(1564-1642)
[Illustration: Galileo-Galilei. [TN]]
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 _a 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 nebulae 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.
About this time (1610-1611) Galileo took up his abode in Tuscany, upon
the invitation of the grand duke, who offered to him his original
situation at Pisa, with a liberal salary, exemption from the necessity
of residence, and complete leisure to pursue his studies. In 1612 he
published a discourse on "Floating Bodies," in which he investigates the
theory of buoyancy, and refutes, by a series of beautiful and conclusive
experiments, the opinion that the floating or sinking of bodies depends
on their shape.
Neither Copernicus nor his immediate followers suffered inconvenience or
restraint on account of their astronomical doctrines; nor had Galileo,
until this period of his life, incurred ecclesiastical censure for
anything which he had said or written. But the Inquisition now took up
the matter as heretical and contrary to the express words of Scripture;
and in 1616, Copernicus's work, "De Revolutionibus," Kepler's "Epitome,"
and some of Galileo's own letters, were placed on the list of prohibited
books; and he himself, being then in Rome, received formal notice not to
teach that the earth revolves round the sun. He returned to Florence
full of indignation; and considering his hasty temper, love of truth,
and full belief of the condemned theory, it is rather wonderful that he
kept silence so long, than that he incurred at last the censures of the
hierarchy. He did, however, restrain himself from any open advocacy of
the heretical doctrines, even in composing his great work, the "Dialogue
on the Ptolemaic and Copernican Systems." This was completed in 1630,
but not printed till 1632, under license from officers of the church,
both at Rome and Florence. It is a dialogue between Simplicio, an
Aristotelian, Salviati, who represents the author, and Sagredo, a half
convert to Salviati's opinions. It professes "indeterminately to propose
the philosophical arguments, as well on one side as on the other;" but
the neutrality is but ill kept up, and was probably assumed, not with
any hope that the court of Rome would be blinded as to the real tendency
of the book, but merely that it would accept this nominal submission as
a sufficient homage to its authority. If this were so, the author was
disappointed; the Inquisition took cognizance of the matter, and
summoned him to Rome to undergo a personal examination. Age and
infirmity were in vain pleaded as excuses; still, through the urgent and
indignant remonstrances of the Grand Duke of Tuscany, he was treated
with a consideration rarely shown by that stern tribunal. He was allowed
to remain at the Florentine ambassador's palace, with the exception of a
short period, from his arrival in February, until the passing of
sentence, June 21, 1633. He was then condemned, in the presence of the
Inquisitors, to curse and abjure the "false doctrines," which his life
had been spent in proving, to be confined in the prison of the Holy
Office during pleasure, and to recite the seven penitential psalms once
a week during three years. The sentence and the abjuration are given at
full length in the "Life of Galileo," in the "Library of Useful
Knowledge." "It is said," continues the biographer, "that Galileo, as he
rose from his knees, stamped on the ground, and whispered to one of his
friends, '_e pur si muove_,' it does move though."
[Illustration: Galileo before the Inquisition.]
Galileo's imprisonment was not long or rigorous, for after four days he
was reconducted to the Florentine ambassador's palace; but he was still
kept under strict surveillance. In July he was sent to Sienna, where he
remained five months in strict seclusion. He obtained permission in
December to return to his villa at Arcetri, near Florence: but there, as
at Sienna, he was confined to his own premises, and strictly forbidden
to receive his friends. It is painful to contemplate the variety of
evils which overcast the evening of this great man's life. In addition
to a distressing chronic complaint, contracted in youth, he was now
suffering under a painful infirmity which by some is said to have been
produced by torture, applied in the prisons of the Inquisition to
extort a recantation. But the arguments brought forward to show that the
Inquisitors did resort to this extremity do not amount to anything like
direct proof. In April, 1634, Galileo's afflictions were increased by
the death of a favorite, intelligent, and attached daughter. He consoled
his solitude, and lightened the hours of sickness, by continuing the
observations which he was now forbidden to publish to the world; and the
last of his long train of discoveries was the phenomenon known by the
name of the moon's libration. In the course of 1636-37 he lost
successively the sight of both his eyes. He mentions this calamity in a
tone of pious submission, mingled with a not unpleasing pride. "Alas,
your dear friend and servant Galileo has become totally and irreparably
blind; so that this heaven, this earth, this universe, which with
wonderful observations I had enlarged a hundred thousand times beyond
the belief of by-gone ages, henceforward for me is shrunk into the
narrow space which I myself fill in it. So it pleases God: it shall
therefore please me also." In 1638 he obtained leave to visit Florence,
still under the same restrictions as to society; but at the end of a few
months he was remanded to Arcetri, which he never again quitted. From
that time, however, the strictness of his confinement was relaxed, and
he was allowed to receive the friends who crowded round him, as well as
the many distinguished foreigners who eagerly visited him. Among these
we must not forget Milton, whose poems contain several allusions to the
celestial wonders observed and published by the Tuscan astronomer.
Though blind and nearly deaf, Galileo retained to the last his
intellectual powers; and his friend and pupil, the celebrated
Torricelli, was employed in arranging his thoughts on the nature of
percussion, when he was attacked by his last illness. He died January 8,
1642, aged seventy-eight.
It was disputed whether, as a prisoner of the Inquisition, Galileo had a
right to burial in consecrated ground. The point was conceded; but Pope
Urban VIII. himself interfered to prevent the erection of a monument to
him in the church of Santa Croce, in Florence, for which a large sum had
been subscribed. A splendid monument now covers the spot in which his
remains repose with those of his friend and pupil, the eminent
mathematician Viviani.
For an account of Galileo's application of the pendulum to the
mensuration of time; his invention of the thermometer, though in an
inaccurate and inconvenient form; his methods of discovering the
longitude, and a variety of other points well worth attention, we must
refer to the Life of Galileo already quoted. The numerous extracts from
Galileo's works convey a lively notion of the author's character, and
are distinguished by a peculiar tone of quaint humor. In conclusion, we
quote the estimate of Galileo's character, from the same masterly
memoir. "The numberless inventions of his acute industry; the use of the
telescope, and the brilliant discoveries to which it led; the patient
investigation of the laws of weight and motion, must all be looked upon
as forming but a part of his real merits, as merely particular
demonstrations of the spirit in which he everywhere withstood the
despotism of ignorance, and appealed boldly from traditional opinions to
the judgment of reason and common sense. He claimed and bequeathed to
us the right of exercising our faculties in examining the beautiful
creation which surrounds us. Idolized by his friends, he deserved their
affection by numberless acts of kindness; by his good humor, his
affability, and by the benevolent generosity with which he devoted
himself, and a great part of his limited income, to advance their
talents and fortunes. If an intense desire of being useful is everywhere
worthy of honor; if its value is immeasurably increased when united to
genius of the highest order; if we feel for one, who, notwithstanding
such titles to regard, is harassed by cruel persecution, then none
deserve our sympathy, our admiration, and our gratitude, more than
Galileo."