Video: Charles Babbage's Difference Machine No. 2 Fully Operational

For those who haven't yet heard, a band of number-crunching nostalgists took the concept design for Charles Babbage's Difference Engine No. 2, and turned it into a real, fully functional machine. But what really makes the Difference Engine amazing is only noticed when you watch its thousands of moving parts in action. Upon first glance, the Difference Engine looks a bit chaotic. But upon closer inspection, it moves with the precision of a Swiss watch while maintaining the fluid motion of a wave about to break. And today, it went on display at the Computer History Museum in Mountain View.

Difference Engine No. 2, designed in 1847, was designed to calculate and tabulate values run through polynomial functions up to the seventh order. It, along with the other Babbage Engines, is considered to be the first automatic computing machine.

For those who slept through all their math classes, think of an equation like y=x^3+4x+4, where you're given a list of integers and asked to solve for y in each instance. Babbage was tired of repeatedly doing this by hand and wanted an automated way to solve polynomial functions. He thought there was too much room for human error, so he put together the Difference Engine, which acts like a super-powered calculator.

The machine is powered by a hand crank, which gets the various gears, levers and springs moving, and uses giant mechanical rods representing number values around to push around a bunch of numbers until—presto, change-o—you have your answers printed on a piece of paper (technical, I know).


The Difference Engine No. 1 design, created in 1821, is one of the earliest concepts for a computer. It was able to handle 16-digit numbers run through polynomials up to the 6th order and print them out in tabulated form. It required 25,000 parts, would have stood eight feet tall and weighed 15 tons.

Difference Engine No.2, finished in 1849, was a sleeker, more powerful beast (similar to the difference between Iron Man's Mark 1 and Mark 2 suits). It was designed to handle numbers 31 digits long, only required 8000 parts, and in addition to printing paper results, could imprint tables into a plaster mold for future reproduction. The specs called for it to stand 11 feet long and weigh 5 tons.

The machine design even features built-in error detection, where the machine jams if it comes across a non-whole number at any point in the process. I'll avoid getting into the nitty-gritty of the forumlas and equations, because frankly, its neither as interesting or impressive as the mere fact that Babbage concocted this in the 1800s. But you can read up on the full computational breakdown here. [Computer History Museum]

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This actually is a solution to the age-old problem of kids bringing calculators into math class and 'cheating'. If they were forced to use mechanical calculators, no teacher in the world would deny a kid who found a way to drag something in like this.