
A cool way to explain logic gates with water [video] - stared
https://twitter.com/page_eco/status/1188749430020698112
======
userbinator
I suppose you could call this "dynamic water logic" because it relies on flow
instead of pressure. I was expecting hydraulic relay valves ("static water
logic"), which are widespread in industrial control applications, and perhaps
even more commonly, the automotive automatic transmission:

[http://www.cogpro.com/chapters/E-CruiseOMatic/images/E-Cruis...](http://www.cogpro.com/chapters/E-CruiseOMatic/images/E-CruiseOmatic0051_jpg.jpg)

Almost all the material I could find about computing with water seems to focus
on dynamic gates, essentially completely ignoring the century-old[1] knowledge
of hydraulics that's been present all along. Perhaps this shows just how
isolated the different disciplines can be.

[1] I have a book from the early 1900s about water-operated elevators,
complete with descriptions of all the valving required to control the
hydraulic ram. They were logic gates, before they were even called logic
gates!

~~~
TuringNYC
The book The Three Body Problem also has a great scene explaining logic and
computational math via ... traditional means :-)

~~~
carlosdp
I was thinking the same thing! Great book, highly recommend

------
6510
I want to build a megalithic computer using a river flowing down a mountain.
The AND gate is a enormous door lifted by an enormous arm attached to an
enormous block hollowed out from the bottom so that it can float.

Input is done by almost lifted doors that can be moved by applying enough man
power.

The display is just enormous blocks lifted up.

It should do something important like play pong.

------
pstuart
Now someone should take this to the next level and makes a fountain that
implements an 8-bit adder.

~~~
kylek
Will 3 bits do?

[https://www.youtube.com/watch?v=6qP9HfUOCN4](https://www.youtube.com/watch?v=6qP9HfUOCN4)

~~~
rkagerer
Is that a text-to-speech voice?

~~~
CGamesPlay
Yeah, lots of science videos do this, particularly when the authors are non-
English-native and (presumably) nervous about their voice/accent.

~~~
rkagerer
It's one of the more interesting TTS voices I've heard, particularly in terms
of where it places emphasis. Any idea what it's named?

------
zemnmez
i don't think this would 'explain' a logic gate to anyone who doesn't already
understand a logic gate. this model doesn't convey any information that would
help someone reason about a logic gate. If you didn't know anything about
logic gates and you saw this, how would it improve your intuition? If I
imagine these water streams in my head, does it help me understand how, why or
what logic gates do?

i learned logic gates playing mods for games I was playing... I could have a
motion sensor and see when I NOT'd it it made its signal the opposite. I could
AND two of my sensors and see that I now had a signal combining both. I think
this kind of thing, a model that simulates _how_ logic gates are used gives a
much better intuitive understanding of what they're for and how to use them.

~~~
Wowfunhappy
It _totally_ worked for me.

I have zero physics background, and this is something I've never understand. I
knew what a logic gate _did_ , but the core idea of "how does a gate just
_know_ whether it's _this_ AND _this_ " always seemed like magic.

I had a serious lightbulb moment with this video. Although, I had to download
it and slowly scrub through several times.

I still don't actually understand how this would work with electricity, but I
can see how it's broadly possible.

~~~
marcan_42
This doesn't help you see how it works with electricity, because it's not
really how it's done with electricity.

Put two valves after each other on a pipe. The water can only flow if the
first valve AND the second valve are open.

Fork off a pipe into two pipes with a tee, put a valve on each side, and
connect the other ends of the valves together with another tee. Water flows
through the whole thing if the first valve OR the second valve is open (or
both).

That's how it works with electricity too. The valves are themselves controlled
with water/electricity too.

~~~
userbinator
Yes, series and parallel connections are the underlying theory behind
electrical logic gates, and work with plumbing too.

I believe something like this is also discussed in Petzold's famous book
([https://en.wikipedia.org/wiki/Code:_The_Hidden_Language_of_C...](https://en.wikipedia.org/wiki/Code:_The_Hidden_Language_of_Computer_Hardware_and_Software)
)

------
emmelaich
I strongly suspect Ted Stevens was thinking of hydraulic systems and logic
when he made the "series of tubes" comment.

He attended engineering school in 1942, around the time that hydraulic systems
underwent a resurgence.

------
tsumnia
I know HN is normally above such low brow things, but since these were made by
the original creator, I think it's okay...

Logic Gates with "Yellow Water":
[https://gfycat.com/radiantimportantfieldmouse](https://gfycat.com/radiantimportantfieldmouse)

Logic Gates with Slurm:
[https://i.imgur.com/UJyNd9T.gifv](https://i.imgur.com/UJyNd9T.gifv)

------
h4kor
So, water is turing complete.

~~~
elfexec
No. No more than electricity is turing complete.

------
sandoooo
cool. now if someone could just explain water flow with logic gates...

------
Jemm
I kind of like the way the Ontario Science Centre taught logic gates which was
by using balls on tracks rather than water.

------
hyperpallium
If the navier stokes equations are turing equivalent there's no analytic
solution.

------
acqq
A typical example that just appears to be "insightful" while what is happening
in the actual logic gates has no similarity with that at all:

[https://www.youtube.com/watch?v=58nSgVvXVbo](https://www.youtube.com/watch?v=58nSgVvXVbo)

so any "intuition" one might hope to gain from these two pipes will be wrong.

Therefore "explain logic gates" is an incorrect title. It can be used to
explain the truth table for AND, but not the gates.

~~~
stared
"Logic gates" is an abstract concept, and yes, it is essentially a truth
table.

You refer to one of the transistor-based implementations of logic gates. Yes,
it works differently.

~~~
acqq
I refer to any kind of logic gates actually used in the devices we use --
otherwise what is there to "explain"?

~~~
saagarjha
The boolean algebra part.

~~~
acqq
For "the boolean algebra part" the table like from here (second slide) is a
real _explanation_ :

[https://courses.cs.washington.edu/courses/cse370/03au/lectur...](https://courses.cs.washington.edu/courses/cse370/03au/lectures/02-Comb.pdf)

"There are 16 possible functions of 2 input variables: in general, there are
2^(2^n) functions of n inputs"

"And" from the original tweet is just one of them.

