Great Astronomers - Robert Stawell Ball (the little red hen ebook .TXT) 📗
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remarkable vicissitudes than does that of Galileo. We may
consider him as the patient investigator and brilliant discoverer.
We may consider him in his private relations, especially to his
daughter, Sister Maria Celeste, a woman of very remarkable
character; and we have also the pathetic drama at the close of
Galileo’s life, when the philosopher drew down upon himself the
thunders of the Inquisition.
The materials for the sketch of this astonishing man are
sufficiently abundant. We make special use in this place of
those charming letters which his daughter wrote to him from her
convent home. More than a hundred of these have been preserved,
and it may well be doubted whether any more beautiful and touching
series of letters addressed to a parent by a dearly loved child
have ever been written. An admirable account of this
correspondence is contained in a little book entitled “The Private
Life of Galileo,” published anonymously by Messrs. Macmillan in
1870, and I have been much indebted to the author of that volume
for many of the facts contained in this chapter.
Galileo was born at Pisa, on 18th February, 1564. He was the
eldest son of Vincenzo de’ Bonajuti de’ Galilei, a Florentine
noble. Notwithstanding his illustrious birth and descent, it
would seem that the home in which the great philosopher’s
childhood was spent was an impoverished one. It was obvious at
least that the young Galileo would have to be provided with some
profession by which he might earn a livelihood. From his father
he derived both by inheritance and by precept a keen taste for
music, and it appears that he became an excellent performer on the
lute. He was also endowed with considerable artistic power, which
he cultivated diligently. Indeed, it would seem that for some
time the future astronomer entertained the idea of devoting
himself to painting as a profession. His father, however, decided
that he should study medicine. Accordingly, we find that when
Galileo was seventeen years of age, and had added a knowledge of
Greek and Latin to his acquaintance with the fine arts, he was
duly entered at the University of Pisa.
Here the young philosopher obtained some inkling of mathematics,
whereupon he became so much interested in this branch of science,
that he begged to be allowed to study geometry. In compliance
with his request, his father permitted a tutor to be engaged for
this purpose; but he did so with reluctance, fearing that the
attention of the young student might thus be withdrawn from that
medical work which was regarded as his primary occupation. The
event speedily proved that these anxieties were not without some
justification. The propositions of Euclid proved so engrossing to
Galileo that it was thought wise to avoid further distraction by
terminating the mathematical tutor’s engagement. But it was too
late for the desired end to be attained. Galileo had now made
such progress that he was able to continue his geometrical studies
by himself. Presently he advanced to that famous 47th proposition
which won his lively admiration, and on he went until he had
mastered the six books of Euclid, which was a considerable
achievement for those days.
The diligence and brilliance of the young student at Pisa did not,
however, bring him much credit with the University authorities.
In those days the doctrines of Aristotle were regarded as the
embodiment of all human wisdom in natural science as well as in
everything else. It was regarded as the duty of every student
to learn Aristotle off by heart, and any disposition to doubt or
even to question the doctrines of the venerated teacher was
regarded as intolerable presumption. But young Galileo had the
audacity to think for himself about the laws of nature. He would
not take any assertion of fact on the authority of Aristotle when
he had the means of questioning nature directly as to its truth or
falsehood. His teachers thus came to regard him as a somewhat
misguided youth, though they could not but respect the unflagging
industry with which he amassed all the knowledge he could acquire.
[PLATE: GALILEO’S PENDULUM.]
We are so accustomed to the use of pendulums in our clocks that
perhaps we do not often realise that the introduction of this
method of regulating timepieces was really a notable invention
worthy the fame of the great astronomer to whom it was due. It
appears that sitting one day in the Cathedral of Pisa, Galileo’s
attention became concentrated on the swinging of a chandelier
which hung from the ceiling. It struck him as a significant
point, that whether the arc through which the pendulum oscillated
was a long one or a short one, the time occupied in each vibration
was sensibly the same. This suggested to the thoughtful observer
that a pendulum would afford the means by which a time-keeper
might be controlled, and accordingly Galileo constructed for the
first time a clock on this principle. The immediate object sought
in this apparatus was to provide a means of aiding physicians in
counting the pulses of their patients.
The talents Of Galileo having at length extorted due recognition
from the authorities, he was appointed, at the age of twenty-five,
Professor of Mathematics at the University of Pisa. Then came
the time when he felt himself strong enough to throw down the
gauntlet to the adherents of the old philosophy. As a necessary
part of his doctrine on the movement of bodies Aristotle had
asserted that the time occupied by a stone in falling depends upon
its weight, so that the heavier the stone the less time would it
require to fall from a certain height to the earth. It might
have been thought that a statement so easily confuted by the
simplest experiments could never have maintained its position
in any accepted scheme of philosophy. But Aristotle had said it,
and to anyone who ventured to express a doubt the ready sneer
was forthcoming, “Do you think yourself a cleverer man than
Aristotle?” Galileo determined to demonstrate in the most
emphatic manner the absurdity of a doctrine which had for
centuries received the sanction of the learned. The summit
of the Leaning Tower of Pisa offered a highly dramatic site for
the great experiment. The youthful professor let fall from the
overhanging top a large heavy body and a small light body
simultaneously. According to Aristotle the large body ought to
have reached the ground much sooner than the small one, but such
was found not to be the case. In the sight of a large concourse
of people the simple fact was demonstrated that the two bodies
fell side by side, and reached the ground at the same time.
Thus the first great step was taken in the overthrow of that
preposterous system of unquestioning adhesion to dogma, which
had impeded the development of the knowledge of nature for nearly
two thousand years.
This revolutionary attitude towards the ancient beliefs was not
calculated to render Galileo’s relations with the University
authorities harmonious. He had also the misfortune to make
enemies in other quarters. Don Giovanni de Medici, who was then
the Governor of the Port of Leghorn, had designed some contrivance
by which he proposed to pump out a dock. But Galileo showed up
the absurdity of this enterprise in such an aggressive manner that
Don Giovanni took mortal offence, nor was he mollified when the
truths of Galileo’s criticisms were abundantly verified by the
total failure of his ridiculous invention. In various ways
Galileo was made to feel his position at Pisa so unpleasant that
he was at length compelled to abandon his chair in the University.
The active exertions of his friends, of whom Galileo was so
fortunate as to have had throughout his life an abundant supply,
then secured his election to the Professorship of Mathematics at
Padua, whither he went in 1592.
[PLATE: PORTRAIT OF GALILEO.]
It was in this new position that Galileo entered on that
marvellous career of investigation which was destined to
revolutionize science. The zeal with which he discharged his
professorial duties was indeed of the most unremitting character.
He speedily drew such crowds to listen to his discourses on
Natural Philosophy that his lecture-room was filled to
overflowing. He also received many private pupils in
his house for special instruction. Every moment that could be
spared from these labours was devoted to his private study and to
his incessant experiments.
Like many another philosopher who has greatly extended our
knowledge of nature, Galileo had a remarkable aptitude for the
invention of instruments designed for philosophical research.
To facilitate his practical work, we find that in 1599 he had
engaged a skilled workman who was to live in his house, and thus
be constantly at hand to try the devices for ever springing from
Galileo’s fertile brain. Among the earliest of his inventions
appears to have been the thermometer, which he constructed in
1602. No doubt this apparatus in its primitive form differed in
some respects from the contrivance we call by the same name.
Galileo at first employed water as the agent, by the expansion of
which the temperature was to be measured. He afterwards saw the
advantage of using spirits for the same purpose. It was not until
about half a century later that mercury came to be recognised as
the liquid most generally suitable for the thermometer.
The time was now approaching when Galileo was to make that
mighty step in the advancement of human knowledge which followed
on the application of the telescope to astronomy. As to how his
idea of such an instrument originated, we had best let him tell
us in his own words. The passage is given in a letter which he
writes to his brother-in-law, Landucci.
“I write now because I have a piece of news for you, though
whether you will be glad or sorry to hear it I cannot say; for
I have now no hope of returning to my own country, though the
occurrence which has destroyed that hope has had results both
useful and honourable. You must know, then, that two months ago
there was a report spread here that in Flanders some one had
presented to Count Maurice of Nassau a glass manufactured in such
a way as to make distant objects appear very near, so that a man
at the distance of two miles could be clearly seen. This seemed
to me so marvellous that I began to think about it. As it
appeared to me to have a foundation in the Theory of Perspective,
I set about contriving how to make it, and at length I found out,
and have succeeded so well that the one I have made is far
superior to the Dutch telescope. It was reported in Venice that
I had made one, and a week since I was commanded to show it to his
Serenity and to all the members of the senate, to their infinite
amazement. Many gentlemen and senators, even the oldest, have
ascended at various times the highest bell-towers in Venice to
spy out ships at sea making sail for the mouth of the harbour,
and have seen them clearly, though without my telescope they
would have been invisible for more than two hours. The effect
of this instrument is to show an object at a distance of say
fifty miles, as if it were but five miles.”
The remarkable properties of the telescope at once commanded
universal attention among intellectual men. Galileo received
applications from several quarters for his new instrument, of
which it would seem that he manufactured a large number to be
distributed as gifts to various illustrious personages.
But it was reserved for Galileo himself to make that application
of the instrument to the celestial bodies by which its peculiar
powers were to inaugurate the new era in
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