From ancient Gears and Screws to Quantum Mechanics

The geared mechanical clock, like the pipe organ and the Gothic cathedral is a defining symbol of Western Civilization. Division of the day into mechanically measured hours  unrelated to the movements of the sun is a mechanical symbol of the defeat of the tyranny of nature by human ingenuity and machine culture. The hours of the day used to be something measured locally by the position of the sun. The liturgy of the hours of the Catholic Church caused north-western Europeans to go all spergy and design intricate machines to tell the monks when to say their prayers, rather than using arbitrary times. After all in the sperdo north, it’s often cloudy or dark very early or barely at all: you need something better than the sun to tell the time.

There’s an oldest surviving clock; that of the Salisbury Cathedral (allegedly 1386). It’s an interesting enough looking mechanism, foliot and verge escapement (the first known mechanical escapement for counting the seconds); you can see it running here. These early clocks had the advantage over water clocks in that you didn’t need to haul water up the tower, and they didn’t freeze in the cold northern winter.

One of the interesting mysteries of technological history; nobody knows where gears came from. A gear is sort of like a wheel, or a pulley system, both of which existed long before the gear. There are claims that the Chinese had them before anyone else; the south-facing wagon is a postulated example, though the first document of it was by Yen-Su in the 11th century, long after such mechanisms were in common use in the West.  As with most of early Chinese history, this isn’t well documented and it may have been nonsense. Unless they influenced the Greeks directly, which doesn’t seem to have ever happened otherwise, the Chinese developments weren’t important in a world historical context.

As with most things, the first documented gears are Greek. Aristotle wrote about them in his physics book around 340BC -around the time of Alexander the Great. Ctesibius was first we know of to write about the things (~250BC) being used in interesting ways; his stuff all lost, but written about by later thinkers; he also invented the pipe organ. It has been suggested that water wheels using lantern pinions were the first gears: we learn of them via Vitruvius (probably originally Ctesibius). We know that Heron of Alexandra had well developed gear trains; he described some effectively like the backgears in a lathe. Archimedes invented the worm gear and pinion used in modern clockworks; possibly also the spiral bevel gears used in differentials.

The most shockingly advanced early geared mechanism is the Antikytheria mechanism. It’s one of those things people didn’t for some reason expect, but if you read old astronomy books, I’m virtually certain such mechanisms are much older. The epicyclic theories of Eudoxus (375BC) and Callippus (330 BC) were pretty explicitly gearworks; later expanded by Hipparchus and Claudius Ptolemy, who was contemporary with the Antikytheria mechanism. It’s entirely possible there were no gearworks before Posidonius (maybe) brought us the Antikytheria mechanism. I suppose it’s possible there were no gearworks after. But it seems vastly more likely we didn’t just randomly pick up a unique space alien technology toy off the sea bed, and there are probably more such treasures still buried in other places, perhaps even sitting somewhere in a Museum storage closet.

My pet theory, for which there is exactly zero evidence, is that gears were very ancient and lost with the late Bronze age collapse. Certainly they had brasses and small drills and the ability to fabricate elaborate objects out of much harder materials. Since the Greeks didn’t mention where they got the basic gear idea, I’m assuming it existed before they started making more clever versions of it. I suppose such things could have existed in some other culture (Sumerian, Egyptian, whatever), but it’s my pet theory; feel free to come up with your own.

The Screw might have been an invention of Archimedes as well, though some historians attribute it to a more forgotten artificer called Archytas (my pal Eudoxus‘ teacher from the time of Plato). Screws were used in the Mediterranean region for olive and grape presses. There is a widespread misapprehension that the science of the ancient Greeks was some kind of theoretical construct: not so. The mechanical and scientific ideas of the great ancient philosophers and the Alexandrian Museum were used by ordinary people on a daily basis. From screw presses to waterwheel contraptions, the Hellenistic and Roman world benefited from the applications of Greek thought.

Gears allow one to change the plane of rotary motion, or the angular velocity of the rotary motion. Screws turn rotary motion into linear motion, generally considerably stepped down in velocity. You need both to make something like a modern clock or a mechanical lathe. Screws are commonplace now and used everywhere, but they really are a wonder. An inclined plane wrapped around a cylinder. Early screws were made with tools like hammer and chisel, with taps and dies made in the same way, various kinds of ingenious mechanisms to assist the process.

Making the first set of standardized and precise screws took until around 1800, culminating in Henry Maudslay‘s screw cutting lathe which was one of the most important inventions in human history. The screw cutting lathe required a screw and gears, combined together on a rigid lathe bed. The lathe bed is effectively a plane, allowing for precise motion. You can make these with a chisel and scraper/file out of arbitrary chunks of steel or cast iron; hobbyists still carve and scrape their own lathe beds. The leadscrew allowed the cutter to automatically move along a piece of rotating stock to cut another thread in a piece of rotating stock. Changegears allowed one to cut arbitrary threads from stock, by altering the ratio of screw linear motion to workstock rotation. With all these ingredients you can move a cutter along a piece of rotating screw blank an arbitrary amount, making arbitrary pitch screws. What’s more, you can amplify the accuracy of your leadscrew to a certain extent. There are heroic tales of Maudslay creating his master leadscrew that are in their own way as glorious and Promethean as Benvenuto Cellini casting his Perseus statue.

Maudslay is one of those guys who created a whole center of excellence around himself; he was a blacksmith/locksmith who built a classic Klein type-1 organization. He invented all manner of clever devices we now take for granted, from micrometers to various kinds of steam engine and telescope; he was even involved with the father of Isambard Kingdom Brunel building machines for his various ventures. Maudsley’s students (it wasn’t a school, it was a high technology business) went on to make numerous further innovations and form their own high technology companies. Joseph Whitworth invented all kinds of machine screw standards (BSW still in use today) machine tools and measuring devices, guns and so on and became enormously wealthy. Joseph Clement built the first version of the difference engine.  William Muir manufactured machine tools, Richard Roberts made locomotives and  power looms, and James Nasmyth invented the steam hammer and shaping machine.There aren’t any substantive books written about this amazing group of men, and the one I know about is expensive and out of print, but if done properly it would make an excellent case study of a Klein type-1 organization. All of these guys were giants of invention and industry and they all got stinking rich inventing new technologies and increasing man’s power over nature. There’s a sort of pamphlet about Maudsley available on archive, which is slightly better than nothing.  I assume there were contemporaries who wrote about them, but they’re mostly forgotten today.

Back to screws; using a screw, you can precisely position things on a nanoscale. I’ve done it, using these little buggers called picomotors. You can buy big giant screws made in temperature controlled oil baths which are capable of similar tricks while retaining their accuracy as well. It boggled my mind when I first read about how this is accomplished; basically the same way most mechanical accuracy is achieved; by lapping with abrasives. You can read all about it in the old Wayne Moore book “Foundations of Mechanical Accuracy.”

Which brings me back to Henry Rowland, father of American physics. It was Rowland who invented the techniques for creating the ultra precise nanoscale screw by manually lapping the screw in a giant split nut. He did this to create diffraction gratings using a “ruling engline.” Diffraction gratings are responsible for the origin of modern physics, as scientists needed them to resolve atomic spectra. And of course as I said in the previous blog, Rowland was by his own self largely responsible for American physics activities in general.

The story of the ultra-precise screw and ruling engine is so insanely awesome I’ll dedicate a later blerg or two to the topic.