Hi. It's Paul Andersen and this is Crosscutting Concept 4. It's on systems
and system models. What is a system? Basically a system is anything that's separate from
the universe. And it allows us to study it and make sense. Because in science systems
and system modeling allows us to understand phenomena. And in engineering we can build
systems and by improving those it allows us to improve design. And so what do we study
in science? Remember we study the universe. We try to understand how the universe works.
But that's too big. And so how do we make sense of it? We divide it into what's called
systems. And so a system is a portion of the universe that's separate from the universe.
And it just makes it easier for us to understand how it works. And so how does a system work?
Well basically you can have forces that are applied to the outside of a system. You can
also have matter and energy that move through a system or recycled in a system. And we're
going to talk about those more in the next concept. But basically you set aside this
one system and then you can use that to do your studies. And so what could be a system?
An elephant is a system. So is a galaxy. So is a machine. So is a nuclei or a fundamental
particle, excuse me. So is an idea. And so basically if you have a system like this,
this is a system that is going to show us how a frog eats, there are few characteristics
that they have. First of all you're going to have a boundary. In other words a boundary
between the universe and your system. You're going to have components or the parts in this
case it would be parts of the frog. You're going to have resources that move in or matter
that moves in and energy that moves into the system. You're going to have flow of that
material and some times it's recycled. And then you're going to have some kind of a feedback
mechanism that allows it to remain at stasis. And so how does a frog eat? Well you might
have a mental model of how that works. You might know how a frog eats. You might think
that. But the problem with a mental model is that it's just yours. It's internal, unstable.
It's incomplete and it's going to be different in every one of us. And so we don't use mental
models when we're talking about science or studying systems. What we use is called a
system model. A system model is simply a way that we understand how a system works. The
nice thing about these is that they're clear, shared by everyone. And they're also external.
So this would be a nice system model for how a frog is taking in energy. And so there are
a few things that you should notice about models. Number one, or system models, is this
idea of emergent properties. In other words when we start at the very small. So this for
example is a chlorophyll molecule. We don't see a lot of properties that will eventually
become apparent as we move towards bigger and bigger systems. And so chlorophyll is
going to be found inside a chloroplast. Once we get to the level of a chloroplast, there
are going to be emergent properties. In other words, properties that show up at this level
that didn't show up before. Or even as we move to a leaf, now we're taking in carbon
dioxide that can be utilized by the chloroplasts. And so now we even have greater emergent properties.
Or the emergent properties of a tree or even a forest. And so to understand a system, we
basically have to choose one level but know there are going to be things above that and
below that that we don't necessarily see. In engineering, system models are important
because we can look at a specific system and we can try to control inputs and outputs.
And the whole idea of systems engineering is looking at a really big project. For example
the space station, and then trying to get a grasp of all the systems contained within
it. And then a way to actually engineer that and get all of the people working together
on a common project. And so what's the goal in a science classroom? We want our students
to construct system models. So how do we start? We begin in the lower classes by doing drawing
and then descriptions. We want to then include invisible structures in those drawings and
diagrams. We want to then include mathematical relationships. And finally we want to talk
about the limitations and the assumptions found within those system models. And so what's
the progression? Where do we start? Well in the lower elementary grades we want our students
constructing system models right away. In other words we want them throwing darts at
a dart board and getting better and better and better over time. And so a good way to
start that is with a science notebook. You want students collecting data and everything
goes in the notebook. This is funny. This is from Apollo 17. Basically when they sent
them to the moon they asked them to do drawings of the aurora. In other words these coronal
interactions as the solar radiation from the sun is hitting the moon. And they got all
of these phenomena, but these are pictures that the astronauts were actually drawing.
And so that's a great way to start. Modeling is important as well. And so this would be
an example of an activity you can do in elementary, lower elementary grades. You could give them
some lego pieces. You could then have them construct a model. And then you could come
up with a description so they could hand those parts to somebody else and they could build
that model as well. We want to start talking about invisible features as well. And so there's
lots of things that you can't see. And those are things like forces or matter that's invisible.
And so one thing that's between the two of us right now is carbon dioxide. But you don't
see it. And so lots of times we don't think that it exists. And so a really important
cycle that we have is called the carbon cycle. In other words carbon in the atmosphere is
going to be used by plants. That carbon becomes part of the plant. And if you eat a plant,
then it becomes part of you. We then eat plants or things that eat plants and that carbon
moves into us. And so you're literally made of what you eat. And so we want students not
only drawing systems and drawing system models, but we want them labeling things that you
can see and also labeling things that you can't see. In this case if you don't see carbon
dioxide you tend to think that it's really not there. As we move up into the middle school
grades then on to high school we want to start talking about mathematical relationships.
And so this is a climograph. Climograph is a way to look at the precipitation and temperature
in a certain area. And so in a certain biome. And so we could look at a desert and compare
that to tundra. And so we could now start looking at mathematical relationships. Ways
to quantify the data in an area. Or we could be studying gears from example, when we're
talking about simple machines. And we could start using math and looking at relationships
between the two. So we could look at the teeth on this gear, the teeth on this gear and there
are going to be mathematical relationships that we could find that relate those two.
In other words, let me spin the gear for a second and you'll notice that this gear right
here is moving really really slow. And this one is moving fast. But again, everything
in science is built on math. And so we want our kids starting to build those mathematical
relationships as well. So as we build these models and they get better and better and
better, we want our students looking at them. And we're looking for limitations or assumptions
that we're making. In other words this right here is the carbon cycle and it's trying to
quantify mathematically the amount of carbon at different levels. But it's just a model.
It's a model for a system. It's not the system itself. And so we want our students using
argumentation to talk about these systems as well. And where there is good evidence
and where there is bad evidence as well. And then when we get to engineering, in system
models, it's really important that we look at limitations. Limitations of a design. And
so this is from the first robotics competition. Basically they had to design a robot that
could move these inner tubes from one place to another. And so that robot becomes a system
and it's important as you look at that from an engineer, where are the limitations. Where
can we improve it? What assumptions have we made that are wrong? In other words we want
to get better and better and better at building these system models because they allow us
to understand at least a portion of the universe. And I hope that was helpful.