Talk:Slide rule

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[edit] Obsolete or not?

are slide rules completely obsolete? surely they'd be useful in places or situations where there is no electric power, or as a backup.

Solar-powered claculators generally fit the bill, and are now cheaper to get than (now antique and no longer made) slide rules. Some older engineers who owned slide rules and know how to use them do indeed use them as a (nostalgic) backup, but even that use is uncommon. They can be useful in education, though--I had a math teacher who hauled a bunch out to teach logarithms quite nicely. Also, as the article says, airline pilots are still required to have and understand specialized circular rules.

[edit] The c in c log(x)

This page doesn't explain the "c" in c log(x). Obviously a constant, but what determines its value?

Any value of c will do. It is the distance between the two index marks, so it's determined by the length of the wooden sticks that the slide rule is printed on. - Dominus

[edit] Size of rule pics

The instructional slide rule illustrations are great, but could they be reduced in size somehow, without destroying the instructional value? The present figures exceed the width of a web browser window even at high resolutions. --Wernher 00:00, 19 Apr 2004 (UTC)

I have now scaled down the pictures a little. They obviously can't be scaled down much further without the markings becoming undistinguishable from each other, but the present size at the very least should be more suitable than before. --Wernher 23:37, 26 Apr 2004 (UTC)
I drew the instructional pictures, and I could redraw them to a new width if desired. But (1) when you say "they exceed the width of a web browser window" you mean they exceed the width of your web browser window; regardless of how small I make them they might still exceed the width of someone's web browser window. So how would I decide how wide to make them? And (2), even if they do exceed the width of your web browser window, so what? I do not see what the problem is. Please explain. -- Dominus 10:14, 27 Apr 2004 (UTC)
What I meant was that, as I said in my first comment, even at high resolutions like with my own browser window (roughly 1000 pixels wide, of which perhaps 800 is available for articles after Wikipedias left margin is accounted for), the pictures exceeded the window width and thus necessitated sideways scrolling (the "so what"). This should answer your two questions. In principle, yes, one never knows how small a browser window anyone uses, but one may assume that few users today strive with less than 800×600 pixel displays (and with the falling prices on 15" LCD screens of 1024×768 resolution, and the related sharp price drop of CRTs, I suspect that even 800×600 will soon be a thing of the past including almost all budget installations). --Wernher 17:58, 27 Apr 2004 (UTC)
With IE and Opera at least, there is no problem with wide pictures: they do not make the text wider as well.--Patrick 10:49, 27 Apr 2004 (UTC)
Yes, a good thing, no problems with the text; but still I think one should try and avoid the need for sideways scrolling entailed by very wide pictures. --Wernher 17:58, 27 Apr 2004 (UTC)
Sorry, I still don't understand. Yes, having wide pictures means that you have to scroll to see the whole thing. But you shouldn't have to scroll to see the parts of the diagrams that are referred to by the article text, so I don't see why this matters. In my opinion, it's more important that the part of the slide rule that is disucssed in the text be clear and legible than it is for the other parts to be visible at all. If you like, I can chop the rightmost end off of each picture; then they will fit and you won't have to scroll. -- Dominus 15:40, 28 Apr 2004 (UTC)
I must say I had no intention of stirring up this matter into some kind of 'hot' discussion. The pictures as they stand now is perfectly all right, and with my infinitesimal changes they are also within the width of a much larger proportion of the reading public's browser windows. Not all readers, of course, but I dare say many more than before. So why spend more time on this? I have no problem seeing it from your/the general point of view, but I can't quite say I see any motivation for much further arguing about the matter as it stands. --Wernher 02:28, 29 Apr 2004 (UTC)
That is not responsive to my questions. Since you don't seem to have a good reason for your change, and since you dont seem to want to discuss it, I am going to put it back the way it was. Thanks for your other contributions to this article. -- Dominus 11:26, 29 Apr 2004 (UTC)
Well, if that's how you feel, how about your earlier suggestion of chopping off the rightmost non-essential/ instructional part of the pictures? I still feel there is some merit in trying to avoid sideways scrolling. And I have no problem discussing this -- in fact I very much want to do so, contrary to the impression you may have got from my comments. In that case I have not expressed myself clearly. As the discussion stands now, I almost feel some kind of hostility(?). --Wernher 21:36, 29 Apr 2004 (UTC)

[edit] Photo overlapping TOC

Hi, Wernher -- I reverted your change to the location of the first photo, because it wasn't rendering properly in Firefox -- the photo was coming out on top of the table of contents. Hope that's OK. Reading over your dialog with Dominus above, I agree with you that Dominus's figures were too wide. Although he's right in theory that scrolling to the right is not necessary in order to understand the figures, it looked ugly, and the reader would not necessarily realize when first going through the examples that scrolling was not needed. I've tried to solve the problem by replacing the figures with new ones representing single-decade scales rather than double-decade ones. This allows all the examples to fit within a comfortable width. --Bcrowell 04:54, 30 Apr 2005 (UTC)
Heh, this is interesting: the reason I changed the location of the uppermost photo in the first place was that it came up on top of the table of contents! :-) Strange. Or does it mean that my browser (no prize for guessing which one...) places the TOC on the left hand side by default while Ff does the opposite? Oh well. I think we might have a "double Murphy" here. BTW, thanks for fixing the other figs. --Wernher 05:14, 30 Apr 2005 (UTC)
Ugh -- what a pain! My browser also puts the TOC on the left, but the overlapping happens when I use "right" for justification, not when I use "none." So are you saying that in its current state, it overlaps for you? Its current state is "Image:pocket_slide_rule.jpg|frame|none|A slide rule being used to multiply by 2. Each number on the D scale is double the number above it on the C scale." In this state, it does not overlap for me. --Bcrowell 15:14, 30 Apr 2005 (UTC)
I've posted at the Wikipedia:Help desk to see if anyone knows how to fix this. --Bcrowell 17:13, 30 Apr 2005 (UTC)
I tried adding a fix suggested by the help desk. Wernher, can you tell me if it fixes it?--Bcrowell 15:06, 1 May 2005 (UTC)
Nope, the photo still appears above the TOC, leading to unnecessary waste of vertical display area IMO. :-( Hmm, perhaps the question then becomes: what is the most common browser as of this writing? Should one let that decide what code to use? Or, is that a despicable view, since it may depend on an error in the rendering engine in the dominant browser (how do we determine which browser is at fault, BTW?). --Wernher 00:54, 4 May 2005 (UTC)
Oh, I see -- you just don't want it above the TOC? You must have a wide screen -- on mine, there's no possible way for that wide figure to fit side by side with the TOC. I think it's right the way it is.--Bcrowell 04:14, 4 May 2005 (UTC)
Argh, now I understand---I misunderstood the term "on top of" to equal "above"... Now, what you have been telling me all along is that the photo actually overlaps the TOC like a "double exposure"? That I most certainly agree is a Bad Thing™. :-) You see, I was about to suggest the following:
"If the figure turns up above the TOC for you (and likewise for others with not-very-wide screens) no matter what we do with the WKP src code, why not use the <align=right> scheme anyway---so that everyone get what they want? :-) There's not any drawbacks with that, is there?"
But that is really not an option if I understand you correctly, then. Oh well. As the laywers say (on TV, at least): "I have nothing further"... Sincerely sorry for wasting (y)our time. --Wernher 11:25, 4 May 2005 (UTC)

[edit] Sci/eng calcs

The rationale behind my qualifying the word 'calculators' with 'scientific/engineering' in the intro paragraph is that slide rules were not essentially replaced by simple four-function calculators unable to compute trigonometric and logarithmic functions as well as roots. Only with the advent of scientific pocket calculators were slide rules definitely obsolete, although the price point of those calculators kept them out of reach for large parts of the potential user base until the latter half (the end, really) of the 1970s. --Wernher 11:48, 17 Aug 2004 (UTC)

[edit] Listing on Peer review

This article has been listed on WP:PR to gain wider commentary. Please see the comments there and try to help collaborate in improving this article. Thanks - Taxman 22:41, Aug 23, 2004 (UTC)

These are the comments from WP:PR; this article has now been removed from that page due to inactivity. Alanyst 17:40, 18 Sep 2004 (UTC)

[edit] Peer review comments

Thinking of nominating this for featured status. Anyone interested in helping? Seems to be a very good start. Alanyst 02:52, 15 Aug 2004 (UTC)

  • The opening sentence seems a bit odd- it defines the slide rule solely by contrasting it with an instrument that replaced it. How about someting saying what the slide rule is, not what it isn't? Markalexander100 05:56, 15 Aug 2004 (UTC)
    • Good suggestion. I have revised the intro. Anything else? Alanyst 15:00, 17 Aug 2004 (UTC)
  • Good article. I like it. A few notes: The history section needs to be expanded. When were they first used or developed, and what were the precursors? Also the section on standard linear rules says 2 or 3 significant figures of precision are possible, but I thought with custom, longer units, higher precision was possible? I remember looking at the Guiness record for the longest slide rule. In addition a picture of a circular slide rule would be very good to show the contrast. I had never reallized there were circular slide rules. Mention of the cultural impact of slide rules being so widespread and then replaced so that current students only learn about them as a history lesson might be appropriate. I think the slide rule is the MIT or MIT math club symbol too. - Taxman 20:39, Aug 19, 2004 (UTC)
  • I'd like to point out that the scales in the figures don't look quite right; some numbers seem to be positioned linearly instead of logarithmically. For example, 4.5 is shown midway between 4 and 5; that physical location should correspond to (approximately) 4.3. --Coneslayer 21:46, 2005 Mar 10 (UTC)
    • Never mind, I was thinking wrong. --Coneslayer
      • You were thinking more or less correctly---the 4.5 mark should not in fact appear midway between 4 and 5. The distance between the 4 and 5 marks is log(5) - log(4) = 0.223, and the distance between the 4 and 4.5 marks is log(4.5) - log(4) = 0.118, so the 4.5 mark appears 0.118/0.223 of the way from the 4 to the 5, or about 53%. Careful inspection of the diagram will reveal that it is indeed slightly more than halfway over. I very much appreciate that you took the time and touble to examine the diagram so carefully. Thanks! -- Dominus 14:49, 11 Mar 2005 (UTC)

[edit] E6B or E6-B or E-6B?

The "E-6B" name variation used in the article was never introduced to me by any of my flight instructors. They used E6B or E6-B. However, a google test says that all of the spellings are widely used: E6B - around 20,000 E6-B - slightly over 10,000 E-6B - (the one used in the article) - the least popular, albeit just about 10% less than E6-B

Change to E6B? BACbKA 10:21, 27 Sep 2004 (UTC)

I just created a new article on the E6B for Wiki; very very rough outline, but it's there. I'm using 'E6B', and just edited this page to use that format. I've even see people use all three spellings in the SAME paragraph elsewhere. Comments & help with the new E6B article welcome! --Madpilot 02:16, 13 Mar 2005 (UTC)
Ah. As you can tell from my recent lengthy entry in the E6B history section, the original military name was E-6B. Later manufacturers apparently moved or removed the hyphen to, I don't know, perhaps avoid copyright problems. In any case, the most popular one sold today is named E6-B, which causes a lot of people to assume that's the original name. It is not, and frankly, it drives me nuts <g>, because it's helping people to lose a precious piece of history. But I'm willing to put up with E6B, which doesn't have the same commercial ring to me. --Kevindarling

[edit] von Braun photo

I would like to have some comments on the photo of von Braun which is used in the article about him -- I wonder if that is one of his slide rules being partly visible in the picture. Please comment at the photo's talk page. --Wernher 15:39, 10 Dec 2004 (UTC)

Bah -- the photo was removed a while ago due to copyvio doubts. The replacement photo does not show any trace of what I believe might have been a slide rule. Oh well. I might try to find the original photo somewhere, though, just to have a closer look. --Wernher 8 July 2005 00:53 (UTC)

[edit] Inventor

While I see many people mentioned, I don't see one I've heard credited, Peter Roget. Comment? Trekphiler 10:20, 14 December 2005 (UTC)

Roget invented the log-log scale for powers and roots. Dicklyon 15:42, 29 April 2006 (UTC)

[edit] Scale Length

I think it's unecessarily ponderous to talk about the scale length to 3 significant figures of precision. And, on this Staedtler-Mars No. 94428 I have here, some of the scales are 250 mm long and some are 270 mm long - this is done so that numbers a little bigger than 10 or a little smaller than 1 are still readable. --Wtshymanski 22:53, 10 February 2006 (UTC)

If you check, I think you will find the distance between 1 and 10 on the C and D scale is exactly 250 mm, to limits of their manufacturing precision. All the 10" slide rules I know about are actually 25 cm units sold as "10 inch" models. The L scale could be used as a measurement ruler in a pinch if you knew this fact. Also I think is is important to make clear that log x refers to base 10. Finally, slide rule use diminished gradually as computers became more common, not abruptly in the 1970's --agr 04:48, 27 February 2006 (UTC)
If a distance on a scale is proportional to the base-10 log of x, then it is also proportional (with a different proportionality constant!) to logarithm of x to any other base, is it not? How much ponderosity can we stand in one sentence? My impression of the decline was that it was rather abrupt -digital computers were scarce well past the 1950's, at least. Weren't the big atom-bomb calculations in the early 1940's done by rooms full of clerks on mechanical adding machines? When I registered for university in 1977, the book store still sold slide rules, but they were completely gone a year or two later ( I still have a few I bought at clearance). --Wtshymanski 18:58, 27 February 2006 (UTC)
It's not that the distance is proportional to log10, it is log10, normalized to the length of the ruler. Thus the '8' mark on your slide rule will be exactly log10 (8) x 250 mm = 225.77 mm from the index. The slide rule takes advantage of the unique property of the common log that the stuff to the left of the decimal merely tracks powers of ten and can be ignored. I agree that the sections in question are ponderous and need work, but this is an important fact to preserve.
As for the slide rule's demise, a lot happened between the 1940s and the 1970s. Computers were a very scarce resource in the mid-1950s but became much more available to technical workers during the 1960s. The introduction of Fortran in 1957 made computers practical for solving modest size mathematical problems. IBM introduce a series of more affordable computers, the IBM 650 (1954), IBM 1620 (1959), IBM 1130 (1965) addressed to the science and engineering market. John Kemeny's BASIC programming language (1964) made it easy for students to use computers. Wang Laboratories introduced desk-sized calculators starting in 1965. The PDP-8 minicomputer was introduced in 1965. Also computers changed the nature of calculation. Before them, there was a great emphasis on working the algebra to get expressions into the most computable form. Small terms were approximated or dropped. With computers and Fortran, complex formulas could simply be typed in from text books. Numerical integration was often easier than trying to find closed form solutions. More complex problems could be atacked. The young engineer asking for computer time to solve a problem that could be done by a few swipes on the slide rule became a humorous cliche. Many computer centers had a framed slide rule with a note "In case of emergency, break glass." By the time the pocket scientific calculator was introduce in 1972, slide rules were mostly used in schools, where textbook and exam problems were designed to be solved on them. That market dried up quickly once scientific calculators became affordable.--agr 15:00, 28 February 2006 (UTC)

[edit] Tedious Explanation

I would like to explain the above "in case of emergency" line, since the punch line (such as it is) might not be obvious to many people. In many settings of the period (around 1950 +/- a few decades), small fire extinguishers would be available in case a fire broke out. Since easily available fire extinguishers would be subject to vandalism or inappropriate use, many of them were placed behind an easily broken pane of glass, the theory being that a person would be less likely to use it unless there was a pressing need. The wording "In case of emergency, break glass" would usually be printed on the glass.

Some computer centers had the same type of frame and warning with an abacus inside.

That said, I'm not sure if this information should be added to the article, since it doesn't directly address the uses of slide rules, and anyway, if a 'joke' has to be explained, it loses much of the humor.

I'd be happy to leave the explanation here in the talk page. If anyone thinks it should be added to the article itself, please be my guest. Bunthorne 05:30, 23 March 2006 (UTC)

[edit] We need one special picture

A really frustrating aspect of all nice and large pictures of slide rules on the net is that there's always a cursor somewhere in the middle. That means you cannot take the picture and make a functional computer simulation of this particular model. Besides the pictures are way too small for serious simulation. If I had a nice-looking slide rule I would scan it really large without the cursor and place a link in Wikipedia so that anyone could download it and play with it :)

[edit] Revised intro

I didn't think the term "calibrated" was right. "Divided" is more appropriate. Any better ideas?

The part about usage waning in the 1950s and 1960s contradicted everything I know about the booming and proliferation of American, European, and Japanese slide rule companies in those decades, and my own experience as a 1970 high-school graduate. Anybody have good references or data? Dicklyon 15:45, 29 April 2006 (UTC)

[edit] Dubious Assertions

I don't believe either of these assertions:

Pickett brand slide rules were the standard in the Apollo program; Pickett's slide rules of the era often included a NASA or Apollo logo to promote the fact... Pickett N600-MES (6 inch, magnifying cursor, "Eye-Saver" yellow) was standard equipment on all Apollo flights.
Another mechanical pocket calculator, the Curta a.k.a. "pepper grinder", was also popular among scientists.

A Pickett went on at least one Apollo flight, but that's about it, as far as I've heard.

And nobody I knew ever had a Curta. When I discovered them years later, I found that their popularity was within the car-rallye set, not scientists and engineers, who had more appropriate tools for their trade (desktop digital mechanical calculators, and slide rules). And the Curta was never "known as" "pepper grinder".

Unless someone defends them, I'll probably remove them. Dicklyon 15:56, 29 April 2006 (UTC)

See the SciAm ref on Keuffel and Esser. That article makes the above assertion about the Pickett rules, but it's a different article that talks about the Curta. Unless it can be proven that the SciAm people looked it up on Wikipedia, I'll return the info for now. --M1ss1ontomars2k4 | T | C | @ 05:35, 20 May 2006 (UTC)
The SciAm author, Clifford Stoll[1], is not a slide-rule historian; he came to two west-coast meetings of the Oughtred Society and picked up a few fun things to write about, but his article is full of errors, so it is not a credible source of this rumor, which has been bandied about long before the wikipedia. I'm taking it back out. Dicklyon 17:18, 20 May 2006 (UTC)
Ok. I never put it back in anyway... --M1ss1ontomars2k4 | T | C | @ 18:14, 20 May 2006 (UTC)

I had an uncle who had and used a Curta; he was an actuary. htom OtterSmith 03:22, 20 June 2006 (UTC)

A Curta is not a slide rule, but for an actuary it's a better tool. Dicklyon 05:19, 20 June 2006 (UTC)


[edit] ST Scale

Some places, [2] mention that the ST scale is used for Sine, Tangent, and conversion to radians. We might note that for slide rules with an S scale but no ST scale, (a Pickett 520, or example) the users would convert degrees to radians directly by dividing by 57.3 ('R' at 573 on C or D) and use the x = sin(x) = tan(x) approximation for x < 5.7 with less than 0.3% error. See [3] for x=sin(x)= cos(x) . 70.186.213.41 06:33, 14 September 2006 (UTC)

Thanks for pointing out that such a thing exists, in spite of my disbelief. Funny thing is, I actually have that one. I'm still not convinced it needs to be said, since it's such a strange fluke, but I can't really object I guess. Dicklyon 06:45, 14 September 2006 (UTC)
For small x, x ~= sin x ~= tan x != cos x ; as x goes to 0, cosine goes to 1. --htom 03:42, 21 September 2006 (UTC)
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