What Models Can and Cannot Show

By the end of this lesson, you will be able to tell what a model does well and where it falls short.

A model is something people make to help them study a real thing. A model can be a drawing, a globe, a computer picture, or a small object you can hold. Scientists use models when the real thing is too big, too small, too far away, or too dangerous to study up close.

Think about the solar system model hanging in a classroom. The sun is a foam ball, and the planets are smaller balls on wires. This model is helpful because you can see the order of the planets and how they circle the sun. You could never see that by just looking up at the sky.

But that same model has limits. The foam sun is only a little bigger than the planets, and in space the real sun is huge enough to hold more than a million Earths. The model also uses the wrong scale, which means the sizes and distances in the model do not match the real sizes and distances in the same way. Real planets are separated by millions of miles, not a few inches of wire. The model's materials are wrong too. Foam is not hot gas, and plastic is not rock.

So a good scientist asks two questions about every model. What does this model show me correctly? What does it leave out or get wrong? A model does not have to be perfect to be useful. It just has to help you understand one important idea, like order, shape, or motion. Knowing a model's limits keeps you from believing something untrue about the real world.

Try it: If you built a model of a Texas longhorn out of clay, what would the model show you well, and what important thing about a real longhorn would it not show?