very simple kinds of computer programs discussed in this chapter. But outside of mainstream science, some work along such lines was done. And for example in the 1960s early computer enthusiasts tried running various simple programs, and found that in certain cases these programs could succeed in producing nested patterns.

Then in the early 1970s, considerable recreational computing interest developed in a specific two-dimensional cellular automaton known as the Game of Life, whose behavior is in some respects similar to the rule 110 cellular automaton discussed in this chapter. Great effort was spent trying to find structures that would be sufficiently simple and predictable that they could be used as idealized components for engineering. And although complex behavior was seen it was generally treated as a nuisance, to be avoided whenever possible.

In a sense it is surprising that so much could be done on the Game of Life without the much simpler one-dimensional cellular automata in this chapter ever being investigated. And no doubt the lack of a connection to basic science was at least in part responsible.

But whatever the reasons, the fact remains that, despite many hints over the course of several centuries, the basic phenomenon that I have described in this chapter was never discovered before.

It is not uncommon in the history of science that once a general new phenomenon has been identified, one can see that there was already evidence of it much earlier. But the point is that without the framework that comes from knowing the general phenomenon, it is almost inevitable that such evidence will have been ignored.

It is also one of the ironies of progress in science that results which at one time were so unexpected that they were missed despite many hints eventually come to seem almost obvious. And having lived with the results of this chapter for nearly two decades, it is now difficult for me to imagine that things could possibly work in any other way. But the history that I have outlined in this section—like the history of many other scientific discoveries—provides a sobering reminder of just how easy it is to miss what will later seem obvious.