From: Wade T. Smith (email@example.com)
Date: Thu 06 Mar 2003 - 02:44:27 GMT
The Real Scientific Hero of 1953
By STEVEN STROGATZ
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
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
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.
Steven Strogatz, professor of applied mathematics at Cornell, is author
of "Sync: The Emerging Science of Spontaneous Order."
Copyright 2003 The New York Times Company
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