Tuesday, May 26, 2009

Jaki on precision and discovery

For your consideration, an important commentary on precision and discovery...
--Dr. Thursday

The instances taken from nineteenth-century physics could be multiplied at some length to illustrate the fundamental importance that increased precision in experiments plays in establishing new laws or theories. Ohm's law, the laws of radiation, the gas laws, to mention only a few, were but triumphs in precision. The establishment of well-equipped physical laboratories, first in German and French and later in British universities, clearly evidenced the general recognition of the extraordinary importance precision has in physics. The rewards were at times spectacular, particularly when unknown entities, such as new elements, were discovered. The case of argon was perhaps the most characteristic, resting as it did on the worries of Ramsay and Rayleigh as to why some samples of nitrogen had a weight of 1.257 grams per liter instead of only 1.256. As it turned out, an unknown element, after its discovery called argon, caused this discrepancy. The identification of other inert gases followed in quick succession.
Great as such successes were, they represented nothing essentially new. Actually they meant rather the discovery of some missing building blocks in an already firmly outlined system. Most of the measurements that were being carried out in the newly organized laboratories related to refinements of older data, and this gave rise to the view that Maxwell in 1871 described in this way: "The opinion seems to have got abroad, that in a few years all the great physical constants will have been approximately estimated, and that the only occupation which will then be left to men of science will be to carry on these measurements to another place of decimals." A younger colleague of Maxwell, A. Schuster, recalled this mentality several decades later in a passage that sketches the "decimal" state of mind with memorable vividness:
I think I interpret correctly the recollection of those who passed through their scientific education at the time, when I say that the general impres-sion they received was that, apart from theoretical work, a reputation could be only secured by improved methods of measurement which would extend the numerical accuracy of the determination of physical constants. In many cases the student was led to believe that the main facts of nature were all known, that the chances of any great discovery being made by experiment were vanishingly small, and that therefore the experimentalist's work consisted in deciding between rival theories, or in finding some small residual effect, which might add a more or less important detail to the theory.

Schuster added, however, that some scientists, like Maxwell, refused to go along with such a pedestrian appraisal of the role played by precision in the progress of physics. In his "Introductory Lecture in Experimental Physics," which he delivered after the opening of the Cavendish Laboratories in 1871, Maxwell pointed out that precision leads to the subjugation of new regions, to new fields of research, to new scientific ideas. In spite of all his conviction about the new aspects that precision might unveil in physics, Maxwell could little surmise (if at all) the revolutionary dimensions of the newness that was in store for physics, changes due in no small measure to highly refined experiments carried out in the very same Cavendish Laboratories only a generation later.
Still in this respect too, Maxwell saw farther than most of his colleagues. How the great majority of first-rank physicists in the late nineteenth century looked upon greater accuracy was perhaps best expressed by Michelson. According to him, heightened precision was meant only to clarify apparent discrepancies and point out new applications of already known laws. The chance that these laws would ever be supplanted by new discoveries or by more precise measurements was in Michelson's eyes "exceedingly remote." "The extreme refinement in the science of measurement," in which Michelson had few peers in his day, was for him a tool of putting the final touches on an already firmly established edifice. Although he admitted that "it is never safe to affirm that the future of Physical Science has no marvels in store even more astonishing than those of the past," he voiced the conviction that further advances, future discoveries, indeed the "future truths of Physical Science are to be looked for in the sixth place of decimals."

[SLJ The Relevance of Physics 254-6, attributions omitted]

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