Editor's comment

Jacob Bronowski's book and TV presentation The Ascent of Man turned this scientist into one of the premier popularizers of science.

Here, in clear language, he explains why time goes in the direction of increase in entropy (disorder).


Bronowski, Jacob "The Arrow of Time" [excerpt – 250 words] — order and disorder explained

The direction of time in the universe is marked by increasing disorder. Without clocks and without an inner sense of time, we could tell later and earlier. Later is characterized by the greater disorder, by the growing randomness of the universe.

We ought to be clear what these descriptive phrases mean. Order is a very special arrangement; and disorder means the loss of what makes it special. When we say that the universe is becoming more disordered, more random, we mean that the special arrangements in this place or that are being evened out. The peaks are made lower, the holes are filled in. The extremes disappear, and all parts sink more and more towards a level average. Disorder and randomness are not wild states, they are simply states which have no special arrangement, and in which everything is therefore near the average...

The movement towards randomness is not uniform. It is statistical, a general trend. Here and there, in the midst of the flow towards an average chaos, there are places where the flow is reversed for a time. The most remarkable of these reversals is life. Life as it were is running against time. Life is the very opposite of randomness. It perpetuates itself against the disorder of time.