COMPUTING SCIENCE
Undisciplined Science
Brian Hayes
Fishing Expeditions
The lattice models constitute a set of problems and tools that span
an impressive diversity of disciplines. But which of those
disciplines is their true home? Who owns those models?
From one point of view, such a question doesn't even deserve an
answer. The "intellectual property" of the pure sciences
is still considered a public trust, freely available to anyone with
the wit to use it. You don't have to be a licensed mathematician to
write a differential equation. And unsolved problems are like fish
in the sea—there for the taking by anyone who has the right
bait and tackle. Nevertheless, academic communities get nervous when
foreign fleets begin trawling in local waters. And no wonder. When
you've been chasing the big fish all your life, it takes an
uncommonly generous turn of mind to rejoice in watching someone else
land it.
A scientific discipline—whether physics or mathematics or
anthropology—is more than just a body of knowledge. It's also
a community of people, together with the organizations and cultural
traditions that bind them together—the journals they read, the
meetings they attend, the jokes they tell. Such institutions resist
change, and most of them are quite stable over the span of a human
lifetime. But upheavals are not unknown. In retrospect these events
may look exciting and rejuvenating, but some of the participants
must have found them traumatic. Two historical examples worth
pondering are the rise of astrophysics in the 19th century and the
invention of molecular biology in the 20th.
Astronomy had its first close encounter with physics in the era of
Kepler and Newton, but the consequences of that conjunction extended
only to the limits of the solar system. Astronomy as applied to the
stars remained the kind of science that Rutherford derided as stamp
collecting. There wasn't much you could do with the stars but
catalog them—give them names and note their positions, their
brightness, and perhaps some hint of their color. Nothing was known
of their mass and size, their composition, their age or the source
of their radiant energy. The French philosopher August Comte cited
the chemistry of the stars as an example of something that would
remain forever unknowable.
What overturned this pessimistic assessment was an infusion of new
instruments and methods, most notably spectroscopy. The discovery
that narrow lines observed in stellar spectra could be matched up
with corresponding lines in the spectrum of a candle flame brought
the stars right into the laboratory. Almost immediately,
spectroscopists were identifying chemical elements in the stars
(including, in the case of helium, an element that had not yet been
found on Earth). Later, subtler features of the spectra allowed
inferences about temperature and pressure in stellar atmospheres,
and even the measurement of stellar magnetic fields. This new style
of stellar science was thoroughly multidisciplinary. There were
astronomers (John Herschel) but also chemists (Robert Bunsen),
physicists (Gustav Kirchhoff) and even a polymath pioneer of
photography (William Henry Fox Talbot). The instigator of the whole
spectroscopic revolution was an optician (Joseph von Fraunhofer).
The term astrophysics, coined by the German physicist J. K.
F. Zölner, must have sounded odd at the outset—as
sociophysics and econophysics do today—but
it has entered the mainstream now. In most universities, the
Department of Astronomy is now named Astronomy and Astrophysics.
In biology, the quest to understand the molecular basis of life also
involved ideas and personnel recruited from other disciplines, and
yet the story is a little different. The prominent role of
physicists in this undertaking is often remarked. Of the four people
most closely associated with the double-helix model of
DNA—Francis Crick, Rosalind Franklin, James Watson and Maurice
Wilkins—three began their careers in physics or physical
chemistry. Another seminal figure was Max Delbrück, who studied
quantum physics with Niels Bohr before turning to biology. At least
one major technology was imported from physics: X-ray
crystallography became a tool for mapping the structure of
biomolecules. Although Delbrück and Crick brought no new
instruments with them, perhaps they passed along a physicist's style
of problem-solving. Delbrück set out to find the simplest
possible biological system for investigating the mechanism of
heredity—he chose the bacterial viruses called
phages—much as a physicist would reduce a magnet to a lattice
of spins. Still, however much molecular biology may have been
influenced by the physicists who helped create it, the field remains
a province of biology, not a colonial outpost of physics.
In describing events like these, the choice of a metaphor makes all
the difference. When physicists turned their attention to genes and
proteins, did they come as a plundering horde, descending on the
defenseless villages of innocent biologists? Or were they refugees
from the war-blasted landscape of physics, grateful for a new home
in a more peaceable realm, and eager to earn their keep by helping
with the chores? Or was it an alliance, a marriage of equals but
opposites, demonstrating the benefits of hybrid vigor? It would
doubtless make everyone feel better if we could adopt the last of
these fables, but such symmetrical unions are rare. For one thing,
some disciplines just have more to export, whereas others tend to
run a trade deficit. Physics and mathematics are defined as much by
their methods as by their subject matter, but in fields such as
geology or entomology the tricks of the trade tend to be more specialized.
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