Clinging to bad science is easier than getting it right

December 7, 2002

Misconceptions about science often persist in the face of contrary evidence. The misconception and the evidence can co-exist even in the same person's mind. Mine, for example.

My Christmas letter this year will contain a correction. When I moved to my new high-rise two years ago, I wrote about the great view, and added the offhand remark "at this latitude the sun is always in the south."

Oh, I know, it's a silly pedantic thing to say in a holiday letter, but pedantry comes naturally to me and I decided to leave it in.

Wrong. What I said was untrue; in fact, it was exactly backward. The farther north you are, the farther north the sun appears to rise and set, until at the Arctic Circle on the summer solstice, sunrise and sunset are simultaneous and the sun just kisses the horizon due north.

At least I think I've got that figured out now.

But I should have known what I said was wrong. I had plenty of evidence. My place is a little south of the Capitol building, and I have a lovely photo of the late-summer sun rising north of the golden dome. At the autumn equinox, the sun rises directly east and is right in my eyes as I wake up. At the time I was writing my Christmas letter, it was rising about as far south of east as it ever gets.

I've been camping in Alaska in the summer, when what the sun is doing at 2 a.m. is highly relevant to someone who is trying to sleep in a tent. And I've been in St. Petersburg, Russia, during the June "white nights" when there's hardly any night at all.

But the penny didn't drop until I heard someone who'd overwintered in Antarctica describe the sun circling in the sky, dropping lower as winter approached.

Why is this so hard?

Carl Weiman, professor of physics at the University of Colorado at Boulder and the 2001 Nobel laureate in physics, said in an e-mail, "Any physics teacher who is paying attention to students knows that it is profoundly difficult to get students to apply ideas from physics class to the real world, and it is even more difficult to get them to give up their old wrong ideas about the world by teaching them what is correct."

He gives this example from the class, "Physics in Everyday Life," that he teaches for nonspecialists. "If a small sports car is driving down the street and has a head-on collision with a large truck, how does the force the car exerts on the truck compare with the force the truck exerts on the car?"

Students invariably say the truck exerts more force. "The correct answer, which you may find hard to believe," Wieman writes, "is that the car exerts exactly the same force on the truck as the truck exerts on the car."

Well, yes, that's what Isaac Newton said. But it's counterintuitive.

Wieman demonstrates the principle with toy vehicles equipped with force sensors, he says, and if he spends enough time on the lesson, as many as 70 percent of the students will get it right on the final.

"Getting them to commit to a prediction before the experiment is very important," he says. "When they see the results do not agree with what they predicted it has a much bigger pedagogical effect than just showing them the demonstration."

I can believe that, but with my astronomical puzzles, I can't visualize the spatial geometry well enough even to make predictions. It's especially difficult to reason from what an extra-terrestrial visitor would see approaching the solar system from above to what I as an observer on the Earth see in my sky. Why is that so hard?

What accounts for the odd fact that the earliest sunset happens two weeks before the winter solstice? According to the U.S. Naval Observatory, sunset is at 4:36 p.m. in Denver, from Dec. 1 through Dec. 12. The latest sunrise occurs about two weeks after the shortest day. Why is that? What happens as you move away from or toward the equator? Is the pattern reversed in the Southern Hemisphere? At the summer solstice?

Of course I could find someone to ask, but I have no idea how I'd start to figure it out without help.

Why is that?