Hi. It's Paul Andersen and this is Science and Engineering Practice 6. It's
on constructing explanations and designing solutions. And so the big theme that this
practice is about is about theories. Because theories are used in science to construct
explanations for how the world works. How the universe and phenomena in it operate.
And it's also used in engineering to design and test solutions. And so theories are incredibly
important but we should talk about what a theory is. Because if you say I've got a theory
on who stole my sandwich out the refrigerator, that's just a guess. It's not a theory. How
are theories created? Well let's look through a flow chart. First of all you come up with
an idea. And so maybe we're looking at the phenomena of infectious disease. How disease
is transmitted from one person to another. Scientists came up with ideas to explain that.
You then preform an experiment and if the evidence supports the idea you can move one.
But if it doesn't support the idea, no, then you've got a bad idea. So you've got to go
back again and we have to start all over. So I have to come up with an idea, design
an experiment, test my theory, if it doesn't fit, got a bad idea and I start over again.
But if it does fit, eventually I could come up with a theory. And that theory is used
to explain phenomena in the universe. It's awesome. But it's developed over a long period
of time by scientists and lots of experiments. But we're not done yet. What do you do next?
Well you discover new evidence. And if that evidence can be used to modify our theory,
to explain the new evidence, then we improve the theory and we have a better theory. And
so the theory gets better and better and better over time. So we've got this feedback loop.
But occasionally we'll come up with new evidence that can't modify our theory and so we have
something called a scientific revolution. So we have to start over again and we have
come up with a brand new idea. And so theories are big things in science. They've been developed
over years and years and years. Let me give you an example of one. The big bang theory
was first proposed by George Lemaitre and he was a priest but also an astrophysicist,
an astronomer and he came up with this idea of the Big Bang theory. That the universe
is like a giant loaf of bread. That all began at one point and has gotten bigger and bigger
and bigger over time. And so we are sitting within this loaf of bread and we continue
to move apart from everything in the universe. It seems like a crazy idea. Well, evidence
started to pile up. Some of the evidence from Edwin Hubble who was looking into space using
a telescope and found that the light every where in the universe was shifted to the red.
What does that mean? It means that everything in the universe is moving away from us. And
if everything is moving away from us then we could play the time backwards and we get
back to a point where the singularity where everything began. And so evidence has piled
up over year after years after years and we've come up with this Big Bang theory. Or maybe
the theory of natural selection, which is sometimes confused, it's simply an explanation
for how species evolve. And so right here there are two moths. There's a dark peppered
moth and a light peppered moth. And you might say, "Well, wow. This one blends in perfectly.
Wonderful camouflage." Well scientists tried to come up with an idea of how they could
evolve to a climate. Some people thought they just were created that way. One of
the first ideas was the idea somehow purposed by Lamarck that they can somehow will themselves
to change. So for an example a giraffe got a long neck by stretching up to reach leaves
higher in the tree. They didn't understand how genetics worked and how information was
passed from generation to generation. And eventually Charles Darwin came up with this
theory of natural selection. You have variation in a population. So you have moths that are
dark and moths that are light and then the ones that don't fit in are selected. In other
words they're eaten by birds. And so over time species are going to start to adapt to
their local climate. So there was argument about this. And over next fifty years it became
established as the scientific theory. And we really haven't changed it much since the
time of Darwin to explain how evolution occurs. Let me give you another one you maybe never
heard of. It's called the Miasma Theory. This was a theory that explained infectious disease.
The idea went like this, that organic material, when it dies, give off this bad air or this
miasma that moves through. So this is an explanation for how typhoid fever would spread throughout
people. And this is a book on the prevention against bad air. Well science didn't stack
up to support the Miasma Theory and so it was thrown out and replaced by the Germ Theory.
Scientists like Louis Pasteur, and this is his pasteur flask, started to study, well,
how does something go bad? How does something spoil? And at this time we were also using
microscopes to look at microscopic life. And so eventually we came up with this germ theory.
That bacteria and viruses are passed from one organism to another that cause disease.
And evidence started to pile up and now we have the germ theory. But it could eventually
be replaced by something else. And so when we're talking about a theory it's well established.
Well in the science classroom then what is a hypothesis? It's not a scientific theory.
And it's not like a lot of teachers will say, it's not an educated guess. What is a hypothesis?
A hypothesis is a plausible explanation for what we are seeing or our observations. And
so it's not just a wild guess. It's an explanation of what we think is going on. And this works
best through analogy. So basically we sit here with all of these scientific theories
and then we make new observations. And those observations we can bridge the gap between
theories and observations using explanations. Using hypothesis or hypothesis testing. Now
in engineering it's a little bit different. They also come up with guesses and explanations,
but they use that as a part of what's called the cycle of design. So basically you start
by planning. So you come up with a problem or a human need that we have to fulfill. You
then design a solution to that. You create the solution and then you evaluate it. And then
after you've evaluated it, then we may improve upon a new design, a better design. We create
that. Test it and then we do that same thing over and over again. So there still is this
idea of me explaining what happened, what went wrong, what went right. Here's an example.
So this is the first apple computer. Basically it just shipped you the motherboard and you
had to build everything around the outside of it. That was improved by the Apple II.
That was my first computer. And then the MacIntosh, the IMac and now the IMac that we have today
was created through design and the cycle of design getting better and better and better
over time. But it starts with an explanation of first define the problem. What do we have
to solve? And then let's solve it. And so the goal in science education is to have our
students constructing explanations and then designing solutions. And so what's a nice
progression for that? In other words, if we think of the analogy of a bulls eye, we want
our students from day one in elementary school throwing darts at this board, constructing
explanations. And then over the years we want them to get better and better and better and
better. Closer to the bulls eye. So the framework suggests owl pellets as a good way to get
started in elementary. So basically you order these owl pellets. These are from a long eared
owl. Student's break it apart. They get the bones out of it . They use a sheet to figure
out what rodents are in there and then they're trying to construct an explanation. So what
are they trying to come up with? What do these owls eat? What does their diet consist of?
You want students making guesses really early in their education. Or we could give them
plant growth for example. So students could be growing plants in school. They could make
guesses as to what could increase plant growth. So they might come up with the idea of sunlight,
so they need a certain amount of light. And so you could increase the amount of light
and see how that affects plants. But maybe you don't water them and they die as a result
of that. Well now this is a new explanation so we have to get better and better and better.
You want students making guesses and you can do that individually or as a class. As you
move into middle school the problems can be harder but the explanations are very important.
So an example, this is one I ask my students all the time, why does boiling water bubble?
Like, where are the bubbles coming from? And a really common guess is that it's hydrogen
and oxygen gas, because we know that there's H2O. That would be scary if you had hydrogen
and oxygen gas coming out of boiling water because they're both, I mean it's hugely explosive.
So it's not that. So you want them making guesses and then modifying those guesses to
fit with the established theories that we have. It's also important that they start
designing solutions. And so you can do this in elementary. Like bridge building are great
competitions that you can do. Where we can test out different designs. And that can move
all the way up through high school and big designs. Like this is a solar car competition
and obviously you can't do that in a classroom, but it's something your school should be working
on. And we could do this, like this is something I do in my class. We do water quality testing
where we're looking at the quality of the water in the creek that just goes right outside
of our school. But we can also build upon that. How can we make it cleaner? How can
we clean up the water in this creek? And so designing solutions are important. We want
students doing it from day one, but the sky's the limit. In high school we can do incredible
projects. We can make the world a better place and I hope that's helpful.