Hi. It's Paul Andersen and this is Science and Engineering Practice 2, Developing
and Using Models. Models are important in science and engineering for a couple of different
ways. In science we use models and modeling to explain phenomena. Or to share an understanding
of how the world works. In engineering we us it to analyze systems. And lots of times
we'll do simulations or build models to see how a design is going to perform. And so before
we get to models though, I really want you to understand what a model is. And so I am
going to start with a couple of questions. So first of all in the drawing right here,
which square do you think is darker? A or B? Pause the video if you want to take a look
for a second. And of course it's a trick question. They both are going to be the same level of
darkness. We could even reconstruct this. So if we take those two squares, A and B,
and rebuild the optical illusion, watch carefully, all of a sudden B gets lighter. And so we're
tricked by the shadow of this cylinder. And so that would be a mental model you're using
to figure out which of those is darker. Let me one up with another question. So this is
a diagram of the earth and the moon. The scale is okay but they would be way farther apart.
You can see that one half of them is lit and then I've put the North Pole on the earth
so you can know where that is. So if you were standing here. If you were to stand right
here on the earth in the northern hemisphere, what would the moon look like, as seen from
the earth? So if you want to take a little bit of time you could pause the video. And
the right answer is D. If you missed that one, then your mental model might not be working.
Your mental model of the way the earth and the moon and the phases of the moon work might
be ineffective. And so to solve problems to understand the world, we use mental models.
And they're great. That's the way that you work. The problem with mental models is that
they're just yours. They're yours alone. They're inside your brain. They're unstable. They're
idiosyncratic, that means that they're going to be different in every individual and also
they're lots of times incomplete or ineffective. And so the mental model is not what we're
talking about when we're talking about modeling. What we're talking about are physical, conceptual
models. And so those are clear. They're shared by every one. They're external and they act
as an analog. In other words they're an analogy for how phenomena work or how designs work.
And so those analogs can basically be structural. This is would be the structure of DNA in a
model. We don't really, we haven't seen DNA per se. We can't see it. It's too small. But
we can building models that explain how it works. It could be behavioral model. How it's
going to perform. So this right here is going to be ants foraging or we could look at a
wing in a wind tunnel. That could be a behavioral model. Or we could look at it's functions.
These are going to be the lines of magnetism around the different fields of a magnet. And
so these are different analogs. And then we can manifest those analogs in a number of
different ways. And so you could make a model that's just simply a diagram. This was a diagram
created by Charles Darwin when he was trying to explain how speciation occurs. And he draws
this branching diagram from a common ancestor. Or this could be a computer simulation of
a protein. This is myoglobin. We could use an analogy as a model. For example, if I understand
how fluid moves through a hose I could use that to explain how blood is going to move
through the vessels or I could use just a mathematical model. So this could be the ideal
gas law. It's simply a formula that explains what happens as we increase pressure or decrease
volume or increase temperature. We can understand what's happening. Or even a simulation. This
is a simulation of osmosis as water moves through a semi-permeable membrane. The computer
simulation. These are all different types of models. In engineering we use models, lots
of times to test a design. So this crash test, and the crash test dummies and all of the
material we're getting back from that is allowing us to see how well a design works. We can
also use models to build designs. And so we can use computer aided design software, CAD
software to build material. We can physically build it now. So this would be a three-dimensional
printer. A 3-D printer where we can print materials. We could actually print like this
part of a motor and then we can see how that performs. And so again models are going to
by physical, shared, clear understandings. And they're really the manifestation of mental models.
And so the goal in science education is help students to develop models. And they do that
first of all by constructing drawings and then representing phenomena. And then finally
we're going to use those models. We can use models through simulations. And then we can
also test designs. And so let me talk about a nice progression for this. In other words
going back to the analogy of throwing darts at a dart board. We want our students from
the time they begin education to start developing and using models. And we want to refine those
through the years and get better and better and close and closer to the bulls eye. So
when there seniors in high school they really are good at using models. And so what would
be a good way to start this in the elementary. Well you could show them a picture of an insect
and have them draw an insect and then draw the parts the insect. Or you could give them
a demonstration and then have them draw parts of it. So for example a car on a ramp before
studying how fast material moves down a ramp, make sure you get students right away constructing
drawings. You know drawing water and how it warms up during the day and how light effects
plants. And so the more drawing we can do earlier, the more model building we can do
earlier the better. As we get older we can start to refine those models. And so we can
represent actual phenomena. And so now as we get into middle school and on to high school
we could label forces acting on that same drawing. And so this would be a force diagram.
As we move on we also want to start using simulations. And there's a number of different
simulation softwares out there that you can use to build models, like Google Sketch-Up
is an example of one where you can build designs. But if you want to do scientific modeling
a great choice would be Netlogo. You can download it for Mac & Windows. And basically they have
a number of different simulations. So you can simulate phenomena and then you can kid
of interact with that. And so this one right here is a Netlogo simulation where you're
looking at wolves and sheep. And then the food for the sheep and how they'll move over
time. This one is a video I created of ants. And so basically what you have are ants that
are foraging on food and then when they pick up food they're going to bring that food back
to the nest which is in the middle. But they're going to drop off chemicals as they move back
and that's going to diffuse out. And so again this is simply a computer model that shows
how ants feed but then students can interact with a lot of the inputs and so they can play
around with it and they can see how that model is used. And they can also create models themselves
if you know any kind of programing. You can produce these really powerful models in Netlogo.
And then finally, we can test designs. And so the best way to really figure out the importance
of testing designs is to actually do competitions. And so mousetrap cars is something that I've
done before. Basically you're creating a car that can move just through the power of a
mouse trap. And when you give students a question or a problem like how can you do that and
competition, they're going to come up with ideas that are simply amazing. And so not
only are they building models, they're building physical models that they can test. And so
they're really doing engineering. They're doing science. They're putting it all together.
And so what are models again? They're really a physical manifestation of this mental model
that we can all share and we can use that to explain phenomena and also test designs.
And I hope that was helpful.