September 27, 2003

Can a Theory Evolve into a Law?

In general when we refer to a theory we mean something that’s not proven yet. In science it’s a bit different. Today, on “A Moment of Science,” we are clearing up the difference between a scientific theory and a scientific law. Well, the definition of a law is easy. It’s a description–usually mathematical–of some aspect of the natural world.

The law of gravity describes and quantifies the attraction between two objects. But the law of gravity doesn’t explain what gravity is or why it might work in this way. That’s because that kind of explanation falls into the realm of theory. And the theory that explains gravity is the theory of general relativity.

According to the National Academy of Sciences, a scientific theory is a “well- substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.” In other words, all scientific theories are supported by evidence, and you can test them, and–most importantly–you can use them to make predictions.

Based on that definition, theories never change into laws, no matter how much evidence out there supports them. Formulating theories, in fact, is the end goal of science.