COMPUTING SCIENCE
Undisciplined Science
Brian Hayes
"All science is either physics or stamp collecting" said
Lord Rutherford, who was not a stamp collector. The remark did
nothing to win friends for physics among practitioners of other
sciences. But Rutherford got his come-uppance: When he was summoned
to Stockholm in 1908, the prize awaiting him there was not in
physics but in chemistry.
A century later, surveying the state
of physics and its relations with other fields, I am tempted to give
Rutherford's quip an even more inflammatory reading, though he never
intended it. "All science is physics" might be taken as a
territorial claim, annexing other disciplines as provinces to be
ruled by the laws of physics and administered by physicists. This
imperial vision of the destiny of physics is not entirely without a
basis in history, or at least etymology. At one time, the term
physics had a very broad meaning, roughly synonymous with
natural science. The 18th-century
Encyclopédia of Diderot and d'Alembert listed under
the rubric physique particuliere everything from astronomy
and cosmology to meteorology, mineralogy, chemistry, zoology and
botany (but not stamp collecting).
Browsing through recent issues of Physical Review E
(a section of the main journal published by the American Physical
Society), one could form an equally expansive view of the scope of
21st-century physics. Within the past year, the Phys Rev E
table of contents has included titles such as "Outbreaks of
Hantavirus induced by seasonality," "Large-scale
structural organization of social networks," "Topology of
the world trade web," "Generating neural circuits that
implement probabilistic reasoning" and "Number fluctuation
and the fundamental theorem of arithmetic." Evidently, the
boundaries of physics are elastic enough to take in aspects of viral
epidemiology, sociology, market economics, cognitive neuroscience
and number theory. Are all of those fields now absorbed into the
empire of physics?
The story I want to tell here is not about sleeper cells of militant
physicists plotting a coup in the biology department. As a matter of
fact, although physics provides the most dramatic examples, several
other disciplines also have boundaries that seem to be shifting or
growing porous. Intellectual migrants are wandering back and forth
across many academic frontiers, generally without stopping for any
formalities at the customs house. In some cases, the same paper
might be classified as physics, biology, mathematics or computer
science, depending more on the author's affiliation and where it was
published than on the subject matter.
Departmental reshuffling and realignment goes on all the time, but
the present moment seems to be one of particular ferment. Among many
possible causes, I would point to the changing role of computation
in the various sciences. A number of earlier upheavals in the
structure of scientific disciplines have been triggered by new
techniques and instruments, sometimes imported from other fields.
Today, computation is the common thread in many of the areas that
are having a disciplinary identity crisis. Some of these areas rely
heavily on computer simulations or experiments, and others analyze
large data sets accessible only with computer technology. Computer
science also exerts a subtler but deeper influence when laws of
nature are expressed in algorithmic form.
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