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- So many people sent me this simulation
of water pouring through
a maze by Bergman Joe.
And it makes sense that you sent it to me
'cause this is the kind of thing
that I would make for real.
So of course when I saw it,
I had to make it for real.
I actually made four mazes in total,
a simpler one and a more complex one,
and I also made large
versions of those two mazes.
Let's look at the small mazes first,
because when you see
what happens with those,
it'll be obvious why I
made the larger versions.
And by the way, this simulated version
does eventually fill up
completely with water
and it's very satisfying.
But if you want to see that ending,
you'll have to go to
Bergman Joe's profile,
link in the description.
Okay, so here's the simpler maze first.
And what we find brilliantly
is that the water simply solves
the maze without taking
any wrong turns at all.
And actually that makes sense
because every time the water comes up
against an incorrect path,
well, the air inside the
path has nowhere to go.
So while the water is
trying to push itself
into the incorrect path,
the air pressure inside that
closed space is pushing back.
If I had to characterize this
as a maze solving algorithm,
the algorithm would be something like,
try all paths simultaneously
using air pressure,
which is cool.
When the tank runs out it's fun to watch
the air bubbles solve the maze as well.
And actually it's quite different
to Bergman Joe's simulation
where the water eventually
tries every path,
even after it's found the solution.
What about the more complex maze?
Well, first one, I chose the
maze where the solve path
takes the player all the way
back up to the very top again.
Well, already something seems to be amiss,
like there shouldn't be any water here,
or at least not yet.
And there shouldn't be
any water here either,
or at least there
shouldn't be if this maze
is following the same
rules as the previous maze.
So what's going on here?
Well, the explanation is quite simple.
I just didn't build a watertight maze.
The reason I didn't
build a watertight maze
is because it's really difficult.
Like I've got three layers
of laser cut acrylic here,
a black layer, that's the maze itself,
and two clear layers
sandwiching the black layer.
And the best way to bond
these layers together
is with solvent that literally
dissolves the acrylic
on both sides so that they weld together
when the solvent evaporates.
That's easy enough when
you're bonding the black layer
to the first clear layer.
The solvent simply seeps
between the two bits of acrylic.
But then when you put the
second clear layer on top,
well, how'd you get the solvent in there?
A fun side note.
One thing you realize very quickly
when you laser cut a maze is that mazes
are always made of two separate pieces.
I mean, it's obvious
when you think about it,
but it's quite cool to see.
Actually a maze becomes very easy to solve
if you color the two parts separately.
But anyway, why did I
build the larger mazes?
Well, look, I stated that the reason
water doesn't go in here is
because there is air in the way.
But why doesn't the air just bubble out
so the water can get in?
Well, it's because of surface tension.
The air is unable to bubble past
to the surface tension of the water.
So if we make the maze bigger
until surface tension
isn't significant anymore,
we should expect the maze to
be solved in a different way.
We should expect the water to use
a different solving algorithm.
Maybe something closer to
what Bergman Joe showed
in his simulation.
By the way, for the larger maze,
I had the genius idea of
laser cutting thin channels
into the outer clear
acrylic so I could squirt
the solvent in once the
clear sheet was in place.
But anyway, here's the
simple maze in action.
And you can see without the
power of surface tension,
the water finds the lowest
possible place it can go to.
Sometimes momentum plays a part
so it will fill certain paths
before others as a result.
But broadly without surface tension,
the water tries more paths
before finding the correct one.
If I had to describe it in
terms of a solving algorithm,
it would be something
like, always take the path
that takes you lower
until you can't anymore,
and then take the next lowest path.
We'll get to the more
complex maze in a second.
But first, let's compare this
to Bergman Joe's simulation.
More of the maze becomes full of water,
but it doesn't fill up like
it does in Bergman Joe's.
Like water can never get into this region,
or this region, or any of these regions.
And you can see why.
Again, it's air pressure.
Except it's not surface tension
that's holding the water back,
it's just the geometry of the thing.
Like air would have to go down
before it could go up in this scenario.
So it simply doesn't because
air is less dense than water.
So my hunch is that what's going on
in Bergman Joe's simulation
is that there is no air in his simulation.
It'd be very difficult for me to recreate
that with my setup.
Like even if I could do this in a vacuum,
well, in a vacuum the
water would just boil.
Maybe I could try it with
a liquid that doesn't boil
in a vacuum.
That sounds hard.
Here's the more complex maze.
There is a slight leak here,
but it's water leaking from
the tank to the outside world.
I don't think there's any
significant leaks happening
within the maze itself,
which is a huge relief.
And just like with the simpler maze,
the water goes to all the
lowest parts it can do
before it's locked out by the geometry.
They say that if you are
ever stuck in a maze,
just put one hand on the wall
and keep walking forwards
and you'll eventually get out the maze.
Though, I suppose if there
are two possible paths
through the maze, then the
maze will necessarily be made
of three parts instead of
the two parts of acrylic
that I showed you before.
And if you happen to put
your hand on the middle part
then you'll just be
walking around forever.
But anyway, one thing I
really wasn't expecting
with this water maze
was that the whole thing
grinds to a halt when there's
still water left in the tank.
And I think that's because there are lots
of little bits of surface
tension all around the maze
that need to be overcome.
But together, those little
bits of surface tension
add up to enough resistance
so that the pressure of water
from the tank just isn't enough
to force everything through.
Like there's a little bit
of surface tension here
that's preventing the
water coming over this lip.
Another bit of surface tension
here, here, here, here, here.
They're all resisting the
flow of water slightly,
but together they present
a significant amount
of resistance.
It's a bit like those coin games.
You know, you roll your coin in,
it gets pushed off the first shelf,
but then nothing happens
on the second shelf.
Or maybe something does
fall off the second shelf,
but there's no way anything's
happening on the third shelf.
The final thing I want to
show you is what happens
if I change the color of the
water once the maze is solved.
It's fun, isn't it?
You can see that the
red dye solves the maze
and slowly starts to creep
into those stagnant areas.
So there you go, water can solve a maze.
It doesn't look anything like
Bergman Joe's simulation,
not that Bergman Joe's
simulation is wrong,
it's just simulating something
that I couldn't recreate
here in my studio.
When I was given careers advice at school,
I can tell you for sure
that making science videos
on YouTube was not one of the
suggestions that they made,
mainly because YouTube
didn't exist back then.
But also I feel like they
probably weren't asking
the right questions.
So how do you find good careers advice?
Well, for people that
are interested in finding
a fulfilling career that makes
a difference in the world,
then I strongly recommend checking out
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And I'll say at the top
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so check out 80,000 Hours today.
I hope you enjoyed this video.
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