Saturday, December 12, 2015
  Why no Babylonian amplifiers?

Following on this.

Despite the universality of valves and diodes in Nature, the valve didn't get no respect from historians. It's not on any of the Big Lists Of Major Inventions that I can find. This long list by Encyclopedia Britannica includes a number of Babylonian and Roman inventions, but not the valve.

Early humans mastered the art of diverting flow in the context of irrigation and dams. Babylon had mechanical wells and pipes but apparently didn't use valves. Rome had checkvalves on pumps (diodes) and controllable faucets. So 'real' valves have certainly been familiar for 2300 years, maybe longer.

Well then. Why did it take so long for humans to figure out the principle of the amplifier? Why did it have to wait until the early experiments with electricity?

The engineers who developed those fantastic water clocks around 1100 AD must have noticed the power of valves. A small hand force can create a massive change in flow, which can move just about anything. With enough flow, you can move a house with your little finger. In fact water clocks used digital fluidics (eg flip-flop) but not analog fluidics.

Amplifying sound wouldn't work well with water-based fluidics, but the Romans could have developed a servomechanism to power a construction crane or stone-lifter. Control a big strong arm with your little weak arm. They could have adapted their existing catapult:



Hmph. I thought this was going to show how Romans could use analog fluidics to advantage, but it shows the opposite. If the lever arm was properly balanced, Polistra could control it easily with a rope tied to the long end. No water needed! Or for more precision, she could use a cranked winch to regulate the rope.

In other words, the catapult as originally designed was sufficient for this job. Lever, crank, windlass. Classic machines solved classic problems.

The idea of the amplifier was first imagined in 1840, as part of the huge burst of electrical invention. By bringing a static field near a wire, could you repel part of the charges in the wire and thus 'pinch off' the flow gradually? The idea didn't work with a wire because the charges move too easily. It was like trying to restrict a deep river with a single tree. The idea had to wait until we could run the whole river through a gravel bed, making it harder for the flow to reunite behind the tree. Semiconductors finally provided the gravel bed.

But why was the amplifier necessary (thus imaginable) for electricity when it hadn't been needed before? The answer pops out. When you're trying to control fast precise movements in an intangible medium, levers are useless. You need amplifiers. The first amplifier was digital: the telegraph relay. After the signal has weakened over miles of wire, the relay uses the faint ons and offs to switch current from a 'new' local battery. Much later, after the telephone introduced analog signals, the triode tube finally used the original 'pinch valve' idea with vacuum as the gravel bed. Better materials led later to the field-effect transistor, which is an EXACT implementation of the 'pinch valve' with silicon as the gravel bed.

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Polistra was named after the original townsite of Manhattan (the one in Kansas). When I was growing up in Manhattan, I spent a lot of time exploring by foot, bike, and car. I discovered the ruins of an old mill along Wildcat Creek, and decided (inaccurately) that it was the remains of the original site of Polistra. Accurate or not, I've always liked the name, with its echoes of Poland (an under-appreciated friend of freedom) and stars. ==== The title icon is explained here. ==== Switchover: This 2007 entry marks a sharp change in worldview from neocon to pure populist. ===== The long illustrated story of Polistra's Dream is a time-travel fable, attempting to answer the dangerous revision of New Deal history propagated by Amity Shlaes. The Dream has 8 episodes, linked in a chain from the first. This entry explains the Shlaes connection.

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