It’s the Law!

Written by Bruce R. Copeland on September 01, 2008

Tags: 1st law, 2nd law, 3rd law, conservation of energy, conservation of momentum, gravity, law, law of natural selection, law of nature, mechanism, misunderstanding, science, stability, uncertainty principle

Many of you have heard the humorous expression or seen the bumper sticker “Gravity: It’s not just a good idea. It’s the Law!” No one really seems to doubt the Law of Gravity, though more than a few of us occasionally fail to take full account of it. But obscured by the politicization of science and the rancorous public debates over evolution (The Law of Natural Selection, etc.) and climate change is the fact that science recognizes and codifies a number of important laws of nature. Like the Law of Gravity, most of these laws are not even remotely in question. Yet whether from indifference or lack of science education, many people seem to be either unaware of the importance of these laws or else have come to believe that they somehow don’t apply. Nothing could be further from the truth.

Among the important laws of nature are Newton’s Universal Law of Gravitation (gravity), Conservation of Momentum, Conservation of Energy (1st Law of Thermodynamics), Bernoulli’s Principle, the 2nd Law of Thermodynamics, the 3rd Law of Thermodynamics, and the Uncertainty Principle.

Mechanism plays an important role in operation of most of these laws, in effect establishing a timescale over which the laws apply in different situations. This sometimes clouds human understanding and interpretation of these laws. Years ago when I taught thermodynamics, I used something called the Nuclear Bomb in the Room Example to drive this point home. Imagine a room with a table, chairs, and a nuclear bomb. As long as the bomb isn’t detonated, the chairs, table, and other room contents are basically stable. However, if the bomb is detonated, the most stable state of the room is vapor and maybe a small amount of debris. We might say that the room is in a metastable state when the bomb is undetonated, and it is in a stable state after the bomb is detonated. But a better way to look at the situation is to recognize that stability depends on mechanism. As long as there is no mechanism by which the bomb can be detonated, it is perfectly reasonable to regard the room with chairs, table, etc. as a stable state. Only if we believe there is some likelihood the bomb will detonate should we consider the atomized room as the stable state.

So it goes with most of human endeavor. We can build all kinds of complex structures, systems, and devices as long as we ensure that mechanisms don’t exist to allow those structures, systems, and devices to devolve to some more stable (and usually much more disordered) state.

When things DO go wrong in our society, it usually occurs because we have either failed to know/acknowledge the applicable laws of nature or we have failed to consider all mechanisms by which the laws may manifest themselves. That house sitting on the edge of a bluff may be engineered to be stable under ordinary conditions. Let us never forget, however, that mechanisms DO exist (earthquakes, storms, structural deterioration, etc.) which may destabilize that house. And we don’t ever want to lose sight of the fact that Gravity is still The Law!