Great Astronomers by Robert Stawell Ball (best ereader for students .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