flushable computing

April 4, 2016 9:06 PM

In electrical engineering class, I was told to think of electric circuits with a kind of hydraulic analogy. But could you extend this to entire computers? The Rube Goldberg Machine That Mastered Keynesian Economics, built by John Horton Conway[PDF] from a urinal flush mechanism.

He wasn't the only one: Kiwi engineer-turned-economist Bill Phillips built Phillips machine, or MONIAC at Cambridge to model the complex, interconnected British economy.
It had to be put back together by Allen McRobie from the engineering department - "no economist could work out quite how Phillips had pieced the original machine together."

The Crypto-Water Computer. Gloop.

In 1936, Vladimir Lukyanov built a water computer to solve partial differential equations, the "water integrator."

Everything old is new again: Moore's Law Is About To Get Weird

posted by the man of twists and turns (21 comments total)

Wait until you see my system for computing convex hulls in O(1) time.
posted by GuyZero at 9:16 PM on April 4, 2016 [4 favorites]

Not unless you have a way to manufacture arbitrarily large rubber bands in O(1) time!
posted by J.K. Seazer at 9:26 PM on April 4, 2016 [3 favorites]

Of course, as Keynes himself once said, "In O(1) time, we are all dead."
posted by J.K. Seazer at 9:33 PM on April 4, 2016 [9 favorites]

Terry Pratchett refers to MONIAC in his novel Making Money. He talks about how the system seems to leak money for unexplained reasons.
posted by irisclara at 9:37 PM on April 4, 2016 [4 favorites]

Not unless you have a way to manufacture arbitrarily large rubber bands in O(1) time!

I said "compute". Setup time doesn't count. Besides, even if you include the pushpins, it's still O(n).
posted by GuyZero at 9:40 PM on April 4, 2016 [1 favorite]

I swear there was a hydraulic computer in the Seattle Science Center at one time but I can find no record of it.
posted by Mei's lost sandal at 10:32 PM on April 4, 2016

Way back when in Martin Gardner's "Mathematical Recreations" there was a design for a fluid digital computer that used glass tubing and water - you could build a not gate (easy) and other logic gates (some rather more difficult). I can't find a link for it now, but I once built a few of the gates and tried to assemble a two bit adder from them. Didn't manage it, but i was dealing with a home made setup and a vague recollection of the column.

Learned a lot about digital logic - one interesting facet is that water moves slowly enough to be easily visible, so you can watch gates change state. You also need to introduce a clock so you know when to measure the output, and clock pulses travel slowly enough that timing is important.

A couple of times I thought it would be good to build a random number generator and make it into a kind of water sculpture, but never managed it.
posted by Death and Gravity at 11:17 PM on April 4, 2016 [2 favorites]

Mad genius woodworker Mathias Wandel has put together a binary marble adding machine.
posted by Harald74 at 11:18 PM on April 4, 2016 [2 favorites]

> He talks about how the system seems to leak money for unexplained reasons.

That seems like a more accurate representation of economic systems, to be honest.
posted by kriox at 12:08 AM on April 5, 2016 [2 favorites]

Look, make up your mind whether you're analog or digital before you start your water games with me, you permorphous polyvert.
posted by Segundus at 2:11 AM on April 5, 2016 [1 favorite]

You just need to be able to compare and invert states, and there's your basic unit of computation. Which I find rather hard to grasp, even though I know (perhaps knew) how to build up from there to gates, combinational logic, processor architecture, instruction sets, software, [...], profit! The big stuff is hard to understand because it's so complex, the simple stuff is hard to undertand because it's so simple. I live in my own Overton window of comprehension, and it's really hard to push it either way.

Implicit in comparing is holding and transmitting, but if you can build a machine that can do that small set of things - hydraulic, mechanical, electrical, electronic, monks - you can compute. The rest is a detail of implementation. To be useful, you then have to build a good model of the system you want to study, which is where most of this falls down in the end - but, usualy, not before doing some worthwhile things.
posted by Devonian at 2:17 AM on April 5, 2016

Mei's lost sandal, it was a hydrology model of the Puget Sound, with simulated tides sped up so they visibly came in and out. You could push buttons and drop a bit of dye into particular places throughout the map. I was always fascinated by it.
posted by Hello Dad, I'm in Jail at 2:31 AM on April 5, 2016 [2 favorites]

One of the early Star Wars spin-off novels talked about the Falcon having "fluid-state electronics" (which sprayed all over when they got damaged in a ship-to-ship fight), and even as a kid I couldn't accept that anything as complex as a starship could be run by a system that would need to be so damn big to do meaningful work.
posted by wenestvedt at 3:22 AM on April 5, 2016 [1 favorite]

What do these hydraulic computers tell us about trickle-down economics? Do they show that a rising tide does, indeed, lift all boats?
posted by TedW at 5:42 AM on April 5, 2016 [1 favorite]

What do these hydraulic computers tell us about trickle-down economics? Do they show that a rising tide does, indeed, lift all boats?

To model trickle down economics on a Keynesian water computer, drill a hole under the tax bucket and watch the results. They'll show you that your economy will trickle down to the floor.

In other words, quite accurately.
posted by eriko at 6:21 AM on April 5, 2016 [6 favorites]

Danny Hillis describing this in The Pattern on the Stone really made a lot of things about programming click for me, even tho I've been coding since elementary school.
posted by annathea at 7:38 AM on April 5, 2016

It was called fluidics. I remember it was the next big thing a long while ago.
posted by njohnson23 at 8:53 AM on April 5, 2016 [2 favorites]

The thing with analog computers isn't that you can represent bits with water but that you can do differential or integral equations or things like signal convolution which take anlot of work to do in the digital domain. The economy simulator is really doing a bunch of pdes, something you need to do pretty carefully digitally.
posted by GuyZero at 12:53 PM on April 5, 2016

In electrical engineering class, I was told to think of electric circuits with a kind of hydraulic analogy.

This is one of those things that engineering professors think will be helpful but ends up making me understand even less. JUST TELL ME WHICH DIFFERENTIAL EQUATION TO USE. I PROMISE I WILL USE THAT ONE.
posted by maryr at 1:25 PM on April 5, 2016 [4 favorites]

...I am now a biologist. YMMV.
posted by maryr at 1:26 PM on April 5, 2016 [1 favorite]

It was called fluidics. I remember it was the next big thing a long while ago.

We're not easy to talk to, Zero and l. We're a little confused again here today. It's embarrassing to misplace things.

You've misplaced some data?

Mmm; the whole of the 13th century. . . . We're always moving things around, getting organised . . . But this is Zero's fault. Zero, he's the world's file cabinet.

Pity. Poor old 13th century. . . . Not much in the century -- just Dante and a few corrupt popes. But it's so distracting and annoying.

What about the books?

Books, books? They're all changed, transcribed. All information is here. We've Zero, of course. He's the central brain, the world's brain. Fluid mechanics, fluidics. He's liquid, you see. His waters touch all knowledge. . . . He flows out into all our storage systems. He considers everything. But he's become so ambiguous now, as if he knows nothing at all.

Could you tell me about the corporate wars?

Wars? We have them all here. Punic War, Prussian War, Peloponnesian War. Crimean War, Wars of the Roses. One doesn't recall them in sequence . . . But Zero will or can, I'm sure, tell you anything. A memory pool, you see. He's supposed to tell us where things are and what they might possibly mean.

Look, Zero. A visitor. Ask anything, he'll find it for you, section and lot. Won't you, Zero?

-- Ralph Richardson and James Caan in Rollerball, 1975.

posted by Herodios at 3:03 PM on April 5, 2016 [1 favorite]