Hidden wonders: Why we should teach our students about scientific uncertainty

03/30/2013
STEM
GREG DICK

Picture this. You get the newspaper and there’s a new scientific discovery, something that flies directly into the face of something you learned in school. Velociraptors had fuzzy feathers, like baby ducks. If your grandparents starved as teenagers, you are more likely to get diabetes now. More than half of the universe is made up of some unknown “dark” substance, not a particle of which has ever been found. In science things are always shifting. How do you respond? How do we, as teachers, want our students to respond?

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The worst response is a deep-seated sense of mistrust of science. Scientists don’t know what they’re talking about: they’re always changing their minds. Why did I bother learning this?

The better response is excitement. A new discovery! I wonder where that will take us.

How do we take our students from response A to response B — from bitterness to wonder?

I think it’s all about how science is taught. For instance, when I teach physics I like to start with a hands-on puzzle. I build a sandwich of two boards with an object hidden between them. I give the students marbles to shoot in at the hidden object. Some of the marbles pass through, while others bounce back. The ones that bounce do so at various angles. The students put a piece of paper on top of the top boards and trace the marbles’ paths. From that, they can easily build a picture of the hidden object. They are building a mental model.

The obvious next step would be to lift the top board and check the model against the reality. Ah-ha: it’s a star made of Styrofoam, and it’s 10 centimeters in diameter. We were able to measure that with 15 percent accuracy.

But it’s actually more scientific never to lift the board.

Most of what scientists study can never be directly observed. We can’t go pet a velociraptor. We can’t see what’s inside a black hole. Scientists build models based on evidence, but very often those models can never be compared directly against reality. Science, therefore, is always at least a little bit uncertain. You can do a million experiments that confirm your predictions and still not be absolutely certain your model is correct. Because if you do one experiment that consistently breaks your expectations, you’ll know your model is wrong.

Newton’s model of gravity, for instance, worked flawlessly for centuries, until certain seemingly unrelated questions about the nature of light came together in the mind of Albert Einstein, and gave us a new theory of gravity — general relativity. A single experiment whose results Newton’s theory couldn’t predict and Einstein’s could was enough to turn the scientific tide.

Does it seem risky to teach children that science means uncertainty? I think it probably does. After all, how often have we heard that something with a great weight of scientific evidence behind it is “just” a theory? Scientists and science teachers cringe over that “just.” We struggle to explain. It seems unfair that we’re called on to admit to people who do seem completely certain that science is not and cannot ever be completely certain. Sometimes we feel caught in a battle that we never volunteered to fight. Why should we give this ground?

But we should teach science this way, because we need to teach students what science is. We live in a scientific age, and we need to be able to evaluate scientific claims. Decisions range in scale from whether we should take a multivitamin to whether we should commit our entire society to fighting global warming depends on our ability to understand science.

Let me go back to my Styrofoam star being bombarded with marbles. It’s a lesson that can go in many directions. Students who are interested in history might want to hear that in 1909 Ernest Rutherford discovered the nucleus of the atom in just this way, which is why the process is called Rutherford backscattering. Advanced students might be intrigued by a second experimental set-up that contains not a Styrofoam star but a Styrofoam depression — a dimple in the bottom board. Suddenly they’ll find that the paths of their marbles don’t bounce back, but are bent on their way through. This dimple, too, can be mapped, but it’s harder. What a great introduction to the idea of gravity as a curve in space-time! Suddenly that deeply abstract concept becomes something they can fiddle with, something they can very nearly touch.

But every very young student can learn a lot from the star made of Styrofoam. Imagine setting third graders loose on such a project. Can they map the star? Perhaps not: the geometry might well be beyond them. But imagine letting them compare the hidden star with marbles bounced off objects they can see. Quickly they’ll learn the differences between marbles bounced off a cube and marbles bounced off a hemisphere. Between a cube and a triangle. Between a large hemisphere and a small one. They could even begin to imagine the limits of scientific knowledge: if a sphere is hollow, there is no way for the marbles to know.

I believe that even very young children can and should learn to think this way. Given enough time and fiddling, they can learn to gather evidence, build mental models, compare, test, predict. They can learn the power of indirect observation. If you doubt that, imagine telling a classroom full of kids who just bounced marbles off a hidden star for an hour that there is nothing under the board. They won’t believe you. They may not be able to prove the existence of the hidden star absolutely, but they will be sure of their evidence. Just listen to them argue. These are the children our scientific society needs. These are the children who will meet news of a new discovery not with bitterness, but with wonder.

Science isn’t a body of facts. It’s our best guess, put into the shape of models. Many of these models work very, very well, but we know that there are places where they fail. We know we don’t know everything.

At Perimeter Institute for Theoretical Physics, where I work, I have a colleague who used to exchange letters with Einstein. The very first from Einstein begins this way: “Our situation is the following. We are standing in front of a closed box which we cannot open, and we try hard to discuss what is inside and what is not.”

We owe it to our students to share this sense of wonder.

Greg Dick is the Director of Educational Outreach at Perimeter Institute for Theoretical Physics. For more information visit www.perimeterinstitute.ca.
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