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In the novel, did they assume that difference engines took over or analytical engines? A world full of difference engines wouldn't be too exciting I'm afraid.
I don't have a copy with me, but I believe it was various Babbage engines, from difference engines to analytical engines and beyond. --The Cunctator
Does anyone know where I might find plans of either engines?
BrentB
The example of the polynomial is not correct. It states: 'A difference engine only needs to be able to subtract'. Though, the Difference Engine could only add. What's wrong is that the differences in the second column (column of 1st difference) are not subtracted correctly and need a minus sign. SvenPB 19:24, 6 August 2005 (UTC)
I would also like to add that transcendental functions can only be approximated by polynomials. And thus in those cases you'll not find the constant value at the end. In those cases you can only do so good as the number of columns in the difference engine. For example a sine on the difference engine can only be calculated to about PI/2 or so. After that it will just disapear into plus or minus infinity. SvenPB (talk) 15:06, 11 May 2008 (UTC)
- That is not correct. It is possible to produce appropriate polynomial approximations for any portion of the domain of the sine functions. However, a single approximation will not be suitable for the entire domain. That is true for many other transcendental functions as well, including logarithms. This was well-known in Babbage's time; even with the Difference Engine it still would have been necessary for mathematicians to derive the appropriate polynomial approximations for various portions of the domain, and use each polynomial for only a portion of the tables being generated. --Brouhaha (talk) 20:01, 12 May 2008 (UTC)
The difference engine could both add and substract, using the trick of adding negative numbers. The engine has no signs for numbers so you have to express them in arithmetical nine's complement (e.g. -6 would be 999999999999994).
Example:
You want to calculate the height of a rock being thrown. For simplicity, asume the engine has only 4 digits per number.
- Display Column = 0000 (initial height, floor level)
- First D.Column = 0005 (initial speed, upwards
- Second D. Column= 9998 (acceleration = -2)
This yields this:
0005 0005 9998
0005 0003 9998
0008 0003 9998
0008 0001 9998
0009 0001 9998
0009 9999 9998
0008 9999 9998
0008 9996 9998
...and so on. The final list would be 0 5 8 9 8 5 0 -7 etc. RedNifre (talk) 21:22, 26 June 2008 (UTC)
This 'method of differences' looks a bit like differential calculus to me. Is that wrong? E.g.: the first column is the function; the 2nd is the 1st derivative, and the 3rd is the 2nd derivative. Note that the third column of a 2nd-degree polynomial is constant, like the 2nd derivative. --Taejo 12:52, 27 August 2005 (UTC)
- The "method of differences" uses difference equations; "differential calculus" uses differential equations. They are very similar, except the first uses finite steps and the second infinitesimal steps. -- RTC 20:07, 7 September 2005 (UTC)
I'm not a computer science major, an engineer or anything of that sort, but this article seems terribly incomplete to me. There's no historical information (when was it designed, why wasn't it built), there's no discussion of the engineering principles. Cansomeone please work on this? Zaklog 03:01, 12 February 2006 (UTC)
student
im doing a power point on this topic i was wondering if anyone could plz add the history of the people's live's involved with the machine? thnx
-- Be BOLD. :-)
Now there are two
http://www.computerweekly.com/Articles/2008/03/31/230058/babbages-vintage-supercomputer-heads-to-us.htm
http://www.electronicsweekly.com/Articles/2008/04/01/43442/babbages-difference-engine-heads-for-california.htm
http://www.wired.com/gadgets/miscellaneous/multimedia/2008/04/gallery_babbage
Conrad T. Pino (talk) 02:51, 10 April 2008 (UTC)
Intentional Error
Is there any documented evidence of the notion that the errors found in Babbage's plans were intentional mistakes--a sort of insurance against patent theft? And if so, should the article reflect that in its coverage of the errors? I've heard this idea from many a good mind, but no one has offered evidence. O0drogue0o (talk) 09:38, 17 September 2008 (UTC)