Difference Engine – Babbage would have been proud

Posted by jerry on March 2nd, 2007 — Posted in New media, Technology

I had been re-reading Willim Gibson/Bruce Sterling’s book The Difference Engine and recalled the one built in the London Science Museum which was built as far as possible with the metallurgy and tolerances available to Charles Babbage in the 1820s. And the machine works well.

Difference Engine

Seeing the (re)production machine which weighs in at around 2.62 tonnes and occupies an area 12.65 feet by 6.65 feet and 8.21 feet high – this is a seriously impressive machine. It can solve 7th order polynomials to 31 digits of accuracy – certainly greater than the average pocket calculator today.

But then a quick search showed that some enterprising souls have been making good use of multi-modal construction toys like Meccano® and Lego® to re-create at least part of Babbage’s Difference Engine Number 2.

Tim Robinson set about building his in Meccano® to achieve a successful working model – eventually he hopes to power it with a Meccano (Mamod?) steam engine to realise fully the steam-punk dream.

Meccano Difference Engine

Andrew Carol’s approach was different, setting about solving the challenges posed by flexible plastic components to produce a 3 order polynomial machine built in a modular way using Lego®

Lego Difference Engine

One way to understand these machines better is to take a look at the instruction manual for the Science Museum machine – it certainly brings home the breadth of the achievement in building Babbage’s Difference Engine. And you can look here for technical specifications of the machine on Ed Thelen’s web site.

And in 2000, nine years after the Difference Engine No2 was completed, engineers at the London Science Museum completed the printer element of the engine, thus giving hard-copy output to the set of numbers.

Babbage printer

All up these are a great way to come to grips with a remarkable precursor to modern computers. Babbage stopped working on his Difference Engine No2 in order to devote time to develloping the true precursor to the modern computer – the Analytic Engine – which, thanks to Ada Lovelace’s programming genius, would have been able to perform any kind of operation, using IF/THEN logic not just the pre-set operations.

One could well speculate, as Gibson and Sterling have done, what might the Victorian era been like in the UK if the Analytic Engine became as widespread as computers today. I’m inclined to think, however, that it would have required a social change to see the need for these machines before they would have emerged into wider society’s use.


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