By all accounts, teachers should love models. They make it easier to understand things that are too big or far away to see in person, and they can simplify complex ideas to help students see the things that are really important about an object or concept. But models have one big problem: they lie.

All Models Are Wrong

Because they try to do one thing well, models always make compromises. If they're trying to emphasize the different parts of something, they might leave out some similarities. If they're trying to show the big picture of how something works, they need to leave out the details. This doesn't mean they aren't helpful, but just that we need to know what simplifications any model has made. The statistician George Box is famous for saying that all models are wrong, but that some are useful. This is definitely true for models we use in the classroom.

The Real Problem with Models

As we know, models represent only parts of how the real thing appears or functions. Students, on the other hand, don't always realize this. Even when they do, students may not realize the extent or details of the differences between a model and the thing it represents. This can easily lead students to confusion and reinforce or create misconceptions for them. For example, when a diagram of the solar system is shown from a tilted view, students may gain the impression that the orbits of the planets are much more elliptical than is really the case.

It is important to help students realize these differences whenever using models. To do this, the authors of Understanding Models in Earth and Space Science suggest four helpful questions you can ask yourself (and teach your students to ask):

• How does this model work the same as what it represents?
• How does this model work differently from what it represents?
• What are the strengths and weaknesses of this model?
• How does this model compare and contrast with what it represents?

Learn to ask these questions of models you plan to use in teaching, and be ready with the answers yourself. Then find ways you can bring your students to ask and answer the questions for themselves, rather than simply providing them the answers for them. If students miss opportunities to understand the answers to these four questions, the possibility that they may retain incorrect ideas from the model is increased, so make sure to note any important answers that students have not found through their own discussion.