WEEK IN REVIEW: June 16, 2002

SCIENCE is a cumulative, fairly collegial venture. But every so often a maverick, working in self-imposed solitude, bursts forth with a book that aims to set straight the world with a new idea. Some of these grand schemes spring from biology, some from physics, some from mathematics. But what they share is the same unnerving message: everything you know is wrong.

A self-employed British theorist named Julian Barbour recently argued that time doesn't exist, and Frank Tipler, a physicist with a theological bent, offered scientific proof, in "The Physics of Immortality," of an eternal hereafter. People still read Julian Jaynes's imposing 1976 book, "The Origin of Consciousness in the Breakdown of the Bicameral Mind," which pinpoints when humanity first became self-aware, and (also from that era) the work of James Lovelock, inventor of the Gaia Hypothesis, holding that the earth — rocks, air and all — is a living, breathing superorganism.

But for sheer audacity — and intellectual salesmanship — it would be hard to beat Stephen Wolfram, whose 1,263-page, self-published manifesto, "A New Kind of Science," was holding its own last week atop Amazon's best-seller chart, along with "Divine Secrets of the Ya-Ya Sisterhood" and "The Nanny Diaries."

In the long tradition of the scientific loner, Dr. Wolfram, a freelance physicist known among his colleagues for his abrasive and self-aggrandizing ways, has yanked the spotlight onto a strikingly counterintuitive idea — that the universe is really just a big computer, something that can best be described not by analyzing equations but by trying to figure out what kind of software it runs.

That, however, is just half the story. By short-circuiting the traditional formalities of scientific publication, he has managed to offend not just scientists who think he is wrong but also some who think he is right. What hasn't always come across in the debate, which is shaping up as the intellectual skirmish of the season, is that Dr. Wolfram is not a lone voice in the woods.

Interesting ideas rarely spring up in isolation. The vision Dr. Wolfram has so meticulously laid out in such an arresting manner is part of a movement some call digital physics or digital philosophy — a worldview that has been slowly developing for 20 years.

Just last week, a professor at the Massachusetts Institute of Technology named Seth Lloyd published a paper in Physical Review Letters estimating how many calculations the universe could have performed since the Big Bang — 10120 operations on 1090 bits of data, putting the mightiest supercomputer to shame. This grand computation essentially consists of subatomic particles ricocheting off one another and "calculating" where to go.

As the researcher Tommaso Toffoli mused back in 1984, "In a sense, nature has been continually computing the `next state' of the universe for billions of years; all we have to do — and, actually, all we can do — is `hitch a ride' on this huge ongoing computation."

This may seem like an odd way to think about cosmology. But some scientists find it no weirder than imagining that particles dutifully obey ethereal equations expressing the laws of physics. Last year Dr. Lloyd created a stir on Edge.org, a Web site devoted to discussions of cutting edge science, when he proposed "Lloyd's hypothesis": "Everything that's worth understanding about a complex system can be understood in terms of how it processes information."

Naturally a lot of researchers, who consider computers no more than useful tools, react huffily to the suggestion that what they are doing is "old science." So far no one using the alternative approach has been able to match the equations of calculus in predicting, for example, the exact moment of last week's solar eclipse for any spot on the planet.

What the detractors are less likely to emphasize is the track record of traditional mathematical methods in forecasting, say, the recent gyrations in the stock market or the way a forest fire will burn. Here the usual methods of science are stretched to the limit — and that is where an influential minority of scientists quietly agree on the kind of cure Dr. Wolfram is so loudly prescribing: replacing equations with a different kind of mathematical device called algorithms, simple little computer programs.

THIS would represent a true upheaval. **Mainstream science is rooted in
the notion that space and time form a continuum: a perfectly smooth expanse
that can be precisely described by what mathematicians call the real numbers,
those that can have an endless string of digits after the decimal point.
This kind of mathematics — the basis of calculus — is undeniably
powerful. Physicists can predict the characteristics of a single subatomic
particle with an accuracy equivalent to, as Richard Feynman liked to say,
estimating the distance between New York and Los Angeles within the width
of a human hair. Why even think about replacing something that works so well?
The problem is that when you put a few electrons together and throw in a
sprinkle of neutrons and protons, the system that emerges rapidly becomes
so complex that exact predictions are impossible. The infinitesimally precise
numbers have a way of causing the equations to crash.**

**And that is where the contrarians rush in, proposing that reality is not
continuous but discrete, with a smallest possible length and a smallest possible
duration of time. Picture space-time as a kind of grid on which the universe
unfolds tick by tick, like a pattern in a kaleidoscope or a program running
on a computer.**

In expressing their awe at the mathematical nature of creation, physicists have playfully suggested that God is a mathematician. Why not make him a software engineer? The result, says Edward Fredkin, another early promoter of digital physics, "might be the beginnings of a new intellectual revolution comparable to what was spawned by the development of mathematics." (His own treatise is available on the Web at digitalphilosophy.org.)

Had Dr. Wolfram been more demonstrative in parceling out credit to those who share his vision (many are mentioned, in passing, in the book's copious notes), they might be lining up to provide testimonials. It's the kind of book some may wish they had written.

Instead they were busy writing papers, shepherding them through the review process, presenting them in conferences, discussing them at seminars and workshops — going through the paces of normal science. That is how an idea progresses. But sometimes it takes a bombshell to bring it to center stage.

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