Introduction

Once, while visiting the University of Texas in 1981, I joined John Wheeler and a group of students and postdocs for lunch. As he often did, John posed a provocative question for discussion. This time he asked something like the following, “Perhaps when we die, Saint Peter gives us a physics test to determine if our time spent on earth searching for knowledge for our fellow human beings has been well spent. Because the experience can be traumatic, and we are likely to forget details, we are allowed to bring along a crib sheet, to jog our memories. But as the point of having laws of physics is that they must be simple and general, the crib sheet is only allowed to be a 3 by 5 inch file card. What would you write down on your card?”

Of course, beyond the theological issues, John was making a simple and fundamental pedagogical point. If we believe that the laws of nature are simple, a measure of our understanding of them is the compactness with which they can be expressed. As individuals and as a community, the better we understand the laws of physics, the less the space that will be required to write them.