The Tides ...

(Lord Kelvin) William Thomson's first tide-predicting machine, 1876.
Built by A. Légé & Co., 20 Cross Street, Hatton

Tide-predicting machine designed by William Thomson (later Lord Kelvin), built by A. Légé & Co., 20 Cross Street, Hatton Gardens, London, 1872. The machine is a mechanical analogue computer which traces the tidal curve for a given location, by combining ten astronomical components. It is the first working machine of Thomson’s design, based on his application of harmonic analysis to tidal phenomena.

Knowledge of the tides is valuable not only for navigators, but also engineers building coastal structures, and fishermen working in shallow waters. Since tides are affected by many astronomical cycles with differing periods, predicting them is mathematically complex. William Thomson had applied the technique of harmonic analysis to tides and, in conjunction with the instrument-maker Alexander Légé, designed this mechanical computer to predict the tide curves for any given location.

As stated in the Science Museum Group's article, predicting the tides is rather crucial as civilization needs to know the extent of the rise and fall of the twice-daily movement of tides in order to successfully cope with this crucial aspect of the ocean, a process, prior to Lord Kelvin's invention of the modern analog computer in 1876, given to ad-hoc guesstimates for as long as humans have resided on planet earth. With the advent of digital, analog systems, like Kelvin's, withered away but no longer as AI needs to handle the vagaries of the real world in real-time using neural nets, the analog construct AI must have in order to function. Digital can do the job but only at enormous cost in terms of efficiency and power, something becoming increasingly problematic as society moves further into the 21st century.

Polish analog computer AKAT-1, 1959.

Arising from the dead.

Why digital has problems ...

GOING BACK TO the concept of dropping a ball, and my interest in finding out how far it travels during a period of time: Calculus solves that problem easily, with a differential equation—if you ignore air resistance. The proper term for this is “integrating velocity with respect to time.”

But what if you don’t ignore air resistance? The faster the ball falls, the more air resistance it encounters. But gravity remains constant, so the ball’s speed doesn’t increase at a steady rate but tails off until it reaches terminal velocity. You can express this in a differential equation too, but it adds another layer of complexity. I won’t get into the mathematical notation (I prefer to avoid the pain of it, to use Sara Achour’s memorable term), because the take-home message is all that matters. Every time you introduce another factor, the scenario gets more complicated. If there’s a crosswind, or the ball collides with other balls, or it falls down a hole to the center of the Earth, where gravity is zero—the situation can get discouragingly complicated.

MNow suppose you want to simulate the scenario using a digital computer. It’ll need a lot of data points to generate a smooth curve, and it’ll have to continually recalculate all the values for each point. Those calculations will add up, especially if multiple objects become involved. If you have billions of objects—as in a nuclear chain reaction, or synapse states in an AI engine—you’ll need a digital processor containing maybe 100 billion transistors to crunch the data at billions of cycles per second. And in each cycle, the switching operation of each transistor will generate heat. Waste heat becomes a serious issue.

Using a new-age analog chip, you just express all the factors in a differential equation and type it into Achour’s compiler, which converts the equation into machine language that the chip understands. The brute force of binary code is minimized, and so is the power consumption and the heat. The HCDC is like an efficient little helper residing secretly amid the modern hardware, and it’s chip-sized, unlike the room-sized behemoths of yesteryear.

To see why Analog's elegant and cool, click the Veritasium video below 

Remember, analog measures, digital counts. :)