember hearing in grade school that one of then was actually calibrated with cow body temperatures. Don't remember which scale, though.

I've definitely heard that as well.

Where it comes from, I think, is that cow body temperatures are about 100°F, and someone assumed that the scale must have been calibrated using 0° and 100° as specific endpoints.

According to Wikipedia, Fahrenheit seems to have chosen 32°F as the reference point for the freezing of water [it's not clear why this number specifically], and found the body temperature of a human to be 64° more than 32°F [i.e., 96°F]--it being much easier to divide a unit distance in 64 = 2⁶ than to divide it in 100ths.

That does bring up an interesting point, though: while we modern people may think of the metric, base-10 system as being much easier to work with since it's all about lopping off digits, trying to divide a unit length into tenths with high precision is actually far more difficult than halves or thirds. This is why pretty much every customary system involves a lot of units that are twice or three times the next smaller unit. The metric system isn't really feasible until you get the dividing engine [1], which doesn't show up until about the 1760s.


Your [1] seems to be missing.

> This is why pretty much every customary system involves a lot of units that are twice or three times the next smaller unit.

I think easily of units that step up by a multiple of 6 (inches and the various time steps), but nothing immediately occurs to me where one unit is directly twice or thrice another. (Oh, except tablespoons, which are three teaspoons.) What examples am I missing?

Unnecessary accuracy is technical incompetence.

I think you mean precision in this case. If you're going to be all high and mighty you should probably get your facts correct.

Alas! No specific mention of the circular slide rule [0]. I have one in my desk drawer that I inherited from my dad - who used it in the 1970s to confirm his hip hacker credentials to his colleagues (they were building the control circuits for early radio-therapy machines in a cancer research institute).

[0] https://americanhistory.si.edu/collections/object-groups/sli...

Circular slide rules tend to have smaller scales which may be harder to read but being circular has a great advantage. Look at how much effort in the OP is devoted to cases where the answer would ordinarily be off the end of the scale.

I was curious about circular slide rules, and found one on eBay for a few bucks, so what the heck. It turned out that it was a give-away from a company that used to be in my town, so I ended up having a nice conversation with the seller about his history with the company and so forth. He was a long retired engineer.

Anyway, I started playing with ratios, and noticed that the thing is inaccurate! Further inspection and hypothesizing led me to discover that the scales were not printed concentrically with the mechanism. It's very slight, and not critical to my work in any way, so I treat it as part of the learning experience.

Still very much in use: the E6B! https://en.wikipedia.org/wiki/E6B

My dad was a USAF fighter pilot; he kept his in-flight circular slide rule around for years. Unfortunately I didn't see it around when clearing out the house out after he and my mother died; I know I'd have kept it (because I've still got my yellow Pickett aluminum Model N-500-ES, © 1962).

Slide rules to calculators was an incredibly fast technology transition for the sort of people who would have been using slide rules in the first place.

A 5-function calculator was about $100 in 1974 (so about $350 in current dollars) and an HP scientific calculator was 3 or 4x as much. By about the next year, a TI scientific calculator was about the same and by a year or two later you could get an HP--which was the gold standard for about the same amount.

And that was around the price point where making them not just OK to use but mandatory was reasonable at least in higher ed. I was one of the first classes in college where calculators were the norm and slide rules were maybe something you brought for backup at exams. (Calculators were still LEDs so you had to keep them charged.)

One of the nicest things about a slide rule is, you can easily see the sensitivity of the result to variations of your last input.

With a calculator, you get precision. With a slide rule, you get a value and its sensitivity.

One unexpected advantage in some circumstances of a slide rule over current portable computing devices is that it does not have memory.

You are allowed to bring a calculator to ham radio license exams in the US, but you have to clear its memory (both data and program memory for programmable calculators) first. If the examiners aren't sure you have done so, they are supposed to disallow the calculator.

Unlike many other standardized tests, there is no specific list of what calculators are allowed. I brought my HP-15C, but wasn't sure that the examiners would be familiar with it and so wasn't sure I'd be able to convince them that I had cleared it.

I also brought a slide rule. That way if the examiners disallowed my HP-15C I'd still be covered.

They did allow the HP-15C, and it turned out that even though I took all three exams (Technician, General, and Extra) that day, I only actually used the calculator once. The questions are all multiple choice, and there was only one where a quick mental approximation wasn't enough to identify the right answer.

Nitpick: a slide rule does have memory, but it is small and gets cleared when doing computations. One typically can store one number by moving the slide and another one by location of the cursor.

It also is fairly hard to hide the fact that the memory isn’t cleared.

Many slide rules also have some read-only memory, for example ’storing’ the constant π.

The “E6B Flight Computer” is a slide rule designed to perform various navigation calculations and is still a part of flight training for many pilots today. Once mastering it the old way student pilots are then allowed to use electronic versions or iPad apps that do all the calculations instantly.

When I was in university, if you forgot your slide rule at an exam they kindly had a supply of log tables you could pick up from the proctor.

Cool, now I finally know how to use this rule that I got when me and my siblings were clearing up the family house after my parents passed away.

It's really fascinating, I will show my nephews when I am back in the home country :)

Thanks for posting!

Circular slide rules are still used today in aviation in the form of the E6B flight computer.


Back when slide rules were still widely used and even after calculators had recently come in, you also saw a lot of industry-specific cardboard sliding scales that were basically slide rules with different types of units.

Oh this is wonderful. I first learned about slide rules from a math teacher back in junior high. I wasn't until a few years after that that my little sister gave me a slide rule for Christmas. \o/

After graduating high school I spent two years in Germany. Whenever I found a flea market or an antique store, I'd search for slide rules. I found two that were in pretty good condition. People always seemed a little confused as to why I wanted these. I guess they just didn't see the beauty in these simple, elegant devices.

I've been trying to figure out how to use my grandfathers Dietzgen Maniphase Multiplex Decimal Trigtype Log Log rule. I found the manual on this site! Very cool!

I'm old enough that I had a slide rule when I was in school. Everyone did. They were built in to our pencil boxes.

Most of us didn't use them, except the fancy-pantses who also insisted on using mechanical pencils. But we all knew how to use them.

I'm graybeard enough that even through college, electric calculators were prohibited in class because they would give you answers without helping you understand the problem.

I graduated in 2009 and in my engineering courses calculators were disallowed for similar reasons. I have found that courses that disallow calculators generally have the problems set up in a more elegant manner. E.g done properly the results end up in whole numbers or radicalize well rather than just an incoherent string of decimals. Courses that were focused on physical phenomenon like device electronics allowed calculator use because multiplying with Planck's constant by hand gets old quickly.

> answers without helping you understand the problem

This is my problem with common core math. It shows how to get to an answer, but I feel it bypasses fundamental understanding on why the answer is what it is.

"Common core" can mean different things to different people. When my kids were in grade school, I found that a few states have put their common core standards in fairly readable form. My impression is that common core is remarkably similar to what my siblings and I learned in K-12 math class. It actually led me to wonder what all of the fuss is about.

The main thing that seems to be lacking in K-12 math today, is proofs. Those were my favorite part of math.

With that said, K-12 math teaching in my generation wasn't all that successful.

I feel that common core focuses more on teaching the various methods than embracing the idea that correct answers and understanding are largely what matter rather than any specific method.

> correct answers and understanding

It's natural to lump these together as if they are a unit, but I think it's important to be explicit about the fact (which of course you know) that they are all too easily separable: it is incredibly easy, given sufficiently powerful tools, to get correct answers with little to no understanding. True understanding (not just "oh, I think I get it") that doesn't help to get answers is not nearly as common, but of course it exists, too.

Yes I totally agree with your sentiment that it is vitally important to separate the correct answer from the method by which it is achieved. Honestly understanding mathematics is more important at some level than getting the right answer to a particular problem. That's the whole point, once you understand the grammar and vocabulary of mathematical thinking you can attempt to solve problems that are totally unrelated to things you know and still sometimes get useful results. The overwhelming question of the ages is how do you teach with that goal in mind and take account of all of the different learning pathologies while doing it in a universally accessible and measurable way. I think the problem is intractable as it is currently being approached.

That's hardly a new thing with common core. See Tom Lehrer's "The New Math."

"...But in the new approach, As you know, the important thing is to understand what you're doing, Rather than to get the right answer."

Interestingly that song is apparently about the first time they tried to massively redesign the mathematics curriculum based on on fuzzy math that we were falling behind the Soviets or whatever. My parents tell me they rebased around set theory early etc but it foundered on nearly the same rocks that common core mathematics is now - teacher must be well educated in the pedagogical paradigm and fully understand it. E.g. you can't just take the same set of teachers from math v1.2.1 and slam them into math v2.1.0 or whatever without significant issues the two approaches are not abi compatible. That's why in my with opinion common core we are seeing teachers test finding answers via method 1 specifically or method 2 specifically rather than encouraging the use of either to get a correct answer by an understood method. /rant

That all sounds about right. The song was from around the time I was in elementary school.

I suspect that part of the problem is that teaching math concepts is at least somewhat orthogonal to drilling kids on being able to perform basic arithmetic operations fluently. Of course, these days I assume at least some of the debate probably gets into the fact that being able to do, say, long division quickly has about the same utility as learning Palmer script.

In an era marked by renewed interest in vinyl records, shouldn't there also be a corresponding interest in slide rules?

I dunno, man. I'm pretty well-versed in math and I find this page kind of baffling. I'm sure it's one of those things that is very easy to use once you learn it, but at least this introduction is very daunting. To do a basic multiplication (step 1 in the linked page) I need to use the C and D scales, each for two different purposes. Why not A and B? How do I remember it's C and D? Which part goes on C and which part goes on D? Then step 2 describes what to do if it goes off the edge of the scale, and it involves making an approximation. How do I know how accurate my approximation must be? Why is it to the tens digit? If I get larger numbers do I continue to use the tens digit, or some higher factor? We're only on step 2 and I'm already lost.

This definitely looks like a great tool, and I'm kind of sad I don't have one or understand how it works, but this kind of complex learning and memorization up against dropping a needle on a record you like isn't really a great comparison.

It works better if you know how the scales are constructed and get familiar with properties of logarithms (mainly variations on log ab = log a + log b)

C and D are plain log scales, where one decade is the length of the rule. They're sort of the default scales to use.

Multiplication is commutative, so you put either number on either scale. The important thing is that the distance from the left index of the scale is proportional to the log of the number (reading the scale as 1 to 10), so you want to arrange the scales to add the lengths corresponding to your numbers such that the lengths add up. (Or so that you subtract the length of the divisor from the dividend, if you're dividing).

You can get by without the approximation if you're willing to set up the multiplication, see that the product is out there in thin air, then move the slide to put the right index where you originally put the left index. (3 times 5: on the d scale find 3 and put the left index of the C scale there; opposite 5 on the C scale read nothing because there's no D scale there; try again using the right index of the C scale, which is the same thing as having another copy of the D scale out there to the right where the air was).

A and B are each 2 copies of a log scale. You can absolutely use the left side of A and B for your numbers to multiply, and the product will always be on the scale.

People normally use(d?) C and D because the precision is better and because the rest of the scales (like the trig and log-log) are constructed to work with them.

Nit: while multiplication is commutative, the property you meant to use was symmetry. I'm sure it was a mistake and you know this, I'm just pointing it out to prevent confusion for others.

Edit: s/competitive/commutative/

Huh. I heard (US high school algebra in a recent unspecified century) the fact that ab=ba called "the commutative property of multiplication", and the "symmetric property of equality" meant a=b <=> b=a, and didn't run across anything later on (comp sci from a department of the engineering college rather than the math department) inconsistent with that. Symmetry sounds like a reasonable term for both, but it sounds like there's a distinction I don't get?


> In mathematics, a binary operation is commutative if changing the order of the operands does not change the result.

Are you saying you disagree?

No, I had a brainfart and was thinking of associativity. I have no idea how it happened. Very embarrassing.

Don't be fooled, slide rules are really easy to use. It took me less than a minute to learn how to do multiplication, and I wasn't an adult yet.

The A/B/C/D names are from Amédée Mannheim, who in 1851 designed the "modern" slide rule & give those scales those names. In practice, you normally just use the C & D scales when you want to multiply. Here's a history of the "cursor" on a slide rule, that also provides a clear history of the slide rule itself: https://www.nzeldes.com/HOC/Cursors.htm

I've never had a practical reason to use a slide rule over a calculator. But I've had fun with them, & that means something.

A lot of slide rules have a bunch of scales but there are only a few you routinely use. Using a slide rule is very easy to pick up. That said, you do need to handle the order of magnitudes mentally and precision is necessarily limited.

And slide rules don't do addition or subtraction.

So they were useful in the absence of calculators as a way to avoid using log and trig tables but you wouldn't realistically use them in place of calculators today. (But then I think vinyl records are pretty silly too; and I say that as someone who grew up with them and actually owns a turntable.)

12 years back, I saw a site peddling a story about slide rules forgotten in a warehouse for 40 years, even apologizing for dog eared boxes. They said they promote skills athropied by calculators.

Our math teacher, a former engineer, once brought his slide rule to class when we were in grade 9. He posed a problem and raced us to the solution, slide rule vs. calculators. He beat us all...

I actually spent a bit of time learning about Slide Rules a few weeks ago as my Dad had put together a very cool interactive slide rule in JavaScript that I wanted to have a play with.


One thing that struck me was that it does require a good instinct for the magnitude of numbers to use. Lots of fun though and surprisingly quick to use.

Simply put, I love a slide rule. My dad gave me mine for my 17th birthday, 48 years ago and I’ve treasured it ever since. It’s the Pickett trig model and it served me well into my 3rd year of college as a EE. Its simple to use after you’ve been trained and totally reliable. It can also be quick as your skill using it develops. It sits in a drawer today but I take it out occasionally to play with. It truly is like a friend.

There's a 'Professor Herning' whose YouTube channel has both good tutorials on their use, as well as comparing many models (and the various scales they have):

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

Being in Junior College in 1973, some of the kids had 4 function calculators hanging off their belt. The rest of us in a tech track usually carried a slide rule.

I did take a technical math class that involved programming a desktop calculator. Basically the first programming class I had.

I wish I remembered what brand it was, I'd like to try to pick one up if I could find one.

I think practice with a slide rule also gets you to sanity check your method and think whether the answer can be correct.

Given how you could forget and inadvertently reverse the scales, etc, you have to think whether the answer you're getting makes sense by looking at the trend of the numbers. Plug and chug into a calculator takes some of that away.

I'm of the generation that missed out on slide rules by a decade or so. My parents had one thta i played with as a kid, and I learned to do multiplicication and division with it.

I'd like to get one now, mainly for fun, but if you want to buy one on Ebay in good condition, you have to pay quite a bit of money.

Plastic "student" slide rules are cheap on eBay. But, yes, quality K&E's etc. are expensive.

Since this is something I want to keep on my desk, not only for decoration but for actually copute things if I'm bored, I really want tone of the nicer ones.

It seems around 35 EUR is a normal price.

Quality slide rules probably cost a lot more than that when they were still being manufactured :-)

Quality K&E's were never cheap :-).

Seems to me that this is also a lovely use for a desktop laser cutter. Dig out a copy of Pynomo or something and make your own scales that suit whatever specialty application you have in mind.

Came here to say nomograms are slide-rule-adjacent.


One of my favorite scenes in "Apollo 13" has a CO2 hazy Jim Lovell asking Houston to double check his math, and it cuts to a room full of engineers as they all grab their slide rules to calculate the answers Jim had just done in his head/scratch pad.

My Dad, an engineer for GM/Cadillac, gave my brother and I each a slide rule back in the 60's. I remember marveling at the precision of it, and I did learn to use it for some calculations, but not to a level that impressed him :).

I love playing with slide rules because it wraps my brain into using logarithms everywhere.

The game of Go also redecorates my thinking, in a way I cannot put into words.

Slide rules!

Also check out the quarter-square method and prosthaphaeresis.

Fascinating near invisible yet very high abstraction.

how eccentric! would much rather prefer a yt vid / tutorial pls.

I think the preference is age related: Personally I prefer text over video, as I can process it at my speed, while with video I'm limited to the speed with which it's explained.

My children all seem to prefer video.

> I think the preference is age related: Personally I prefer text over video, as I can process it at my speed, while with video I'm limited to the speed with which it's explained.

> My children all seem to prefer video.

When I ask for text transcripts of our training videos, in place of having to sit through 20 minutes of poorly acted out skits (that, re-certification being a periodic thing, I have sat through some 5 or 6 times already in my 10 years on the job), I am always told "but people enjoy the videos"—as if providing transcripts were somehow exclusive of providing videos.

You're almost certainly right. I hate searching for info on something that could be easily explained in a paragraph and maybe a screenshot and instead I have to watch through some video--usually with an ad. I confess that I really resist making videos of things unless I have no choice but I know a lot of people prefer them.

A well-written and illustrated explanation like this one? I can't imagine preferring a video unless someone just wants some background noise and they don't really care about understanding the subject.

Such tutorials are readily findable by searching for "slide rule tutorial" on YouTube.

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