> After all, Babbage's machine could have been built in his time if funding hadn't run out.
Funding ran out in large part because of cost overruns due to the fact that the technology of the time wasn’t capable of building the analytic engine design.
Funding ran out in large part because of cost overruns due to the fact that the technology of the time wasn’t capable of building the analytic engine design.
Wikipedia has this to say:
In 1991, the London Science Museum built a complete and working specimen of Babbage's Difference Engine No. 2, a design that incorporated refinements Babbage discovered during the development of the Analytical Engine. This machine was built using materials and engineering tolerances that would have been available to Babbage, quelling the suggestion that Babbage's designs could not have been produced using the manufacturing technology of his time.
https://www.amazon.com/Difference-Engine-Charles-Babbage-Com...
(unfortunately overshadowed in Google Search results by a William Gibson book of the same name)
It gives a lot of color on Babbage, but yes the conclusion was that Babbage design basically worked, and could have been built. There were errors in his drawings that they had to correct, but nothing fundamental.
The group at the Science Museum spent over 6 years doing this! This is the group that holds most of his papers, drafts, and unfinished machines.
Although there are a couple things I want to follow up on. They weren't that specific about what computation they did. And does it still work today? It was extraordinarily finicky. It produced a lot of bit errors, as did mechanical computing devices that came later, which sort of defeated the purpose (it was supposed to calculate tables of logarithms and such with higher accuracy than humans.)
1. The concrete computation performed was to use the Finite Difference Method (https://en.wikipedia.org/wiki/Finite_difference_method - hence the "Difference Engine" name) to calculate arbitrary polynomials of degree up to IIRC 10. By using Taylor Series, this method could be used to calculate arbitrary functions, like log and sine. This was in fact the same method used to construct logarithmic tables by hand at the time, and had similar nominal precision; the singular goal was to eliminate the bit errors rampant in the old, manual process.
2. The machine removed not just errors in calculation, but also in typesetting; about half the part-count of the original design was in its printer, which could be configured with all kinds of options for typesetting the results. It would output a "print preview" onto paper locally (this was not publicly demonstrated at the CHM because of the enormous mess of ink spills, but the machinery was run dry), and an identical wax mold ready for use in mass printing. This was because many of the bit errors in the existing log/sine/etc. tables were introduced not by the (human) computers, but by the multiple copying steps involved in transforming calculated values into printed pages.
3. Computation was quite reliable - the machine worked in base 10, and mechanisms were carefully designed to freeze up (and be easily resettable to a known-good state, as demonstrations showed) before introducing errors. As far as I know bit errors were unheard of in the demonstration runs. This reliability, like in later electronic computation, was the motivation for using digital rather than analog logic. (Finickiness was mostly limited to those halting conditions - it proved quite sensitive to clock speed (rate of crank turn), but only by the standards of the hand cranking used in demonstrations; connected up to a steam engine with 19th-century rate governors, input power could have been kept clean enough to run with long MTTF.)
I believe the better link is https://en.wikipedia.org/wiki/Divided_differences
The difference between “takes an expert engineer a month to create” and “can be CNC’d in a day” is enormous, even if the end results are the same.
Also, building something with the benefit of 150 years of technological progress gives you quite a leg up on the past even if you use techniques that would have technically been available back then.
He would still have had the problem of driving typesetting equipment, but that seems like a smaller problem. Output on punched paper tape was the solution the later generation chose, and would have worked.
Amusingly, the original telegraph inventions (plural) output dots on paper, but accidents of finance left us with the inferior audio clickery. Sort of like how we are still using x86.
The ability was potentially there, but the need perhaps was not.
It would have required a generation dedicated to that one task.