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quarta-feira, janeiro 09, 2008

Física = coleção de modelos

Volume: 92 Number: 4 Page: 306

Undisciplined Science

"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). click for full image and caption

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 Higher Stamp Collecting

Setting aside all questions of institutional context, much of the recent cross-disciplinary work—the sociophysics as well as the bioinformatics—is fascinating and fun. Personally, when I scan Phys Rev E, it is the "unconventional" articles, the ones that transgress disciplinary boundaries, that I am likely to read first. If institutional constraints discourage such coloring outside the lines, perhaps the institutions need to be reformed.

Do we need disciplines at all? The idea of organizing universities along topical or departmental lines is not one of those long-hallowed principles without which civilization would crumble. American universities in particular resisted faculty specialization until the middle of the 19th century. Specialist journals and societies came along even later. For example, Physical Review and the American Physical Society are not much more than a century old. (Publications for stamp collectors go back further.) Realistically, though, it is probably too late to bring back professors without portfolio.

What may still be possible is to shake up the Tree of Knowledge. As an armature for classifying ideas, a tree is a rigid structure. Its definitive feature is that branches diverge but never rejoin, so that every node can have but one parent. The proliferation of portmanteau disciplines—astrophysics, biochemistry and so on—suggests that this single-parent principle is under strain. Perhaps we should replace the tree with a matrix: Given n "prime" sciences labeling the columns and rows, we'd have cubby-holes for n 2 combinations. On a campus built to reflect this architecture, you could always find your department by locating the intersection of the appropriate streets. ("Meet me at the corner of Bio and Soc.")

It's no surprise that computation is a conspicuous element in many of the recent disciplinary upsets. The computer has altered the scientist's way of life even in routine affairs (controlling experiments, communicating with colleagues, writing papers). In fields like statistical mechanics the influence is deeper. Where the aim is to understand the collective behavior of vast numbers of interacting entities, computation offers a more direct mode of investigation than has ever been possible in the past. Occasionally the role of computing gets explicit acknowledgment, as in the subdiscipline called computational chemistry. But if all science becomes computational, there's no point in mentioning it. Like mathematics, computation becomes everyone's silent partner.

Computation has even rehabilitated some of Rutherford's stamp-collecting disciplines. Those who compile lists and catalogs, who survey and classify, find their work newly glamorized in the age of data mining. The human-genome project has much to do with this change in attitude. Craig Venter, one of the principals of that project, has now begun another giant list, sailing the Sargasso Sea to create a catalog of all the organisms living there. Astronomy has its own megacatalog: the Sloan Digital Sky Survey will list 100 million objects. What has made such undertakings newly fashionable is the possibility of doing more with the data once the gigabytes have been gathered up. In a sense, the database itself becomes an object of study, in much the same way that physicists study lattices rather than what the lattices model. Rutherford might still insist that all science is either physics or stamp collecting, but maybe he would confess some interest in the physics of stamp collecting.

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Um comentário:

João Carlos disse...

Generalzação banal e bem escrotinha!...