Full transcript
0:04Hi. It's Paul Andersen and this is Science and Engineering Practice 2, Developing
0:08and Using Models. Models are important in science and engineering for a couple of different
0:14ways. In science we use models and modeling to explain phenomena. Or to share an understanding
0:21of how the world works. In engineering we us it to analyze systems. And lots of times
0:26we'll do simulations or build models to see how a design is going to perform. And so before
0:34we get to models though, I really want you to understand what a model is. And so I am
0:37going to start with a couple of questions. So first of all in the drawing right here,
0:41which square do you think is darker? A or B? Pause the video if you want to take a look
0:47for a second. And of course it's a trick question. They both are going to be the same level of
0:53darkness. We could even reconstruct this. So if we take those two squares, A and B,
0:59and rebuild the optical illusion, watch carefully, all of a sudden B gets lighter. And so we're
1:05tricked by the shadow of this cylinder. And so that would be a mental model you're using
1:11to figure out which of those is darker. Let me one up with another question. So this is
1:15a diagram of the earth and the moon. The scale is okay but they would be way farther apart.
1:21You can see that one half of them is lit and then I've put the North Pole on the earth
1:25so you can know where that is. So if you were standing here. If you were to stand right
1:29here on the earth in the northern hemisphere, what would the moon look like, as seen from
1:35the earth? So if you want to take a little bit of time you could pause the video. And
1:41the right answer is D. If you missed that one, then your mental model might not be working.
1:49Your mental model of the way the earth and the moon and the phases of the moon work might
1:54be ineffective. And so to solve problems to understand the world, we use mental models.
2:01And they're great. That's the way that you work. The problem with mental models is that
2:06they're just yours. They're yours alone. They're inside your brain. They're unstable. They're
2:12idiosyncratic, that means that they're going to be different in every individual and also
2:16they're lots of times incomplete or ineffective. And so the mental model is not what we're
2:23talking about when we're talking about modeling. What we're talking about are physical, conceptual
2:29models. And so those are clear. They're shared by every one. They're external and they act
2:34as an analog. In other words they're an analogy for how phenomena work or how designs work.
2:42And so those analogs can basically be structural. This is would be the structure of DNA in a
2:47model. We don't really, we haven't seen DNA per se. We can't see it. It's too small. But
2:54we can building models that explain how it works. It could be behavioral model. How it's
2:59going to perform. So this right here is going to be ants foraging or we could look at a
3:04wing in a wind tunnel. That could be a behavioral model. Or we could look at it's functions.
3:08These are going to be the lines of magnetism around the different fields of a magnet. And
3:14so these are different analogs. And then we can manifest those analogs in a number of
3:19different ways. And so you could make a model that's just simply a diagram. This was a diagram
3:23created by Charles Darwin when he was trying to explain how speciation occurs. And he draws
3:28this branching diagram from a common ancestor. Or this could be a computer simulation of
3:33a protein. This is myoglobin. We could use an analogy as a model. For example, if I understand
3:39how fluid moves through a hose I could use that to explain how blood is going to move
3:44through the vessels or I could use just a mathematical model. So this could be the ideal
3:49gas law. It's simply a formula that explains what happens as we increase pressure or decrease
3:55volume or increase temperature. We can understand what's happening. Or even a simulation. This
4:00is a simulation of osmosis as water moves through a semi-permeable membrane. The computer
4:06simulation. These are all different types of models. In engineering we use models, lots
4:11of times to test a design. So this crash test, and the crash test dummies and all of the
4:17material we're getting back from that is allowing us to see how well a design works. We can
4:22also use models to build designs. And so we can use computer aided design software, CAD
4:27software to build material. We can physically build it now. So this would be a three-dimensional
4:32printer. A 3-D printer where we can print materials. We could actually print like this
4:37part of a motor and then we can see how that performs. And so again models are going to
4:42by physical, shared, clear understandings. And they're really the manifestation of mental models.
4:49And so the goal in science education is help students to develop models. And they do that
4:55first of all by constructing drawings and then representing phenomena. And then finally
5:00we're going to use those models. We can use models through simulations. And then we can
5:05also test designs. And so let me talk about a nice progression for this. In other words
5:10going back to the analogy of throwing darts at a dart board. We want our students from
5:17the time they begin education to start developing and using models. And we want to refine those
5:23through the years and get better and better and close and closer to the bulls eye. So
5:27when there seniors in high school they really are good at using models. And so what would
5:32be a good way to start this in the elementary. Well you could show them a picture of an insect
5:37and have them draw an insect and then draw the parts the insect. Or you could give them
5:43a demonstration and then have them draw parts of it. So for example a car on a ramp before
5:48studying how fast material moves down a ramp, make sure you get students right away constructing
5:55drawings. You know drawing water and how it warms up during the day and how light effects
6:01plants. And so the more drawing we can do earlier, the more model building we can do
6:06earlier the better. As we get older we can start to refine those models. And so we can
6:12represent actual phenomena. And so now as we get into middle school and on to high school
6:17we could label forces acting on that same drawing. And so this would be a force diagram.
6:24As we move on we also want to start using simulations. And there's a number of different
6:28simulation softwares out there that you can use to build models, like Google Sketch-Up
6:32is an example of one where you can build designs. But if you want to do scientific modeling
6:37a great choice would be Netlogo. You can download it for Mac & Windows. And basically they have
6:42a number of different simulations. So you can simulate phenomena and then you can kid
6:47of interact with that. And so this one right here is a Netlogo simulation where you're
6:51looking at wolves and sheep. And then the food for the sheep and how they'll move over
6:57time. This one is a video I created of ants. And so basically what you have are ants that
7:03are foraging on food and then when they pick up food they're going to bring that food back
7:08to the nest which is in the middle. But they're going to drop off chemicals as they move back
7:12and that's going to diffuse out. And so again this is simply a computer model that shows
7:17how ants feed but then students can interact with a lot of the inputs and so they can play
7:24around with it and they can see how that model is used. And they can also create models themselves
7:29if you know any kind of programing. You can produce these really powerful models in Netlogo.
7:35And then finally, we can test designs. And so the best way to really figure out the importance
7:41of testing designs is to actually do competitions. And so mousetrap cars is something that I've
7:47done before. Basically you're creating a car that can move just through the power of a
7:52mouse trap. And when you give students a question or a problem like how can you do that and
7:57competition, they're going to come up with ideas that are simply amazing. And so not
8:02only are they building models, they're building physical models that they can test. And so
8:05they're really doing engineering. They're doing science. They're putting it all together.
8:09And so what are models again? They're really a physical manifestation of this mental model
8:15that we can all share and we can use that to explain phenomena and also test designs.
8:19And I hope that was helpful.