Thursday, June 12, 2008

Laws and Theories

There’s a misconception among people who are not scientists or science enthusiasts that a scientific law is somehow superior to a scientific theory, as if a law is “proven” while a theory is just an educated guess. Apparently people confuse a theory with a hypothesis, which really is a guess based on the available facts (it doesn’t help that “theory” has the same meaning as “hypothesis” in common use). Hypotheses that withstand rigorous testing can go on to become theories, but there is no equivalent “upgrade” from theory to law. There is no such thing as a theory or law that is “proven true”; there are only theories and laws that are consistent with the evidence.

A theory, then, is an explanation for some observed phenomenon that fits all the known facts. It is quite possible for more than one theory to explain a particular phenomenon; that’s where the principle of parsimony or “Occam’s Razor” comes into play. Basically, this principle says that any component of the theory that isn’t absolutely necessary to explain the phenomenon doesn’t belong in the theory.

The most blatant example of how laws are not superior to theories is Einstein’s Theory of General Relativity, which supersedes Newton’s Laws of Motion. Einstein’s Theory or Newton’s Laws both describe the motion of matter, and either can do the job well most of the time, but Newton’s Laws are usually easier to use: the math is just simpler to do. However, Einstein’s Theory is actually more accurate, especially in unusual situations, such as when an object is moving extremely quickly (as in “approaching the speed of light” quickly).

Keep this in mind the next time you hear someone try to dismiss a scientific theory as “only a theory” (a very popular phrase among pseudo-scientists and anti-scientists).

No comments: