Theories: Explanatory Power is Where Its At

One of the truly excellent things about science is the precision with which our ideas are communicated. The objective is always to make what we are trying to say as accurate and unambiguous as possible. That is where we scientists get our credibility. Compare this mentality with that of someone that is trying to sell you something. However, even though we scientists generally speak English (at least in the USA), it is not always the same English that we would use in a non-scientific context. I am not referring to scientific jargon like the names that we use for processes or structures that seldom come up in polite conversation (for example, osphradium and tokogenetic). Even for other scientist outside their chosen field, that sort of jibba’ jibba’ can be impenetrable. I am talking about those words that we all use that might have a different meaning in a scientific context. Words like “normal,” “possible,” and, among the most abused science words, “theory.” Whenever someone has an anti-science agenda — flat-earthers, creationists, auto industry lobbyists — “theory” is the word that they grab onto to try and make their case. E.g., “Evolution by natural selection is only a theory. It isn’t a proven fact.” The objectives of this essay are to discuss the different uses of the word “theory,” especially to establish what scientists mean when they use it.

In non-scientific contexts (I wish there was a better word for “non-scientist.” Like “muggle” or something. That might be less pretentious than just calling them “regular people.”), the word “theory” is synonymous with speculation. There is what you know, the things that you have seen happen (or that you have heard from a reliable source), and the things that you aren’t sure about. The latter are theories. You could observe that your car smells like sulfur and develop a theory that your catalytic converter has failed — just one of the possible explanations. Once you crawl under your car and see that rusted out metal tube, your theory has become a fact. It is true. Otherwise, you would have seen that the catalytic converter was fine, and your theory would have ceased to be a theory. It is now just a crazy idea that you had, and now you need to check your fuel injector or see if the neighborhood kids egged your car.

In a scientific context, the definition of “theory” really isn’t that different. A theory begins its tenure as speculation, as an explanation for some set of observations. The difference between scientific and non-scientific theories is that they are never considered to be proven true. A favored scientific theory is merely the best explanation for some set of observations, and it remains useful until it is shown to be false and replaced by a new theory — that might simply be a rewording of the original). A theory is really a synopsis of a set of observations, including those that haven’t been observed by anyone yet.

Rather than continuing abstractly (I know how muggles hate that), I think that I can make my point with a couple examples. If I pick up a rock and let it drop, it falls. Same thing if I use a different rock, or a fork or something else. Ah ha! What goes up must come down. Cool. I no longer need to keep picking up things and dropping them to find out what will happen. Now whenever something falls, I can understand that that is just what things do. That theory will be useful until I find something that doesn’t come back down.

“That,” you might say, “is trivial.” To which I would respond with a furrowed brow and muttering under my breath about your impatience. Perhaps another “trivial” example will be more fruitful. Let’s take that same rock and set it on a table. After two days it’s still there. Ah ha! Things that are at rest will stay that way until something else moves it. “Duh, Dan,” you say, “That is inertia.” And then, to impress me, you tell me all about momentum, that an object in motion will continue in motion unless something stops it. Fantastic. Two more theories as wonderfully obvious as the one in the preceding paragraph. Except that they aren’t strictly accurate.

What if you, the table and the rock — all at rest together — are on a moving train? I, standing motionless and handsome upon the station platform, watch all three of you come whizzing by. From where you are sitting, that rock is not going to start moving until some force overcomes its inertia. But, from where I am calculating, it isn’t going to stop moving away from me down the track until some force overcomes its momentum. Hmm. It would seem that inertia and momentum are the same thing. The difference isn’t in the object, it is relative to a frame of reference. Did you hear that? It was the sound of Einstein spanking Newton. You can hear it even better if some or all of us in this story approach the speed of light.

In actuality, it isn’t as dramatic as all that. To my knowledge, Albert Einstein never really spanked Newton, who died more than a century before Einstein had even been born. (If Einstein was anything like me, he did probably make gestures and gyrate his hips at Sir Isaac’s monument whenever he was touring Westminster Abby.) In fact, Newtonian mechanics is still extremely useful in most situations, and its burden of math relative to Relativity, is a breeze. That’s probably a good way to think about scientific theories: not whether they are true or false, but whether or not they are useful. By useful, I mean that they have what we like to call “explanatory power,” they provide an explanation for lots of different kinds of observations. So, we may have a number of competing theories available to explain a set of observations — like the motion of objects — and ones with more explanatory power are more useful than those with less. But that doesn’t make them true, and we should always be looking for new theories to supercede old ones. That is how scientific progress is made.

On the other hand, theories cannot only be shown to be useless, but we can actually rule them out as false. In fact, unless a theory is stated in such a way that it can be “falsified,” it really isn’t appropriate for scientific discourse. That is, if there is not a set of observations (even hypothetical) that could contradict a theory, then it really isn’t that useful. Too abstract? Consider these examples: “All things that are red are red.” Or, “Every time I flip a coin, it will either be heads or tails.” Not very useful. “What goes up must come down.” That is a useful hypothesis because it will be contradicted the moment something goes up and doesn’t come down.

For everyone, theories are tools for understanding how the universe works. Like all tools, the purpose of the tool is to be useful. The real difference between scientific and mugglic theories is that a scientific theory never really becomes a fact, it is never proven true. Truths — Dogma — are weapons against progress. Why should I keep trying to learn about how and why the world functions the way it does if I already know the answer? It is by not understanding (or by intentionally obfuscating) that distinction that competing theories can be assailed in the popular media.