In other words, the brain of this tremendous, this incomprehensible, this complex man, lies at the base of all our literature and of all our modern progress and civilization. The world is hardly big enough for his fame, and the praises of mankind cannot fill the measure of his greatness.[Back to Contents]
GALILEO-GALILEI
(1564-1642)
The great Tuscan astronomer is best known as the first telescopic observer, the fortunate discoverer of the Medicean stars (so Jupiter's satellites were first named); and what discovery more fitted to immortalize its author than one which revealed new worlds and thus gave additional force to the lesson, that the universe, of which we form so small a part, was not created only for our use or pleasure? Those, however, who consider Galileo only as a fortunate observer, form a very inadequate estimate of one of the most meritorious and successful of those great men who have bestowed their time for the advantage of mankind in tracing out the hidden things of nature. Galileo-Galilei was born at Pisa, February 15, 1564. In childhood he displayed considerable mechanical ingenuity, with a decided taste for the accomplishments of music and painting. His father formed a just estimate of his talents, and at some inconvenience entered him, when nineteen years old, at the university of his native town, intending that he should pursue the medical profession. Galileo was then entirely ignorant of mathematics; and he was led to the study of geometry by a desire thoroughly to understand the principles of his favorite arts. This new pursuit proved so congenial to his taste, that from thenceforward his medical books were entirely neglected. The elder Galilei, a man of liberal acquirements and enlarged mind, did not require the devotion of his son's life to a distasteful pursuit. Fortunately the young man's talents attracted notice, and in 1589 he was appointed mathematical lecturer in the University of Pisa. There is reason to believe that, at an early period of his studentship, he embraced, upon inquiry and conviction, the doctrines of Copernicus, of which through life he was an ardent supporter.
Galileo and his colleagues did not long remain on good terms. The latter were content with the superstructure which à priori reasoners had raised upon Aristotle, and were by no means desirous of the trouble of learning more. Galileo chose to investigate physical truths for himself; he engaged in experiments to determine the truth of some of Aristotle's positions, and when he found him in the wrong, he said so, and so taught his pupils. This made the "paper philosophers," as he calls them, very angry. He repeated his experiments in their presence, but they set aside the evidence of their senses and quoted Aristotle as much as before. The enmity arising from these disputes rendered his situation so unpleasant, that in 1592, at the invitation of the Venetian commonwealth, he gladly accepted the professorship of mathematics at Padua. The period of his appointment being only six years, he was re-elected in 1598, and again in 1606, each time with an increase of salary; a strong proof of the esteem in which he was held, even before those astronomical discoveries which have immortalized his name. His lectures at this period were so fully attended that he was sometimes obliged to adjourn them to the open air. In 1609 he received an invitation to return to his original situation at Pisa. This produced a letter, still extant, from which we quote a catalogue of the undertakings on which he was already employed. "The works which I have to finish are principally two books on the 'System or Structure of the Universe,' an immense work, full of philosophy, astronomy, and geometry; three books on 'Local Motion,' a science entirely new, no one, either ancient or modern, having discovered any of the very many admirable accidents which I demonstrate in natural and violent motions, so that I may, with very great reason, call it a new science, and invented by me from its very first principles; three books of mechanics, two on the demonstration of principles and one of problems; and although others have treated this same matter, yet all that has been hitherto written, neither in quantity nor otherwise, is the quarter of what I am writing on it. I have also different treatises on natural subjects—on Sound and Speech, on Light and Colors, on the Tides, on the Composition of Continuous Quantity, on the Motions of Animals, and others besides. I have also an idea of writing some books relating to the military art, giving not only a model of a soldier, but teaching with very exact rules everything which it is his duty to know, that depends upon mathematics, as the knowledge of castrametation, drawing up of battalions, fortification, assaults, planning, surveying, the knowledge of artillery, the use of instruments, etc." Out of this comprehensive list, the treatises on the universe, on motion and mechanics, on tides, on fortification, or other works upon the same subjects, have been made known to the world. Many, however, of Galileo's manuscripts, through fear of the Inquisition, were destroyed, or concealed and lost, after the author's death.
In the same year, 1609, Galileo heard the report that a spectacle-maker of Middleburg, in Holland, had made an instrument by which distant objects appeared nearer. He tasked his ingenuity to discover the construction, and soon succeeded in manufacturing a telescope. His telescope, however, seems to have been made on a different construction from that of the Dutch optician. It consisted of a convex and concave glass, distant from each other by the difference of their focal lengths, like a modern opera-glass; while there is reason to believe that the other was made up of two convex lenses, distant by the sum of their focal lengths, the common construction of the astronomical telescope. Galileo's attention naturally was first turned to the moon. He discovered that her surface, instead of being smooth and perfectly spherical, was rough with mountains and apparently varied like the earth, by land and water. He next applied to Jupiter, and was struck by the appearance of three small stars, almost in a straight line and close to him. At first he did not suspect the nature of these bodies; but careful observation soon convinced him that these three, together with a fourth, which was at first invisible, were in reality four moons revolving round their primary planet. These he named the Medicean stars. They have long ceased to be known by that name; but so highly prized was the distinction thus conferred upon the ducal house of Florence, that Galileo received an intimation that he would "do a thing just and proper in itself, and at the same time render himself and his family rich and powerful forever," if he "named the next star which he should discover after the name of the great star of France, as well as the most brilliant of all the earth," Henry IV. These discoveries were made known in 1610, in a work entitled "Nuncius Sidereus," the Newsman of the Stars; in which Galileo further announced that he had seen many stars invisible to the naked eye, and ascertained that the nebulæ scattered through the heavens consist of assemblages of innumerable small stars. The ignorant and unprejudiced were struck with admiration; indeed, curiosity had been raised so high before the publication of this book, as materially to interfere with the convenience of those who possessed telescopes. Galileo was employed a month in exhibiting his own to the principal persons in Venice; and our unfortunate astronomer was surrounded by a crowd who kept him in durance for several hours, while they passed his glass from one to another. He left Venice the next morning, to pursue his inquiries in some less inquisitive place. But the great bulk of the philosophers of the day were far from joining in the general feeling. They raised an outcry against the impudent fictions of Galileo, and one, a professor of Padua, refused repeatedly to look through the telescope, lest he should be compelled to admit that which he had pre-determined to deny.
It was not long before Galileo had new and equally important matter to announce. He observed a remarkable appearance in Saturn, as if it were composed of three stars touching each other; his telescope was not sufficiently powerful to resolve them into Saturn and his ring. Within a month he ascertained that Venus exhibits phases like those of the moon—a discovery of great importance in confirming the Copernican system. The same phenomenon he afterward detected in Mars. We close the list with the discovery of the revolution of the sun round his axis, in the space of about a lunar month, derived from careful observation of the spots on his surface.