People: Stephen Wolfram & A New Kind of Science

Tuesday, February 10, 2004 - 12:16 PM

Physicist and computer scientist Stephen Wolfram has made his seminal work, A New Kind of Science, available for free online. What is the Principle of Computational Equivalence? Almost all processes that are not obviously simple can be viewed as computations of equivalent sophistication. More specifically, the principle of computational equivalence says that systems found in the natural world can perform computations up to a maximal ("universal") level of computational power, and that most systems do in fact attain this maximal level of computational power.

Consequently, most systems are computationally equivalent. For example, the workings of the human brain or the evolution of weather systems can, in principle, compute the same things as a computer. Computation is therefore simply a question of translating inputs and outputs from one system to another.

What is Computational Irreducibility? While many computations admit shortcuts that allow them to be performed more rapidly, others cannot be sped up. Computations that cannot be sped up by means of any shortcut are called computationally irreducible. The principle of computational irreducibility says that the only way to determine the answer to a computationally irreducible question is to perform, or simulate, the computation. Some irreducible computations can be sped up by performing them on faster hardware, as the principle refers only to computation time.

Israeli and Goldenfeld (2003) have shown that computationally irreducible physical processes can be predictable--and even computationally reducible!--at a coarse-grained level of description. In particular, coarse-grained cellular automata can emulate the large-scale behavior of the original systems without accounting for small-scale details. Furthermore, at least one of these automata is irreducible and known to be a universal Turing machine.

Here's immediate access to the complete book. Starting from a collection of simple computer experiments, Wolfram shows how their unexpected results force a whole new way of looking at the operation of our universe, including the origin of the second law of thermodynamics, the development of complexity in biology, the computational limitations of mathematics, the possibility of a truly fundamental theory of physics and the interplay between free will and determinism.

Biography of Stephen Wolfram: A well-known scientist and the creator of Mathematica. He is widely regarded as one of the world's most original scientists, as well as an important innovator in computing and software technology.

Born in London in 1959, Wolfram was educated at Eton, Oxford, and Caltech. He published his first scientific paper at the age of 15, and had received his Ph.D. in theoretical physics from Caltech by the age of 20. Wolfram's early scientific work was mainly in high-energy physics, quantum field theory, and cosmology, and included several now-classic results. Having started to use computers in 1973, Wolfram rapidly became a leader in the emerging field of scientific computing, and in 1979 he began the construction of SMP--the first modern computer algebra system--which he released commercially in 1981.

In recognition of his early work in physics and computing, Wolfram became in 1981 the youngest recipient of a MacArthur Prize Fellowship. Late in 1981 Wolfram then set out on an ambitious new direction in science aimed at understanding the origins of complexity in nature. Wolfram's first key idea was to use computer experiments to study the behavior of simple computer programs known as cellular automata. And starting in 1982 this allowed him to make a series of startling discoveries about the origins of complexity. The papers Wolfram published quickly had a major impact, and laid the groundwork for the emerging field that Wolfram called "complex systems research."

Through the mid-1980s, Wolfram continued his work on complexity, discovering a number of fundamental connections between computation and nature, and inventing such concepts as computational irreducibility. Wolfram's work led to a wide range of applications--and provided the main scientific foundations for such initiatives as complexity theory and artificial life. Wolfram himself used his ideas to develop a new randomness generation system and a new approach to computational fluid dynamics--both of which are now in widespread use.

Following his scientific work on complex systems research, in 1986 Wolfram founded the first research center and the first journal in the field. Then, after a highly successful career in academia--first at Caltech, then at the Institute for Advanced Study in Princeton, and finally as Professor of Physics, Mathematics, and Computer Science at the University of Illinois--Wolfram launched Wolfram Research, Inc.

Wolfram began the development of Mathematica in late 1986. The first version of Mathematica was released on June 23, 1988, and was immediately hailed as a major advance in computing. In the years that followed, the popularity of Mathematica grew rapidly, and Wolfram Research became established as a world leader in the software industry, widely recognized for excellence in both technology and business. Wolfram has been president and CEO of Wolfram Research since its inception, and continues to be personally responsible for the overall design of its core technology.

Following the release of Mathematica Version 2 in 1991, Wolfram began to divide his time between Mathematica development and scientific research. Building on his work from the mid-1980s, and now with Mathematica as a tool, Wolfram made a rapid succession of major new discoveries. By the mid-1990s his discoveries led him to develop a fundamentally new conceptual framework, which he then spent the remainder of the 1990s applying not only to new kinds of questions, but also to many existing foundational problems in physics, biology, computer science, mathematics and several other fields.