Let's look again at minilife.nlogo. So, to use this you do Setup; it turns all the cells white.
Now, I can either do what I did before, which is randomize by setting a certain percentage of
the cells to black, or I can edit myself. So I can click on Edit, and I then can click on cells to turn
them black, or I can click again on them to turn them white. And so I can decide what I want to use
for an initial configuration. And you can just try and randomly set cells to black, or you can set
specific patterns. Okay, and then when
you're done with this, you can un-click
on Edit, and do Go 1. Okay what this does -- it doesn't actually update the first time I click on it,
and instead marks as green all the cells that are going to either stay alive or come alive. So you
can see before it updates which cells are going to go to black.
Okay, I click again, and it actually
does the update. So, just to clarify, the green is not actually part of
the game of Life, it's just an indicator to show you in this model which cells are going to come alive.
So, let's try that again. All right, so, there we go.
And again, and again, and again.
And notice here, I've gotten to a fixed point,
that is, a configuration that doesn't change.
You could do the same thing again. I'm going to
randomize here, and then if I click Go, the
the Go Forever button,
you'll see it go for a long time,
until it gets to a fixed point, which are
either... I click Go to stop it again.
These are either configurations that don't
change, or that alternate. So for instance,
this one here, this column of three
black cells, at the next time step, that goes
to a row of three, and the next time step, that
goes to a column of three. So that's a "period two"
structure -- you could think of it as a kind
of attractor. You may not know that the game of Life has its own sort of research community associated
with it, people who try and investigate what kinds of patterns you can make in the game of Life that
have interesting properties. We're going to talk about some of those patterns in a little while,
but let me show you one particularly
famous simple one. Okay, I'm going to set up
and then I'm going to click -- oops, I have to edit --
click here, here, here, here, here. This is a pattern,
and let's see what this does.
Okay, we Go once, and check it out! It's the same
pattern, but it's moved down,
and to the right. Let's look at it
going faster... oops, that's
a little too fast... and what you can see
if I speed it up a little bit,
is this pattern is what's called a "glider."
It glides down, keeping its shape.
And it turns out you can build up
very interesting patterns using gliders.
Now, it's time for another quiz.
This time you need to download
minilife.nlogo, and for the first question,
you create a glider, and the question is
how many generations does it take
for the pattern to recreate itself in the
same orientation, but one cell
down and to the right?
The second is for you
to set up this
configuration of two
gliders about to collide,
and run it until they collide
and the pattern becomes stable,
and the question asks you what happens?