Babbage Difference Engine No. 2 Recreation Coming to Computer History Museum


Image: Doron

Staring May 10th, the Computer History Museum in Silicon Valley will be showing off this working recreation of Charles Babbage's Difference Engine No. 2. Admission is free, but you might be required to turn the crank to calculate the amount of children needed to mine the evening's coal.

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  1. I’m an enthusiastic supporter of the Computer History Museum, lucky enough to live in Silicon Valley and able to visit as often as I want. I’m very much looking forward to this exhibit. I also subscribe to the BBC Radio 4 podcast of the show called In Our Time, and they recently did an hour discussion of Ada Lovelace, who was intimately involved with the Babbage Difference Engine. The story is fascinating, and I recommend it to anyone interested in the topic:


  2. I still find it amazing that, even though the replica had to be built with CAD/CAM that would not have been possible without the computer revolution it spawned, the original machine was never completed. The metaphor of the grain mill (input, output, storage, processing) is still relevant and useful. Again, amazing!

  3. As I recall, there were two primary reasons the original was never completed:

    • The machining technology wasn’t up to the task of producing fine enough gears without throwing half of them out
    • Babbage had managed to annoy just about everybody who might have otherwise provided the money required to do it.
  4. No, it was that the metal alloys they had weren’t strong enough. The gears would have broken (“spalled”).

    I like to name my computers after parts of the Analytical Engine — cog, mill, rod, lug, adder — the last two are laptops.

  5. Doron Swade argues very convincingly (see, e.g., the video of his discussion with Nathan Myhrvold at the Computer History Museum —
    that the Difference Engine could have been built in Babbage’s time with the materials and technology available. The team that built the Engines went to great lengths to replicate the alloys and machining tolerances of the period.

    It appears that Swade’s effort in “experimental history” has somewhat vindicated Charles Babbage: there were no technical obstacles, only financial ones with their roots in Babbage’s difficult personality.

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