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.

Technical chronology establishes the structure of calendars and the dates of events; it is, as it were, the foundation of history, particularly ancient history. The chronologer must know enough philology to interpret texts and enough astronomy to compute the dates of celestial phenomena, above all eclipses, which alone provide absolute dates. Joseph Scaliger, so we are told, was the first to master and apply this range of technical skills: Of the mathematical principles on which the calculation of periods rests, the philologians understood nothing. The astronomers, on their side, had not yet undertaken to apply their data to the records of ancient times. Scaliger was the first of the philologians who made use of the improved astronomy of the sixteenth century to get a scientific basis for historical chronology. So Mark Pattison. This verdict can be challenged on a number of grounds. The one relevant at present is simple: Scaliger himself claimed far less. He certainly said that technical chronology had been untouched in modern times — not an entirely fair judgement — but in antiquity it had been practised in exactly the manner he considered proper, or so he believed. In particular he singles out Censorinus, whose De die natali drew extensively on Varro's lost Antiquitates rerum humanarum, books 14–19, for information on chronology. Students of Varro have long appreciated the importance of Censorinus. His dry and compact treatise offers Varronian views on etymology, the human life-span, and the course of history itself, all couched in language so jejune as to suggest that he added little or nothing to what he read.

The last chapter of Politian's first Miscellanea dealt with the amica silentia lunae through which the Greeks sailed back to Troy. He argued that the phrase should not be taken literally, as a statement that Troy fell at the new moon, but in an extended sense, as a poetic indication that the moon had not yet risen when the Greeks set sail. This reading had one merit: it explained how Virgil's moon could be silent while the Greeks were en route but shine during the battle for the city. Yet Politian's effort to identify the phase of the moon described by Virgil was anything but clear: Non igitur aut sera fuerit aut pernox luna, tum nec lunae quidem omnino coitus, sed tempus arbitror potius quamdiu illa non luceret. Accordingly, though his arguments were sometimes repeated by commentators and teachers, they won little assent from scholars who occupied themselves seriously with the passage. In his Adversaria Turnebus took silentia lunae as referring ‘ad noctis taciturnitatem…non ad interlunium’. In the first chapter of his De rebus per epistolam quaesitis Giano Parrasio sharply criticised the fuzziness of Politian's explanation: ‘Ambages istae sunt, ambages’. More important, he quoted a line from the Little Iliad: νξ μν ην μέσση, λαμπρ δ' πέτελλε σελήνη. This he rendered ‘Nox erat intempesta, nitebat et aurea coelo Luna’, and inferred from it that the moon had been up when Troy fell. In his Virgilius collation scriptorum Graecorum illustratus, finally, Fulvio Orsini published a scholium on Euripides' Hecuba, one which quoted both the line from the Little Iliad and an analysis of it by the Peripatetic Callisthenes. He too took the line as refuting Politian.

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.

Summary Tycho Brahe's lunar theory, mostly the work of his assistant Christian Longomontanus, published in the Progymnasmata (1602), was the most advanced and accurate lunar theory yet developed. Its principal innovations are: the introduction of equant motion for the first inequality in order to separate the determination of direction and distance; a more accurate limit for the second inequality although requiring a more complex calculation; additional inequalities of the variation and, in place of the annual inequality in Tycho's earlier theory, a reduction in the equation of time; in the latitude theory a variation of the inclination of the orbital plane and an inequality of the motion of the nodes; a reduction in the range of variation of distance, parallax, and apparent diameter. Some of these were already present in Tycho's earlier lunar theory (1599), but all were changed in notable ways. Twenty years later Longomontanus published a modified version of the lunar theory in Astronomia Danica (1622), for the purpose of facilitating the calculation through new correction tables, and also explained his reasons for parts of the theory in the Progymnasmata. This paper is a technical study of both lunar theories.