LEGO Difference Engine

Andrew Carroll is mad. I don’t mean that in a pejorative sense but I ask you, what else do you call someone who builds a working LEGO version of the Babbage Difference Engine No.2.

Lego Difference Engine
Before the day of computers and pocket calculators all mathematics was done by hand. Great effort was expended to compose trigonometric and logarithmic tables for navigation, scientific investigation, and engineering purposes.

In the mid-19th century, people began to design machines to automate this error prone process. Many machines of various designs were eventually built. The most famous of these machines is the Babbage Difference Engine.

Babbage is another in the long tradition of eccentric British genius. He was born in 1791 and invented amongst other things the speedometer (yes now you know who to blame for the speeding fines), the cowcatcher (British Rail now having lost the excuse of cows on the tracks is forced to resort to “leaves on the track” or the “wrong type of snow” to explain away the late trains) and he figured out the relationship between tree rings and weather. Clever little bunny what?

In 1821 he and John Herschal (who was an astronomer) were examining a set of maths tables that were used as the basis for astronomical, engineering and building works. The generated flaws in the Navy tables which probably caused over a 100- shipwrecks and accidents. The tables were calculated by hand (no… they didn’t have a pocket calculator) and the errors were simply human error.

So Babbage decides to build a steam powered (Electricity is hanging around in the corridor waiting for someone to notice it) calculator and fix the errors. So after stiffing the British Government of the day for nearly 18,000 pounds for Babbage Difference Engine No1, (by the way it needs around 25,000 parts, weighs fifteen tons and stands eight feet high) he figures out it isn’t going to work the way he wants it to. So he designs Babbage Difference Engine No:2 but the government took it’s money and went home. For 18 grand they could buy two battleships back then.

The difference engine was immortalized in the William Gibson and Bruce Sterling collaboration of the same name (and one of my favourite reads), and it would appear that it’s a perpetual source of hacker fascination (Ada Lovelace, Lord Byron’s daughter, financed the Analytical Engine project and invented the idea of software for it because she was interested in handicapping horse races). Computers and gambling… some things just don’t change.

Though Babbage was never able to get his design working (Simon Singh has a some pages about Babbage in his “The Code Book” also a good read),

The Babbage Difference engines construction had to wait until 1991 when the Science Museum in London decided to build the Babbage Difference Engine No.2 for an exhibit on the history of computers.

Babbage’s design could evaluate 7th order polynomials to 31 digits of accuracy but the Lego model can only compute 2nd or 3rd order polynomials to 3 or 4 digits.

Andrew probably ran out of bricks. (Maybe a quick chat with the British Government for some finance… hmmm maybe not).

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