

Are slide rules still useful? - gnosis
http://www.johndcook.com/blog/2011/04/11/sliderules/

======
rfreytag
Pilots use slide rules. Behold the venerable E6B flight computer (aka "Whiz
Wheel"): <https://secure.wikimedia.org/wikipedia/en/wiki/E6B>

Even glider pilots use them to calculate best-speed-to-fly (between thermals):
<http://www.126association.org/glideslide.htm> It takes a cool head to:
navigate, aviate and run the slide rule accurately all the while remaining
aloft without an engine and merely a glide ratio of 12:1!

~~~
artmageddon
Pilot here(private pilot, anyway), and yes: we use the E6B a lot when we're up
there. It's nice that avionics can give us things like true airspeed and fuel
burn rate instantaneously, but that's only as good as your power source is
when it's working correctly. An E6B will never suffer from electrical failure.

~~~
fractallyte
But it might suffer from illumination failure!

~~~
artmageddon
That's why we carry flashlights :)

------
keithba
As a kid I was an avid reader of Heinlein and Asimov, and they were always
talking about slide rules (Astrogators navigated space with them!)

This was the late 80s, and I couldn't find one. So, I found plans for one in
the public library and built one. Later a math teacher gave me his.

Playing with slide rules would be useful. Building a slide rule would be even
more useful.

~~~
root
The following cover from Astounding springs to mind: [http://up-
ship.com/blog/wp-content/uploads/2010/04/feb59a.jp...](http://up-
ship.com/blog/wp-content/uploads/2010/04/feb59a.jpg)

------
mhb
Obviously not the main point, but he says

 _Calculators are obsolete_

and then

 _as far as software for serious math, I use a combination of Python,
Mathematica, C++, and C#. For quick calculations I’d use Python. For
simulations I’d use C++ for maximum speed or C# if I need to interface with
.NET software. I mostly use Mathematica for symbolic computations and
plotting._

Kind of an idiosyncratic justification for the obsolescence of calculators.
Besides if you think a slide rule gives a good intuition for logarithms,
pushing function buttons (e.g., square root) repeatedly on a calculator
provides insight into limits.

~~~
gaius
They are not tho'. It's about the user interface. I have a PC here with 2 big
screens, I have access to a compiler/REPL for any language you can name (or at
least, that I can apt-get) and I still use a calculator, because a purpose-
built interface will always trump a generic one for a specific task. It's why
cars have steering wheels still and not QWERTY keyboards. The only thing the
calculator doesn't do is c'n'p into another window.

------
ajdecon
I actually played with a slide rule quite a bit when I was in middle school
(but not _in_ school), and it was much more useful as an actual learning aid
than my calculator. The visualization of logarithms is in fact rather helpful.

------
hsmyers
I'd suggest that on the same lines, a class in ancient computers might be a
way to spark the imagination. Napier's Bones, Pascal's Adding machine,
Babbage's Difference engine and the like. They did it for me when I first
learned about them and still do--- how about the hand-held navigational device
found in the Greek harbor! Lots of things to add to the list along with the
venerable slide rule.

------
camiller
Online slide rule:
[http://www.engcom.net/index.php?option=com_sliderule&Ite...](http://www.engcom.net/index.php?option=com_sliderule&Itemid=73)

Always thought I should buy a slide rule and learn to use it so if I'm still
around when civilization falls... (I know some might argue that event has
already happened.)

------
jcl
The reason that students are required to purchase graphing calculators is for
tests, not learning; schools believe they have more control over what goes on
during a test if all the students are using the same brand of (locked-down)
graphing calculator.

There's little reason for a non-student to use one. You'd be paying more for
less capabilities, because what you're really paying for is the trust that
schools put in its _lack_ of capabilities.

~~~
samatman
And of course, as every aspiring hacker in high school knows, graphing
calculators come with a Turing Complete scripting language that's powerful
enough to defeat this stricture for most use cases.

Then again, by the time one is done translating an algorithm into TI speak,
one's understanding is as high or higher than a student who spent that time
learning to execute the algorithm by hand...

------
javanix
Despite being cursed with an endless string of horrible (for me - I'm sure
some students did well) math classes from high school through college, the one
thing I came away from with them was an appreciation of how much more
intuitively you can learn mathematics if you don't use a calculator.

The problem with using slide rules as a replacement is that students would
complain too much about learning something they won't ever use to ever get the
deeper understanding that Cook talks about. Most young people who don't want a
career in math, science, engineering, etc do not want a deep understanding of
the principles - they want an A on the test. Unless you can use one of the
external tools as a shortcut they won't be willing to put the effort into
learning from it rather than using it.

Ban calculators, ban slide rules, ban everything except pencil and paper and
hope that people gain some smidgen of understanding through sheer force of not
having any other option.

~~~
JoeAltmaier
...and how would you recommend doing logarithms? Thru a table? Why? You would
learn approximation techniques, sure, but that teaches you nothing about
logarithms, it just spends your time.

Perhaps students could expand a series to approximate a log etc. Again, why?
Spends a lot of time that could be spent moving forward in math.

------
showerst
If anyone wants one, think geek sells them now for $20 US:
<http://www.thinkgeek.com/interests/gamer/be12/>

~~~
tzs
I bought a couple of those out of nostalgia. They aren't very good. The
movement is rough, making them kind of annoying to use.

~~~
ajdecon
Agreed. Sphere sells vintage rules though:
<http://www.sphere.bc.ca/test/sliderule.html>

------
giardini
Slide rules enhance understanding of the functions used (mostly logarithm &
trig) and require keeping mental track of orders of magnitude(so they help
avoid _big_ mistakes in quick calculations).

Slide rules are primarily visual and manipulated non-digitally. Using one is
quite relaxing. The calculator interface demands "numbers as a sequence of
digits" and you must type each digit and operation. But with a slide rule,
numbers are values (usually 3-digit) on a number line instead. The analog
nature of the computation fits the human brain well IMO.

My favorite was a circular slide rule since it eliminated multiplications
(logarithmic additions) that were off the scale (which on most slide rules
mandated a shift of the slide to the opposite side).

One of the initial attractions of electronic calculator when they first became
commonly available was the increased number of significant digits, yet it is
amazing how much was done previously using only three.

------
ctdonath
Snipers use slide rules. The Mildot Master is popular for computing bullet
drop from estimated target size and crosshair grid marks.

Sure, some are going to computers for the math, but laminated paper holds up
better under extreme conditions for almost free.

------
runjake
I have a Dietzgen No. 1757. It's useful for raising my Apple external keyboard
up to be level with my ergonomic wrist pad.

In all seriousness, I don't know how to use it, but I should learn. It could
come in handy when/where power isn't available. It's amazing how much our
knowledge would decline in the event computers & electronic gadgets were
somehow destroyed or unusable. I've always tried to learn the basics. For
example, when out hiking, I use a map, compass, and protractor -- and use my
GPS as a backup.

Anyone have any useful links for non-mathematicians learning to use one?

~~~
tokenadult
_Anyone have any useful links for non-mathematicians learning to use one?_

<http://sliderulemuseum.com/SR_Course.htm>

<http://www.sliderule.ca/intro.htm>

<http://www.sphere.bc.ca/test/howto.html>

<http://www.hpmuseum.org/srinst.htm>

<http://thinkgeek.com/files/slide_rule_manual.pdf>

I am relearning how to use a slide rule (I'm old enough that I had lessons in
using a slide rule in my secondary education) to teach basic principles to the
pupils in my advanced supplementary mathematics course this summer.

<http://www.ecae.net/2011/02/summer-2011-course-schedule/>

~~~
runjake
Thank you for taking the time to post all of these!

------
vault_
One thing that graphing calculators are really useful for is simple number
crunching. In academic settings you frequently need to take down numbers and
then compute statistics about them. Tables and matrices are probably the 2
most useful things you can do with a graphing calculator (they're also among
the least well known, at least among students).

Granted, spreadsheets do all of that and more, but it can sometimes be quicker
to punch it all into a calculator, especially if you're already using one.

------
jordanb
Sliderules can be useful, if you're proficient, for performing repeated
calculations where only one variable changes. You can slide the indicator
along and produce a series of numbers quickly and easily.

I have my grandfather's sliderule as a keepsake, and got fairly decent at
using it a few years back. I've fallen out of practice now, so if I wanted to
produce a series of numbers it'd be quicker for me to write a little python
program than try to remember how to use the sliderule.

------
wazoox
Interesting idea. As a side note, I'm 40 and I've seen an actual slide rule
exactly once, a few years ago, and I haven't got the slightest idea on how to
operate one.

------
thinkingeric
I use a slide rule regularly. It is neither quick nor accurate, but it is
useful in the same way that making approximate calculations in your head is
useful. That is to say, added precision doesn't help you understand the
relationships in a problem and speed can obscure some of what's interesting.
However, this kind of thing is only entertaining and instructive for curious
people.

------
lukeschlather
I like the suggestion that we use slide rules in elementary.

On the subject of graphing calculators, saying that you don't need a $100
graphing calculator because you can buy a $200 netbook is as silly as trying
to compare an e-reader to a netbook.

On the other hand, there's no reason a good e-reader couldn't also be a good
graphing calculator. And the pricing is similar.

------
cafard
We probably have two around the house: mine from high school chemistry, one
that my wife thinks of as a "proportion wheel" from her days in print
production. The proportion wheels were in use with printers and publishers for
some years after the nerds had gone to calculators.

------
ericmoritz
I think learning sin/cos/tan before learning that they are based on a circle
is ridiculous as well. I had an epiphany when I learned that.

~~~
giardini
After concluding plane geometry we took trigonometry. The teacher had chosen
an ugly pink-and-black text from New York State. No less than 3 inches thick,
it was chock full of trigonometric formulae for us to memorize. But on day 1
she put the following on the blackboard:

Indian Chief SOHCATOA:

S=O/H C=A/H T=O/A

where S, C, T, O, A, H are respectively, sin, cos, tangent, opposite,
adjacent, and hypotenuse. The mnemonic stuck immediately.

Surprised, I asked if all the formulae in the 3-inch text were in terms of
those formulae, to which she replied affirmatively. I immediately realized
there was little need to study trig whatsoever, since any of the complex
formulas could be reduced to ratios using the SOCAHTOA principle. I barely
cracked the text that semester. She disapproved somewhat of my methods but
accepted them. My classmates wasted hours memorizing formulas.

~~~
gjm11
I've no idea what was in your ugly pink and black textbook, but I'd have
thought those trigonometric formulae would include lots of things like
cos(A+B) = cos(A)cos(B) - sin(A)sin(B). How do you "reduce that to a ratio
using the SOHCAHTOA principle"? By drawing a diagram with two right-angled
triangles stuck together and doing the relevant fiddly geometry? That seems
like vastly more trouble than remembering the formula. (It took me a minute to
work out how to derive the formula at all that way, and I'm a pro.)

