How can we improve everyone's ideas about the nature of science? I think there are three words that we shouldn't use.

1. “Hypothesis”

In my opinion, this one is the worst. The worst science word ever! Well, not ever, but currently. Go out on the street, stop the first person you see, and ask them what a hypothesis is. Here's what they'll say:

“A hypothesis? That's easy. A hypothesis is an educated guess. Boom! Give me another easy question.”

What is an "educated guess" anyway? That doesn't even make sense.

What does hypothesis really mean? Well, from the Middle French hypothese, it means the basis of an argument. That isn't so bad, but it does not mean a guess.

I think the best current use of the word is this: a testable prediction derived from an idea. For example, suppose I have an idea that a constant net force on an object will cause it to move at a constant speed. This could be tested in actual and real life. (And you'd find out it's wrong.)

So, OK, I will let the phrase "hypothesis testing" stay. But for everyone's benefit, I propose that we ban the use of the word hypothesis from youth science fairs.

2. “Theory”

As long as you've collared that person on the street, ask them about this one too. Here is my generic human answer:

“A theory is a scientist's crazy idea about how something works. When something is a theory, it may or may not be true. You know, like evolution: It's just a theory.”

I'm sorry, I don't mean to sound dismissive. I'm not saying that humans are stupid, only that the common usage of this word has sucked the sense right out of it.

What is a theory, really? A theory can be replaced with another word—more on that in a moment. But for now, a theory is a scientific idea. It's not just any made-up idea or guess (educated or not). It's an idea that is supported by evidence. Does that mean it's true? Wrong question! Science is not about The Truth.

3. “Scientific Law”

My favorite example of a scientific law is the law of energy conservation. This says that in a closed system, the total energy remains the same. OK. Now what is the common idea about laws?

“A scientific law is the next phase for a theory. Once it has been proven to be true, the theory becomes a law. It's like that School House Rock video about how a bill becomes a law.”

Wrong again. A “scientific law” is not an upgraded theory. Rather, it's more like a generalization. The law of energy conservation is general in that it can be applied in many different cases. It can be used when looking at the collision of two particles or light produced from a light bulb or a pot of water boiling on a stove. Does that mean it's true? No. Go back and read #2.

One Word to Replace Them All

We should just take all three of these words out of introductory science texts. They do more harm than good. The problem is that people have firm beliefs that they mean something other than what they're supposed to mean. I don't think we can save these words.

We do have a word to replace them. Are you ready? It's the model. You can call it the "scientific model" if you prefer.

If I say "model," what do you think of? A little plastic Corvette that you can pick up with your hands? Yep, that's a model. We agree on this idea of a model. Science is all about making models, and they can take different forms:

Physical models. A globe is a physical model of the Earth. It has some features that are the same, like the relative locations of the continents, and some that aren't, like size and density. It isn't a perfect representation of the Earth, but it's pretty useful. In fact, it's useful because it isn't an exact replica.

Mathematical models. What happens when you have a net force on an object? That force changes the momentum of the object. I can also write this idea using a pair of equations:

ILLUSTRATION: RHETT ALLAIN

The equation explains the idea. The momentum principle (above) is a great example of a model that is wrong but still useful. We say that the momentum vector is the mass of the object times its velocity vector. This is very useful, but it doesn't work when the object's speed is near the speed of light. There is a better expression for the momentum that is more valid, but it's also more complicated.

Conceptual models. If you rub a nail with a magnet, that nail (if it is ferromagnetic) will then also behave like a magnet. The conceptual model for this phenomenon is the domain model of magnets. It says that a ferromagnetic material is made of magnetic domains. If these domains are all aligned in the same direction, the material will act like a magnet. (This example is from the awesome curriculum for education majors Physics and Everyday Thinking).

Playing With Models

So, how does a model replace the three words I don't like? Well, if we say science is all about making models, you don't have to ever say hypothesis. Instead you can just talk about "testable predictions" that a model yields. A theory is a model, so that would be a one-to-one replacement. And laws? I don't think it would be terrible to also replace the word law with model. Though I doubt we'd ever stop people from saying "the law of energy conservation." Even I would have a hard time with that.

So what is this thing we call “science”? Science is really about making models and playing. Yes, playing. Play isn't just for kids; adults just get better toys. Look at the top image. This is a great example of playing. What is the goal of this paper-clip magnet interaction? There is no point except to play. That is still a great science experiment.

The way many science classes are taught now, it's like studying the parts of a clarinet, the keys and reed and so on, but never playing any music. I just wish grade-level (and some college-level) books would move away from defining things and stating pieces of science, and instead focus on the playing part.