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Gary LaPook, you wrote:
"you know that they invented the tide predicting machine more than a century ago."

Heh.

Sure. Of course. :) But I want a  little one that I can put on my desk, made out of LEGOs would be nice, with a hand crank that I can turn to get the tide level for today's date and time, within some reasonable margin of error. I think it's possible, within some limits.

I suppose part of the reason I had a do-it-yourself analog tide machine on my mind is, via a round-about route, because of... Faraday. You, Gary, brought him up recently. When you posted about that article discussing Faraday and his early journals a couple of weeks ago, I intended to reply since the laboratory-home of Michael Faraday --the Royal Institution and its famous hall for Faraday's Christmas lectures on science-- was my very first stop in London, straight after Heathrow, back in October. I was jet-lagged since I had stayed up most of the night watching that big aurora borealis display, which I realized only after the fact was so very appropriate for my Faraday focus a few hours later. From Faraday it's just a short hop to William Thomson, or Lord Kelvin, who was the designer of that first successful analog tide machine back in the 1870s (*). I've been working my way through a biography of Lord Kelvin, "Degrees Kelvin" by David Lindley, in the past few months when I have a little free time...

To get high-quality tide predictions, we need to include at least a half-dozen harmonic components, each of which can be computed in a modern app by a "sine" term with an appropriate amplitude, frequency, and phase, or in an analog "engine" by a series of gears and other connections. That desire for "high-quality" immediately leads to a relatively large and delicate machine, but that's what the market needed when Kelvin designed and built his engine --see the image below. What I would love to see is a simple analog tide computer, with any luck built from homemade gears and other bits, and involving only the largest two or three ...maybe four harmonic components. 

You --nearly all of you reading this-- know that I have spent a significant part of my life associated with Mystic Seaport Museum and connected to its astronomy and celestial navigation education. In terms of the big picture, the museum's presentation of nautical history, specifically c.1850-1925, what has always bothered me about Mystic Seaport and continues to bother me today, is the near total absence of science, apart from the planetarium, which is treated a world apart --the "other" of the institution. So much is missing... 

Why isn't there any representation of telegraphy at Mystic Seaport? The telegraph opens a vast "sea" of interesting topics, like electric and magnetic phenomena, solar storms, data compression (Morse code is a direct ancestor to the data coding systems that manage every smart device), and of course that "shrinking of the world" that extends from the first transatlantic cable to that ubiquitous creature, the "internet". 

And why is there nothing on tides? The tides cycle, in and out, twice every damn day there in the estuary where Mystic Seaport is located. Yet there's almost nothing to acknowledge this science, which was so revolutionary in the 19th century. And why in the world doesn't Mystic Seaport own (or borrow from another museum) a big, hand-cranked tide engine, in the general family of those created first by Kelvin? So many topics in mathematics, physics, computing, and computing history (throw some Antikythera in there, too!) could follow from the rotations and revolutions of an antique tide engine. But no... And it's likely to stay that way until the museum itself is flooded into oblivion by the rising "tides" of the 21st century... Ironic, yes?

Frank Reed

* Here's a nice article on Kelvin and his tide machine from IEEE Spectrum last year.

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