At COSI we have an exhibit called the Centripetal Generotor. As the device spins, guests are pinned between their own inertia and the inward push of the wall. The friction between the wall and their bodies overcomes the downward pull of gravity, so that even when the floor falls six hundred million nanometers (around two feet), the guests stay stuck to the wall like a radioactive spider.
We recently reopened the Rotor after its winter hiatus. On one of the first days, a young boy described to me his ride. “The floor fell and we stayed stuck to the wall. It was awesome!”
He was clearly excited. “That sounds amazing!” I said. And then, “So why did you stick to the wall?”
“The air pressure pushed against me,” he replied, “and I stuck.”
“Wow, that’s fantastic,” I said, “Have a great rest of your day.”
Misconceptions aren’t limited to young boys on carnival rides, however. Just yesterday I was reading a biography of physicist Lise Meitner for a book I’m writing. I came across this account of her first experience with physics demonstrations.
“Dr. Szarvasy had a real gift for presenting the subject matter of mathematics and physics in an extraordinarily stimulating manner. Sometimes he was able to show us apparatus in the Vienna University Physics Institute, a rarity in private coaching – usually all one was given were figures and diagrams of apparatus. I must confess that I did not always get correct ideas from these, and today it amuses me to think of the astonishment with which I saw certain apparatus for the first time.”
So where do misconceptions come from, and what can we teachers do about them?
I don’t put much stock in most theories of learning. I think the one thing the history of science has shown us is how really, really hard it is to get good data out of nature. Even relatively simple subjects like physics and biology require huge efforts, lots of simplifying assumptions, and repeated trials to get useful results. So when we tackle really complex topics like human psychology, the odds that we’re going to get anything useful are pretty slim. But of the learning theories I’ve encountered, I do at least see some sense in the theories of Piaget – in particular his ideas of assimilation vs. accommodation. And I think that is exactly how we can see misconceptions.
When I see a physics demonstration, I assimilate that demonstration into what I already know of the world and how it works. If I know that heavier things fall faster than lighter things (you’ve seen feathers and bowling balls, haven’t you?), then when the funny guy at COSI drops a tennis ball and a basketball from the same height at the same time and they hit the ground together, well, they must weigh the same, right? I’ve assimilated the demonstration into my view of the world.
If, then, the COSI demonstrator shows that when the tennis ball is on top of the basketball, and they again fall together, the heavier basketball gives a huge push to the lighter tennis ball, I am forced to accommodate my world view to this new piece of information. Wow! Light and heavy things fall at the same speed. That’s amazing!
(OK, to be honest it is probably rare to wipe out a misconception that easily. Most guests probably walk away from the basketball/tennis ball demo with the same set of misconceptions they started with – 0r maybe even more. Remember, even Lise Meitner, who became one of the world’s greatest physicists, developed misconceptions about the demonstrations she saw as an undergraduate.)
So misconceptions are a bad thing, and we as teachers should develop our presentations to combat them. Yes, OK. I agree.
But misconceptions are how we see the world. We each of us create a universe. We populate that universe with our misconceptions. We build our imperfect understanding of the world on our collected experiences. What else could we do?
We are all a big bagful of misconceptions. When we get more sophisticated, we call them “models,” but they’re still misconceptions. The only difference is we know about them now. (Of course I can’t tell you about the misconceptions I have that I don’t know about, sort of by definition really).
For instance, I have a misconception about alpha decay. A radioactive nucleus fires off an alpha particle in one direction and, like the butt of a rifle, the nucleus gets pushed back the other direction by the recoil. I’ve related a microscopic event to a common, everyday occurance, and it makes sense to me.
Only it’s wrong. There’s no mechanism inside a nucleus to fire off an alpha particle. Instead what happens is the alpha suddenly and quite by accident finds itself outside the nucleus through something called quantum tunnelling. Once there, the positive charge of the alpha and the much larger positive charge of the nucleus push against each other, sending the alpha flying one direction and the nucleus recoiling in the other.
Only that’s wrong, too. Alphas aren’t particles, at least not until I observe them. Instead they are waves. The alpha is not in the nucleus, not really, but exists in all parts of the universe. It’s just that the most likely location is inside the nucleus – but just outside is relatively possible, too. And when the wave function collapses, the alpha might be in that relatively possible place that causes the pushing of positive against positive.
Only that’s wrong itself. I’m used to a macroscopic world, where things like refrigerator magnets can repel one another. I know what that feels and looks like, and I imagine it for alpha particles, too. But that’s not right. Instead, virtual photons from the alpha and the nucleus interact, and that interaction produces the positive and negative momentum that sends the alpha and the nucleus flying.
Then there’s the fact that the alpha isn’t really made of two protons and two neutrons, but instead is made of 12 quarks, each of which might actually just be a string, each of which . . .
The point is this: our misconceptions, or models, help us get across the bridge. They help us make sense of the world. When we discover something new, we’re not building on virgin soil. Instead, we’re tearing down the old structure and replacing it with something better, something that matches what we’ve just seen, just heard, just learned a little better. We build the new on top of the old.
When we feel that joy of learning, that amazement at a new and profound idea, we’ve just built a new universe within, constructed from the shattered pieces of the old. It reminds me of my very favorite Emily Dickinson poem:
And then a plank in reason, broke,
And I dropped down and down–
And hit a world at every plunge,
And finished knowing–then–
We need our misconceptions. We need to break through the planks of reason we’ve built. We need to hit new worlds. We need the joy of being wrong.