13. How To Measure Disorder   Previous PageNext Page

We instinctively recognize that the creation of disorder is the natural course of spontaneous events in the real world. In the animations on the right, the motorcyclist, initially moving with a high kinetic energy, hits a brick wall. His kinetic energy of motion is changed into energy needed to break the bricks apart, into a large increase in disorder, and into random molecular motion of the metal parts of the wreckage, which will be warm to the touch. This is the normal, or expected, chain of events. In the drawings below, kinetic energy is changed into work to break down the wall, disorder, and heat to warm the wreckage.

In the third panel this work, disorder, and heat have been recombined and reconverted back into the kinetic energy of the now-unharmed motorcyclist, who goes on his way. We instinctively recognize this as ridiculous. Disorder comes spontaneously from order in our universe, but order cannot come spontaneously from disorder. Random motion (heat) tends to stay random unless we make an effort to "unrandomize" it. For this we must pay a price in energy. We can rebuild the brick wall if we make the effort, but the bricks will not fall into place by themselves, as the bottom scenario would have it.

We now have a second factor to consider in spontaneous processes: disorder. Spontaneous reactions tend to occur in the direction of lower energy, but they also tend to occur in the direction of greater disorder. In some cases both trends may reinforce; in others the result may be a trade-off between two opposing tendencies.

The scenarios shown involve a spontaneous creation of disorder, and is intuitively recognised as possible occurence. In contrast the scene involving spontaneous re-creation of order after a catastrophe,is rejected by common sense and past experience.


  Page 9 of 45 HomeGlossary