Copyright 2003 The New York Times Company
The New York Times
March 4, 2003, Tuesday, Late Edition - Final
SECTION: Section A; Page 25; Column 1; Editorial Desk
LENGTH: 1001 words
HEADLINE: The Real Scientific Hero of 1953
BYLINE: By Steven Strogatz; Steven Strogatz, professor of
applied mathematics at Cornell, is author of "Sync: The Emerging
Science of Spontaneous Order."
DATELINE: ITHACA, N.Y.
BODY:
Last week newspapers and magazines devoted tens of thousands of
words to the 50th anniversary of the discovery of the chemical
structure of DNA. While James D. Watson and Francis Crick
certainly deserved a good party, there was no mention of another
scientific feat that also turned 50 this year -- one whose
ramifications may ultimately turn out to be as profound as those
of the double helix.
In 1953, Enrico Fermi and two of his colleagues at Los Alamos
Scientific Laboratory, John Pasta and Stanislaw Ulam, invented
the concept of a "computer experiment." Suddenly the computer
became a telescope for the mind, a way of exploring inaccessible
processes like the collision of black holes or the frenzied
dance of subatomic particles -- phenomena that are too large or
too fast to be visualized by traditional experiments, and too
complex to be handled by pencil-and-paper mathematics. The
computer experiment offered a third way of doing science. Over
the past 50 years, it has helped scientists to see the invisible
and imagine the inconceivable.
Fermi and his colleagues introduced this revolutionary approach
to better understand entropy, the tendency of all systems to
decay to states of ever greater disorder. To observe the
predicted descent into chaos in unprecedented detail, Fermi and
his team created a virtual world, a simulation taking place
inside the circuits of an electronic behemoth known as Maniac,
the most powerful supercomputer of its era. Their test problem
involved a deliberately simplified model of a vibrating atomic
lattice, consisting of 64 identical particles (representing
atoms) linked end to end by springs (representing the chemical
bonds between them).
This structure was akin to a guitar string, but with an
unfamiliar feature: normally, a guitar string behaves "linearly"
-- pull it to the side and it pulls back, pull it twice as far
and it pulls back twice as hard. Force and response are
proportional. In the 300 years since Isaac Newton invented
calculus, mathematicians and physicists had mastered the
analysis of systems like that, where causes are strictly
proportional to effects, and the whole is exactly equal to the
sum of the parts.
But that's not how the bonds between real atoms behave. Twice
the stretch does not produce exactly twice the force. Fermi
suspected that this nonlinear character of chemical bonds might
be the key to the inevitable increase of entropy. Unfortunately,
it also made the mathematics impenetrable. A nonlinear system
like this couldn't be analyzed by breaking it into pieces.
Indeed, that's the hallmark of a nonlinear system: the parts
don't add up to the whole. Understanding a system like this
defied all known methods. It was a mathematical monster.
Undaunted, Fermi and his collaborators plucked their virtual
string and let Maniac grind away, calculating hundreds of
simultaneous interactions, updating all the forces and
positions, marching the virtual string forward in time in a
series of slow-motion snapshots. They expected to see its shape
degenerate into a random vibration, the musical counterpart of
which would be a meaningless hiss, like static on the radio.
What the computer revealed was astonishing. Instead of a hiss,
the string played an eerie tune, almost like music from an alien
civilization. Starting from a pure tone, it progressively added
a series of overtones, replacing one with another, gradually
changing the timbre. Then it suddenly reversed direction,
deleting overtones in the opposite sequence, before finally
returning almost precisely to the original tone. Even creepier,
it repeated this strange melody again and again, indefinitely,
but always with subtle variations on the theme.
Fermi loved this result -- he referred to it affectionately as a
"little discovery." He had never guessed that nonlinear systems
could harbor such a penchant for order.
In the 50 years since this pioneering study, scientists and
engineers have learned to harness nonlinear systems, making use
of their capacity for self-organization. Lasers, now used
everywhere from eye surgery to checkout scanners, rely on
trillions of atoms emitting light waves in unison.
Superconductors transmit electrical current without resistance,
the byproduct of billions of pairs of electrons marching in lock
step. The resulting technology has spawned the world's most
sensitive detectors, used by doctors to pinpoint diseased
tissues in the brains of epileptics without the need for
invasive surgery, and by geologists to locate oil buried deep
underground.
But perhaps the most important lesson of Fermi's study is how
feeble even the best minds are at grasping the dynamics of
large, nonlinear systems. Faced with a thicket of interlocking
feedback loops, where everything affects everything else, our
familiar ways of thinking fall apart. To solve the most
important problems of our time, we're going to have to change
the way we do science.
For example, cancer will not be cured by biologists working
alone. Its solution will require a melding of both great
discoveries of 1953. Many cancers, perhaps most of them, involve
the derangement of biochemical networks that choreograph the
activity of thousands of genes and proteins. As Fermi and his
colleagues taught us, a complex system like this can't be
understood merely by cataloging its parts and the rules
governing their interactions. The nonlinear logic of cancer will
be fathomed only through the collaborative efforts of molecular
biologists -- the heirs to Dr. Watson and Dr. Crick -- and
mathematicians who specialize in complex systems -- the heirs to
Fermi, Pasta and Ulam.
Can such an alliance take place? Well, it can if scientists
embrace the example set by an unstoppable 86-year-old who,
following his co-discovery of the double helix, became
increasingly interested in computer simulations of complex
systems in the brain.
Happy anniversary, Dr. Crick. And a toast to the memory of
Enrico Fermi.
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GRAPHIC: Drawings (Gregory Nemec)
LOAD-DATE: March 4, 2003