Sunday, November 25, 2007

A Plain and Simple Guide to Theories and Laws (and Hypotheses)

Somewhere growing up I'd gotten the idea that when scientists were figuring out something they'd look at what they'd discovered and make a hypothesis; then as they learned more the hypothesis would be refined into a theory, and once the theory was proven it would become a law.

Theories become laws, right?

But there was something about all this confused me. I grew up as a geeky kid and so I had a vague notion of what the "Theory of Relativity" was about, and one day on the radio I heard the newscaster say that "The theory of relativity is no longer a theory, it's a fact. It's been proven." (I have no recollection whatsoever as to what experimental confirmation resulted in this particular proclamation being made at that particular time.)

So I expected to stop hearing about the "theory" of relativity and expected that there'd be this transition to the "Law of Relativity". But that never happened.

Eventually I figured out why.

This notion that theories eventually become laws once they're proven?

Wrong. Completely wrong. And not just wrong, but the idea itself actually doesn't even make sense.

One other tangent and then I'll explain why.

That's just a theory!

In popular usage the word "theory" means something like "contemplation or speculation" (6), or "guess or conjecture" (7). So you hear "theoretically speaking...", or "It's just a theory..." This is fine, a word can mean whatever people want it to mean, so long as everyone in the conversation understands the intended meaning.

But in different contexts, the same word can have very different, even if somewhat related, meanings.

Take "swear", for instance. On the one hand, you have the "pinky swear", an "informal way of sealing a promise." Which, if you break it, the worst that can happen is that there will likely be anger, a feeling of betrayal, and possibly a damaged or lost friendship.

Then there's swearing to the truth of your testimony in a court of law. Swear falsely there and you may find yourself charged with perjury and subsequently spending time in jail.

So, swearing. Same word, same general meaning, but in different venues its meaning is seriously different.

And the same goes with the word "theory".

So a "theory" is what then, exactly? And "laws" and "hypotheses" too, what exactly are they?

Well, in the world of scientific pursuit, a theory is simply a comprehensive explanation of observations.

That's really it, in a nutshell.

Outside of the nutshell the purpose of a theory is to explain why one is seeing the behavior they're seeing. Thy sky is blue, rocks fall, and cold air sinks. Why? The explanation of each of these comes from a theory (Rayleigh scattering, gravity, and the kinetic theory of gases, respectively). The actual observed characteristics and behaviors can be determined by calculating the results of the theories' associated "laws" that describe what happens.

The Laws are the formulas, the description of what outputs you'll get given a particular set of inputs. A "law" describes the behavior, while a theory attempts to explain why that law functions the way it does.

And the neat thing about theories is that if you've got a good one--one that explains why you're seeing what you're seeing, and why things are acting the way they're acting--you can then go on and start making predictions about things you haven't yet seen. Some scientists did this for Einstein's Theory of Relativity, predicting that satellites orbiting the earth would get "dragged" forward an extra six feet a year because of the relativistic effect of the earth's rotation on its surrounding space. After making millions of measurements over 11 years they saw that this "dragging" was in fact occurring, and their prediction closely matched the measurements, within 1%.

So these are the key notions about the scientific type of theories:
  • They have to logically and coherently explain what's being observed, and why it's acting (or acted) the way it does (did).
  • They have to be able to make predictions that can then be tested.
  • New observations and facts that are discovered and are covered by a theory have to be explainable by that theory.
If a fact contradicts a theory, then the theory is flawed.

Now a theory may not explain everything in its area of concern, but that doesn't necessarily mean it's flawed, only that it's incomplete. And with more research, and more experiments, and more data, and more thinking, those unexplained areas may get filled in over time. This is actually the way science progresses, usually just a little bit at a time as more information is collected, which helps the theories get more and more refined.

Now what gets really interesting is when a well-established theory, like Newtonian Mechanics, finds itself confronted with facts, like the energy levels and sizes of atoms, that contradict what the theory requires. This can result in the creation of a whole new theory, like quantum mechanics, that not only explains those problematic facts, but also has to still be able to explain everything the previous theory did, and do it just as well, if not better.

You forgot "hypotheses"

Yeah, okay. A hypothesis is usually an initial suggested explanation for some phenomenon. It's like the first initial cut at a theory, just kinda suggesting a starting point for a theory that then has to go out and start being tested and confirmed, and continuously refined until it either works itself up into a full-blown theory, or, is disproved and discarded.

Hypotheses can also arise out of a theory, as when trying to fill in an area that the theory doesn't yet explain. A hypothesis can be a candidate explanation, based on what the theory says, for the unknown area. Which is then tested to see if it is valid, with the results of experiments either confirming the hypothesis, thus indicating that it belongs as part of the theory, or disproving the hypothesis, which is useful too since it rules something out of the theory.

Theories become laws? That's silly!

Since a theory is an explanation (and hypotheses are tentative, candidate explanations), and laws are descriptions of behavior, it's easy to see now that the notion of a theory becoming a law is just nonsense. They're two different things.

A theory explains why a law comes up with the results it does.

So the next time someone comes up to you and says, "Most of the theories in astronomy are simply that--theories. Most of the theories have no concrete evidence", you'll now know that they don't really know the first thing about what a scientific theory actually is.

A theory without evidence is by definition not a theory, it's just a guess at best, a fantasy at worst.

So when presented with an actual theory, be aware of what went into developing it, how it has to explain the evidence, and make predictions, and continue to be valid as related new data and phenomena are collected and observed over time.

Theoretically this should help clear things up. I hope it helped!

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