Neal Swerdlow

The purpose of this essay is to show that there was one person, perhaps only one, who developed a rigorously scientific cosmology nearly two thousand years ago. Cosmology is the largest of all subjects, with a long history, and the cosmology considered here is the one that endured for the longest part, nearly three-quarters, of that history. By cosmology I mean a description of the universe as a whole and of the arrangement of its principal parts. But by scientific cosmology, I mean something more. For a cosmology to be considered scientific, three criteria must be met: it must be quantitative, physical, and empirical. Quantitative means that it must assign some scale of distances and sizes to its parts. Physical means that it must rest upon some kind of physical or mechanical principles, causes, for the ordering and motion of its parts. Finally, empirical means that it must either be derived from observation or, if derived theoretically, as from physical or mechanical principles, it must be confirmed by observation. I set out these criteria, which may not be exclusive or exhaustive but are surely within reason, in order to define our subject and exclude mythological or theological cosmologies, which generally meet none of the criteria, and philosophical cosmologies, as those of Plato, Aristotle, and Descartes, which may meet one or two in some way, although not rigorously, but surely do not meet all three. I am not concerned with whether the cosmology or the criteria upon which it is based are correct. Compared to our present understanding, the scale may be off by orders of magnitude, the physics may be entirely mistaken, and the observations may be inaccurate. But if all three are present I would call the cosmology scientific, and if not I would not call the cosmology scientific.

For forty years, beginning with the publication of the first modern English translation of the Dialogue Concerning the Two Chief World Systems, Stillman Drake was the most original and productive scholar of Galileo's scientific work of our age. During that time, he published sixteen books on Galileo, including translations of almost all the major writings, and Galileo at Work, the most comprehensive study of Galileo's life and works ever written. His collection Discoveries and Opinions on Galileohas remained in print since its appearance in 1957 and has become the most widely read of all books on Galileo. In addition to his books, Drake published about 130 papers, of which nearly 100 are on Galileo and the rest on related aspects of the history and philosophy of science. This three-volume collection includes eighty of those papers. Drake's papers are an essential supplement to his translations and other books because it was in his papers that he wrote his most detailed technical studies of Galileo's scientific work. There is hardly a subject in Galileo's science that is not considered. Perhaps the most important is the series on mechanics and motion, in which Drake analysed Galileo's manuscript notes recording the experiments by which he discovered and confirmed the law of the acceleration of falling bodies. There are also papers on the notes in which Galileo recorded his discovery of Jupiter's satellites and on other aspects of Galileo's astronomy, including his defence of the Copernican theory. Other papers consider Galileo's life and scientific work in general, exploring what Drake calls the 'scientific personality' of Galileo along with his scientific method and philosophy of science. In addition to the papers on Galileo, there are a number of papers on medieval and early modern science, principally on mechanics, and on the philosophers A.B. Johnson and J.B. Stallo, both of whom influenced Drake's own philosophy of science.