Antikythera Mechanism: It's A Mirror

      The gadget was found in an an ancient Greek shipwreck, a corroded lump of brass that was pretty obviously a complex mechanism, chock full of gears in a complex arrangement.

      It took a long time for historians and archaeologists to decided what it was probably for, and longer still for them to start figuring out how it worked.  A few dedicated professionals and amateurs have even built their own versions, with logic and guesswork to cover the gaps where the found pieces don't fit.  It's a job for a small-scale machinist or horologist, and that has raised even more questions: how did the Ancient Greeks manage such precise work?

      Through the decades, interpretations of the Antikythera mechanism have been something of a mirror of those who have studied it and their times:
    Complicated device found on a seagoing vessel?  It must be for navigation!  Well, maybe, but in that case, shouldn't we be finding more of them?
     It's too complicated to have been made at the time claimed?  It's a hoax -- or alien technology!  Yeah, nope.
      The gears seem to map and model years and Lunar months: it was used to predict eclipses! Perhaps; but the Babylonians had been doing that trick on their fingers and with observing instruments made of masonry, millennia earlier.  While conveniently predicting an eclipse has been a trope for "civilized man wows the unsophisticated" probably even before Mark Twain and H. Rider Haggard* used it in the late 19th Century, it takes a lot fewer gears.
      It tracks the motions of the planets?  It must be for casting horoscopes!  Yeah, maybe; astrology and astronomy didn't stop sleeping together until about the 18th Century and they both use fancy tools -- and only a cynic would suspect any astrologer with sufficient resources to obtain an analog computer would have made sure to include some way of directly affecting the outcome.

      On and on the speculations go, and every new set of high-tech images of the device shows greater complexity and inspires more guesses.  It's Ancient Greek tech, all right -- the way shafts are pinned and the triangular gear teeth are typical of their work.  But the experts are puzzled: modern versions take a lathe to build, and there's no evidence the Greeks had metal lathes.

      Yeah, about that--  The Ancient Greeks were no slouches when it came to geometry, and they did have wood lathes; a treadle-driven pole lathe is among the simplest and oldest of "power tools;" bow and strap lathes are even earlier.  A lathe and tools that can work hardwood can work brass -- and the kind used for clockmaking are essentially desktop.  So that's not implausible.  But hand powered tools are slow, much slower than power-driven ones, and the simple toolrest used with such lathes means precise work is incredibly demanding, more art than skilled craft.  A machine like the Antikythera mechanism represents months or more of highly-talented labor.  Nor was brass cheap or common; it was usually salvaged and re-used, as were most metals.  It's a wonder that we have found even one example.

      In one of the linked articles, an expert wonders why the Ancient Greeks didn't build clocks.  Of course, they did, but lacking a better power source, they were water-powered.   Without a true escapement, regulation was problematic: an actual clock was a finicky, large-scale machine, requiring expert attention.  Mechanical, 24-hour clocks were a one-per-city sort of thing -- and it took a pretty well-off city to build and maintain one.

      The Antikythera mechanism isn't a pocket watch or an iPad.  It's not even a Lamborghini; it's a one-off luxury item.  Were there more like it?  Almost certainly -- but they were wonders, each one.
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* In A Connecticut Yankee In King Arthur's Court and King Solomon's Mines, respectively.  Highly recommended, by the way.