Galileo and His Judges

by F. R. Wegg-Prosser

CHAPTER I.

Before entering on any details relating to Galileo’s life and works, I propose to give a brief sketch of the progress of astronomical knowledge up to his time; for without this, one cannot appreciate correctly the value of his contributions to science, a value exaggerated or underrated by different writers, each according to his respective bias.

The primitive conception of the Earth as a vast plain with the ocean flowing round it, and the solid firmament in the sky above it, with the Sun, Moon, and Stars driven across by some mysterious agency, need not be noticed from an astronomical point of view; it appeared naturally in ancient poetry and in the forms of speech adopted and continued by popular usage; but it is not necessary to dwell upon it.

The first astronomers with whom we are acquainted were the Greeks, though it is said by some writers that the Chaldeans and Egyptians were really the original astronomers of the ancient world, and what the Greeks knew was borrowed from them.

The vast majority of men from the earliest times down to the birth of Galileo believed that the Earth was the centre of the universe, round which the Sun, Moon, and Stars revolved every twenty-four hours; round which, also (as careful observers had perceived), the Sun had an annual motion, progressing through the various signs of the zodiac; moreover, it had been noticed that the planets moved round the Earth, though at widely differing periods.

Yet there had been some few men, exceptionally gifted, who had guessed (and truly so) that the popular conception was a wrong one. It is said that the old Greek philosopher, Pythagoras, taught his disciples that the Sun was the real centre of our system, and that the Earth and planets circulated round it; but he does not seem to have openly and explicitly published his doctrine, though the tradition of his having so taught has always existed. If he taught it, however, he stands almost alone among the ancients. There were two great authorities in particular, whose opinion carried immense weight, and who were both decided in holding that the Earth was the centre, and the Sun a revolving planet. The first of these, Aristotle, has exercised an influence over succeeding generations which is simply marvellous. How vast was the weight of his name as a philosopher in the age of the schoolmen is well known to every one who has ever glanced at the greatest work of the greatest intellect of that age, the “Summa” of St. Thomas Aquinas. This celebrated writer quotes him as “philosophus,” in his opinion the philosopher par excellence, and besides his general appreciation of him as thus shown, he wrote an elaborate treatise on the “Astronomy” of Aristotle.

Nor has this influence been confined to the schoolmen; it has remained ever since, even to this day and in this country, where in the University of Oxford his great work on ethics is still a standard book of study. At the time of Galileo, such was the reverence felt towards his authority in Italy and in Rome, that the Peripatetici, as those who specially belonged to his school were called, were probably quite as indignant with the revolutionary astronomer for disregarding the teaching of their philosopher, as for going counter to the literal interpretation of Scripture.

But in pure astronomy, apart from all other philosophy, the greatest of all ancient writers was Ptolemy, who in the second century of the Christian era wrote a work called the “Almagest,” which is a complete compendium of the science as known at that date. Ptolemy probably borrowed very much from his great predecessor, Hipparchus, who has been called the father of astronomy, and who was the first to discover—to take a remarkable instance—the phenomenon known as the precession of the equinoxes, involving as it does the difference in length between the solar and sidereal years. The system of Ptolemy was briefly this: The heavens and the Earth are both spherical in form—the Earth being immovable in the centre, and all the heavenly motions taking place in circles. For this he gives his reasons—sound and good reasons for the spherical shape of the Earth; unsound and mistaken, however, for the denial of the Earth’s rotation on its axis, an opinion he evidently knew had been maintained by some persons; one important argument on this latter head being that if the Earth rotated with the great velocity necessary to carry it round in one day, it would leave the air behind it. He places the Earth (as already said) in the centre, then the Moon as the nearest planet revolving round it, the next Mercury, then Venus, then the Sun, and beyond these Mars, Jupiter, and Saturn. All moved in circles, but since, with the exception of the Sun and Moon, simple circles would not account for the motions, he supposes small circles in a retrograde direction forming loops upon the main circle, which he calls epicycles; undoubtedly following in this respect, Hipparchus, who three centuries before had struck out the same idea. It is curious that Ptolemy’s arguments (as above mentioned) show clearly that in his day there were some persons, though their names have perished,[1] some one or two philosophers endowed with a marvellous insight into Nature, who had guessed at the true solution of the great astronomical problem; but they left no enduring mark on their age. The system of Ptolemy accounted for all the phenomena of the heavenly bodies that could be observed without the use of the telescope; naturally it held undisputed sway for many generations.

The first writer who revived the doctrine of Pythagoras as to the Earth’s movement (if, indeed, Pythagoras ever really taught it) was Nicholas de Cusa; he was a German by birth, having, in fact, been born at Trèves, in 1401; but he was educated in Italy. He rose to a high ecclesiastical position, and was created cardinal by Pope Eugenius IV., in 1448; his book just alluded to was entitled “De Docta Ignorantia,” and was dedicated to Cardinal Cesarini.

The first, however, whose work obtained any great notoriety, and who upheld the doctrine that the Earth revolved around the Sun, was Nicholas Kopernik, commonly called by the Latinised form of his name, Copernicus. He, too, was a German, born at Thorn, in 1473; he studied for a time at the University of Cracow, and like Nicholas de Cusa, afterwards in Italy, and was subsequently raised to the ecclesiastical dignity of a Canon. It is probable that he was not a priest (though he is frequently spoken of as such), but a Canon in minor orders. In 1500 he was appointed professor of mathematics at Rome; and such was his scientific reputation that he was consulted by the Council of Lateran, held in 1512, on the question of the reform of the calendar—a reform carried out at a later period by Pope Gregory XIII.