Fire in the Mind
COMPLEXITY, ENTROPY, AND THE PHYSICS OF INFORMATION
Wojciech H. Zurek
In building a tower of abstraction, one must start with a foundation, those things that are taken as given: mass, energy, space, time. Everything else can then be defined in terms of these fundamentals. But gradually over the last half-century some scientists had come to believe that another basic ingredient was necessary: information.
"The spectre of information is haunting the sciences", Zurek's manifesto began.
The Startling World of Artificial Life
CELLULAR AUTOMATON - INFORMATION
Conway thought that the most important aspect of von Neumann's automaton was the fact that it could act as a universal computing machine. This is part of the reason that it took a long time to find the ideal set of roles for Life. Conway had to tinker in order to ensure his version did the same job. In doing this he was trying to establish a profound connection between living things and the logical world.
By picking the right rules Conway believed that he was, in some less complicated way, rerunning a process that takes place in our own universe. At some point (perhaps Planck time) everything was set up, the rules were established and the whole thing was left to run. The same rules determined what happened to new generations of organisms in our universe.
The use of the same rules over and over again, recursively, has once again produced ships, loafs and beehives. This time though they are not made up of squares on a computer screen; instead they are tea clippers, French sticks and homes for honeymaking insects.
Cellular automata are at the heart of ALife. The ideas underpinning them are what makes ALife worth doing.
They forge a link between the complexity of the world we find ourselves in and an artificial world that is easier to study but reveals much about both. The central point is this: living organisms are physical systems made up of elements operating to a set of rules. There is no need, or room, for non-physical forces such as souls to get involved. Some of the rules operating in living things we know about, others are proving harder to grasp and uncover. The number of rules operating, the number of elements involved and the ways they can interact make it difficult to understand what is happening in actual organisms. The blooming, buzzing confusion makes it hard to pick out what is relevant and what is superfluous.
...living organisms are physical systems made up of elements operating to a set of rules
What we need is a way to remove all the extraneous elements to reveal the essence, what it is about living things that keeps them going. CAs are that way. They remove the muscle, flesh and bone and leave the essential rules exposed. Although in the case of CAs the number of rules operating are fewer than in living organisms, nothing, apart from the superfluous, should be lost. Despite the fact that there are only a few rules the complex forms that result and the fact that they emerge out of a system that is computationally universal lends weight to the claim that by studying a CA you are studying life: life in the raw and life that is much more tractable than doing experiments with fruit flies, cats or rats.
The connection between CAs and life is not purely computational. There is evidence that some cells in the body act like computers and process information. A convincing case can be made for a link in this sense but it is not one that CA researchers pursue. They leave that to the robot makers (see Chapter Three). The connection is phenomenological, which essentially means that living things and CAs do the same things. The complex dynamic activity you find in fruit flies, societies and cells is also found in CAs.
Using CAs to model these moving targets makes them easier to study. Boston University physics professor Tom Toffoli thinks that the only reason CAs are worth studying is because of this connection with real life. Toffoli says that mathematically CAs are not that interesting. Although it must be said that the mathematics of CAs are easier to work with than those of other dynamic systems like water flowing round a propeller or air over a wing. Toffoli is another alumnus of Arthur Burks' Logic of Computer group at Michigan. It was there that he did his PhD thesis on what CAs were worth saving for. The conclusion of his thesis was that the saving grace of CAs was their close affinity with reality. Before Toffoli did his research many thought that CAs had little connection with the real world because the basic physics of the two worlds differed widely. But Toffoli was able to show that in fact there were strong affinities between the two. The connection showed that both worked in the same way. As such they could legitimately be used to model and study problems in this field. Once he had got his PhD Toffoli became the first staff member of the newly formed Information Mechanics Group at MIT.
The research group was set up by Ed Fredkin one of computer science's oldest hackers who has made enough money out of the field to buy his own Caribbean island. Fredkin also has an abiding interest in CAs. He set up the Information Mechanics Group as a way of exploring his contention that all physical phenomena are rooted in information.
...all physical phenomena are rooted in information.
«Wir sind nichts Besonderes»
Der Computerwissenschaftler, Physiker und Bestsellerautor Stephen Wolfram über den Motor des Universums, die Intelligenz eines Wassertropfens und die Berechenbarkeit des freien Willens.
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