QR5.6.3 Disorder is Probable

Eggs don’t “unbreak”

All the laws of physics are reversible, so reversing a video of earth orbiting the sun breaks no laws of physics. Yet reversing a video of an egg breaking evokes laughter, even though at the atomic level every event in the egg breaking is just as reversible as the earth’s orbit. In our world, things break apart far more easily than they come together, so an egg that took much time and effort to produce can break in just a second. The formal reason why eggs don’t “unbreak” as easily as they break is the second law of thermodynamics, which states that disorder always increases for a closed system. The informal statement of this principle is Murphy’s law, that if anything can go wrong it probably will. It extends the second law of thermodynamics to society, where its opposite is Adam’s law, that from bad things good can come.

For example, suppose that injects some colored gas into the corner of a sealed box. The second law predicts that it will disperse throughout the box because that is the most disordered state. This happens because gas molecules constantly move to adopt different combinations and the number of combinations where the colored gas is spread out are far more numerous than those where the gas is just in a corner. The colored gas molecules could all move back to the corner, but it is extremely unlikely that they ever will.

The second law is thus a statistical law based on the laws of probability not a causal law. It doesn’t state that objects must become more disordered, just that they are more likely to. In a world where disorder is more probable than order, in a constantly changing world, it sooner or later prevails. So when a combination works to give a result, whether it be a car, a human body or a marriage, there are always more ways for it to go wrong than there are for it to go right. Unfortunately, this principle also predicts that the low-entropy states we call life shouldn’t exist.