Talk:Difference engine

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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)

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)

[edit] 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. :-)

[edit] 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)