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DP and Me

    Ross Rhodes

Digital Physics ("DP") is a suitably neutral scientific term for a breathtaking philosophical concept. It refers to the hypothesis that all of physics -- which is to say, all of our universe -- can be rendered by a digital computer. Everything from melting ice in our backyard to black holes in the cosmos should be expressible as a computer program, according to digital physics. The reason this should be so is that our universe itself is the manifestation of a computer program, being run on some ultimate computer -- not so very different, in principle, from our own computer games and virtual reality simulations.

     Digital physics arose at the intersection of physics and computer science. Physicists have long noted that, at the most elementary level, our universe operates according to mathematical principles. In many respects, the fundamental behaviors observed on the quantum level defy common sense when interpreted as tiny specks of matter. The interpretation that seems best to fit the facts is that these behaviors are related to the mathematical principles in some unimaginably fundamental way. As the science popularizer John Gribbon puts it, "nature seems to 'make the calculation' and then present us with an observed event."

     Meanwhile, computer science has demonstrated ever greater success at "modeling" the behaviors of natural phenomena. That is, by programming a computer with a series of step-by-step instructions for taking one set of information (say, the position of an electron) and changing that information according to a mathematical formula, computer scientists have been able to reproduce on the computer monitor the same puzzling behaviors observed by the physicists in the laboratory.

     At some point in the development of both physics and computer science we could begin to speak of a convergence. Physicists became more and more convinced of the essential mathematical nature of "particle" behavior, and computer scientists became more and more confident of their ability to model the natural world through the strict mathematical rules of computer programming.

It was left to an unorthodox scientist whose career straddled both physics and computer science to put two and two together and suggest that there might be a very good reason for this convergence: it might be that the physicists are actually studying some underlying computer program, while the computer scientists are "reverse engineering" that same program. That is to say, it might be that the natural world as we know it is actually a simulation being run on a computer, and that the computer scientists' programming is actually a kind of re-invention of the existing programming that generates the simulation.

     The physicist/computer scientist who first articulated the connection is Edward Fredkin. Fredkin started his career in the early 1950s as one of the original computer hackers on one of the original computers. He helped to establish one of the world's most prominent research laboratories in computer theory at MIT, and he also found time to study with some of the greatest physicists of our time, including the Nobel Prize-winning theorist Richard Feynman. In his work, Fredkin made fundamental contributions to both disciplines, frequently driven by his unwillingness to accept conventional wisdom in either field. Chance and a native curiosity had placed Fredkin in a unique position to discover the Rosetta Stone that would connect the seemingly unrelated fields of physics and computer science.

     The link turned out to be cellular automata -- a method of programming according to a small number of simple rules which, when repeated over a large number of cycles, can develop the same dense complexity we observe in the physical systems of the natural world. Cellular automata programs have been written to mimic the behavior of gas volumes, electrons traveling down a copper wire, ant colonies, and most famously the evolution displayed in the "Game of Life." Fredkin saw applications of the cellular automata computer architecture everywhere he looked in physics. He began to believe that the match couldn't be a mere coincidence, and he formed the idea which has come to be known as the "Fredkin Hypothesis": the universe is a computer, programmed according to cellular automata principles.

I came to essentially the same conclusion as Fredkin by a somewhat different route. I grew up in the church and readily accepted the moral and social teachings of Jesus. However, I also grew up in the scientific age and I could not easily accept the worldview presented by the scriptures which spoke casually of things that were obviously impossible in the real world. In my twenties, I underwent something of a conversion while meditating on the resurrection of Christ. For me, the world was transformed from the strictly scientific cause-and-effect into a manifestation of the word of God. The vision, in brief, was that a tree was not a tree, a stone was not a stone, unless God willed it to be.

     For many years, this thought remained with me without any basis apart from revelation; it submerged. Then I became oddly fascinated with the operation of quantum mechanics. The most widely credited interpretation of QM holds that there is no underlying reality to the fundamental units of our world. According to this interpretation, we may examine the world in closer and closer detail to find what lies beneath, and we will find that the math is the bottom layer. Making no connection between this bizarre interpretation and my earlier vision, I resisted it. I searched for the gears and wheels below the surface of what I still thought of, at some level, as real.

     While puzzling over a particular quantum mechanical conundrum -- the erasing effect of conscious measurement on some properties which were previously known -- it occurred to me that this could be analogous to the inconstant qualities of computer variables which can be erased and rewritten according to design or to whim. Since no other conceptual model of the workings of QM was offered by any of my texts (the eminent physicist Erwin Schr–dinger once suggested that no conceptual model is available to the human mind), I latched onto this "interpretation" of the physics: the universe is a computer program. I then re-read all of my source material and found nothing contradicting the interpretation; in fact, I found that a great deal of the inexplicable was thereby explained. I then began to think in terms of convergence.

In the beginning was the Word. And the Word was with God and the Word was God. He was with God in the beginning. Through him all things were made; without him nothing was made that has been made.
     Logos ("the Word") is sometimes rendered as "Reason" or "the Creative Rational Principle." In computer terms, the programming embodies the logic of the data manipulation and provides the rules to be applied at each step. A programming rule is given as an instruction in a language. The programming language condenses many layers of subroutines, but ultimately it consists of words which symbolically represent the logic and the rules. The words are typed on the screen and entered into the computer's memory. In Star Trek (and in many current office applications), they skip the typewriter and just speak into the computer. When an instruction is entered into the computer, it generally produces a result on the output device, such as a monitor. If the monitor were our world, the programmer's word could produce flesh as real as my forearm. It is possible to derive the same sense from the Genesis account of creation, in which God speaks and the universe comes into being. With the computer metaphor, these mythical, or mystical, passages can be taken almost literally.

The delight of this view of creation and of the universe is that it allows me to be at once very old-fashioned and very up-to-date. Any and all of the narrative of the Bible is possible in a computer-generated virtual reality universe. "For nothing is impossible with God." I believe in a God who instructs through revelation, scriptural and personal; a God who watches over me and answers my prayers; a God who determines right and wrong and holds me accountable; a God who can enter into my universe (God's own universe) in fully human form; a God who has ample tools to part the Red Sea, change water into wine, or enter into death only to be raised in resurrection. Accordingly, I can look around me and imagine myself as a participant in the virtual reality "game" programmed by God, playing according to the instructions given to Israel, to the church, perhaps to other cultures at other times.

     I do not sense any heresy in this approach, either scientific or theological. It allows me to maintain my respect for the investigatory methods of science which now may be approaching the truth: that we live in a created world. Even as an educated post-Enlightenment cosmopolitan sophisticated Western rationalist, I embrace my faith without the slightest hesitation or equivocation. Digital physics implies the essential insignificance of the material world, and of our worldly ambitions and fears. So does the resurrection of Christ.

Further reading in Digital Physics:
Fredkin, Edward. "Finite Nature." Proceedings of the XXVIIth Rencontre de Moriond. 1992.
-- "A New Cosmogony." Proceedings of the Physics of Computation Workshop. October 2-4, 1992.
-- "Digital Mechanics: An Informational Process Based on Reversible Universal CA." Physica D 45 (1990), at pp. 254-270.
Petrov, Plamen. "Non-replicative Fredkin's rules in homogeneous cellular spaces," PhysComp96, Boston, MAÝ(1996).
Wright, Robert. "Did the Universe Just Happen?" The Atlantic [Monthly]. April 1988, at p. 29.

Related Web Sites:
Digital Physics

Popular Entertainments Useful as Discussion Starters:
The Matrix. (Rated R) Warner Brothers. 1999.
The Thirteenth Floor (Rated R)

Columbia Tri-Star. 1999.

Further Reading in Quantum Mechanics:
Albert, David Z. Quantum Mechanics and Experience. Harvard University Press. (Cambridge 1992) (primarily for chapter 1)
Feynman, Richard P. Q.E.D.: The Strange Theory of Light and Matter. Princeton University Press. (Princeton 1985)
Gribbon, John. Schr–dinger's Kittens and the Search for Reality. Little Brown & Co. (New York 1996)
Herbert, Nick. Quantum Reality. Anchor Books. (New York 1985)
Polkinghorne, J.C. The Quantum World. Princeton Science Library. (Princeton 1989)

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