Ancient Computers

Raise your hand if you know how computers work. Now keep it up if you actually know, and don’t just have a vague idea. That’s more like it.

Deep Thought

The super computer “Deep Thought” from “The Hitchhikers’ Guide to the Galaxy.”

I can’t actually see your hands, but I’m guessing that unless you’re a computer science major you have to admit that a large part of the functioning of computers seems more magical than scientific and in the event there was an apocalyptic event, civilization couldn’t count on you to reinvent them.

So let’s start with the basics then. I’m not a computer science major . . . I’m in English, so we’ll start there. The word “computer” means “a device to perform calculations.” So the earliest computer was your fingers . . . quickly followed by an abacus.

Abacus_2The function of an abacus is simple–it’s just a tool from counting. The bottom line represents ones, and the next one fives, and the next ten, and so on up. These could be any different number of groupings if you’re not using a base ten counting system. (The Mesopotamians used a base sixty, so their abacuses would have reflected this.) No matter how simplistic, however, the abacus is an early calculator and the first step towards modern computing.

No further advances were made in analog computing until the early 1600s with the invention of slide rules and astrolobes. A slide rule was used for advanced mathematics calculations based on the principle of logarithms, and until the era of digital calculators remained the most advanced form of calculator. Not only did all the famous mathematicians use slide rules to perform their calculations, but students as late as the 1950s didn’t have access to the advanced calculators we take for granted today.

An astrolabe is a calculator for determining things like lunar phases and sunrises at various times of the year. Without clocks, or even printing presses, the ancients were obsessed with the sky as the only means of keeping track of the time and seasons. Astrolabe’s were developed as early as 100 BC in Hellenistic Greece, but no significant developments were made until the 1200s in the medieval Islamic world.

At least, that’s what we think.

The nice timeline of analog computing in the pre-modern era is interrupted by one pesky but fascinating device. Known as the Antikythera Mechanism, it was found in 1900 by a team of sponge divers, on a shipwreck dating back to 100 BC. Surrounded by Greek statuary and intricate glasswork, the Antikythera Mechanism stands out like a cell phone discovered in a medieval archeological dig. Metalwork and mechanics that advanced were not to be found again until the 1400’s.

Antikythera Mechanism

The Antikythera Mechanism on display at the National Archaeological Museum in Athens, Greece.

The Antikythera Mechanism is hailed as the world’s earliest analog computer (excepting abacuses, of course), Although it was recovered in fragments, it has been successfully replicated several times. It was built to perform advanced astronomical calculations and can correctly replicate the moon’s orbit, all the way down to its elliptical path, and the nine year rotation of the elipse. It can predict eclipses years in advance, both solar and lunar and even tell the direction of the shadow of the eclipse, and what color the eclipse will be. It can show the correct date in three different calenders, and also predict the path of the planets. It is the only device of its kind ever recovered, but archeologists believe they must have been mass produced, given the quality of workmanship and the miniaturization required. It contains 62 brass gears, some with as many as 235 teeth, and took a team of scientists working worldwide several years to work out what each gear was used for in the completed device.

astrolabe 3

A blend of science and beauty known as an astrolabe.

Such intricate and complex workmanship wasn’t to be found again until the invention of astrolabes by Arab scientists–whom historians believe may have been working off of ancient Greek astronomical texts. But gear-making was taken to new heights with the invention of the marine chronometer in the 1700’s, as a solution to the longitude problem. While not computers precisely, accurate time pieces that remain unaffected by the movement and dampness of a ship at sea are a feat of modern engineering, and would provide the basis for increasingly complex computing.

Fastforward roughly 100 years or so to 1822 and the inventions of Charles Babbage. This inventor wrote to the Royal Astronomical Society with plans for a difference engine–a machine that could accurately calculate astronomical tables. These tables were very difficult and time-consuming to create by hand, so the Society was thrilled at the idea of doing it mechanically and gave Babbage a grant of seventeen thousand pounds to build he world’s biggest mechanical calculator.

Babbage Engine

In 1991, the London Science Museum built a complete and working specimen of Babbage’s Difference Engine No. 2

Babbage’s machine was never finished, and eventually the Royal Astronomical Society stopped giving him money. Rather than continue work on the difference engine, Babbage invented a completely new design–the analytical engine. The analytical engine could receive data input in the form of punch cards, and could output using a printer. Had it been built, it would have been the world’s first general purpose computer but, like so many other geniuses, he was too far ahead of his time, and the world would have to wait until 1940 for general computing.

Computers seem to be a marvel of the modern era, driving every important scientific advancement made today. But it is important to remember that they had their beginnings at the dawn of civilization, with a few merchants trying to accurately count their merchandise. A need to improve on something as simple as counting lead to increasingly complicated mechanical devices, forming the foundation for the machine that will one day take mankind to the stars.


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