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« Idiotarians Gone Wild | Main | The Story Changes Again »

The Noble Slipstick

I was the last of my generation to use a slide rule in college. Scientific calculators had just become affordable during my sophomore year, and the sound of keys clicking during a physics exam was pretty intimidating to those of us still sliding bamboo or twirling plastic.

I think that the younger generation has lost something in not learning to use one--it gives you a powerful insight into the nature of logarithms and mathematics in general, and it enforces an intuitive feel for orders of magnitude, because it doesn't keep track of the decimal point for you. I recall grading exams as a TA that had utterly absurd answers on them because someone made a mistake on their calculator and didn't bother to check it for reasonableness (example: the diameter of a copper atom is 1.3 x 10^12 meters...)

Anyway, they're no longer manufactured, but predictably, people still collect and use them.

[Update on Monday afternoon]

Bill Simon (not the one who ran the incompetent campaign against Davis--the one who is my site designer) sends me a link to a virtual slide rule that really really works (for those who don't even know what one looks like). It's also the most precise slide rule ever designed.

Posted by Rand Simberg at July 13, 2003 10:54 AM
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Rand... I'm shocked...

Not manufactured? Sure they are.

I only know 2 pilots who were allowed by their CFI to use their electronic ones in training.

But I've seen many of them in stores, dollar stores, etc.. Made in China, natch, but even if those have stopped - there are plenty in use. :)

(I had one when I was growing up, it still didn't help my understanding of math much, it does a little bit better now... but then, I don't have a lot of call for it these days, either... cept for the above link. :))


Posted by Addison at July 13, 2003 01:16 PM

*(I might should note, look at the E-6Bs)

Posted by Addison at July 13, 2003 01:17 PM

We must be about the same vintage. I went to UNC-Charlotte in 1975, majoring in architecture, which didn't really require that much in the way of computing, but I had some friends in engineering and all had sliderules. I recall that one friend with a rich dad had a 4-function calculator that cost something in the low hundreds of dollars. Anyway, I dropped out and a couple of years later, enlisted in the AF where I used a programmable calculator to compute link budgets etc, then back to college in aerospace engineering, where I was among the last few who learned to use punched cards.

Now I teach spacecraft design, and dynamics & control -- I completely agree with your comment on the lack of intuition developed by students today. I'd estimate that 90% of today's engineering seniors do not even know the values of the trig functions for simple angles like pi/2.


Posted by Chris Hall at July 13, 2003 01:23 PM

I was referring to the general-purpose ones, not specialized.

Posted by Rand Simberg at July 13, 2003 02:10 PM

I went to Junior College for two years and then to UC/Berkeley as a junior and senior. I still remember the Rite of Passage early in my junior year (1962) when, with my carefully saved money, I bought my very own K&E Log-Log-Duplex-Decitrig slide rule in the student store, with its 24 (25?) scales! For my generation, that was like a Bar Mitzvah for engineers. Years later, I read that K&E had dismantled its slide rule production line and shipped its templates to the Smithsonian Institution - truly the end of an era.

Posted by Bruce Lagasse at July 13, 2003 03:16 PM

I taught myself how to use one in 8th grade ('72-'73) and kept the thing around even after switching over to calculators in high school. Bought a Post VersaLog, with hardbound instruction book, at a political fundraiser in Dallas about 11 years back, and still have it. Wonderful artifact, and a great teaching tool.

Posted by Jay Manifold at July 13, 2003 03:30 PM

I taught freshman physics labs at Ohio State just when pocket calculators had replaced slide rules. The first lab still taught the use of the slide rule, using a 6-foot slide rule suspended from the ceiling. I told the students that the lab was still useful, because it would give them practice at reading numbers off a scale.

They finally got rid of the slide rule lab, years after I left.

Posted by Bob Hawkins at July 13, 2003 05:58 PM

Ahh... nostalgia. Reading your post I walked over to a shelf in my room and brought down the Teledyne Post Versatrig I used at Indiana University back in the early 1970s.

Here it is before me even as I type this comment. I know the manual is around here someplace. Yes, one does develop an intuitive sense using these things. I think I'll hunt for that manual now, and work this for awhile to loosen up the action.

As much fun as using this was, I remember how frustrating it was back then to interact with the lab computer via punch card.

Posted by roscoe at July 13, 2003 06:07 PM

Another one of the joys of eBay -- I was able to pick up two slide rules, one for under $20, the other (from 1948, with manual and case) for under $30. Very cool.

Here's a great site for things slide rule: I love their motto: "Keep in mind, in 50 years, the computer you are using to view this webpage will be landfill, but your trusty slide rule will just be nicely broken in!"

Posted by Sandra at July 13, 2003 07:41 PM

My old slide rule mohagany with melmime laminate. The end plates are machine-cut, drilled-and-threaded aluminum withe the thru-holes slightly elongated so the play could be adjusted out as the slide wore. Whoever designed it wasn't thinking about obsolesence.

This also brings to mind my old HP-41CX calculator. It went bingo-brains a couple of years after I bought it. I never bothered to fix it because desktop computers kind of made them obsolete. But I still have it, the original manuals, box, everything. Now I find I can still get it repaired for about $60. And, since HP stopped making calculators, RPN addicts keep driving the prices up.

Posted by Kevin L. Connors at July 13, 2003 09:33 PM

Out of curiosity does anyone know who still uses analogue computers? I see that aviation still does and I assume that most militaries still do. It's amazing what some special purpose analogue computers can do.

Eg, I recall playing with the analogue computer on the USS North Carolina (the battleship retired after the Second World War). It was used to calculate the trajectory of the shells from the main guns. Various parameters like the ship's speed and heading, the target's speed and heading, wind speed, etc go into the calculation. And of course, it's fast. The moment you twist a knob, it correctly shows the resulting figures you need to correct fire the guns. The whole thing is built into a pedestal inside the turrent. Finally, the thing is incredibly sturdy. I think I'd be hard pressed to damage it.

One thing I think of here, is that we probably could design lightweight specialized analogue computers, completely without electronics, that could perform many functions in space like calculating the correct orientation and burn time for various manuevers (at least in the hands of a skilled professional). Ie, even if all your electronics died, you could still manuever the spacecraft and perform other important tasks. Or maybe do it all with a slide rule.

Posted by Karl Hallowell at July 13, 2003 09:34 PM

For the RPN freaks out there, I have a program in my Handspring (Palm-compatible) PDA that converts the standard calculator to an RPN one, with a stack so deep I don't know how deep it is...

Posted by Rand Simberg at July 13, 2003 09:38 PM

I still have my first slide rule, a K&E Deci-Lon I bought for my freshman year in college. In my senior year (1972) one of the profs had an HP-35 on proud display, but since it cost more than a semester's tuition there weren't many undergrads (or grad students, for that matter) who picked one up. But three years later I had my own TI-16, and I rarely used slide rules after that...

The most unusual one I have is an inexpensive plastic one produced by Irvin Industries; it allows you to easily estimate the basic parameters of parachute performance, and I've seen one used in a meeting within the last fifteen years (the user was an Apollo Program veteran, of course).

Along with the failure to anticipate order-of-magnitude, I think today's calculator-, PDA- and computer-users often don't appreciate significant figures in their calculations; even at NASA, I've routinely seen four-place output from two-place input -- perhaps not too surprisingly, as the old-school engineers are replaced with youngsters fresh out of college.

Posted by Troy at July 14, 2003 12:00 AM

I guess it's time now for someone who never learned to use a slide rule to speak up. My dad had one, though he was never in danger of becoming an engineer -- and I once found one of those circular ones lying on the sidewalk on my way home from school.

But simple calculators were starting to be permitted in math class the year I was in eighth grade; in fact IIRC the teacher actually handed out TI-1200s for our use in class but I don't think we were allowed to take them home.

Posted by Kevin McGehee at July 14, 2003 07:06 AM

I dug my old KE Log-Log DeciTrig out of my footlocker last week, and I found that it still had the belt clip and the rawhide laces that we used to tie 'em low for quick-draw!

You can always tell a slipstick engineer: he can calculate the order of magnitude in his head!

Class of '72 - the LAST slipstick class at RPI.

Posted by Emery at July 14, 2003 11:23 AM

I have worked in a classified lab and they will not allow any transmitting devices past the door... that includes all new HP calculators with the IR port. Needless to say after much bitching and moaning one of the old dog engineers among us came back from his desk with one of his many slide rules. He got the work done.

Posted by Ryan at July 14, 2003 12:49 PM

In HS in the 80's our math teacher still made us learn to use slide rules, for which I'm grateful (see comments about the order of magnitude deficient above!)

I still have a circular slide rule a friend gave me years ago, as he knew I was fond of them. It's one of the neat ones with the periodic table on the back, and a slide-out card with physical constants, conversion factors and theorems in the middle. I'd have to go excavating to find out the manufacturer, which isn't easy as we're moving this week :-)

Glad I learned to use them, even if I was on to Mathematica not too many years later.

Posted by David Mercer at July 14, 2003 09:38 PM

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