Harold L. Burstyn

Galileo's Attempt to Prove That the Earth Moves

N HIS EFFORTS to defend the Copernican theory against those who would have had the Church of Rome condemn it, Galileo sought desperately for physical evidence to clinch the argument, to show once and for all that only the Copernican hypothesis agreed with the facts of nature. His search ended in a theory of the tides set out, with all the brilliance Galileo could muster, as the Fourth Day of the monumental Dialogue on the Two Chief Systems of the World. Here was Galileos hoped-for triumph: the indisputable proof of the earths double motion from a terrestrial phenomenon which could be verified by experiment. But the triumph was not to be. Though accepted by many of his contemporaries, though perhaps capable of furnishing the proof required by its author, Galileos theory of the tides seems never to have had the success its author hoped for. Condemned by the Church, ignored by all but the least talented of Newtons successors and misunderstood by them, Galileos theory of the tides was incorporated into the wider Newtonian synthesis -probably without full realization of its significance and vanished beneath the deluge of results obtained by Newtons successors. Nor has it been appreciated since by students of the physics of the seventeenth century. Yet, though not free from major errors, Galileos theory of the tides, and his associated theory of the trade winds, contain profound insights both into the basis and complications of tidal motion, and into the physical proof of the earths motion.1

Seers of the Sea

One of the more fruitful tensions in the history of science lies between two differing approaches to scholarship: the history of ideas and cultural history. The first emphasizes the sciences as bodies of knowledge whose reification makes the lives of the scientists themselves of less importance than the theories and experiments they hand on to one another through the scientific literature. For cultural history, on the other hand, the nurture of the individuals who contribute to the scientific mainstream, the institutions within which these individuals function, and the general trends of the wider cultural communities to which they belong form the center of scholarly interest. Matter and style in science are related to matter and style in art or in politics. After falling into disrepute a generation ago, largely for ideological reasons, the cultural-historical approach is now rapidly coming back into favor. The chief danger in approaching the history of science from a broadly cultural viewpoint is superficiality. One has to understand the scientific details in considerable depth to penetrate beneath the glib generality, to replace mere temporal contiguity with genuine relationship. Though the sciences of the physical environment, with their long histories both of large-scale enterprise and of repeated questions asked in widely differing cultural contexts, might seem ideal subjects for a broader history of science, they have (except for geology) suffered almost total neglect. Most historians of science, having studied the so-called pure subjects-physics, chemistry, mathematics, biology-bring little basic knowledge of the physical environment to their historical endeavors. Hitherto only a handful of persons (W. E. K. Middleton, an environmental scientist turned historian, is the most eminent) have traced any pathways through the internal history of the enviromental sciences for externally minded scholars to follow. Margaret Deacons pathbreaking monograph is thus especially welcome. In 400 pages she has magisterially surveyed the history of mans knowledge of the oceans from the beginnings to the turn of the twentieth century-the first time this has been done with depth and authority. She has brought together, in a single, largely chronological account, a horde of details gleaned from a careful survey of a vast and mainly unorganized literature. The cultural historian of science who wants to bring environmental problems into the discussion now knows where to turn for a reliable account of the growth of ideas about the physical nature of the worlds oceans. Deacons first two chapters, on ancient and medieval ideas, present familiar material, though in almost every case she has gone back to the original sources rather than relying on secondary accounts. The Greeks first asked where the oceans came from and why the sea is salty; their reasoned speculations gave way to fables in Roman and medieval times. Nevertheless, one finds in the medieval literature some evidence of a rational approach to the real world. Deacon mentions (from Pierre Duhem) a thirteenth-century version of an idea that gained wide support in the seventeenth century: at the equator the sun evaporates water, which is condensed at the poles, thus creating a vertical circulation in which water flows equatorward in the ocean and poleward in the atmosphere (p. 31). A third chapter, on the