As if quantum theory wasn't enough to stretch the limits of comprehension, now information theory is emerging and stretching those limits even further.Black holes acting as incredibly accurate quantum computers? That's just a start. How about the universe itself being a computer?This is the intriguing assertion of Seth Lloyd in his new book, Programming the Universe: A Quantum Computer Scientist Takes On the Cosmos."The Universe is a quantum computer. ...What does the universe compute? It computes itself. The universe computes its own behavior. As soon as the universe began, it began computing."The idea, in various forms, has been around for awhile. Ed Fredkin has been developing the idea since the 60's. Though his website is a bit technical for the average reader, a superb article by Robert Wright in The Atlantic Monthly captures both the essential ideas and the man himself.According to his theory of digital physics, information is more fundamental than matter and energy. He believes that atoms, electrons, and quarks consist ultimately of bits--binary units of information, like those that are the currency of computation in a personal computer or a pocket calculator. And he believes that the behavior of those bits, and thus of the entire universe, is governed by a single programming rule. This rule, Fredkin says, is something fairly simple, something vastly less arcane than the mathematical constructs that conventional physicists use to explain the dynamics of physical reality. Yet through ceaseless repetition--by tirelessly taking information it has just transformed and transforming it further--it has generated pervasive complexity. Fredkin calls this rule, with discernible reverence, "the cause and prime mover of everything."This "prime mover of everything" is a class of computer programs known as cellular automata which were invented by John von Neumann in the 1950s. More recently Stephen Wolfram has explored cellular automata in great detail in his monumental work, A New Kind of Science, in which he sees this form of analysis and understanding as ushering in a new method of doing science. The cellular automaton is a lattice of cells, which can have a finite number of states. These states result from rules which advance in discrete steps and which simultaneously update the lattice. Wolfram explored hundreds of these rules through computer analysis.So the universe could itself be a process of working out these computational processes according to some rule. And if so, then our picture of the nature of reality changes dramatically:Fredkin believes that automata will more faithfully mirror reality as they are applied to its more fundamental levels and the rules needed to model the motion of molecules, atoms, electrons, and quarks are uncovered. And he believes that at the most fundamental level (whatever that turns out to be) the automaton will describe the physical world with perfect precision, because at that level the universe is a cellular automaton, in three dimensions--a crystalline lattice of interacting logic units, each one "deciding" zillions of times per second whether it will be off or on at the next point in time. The information thus produced, Fredkin says, is the fabric of reality, the stuff of which matter and energy are made. An electron, in Fredkin's universe, is nothing more than a pattern of information, and an orbiting electron is nothing more than that pattern moving.This universe is no longer the continuous process that our perceptual system sees. Rather it is a discrete process of events. The physicist John Wheeler entitled an article on this understanding as "It from Bit"-a phrase that has become a popular way of encapsulating the idea.Back to Seth Lloyd. He is working at this interface of computer science and physics-- what Robert Wright calls the "twilight zone of modern science". He surveys the basicprinciples of quantum computing, exploring questions such as: How much information is there in the universe? How much was present at the Big Bang? Can we re-create it on a giant quantum computer? How is information related to entropy? He answers these questions with surprising clarity for ideas that are so foreign to our everyday understanding.The strength in Lloyd's book is the presentation of the core ideas of quantum computing. Those of a more philosophical bent might have wished for more speculation on the implications of his model. However, he does end his book with a "Personal Note: The Consolation of Information," in which he describes the tragic death of his teacher and friend Heinz Pagels. They were hiking together in the Colorado mountains when Heinz slipped and fell. After the rescue efforts, he was left with trying to make sense of what happened. He concludes his book with this reflection:Heinz's body and brain are gone. The information his cells processed is wrapped up in the Earth's slow process. He has lost consciousness, thought, and action. But we have not entirely lost him. While he lived, Heinz programmed his own piece of the universe. The resulting computation unfolds in us and around us: the vivid thoughts and outrageous behavior he impressed on us still flourish in our thoughts and behavior and have their own vivid and outrageous consequences. Heinz's piece of the universal computation goes on.