Re: What's the most important concept in science?

What's the most important concept in science?

I was just wondering what the most important concept in science is. Not only in chemistry or physics, but in all the studies of science.

You'll get slightly different answers from different people, but I'd say the three (not one) most important things in science are reproducibility, explanatory power and falsifiability.

Reproducibility

Measurements and observations need to be meticulously described. In principle (and, usually, in practice) anybody with the requisite training must be able to get the same results from the same procedure.

Generally, non-repeatable measurements are ignored - or repudiated, if they have found their way into print.

Explanatory power

Explanations are valued most if they are not totally ad hoc, that is, if they explain more than the situation they were designed to explain.

ad hoc
For the specific purpose, case, or situation at hand and for no other.

The American Heritage® Dictionary of the English Language, Third Edition copyright © 1992 by Houghton Mifflin Company.

A good example is the quantization of energy. Planck proposed it in 1900 to explain black-body radiation, but it was not considered terribly important until Einstein used it to explain the (seemingly unrelated) photoelectric effect in 1905.

Falsifiability

Philosophers of science say that scientific explanations must be subject to contrafactuals. This means that a theory must make specific predictions that could be proven wrong. But to have a prediction proved wrong is not necessarily the end of a theory.

Often the theory is simply re-adjusted to fit the new facts; sometimes this allows a theory to enjoy a new period of productive life. An example is the solar system model of the atom, which was proposed to explain the fact that all the mass and positive charge of the atom appeared to be concentrated into a volume more than 100,000 times smaller than the atom itself.

Unfortunatlely, this created serious problems having to do with the known properties of accelerated electrons. Bohr saved the solar system model by mixing in aspects of the quantization of energy. This allowed Bohr to use the solar system model to explain the emission spectrum of the hydrogen atom, something the model was never designed to do.

But again, a merely ad hoc readjustment won't do. An example of this is the phlogiston theory of combustion, which said that objects burn, or rust, by giving off phlogiston. When it was shown that metals gain weight when they corrode, while wood (apparently) loses weight, the theory was readjusted ad hoc by proposing that phlogiston can sometimes (but not always) have "negative weight." Eventually phlogiston chemistry fell to the ground of its own (non-negative) weight, and was replaced by the oxygen theory of combustion.