perhaps we do not often realise that the introduction of this method
of regulating time-pieces 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 astronomy. The first discovery
that was made in this direction appears to have been connected with
the number of the stars. Galileo saw to his amazement that through
his little tube he could count ten times as many stars in the sky as
his unaided eye could detect. Here was, indeed, a surprise. We are
now so familiar with the elementary facts of astronomy that it is not
always easy to realise how the heavens were interpreted by the
observers in those ages prior to the invention of the telescope. We
can hardly, indeed, suppose that Galileo, like the majority of those
who ever thought of such matters, entertained the erroneous belief
that the stars were on the surface of a sphere at equal distances
from the observer. No one would be likely to have retained his
belief in such a doctrine when he saw how the number of visible stars
could be increased tenfold by means of Galileo's telescope. It would
have been almost impossible to refuse to draw the inference that the
stars thus brought into view were still more remote objects which the
telescope was able to reveal, just in the same way as it showed
certain ships to the astonished Venetians, when at the time these
ships were beyond the reach of unaided vision.
Galileo's celestial discoveries now succeeded each other rapidly.
That beautiful Milky Way, which has for ages been the object of
admiration to all lovers of nature, never disclosed its true nature
to the eye of man till the astronomer of Padua turned on it his magic
tube. The splendid zone of silvery light was then displayed as
star-dust scattered over the black background of the sky. It was
observed that though the individual stars were too small to be seen
severally without optical aid, yet such was their incredible number
that the celestial radiance produced that luminosity with which every
stargazer was so familiar.
But the greatest discovery made by the telescope in these early days,
perhaps, indeed, the greatest discovery that the telescope has ever
accomplished, was the detection of the system of four satellites
revolving around the great planet Jupiter. This phenomenon was so
wholly unexpected by Galileo that, at first, he could hardly believe
his eyes. However, the reality of the existence of a system of four
moons attending the great planet was soon established beyond all
question. Numbers of great personages crowded to Galileo to see for
themselves this beautiful miniature representing the sun with its
system of revolving planets.
Of course there were, as usual, a few incredulous people who refused
to believe the assertion that four more moving bodies had to be added
to the planetary system. They scoffed at the notion; they said the
satellites may have been in the telescope, but that they were not in
the sky. One sceptical philosopher is reported to have affirmed,
that even if he saw the moons of Jupiter himself he would not believe
in them, as their existence was contrary to the principles of
common-sense!
There can be no doubt that a special significance attached to the new
discovery at this particular epoch in the history of science. It
must be remembered that in those days the doctrine of Copernicus,
declaring that the sun, and not the earth, was the centre of the
system, that the earth revolved on its axis once a day, and that it
described a mighty circle round the sun once a year, had only
recently been promulgated. This new view of the scheme of nature had
been encountered with the most furious opposition. It may possibly
have been that Galileo himself had not felt quite confident in the
soundness of the Copernican theory, prior to the discovery of the
satellites of Jupiter. But when a picture was there exhibited in
which a number of relatively small globes were shown to be revolving
around a single large globe in the centre, it seemed impossible not
to feel that the beautiful spectacle so displayed was an emblem of
the relations of the planets to the sun. It was thus made manifest
to Galileo that the Copernican theory of the planetary system must be
the true one. The momentous import of this opinion upon the future
welfare of the great philosopher will presently appear.
It would seem that Galileo regarded his residence at Padua as a state
of undesirable exile from his beloved Tuscany. He had always a
yearning to go back to his own country and at last the desired
opportunity presented itself. For now that Galileo's fame had become
so great, the Grand Duke of Tuscany desired to have the philosopher
resident at Florence, in the belief that he would shed lustre on the
Duke's dominions. Overtures were accordingly made to Galileo, and
the consequence was that in 1616 we find him residing at Florence,
bearing the title of Mathematician and Philosopher to the Grand Duke.
Two daughters, Polissena and Virginia, and one son, Vincenzo, had
been born to Galileo in Padua. It was the custom in those days that
as soon as the daughter of an Italian gentleman had grown up, her
future career was somewhat summarily decided. Either a husband was
to be forthwith sought out, or she was to enter the convent with the
object of taking the veil as a professed nun. It was arranged that
the two daughters of Galileo, while still scarcely more than
children, should both enter the Franciscan convent of St. Matthew, at
Arcetri. The elder daughter Polissena, took the name of Sister Maria
Celeste, while Virginia became Sister Arcangela. The latter seems to
have been always delicate and subject to prolonged melancholy, and
she is of but little account in the narrative of the life of
Galileo. But Sister Maria Celeste, though never leaving the convent,
managed to preserve a close intimacy with her beloved father. This
was maintained only partly by Galileo's visits, which were very
irregular and were, indeed, often suspended for long intervals. But
his letters to this daughter were evidently frequent and
affectionate, especially in the latter part of his life. Most
unfortunately, however, all his letters have been lost. There are
grounds for believing that they were deliberately destroyed when
Galileo was seized by the Inquisition, lest they should have been
used as evidence against him, or lest they should have compromised
the convent where they were received. But Sister Maria Celeste's
letters to her father have happily been preserved, and most touching
these letters are. We can hardly read them without thinking how the
sweet and gentle nun would have shrunk from the idea of their
publication.
Her loving little notes to her "dearest lord and father," as she used
affectionately to call Galileo, were almost invariably accompanied by
some gift, trifling it may be, but always the best the poor nun had
to bestow. The tender grace of these endearing communications was
all the more precious to him from the fact that the rest of Galileo's
relatives were of quite a worthless description. He always
acknowledged the ties of his kindred in the most generous way, but
their follies and their vices, their selfishness and their
importunities, were an incessant source of annoyance to him, almost
to the last day of his life.
On 19th December, 1625, Sister Maria Celeste writes:--
"I send two baked pears for these days of vigil. But as the greatest
treat of all, I send you a rose, which ought to please you extremely,
seeing what a rarity it is at this season; and with the rose you must
accept its thorns, which represent the bitter passion of our Lord,
whilst the green leaves represent the hope we may entertain that
through the same sacred passion we, having passed through the
darkness of the short winter of our mortal life, may attain to the
brightness and felicity of an eternal spring in heaven."
When the wife and children of Galileo's shiftless brother came to
take up their abode in the philosopher's home, Sister Maria Celeste
feels glad to think that her father has now some one who, however
imperfectly, may fulfil the duty of looking after him. A graceful
note on Christmas Eve accompanies her little gifts. She hopes that--
"In these holy days the peace of God may rest on him and all the
house. The largest collar and sleeves I mean for Albertino, the
other two for the two younger boys, the little dog for baby, and the
cakes for everybody, except the spice-cakes, which are for you.
Accept the good-will which would readily do much more."
The extraordinary forbearance with which Galileo continually placed
his time, his purse, and his influence at the service of those who
had repeatedly proved themselves utterly unworthy of his countenance,
is thus commented on by the good nun.--
"Now it seems to me, dearest lord and father, that your lordship is
walking in the right path, since you take hold of every occasion that
presents itself to shower continual benefits on those who only repay
you with ingratitude. This is an action which is all the more
virtuous and perfect as it is the more difficult."
When the plague was raging in the neighbourhood, the loving
daughter's solicitude is thus shown:--
"I send you two pots of electuary as a preventive against the
plague. The one without the label consists of dried figs, walnuts,
rue, and salt, mixed together with honey. A piece of the size of a
walnut to be taken in the morning, fasting, with a little Greek
wine."
The plague increasing still more, Sister Maria Celeste obtained with
much difficulty, a small quantity of a renowned liqueur, made by
Abbess Ursula, an exceptionally saintly nun. This she sends to her
father with the words:--
"I pray your lordship to have faith in this remedy. For if you have
so much faith in my poor miserable prayers, much more may you have in
those of such a holy person; indeed, through her merits you may feel
sure of escaping all danger from the plague."
Whether Galileo took the remedy we do not know, but at all events
he escaped the plague.
[PLATE: THE VILLA ARCETRI.
Galileo's residence, where Milton visited him.]
From Galileo's new home in Florence the telescope was again directed
to the skies, and again did astounding discoveries reward the
astronomer's labours. The great success which he had met with in
studying Jupiter naturally led Galileo to look at Saturn. Here he
saw a spectacle which was sufficiently amazing, though he failed to
interpret it accurately. It was quite manifest that Saturn did not
exhibit a simple circular disc like Jupiter, or like Mars. It seemed
to Galileo as if the planet consisted of three bodies, a large globe
in the centre, and a smaller one on each side. The enigmatical
nature of the discovery led Galileo to announce it in an enigmatical
manner. He published a string of letters which, when duly
transposed, made up a sentence which affirmed that the planet Saturn
was threefold. Of course we now know that this remarkable appearance
of the planet was due to the two projecting portions of the ring.
With the feeble power of Galileo's telescope, these seemed merely
like small globes or appendages to the large central body.
The last of Galileo's great astronomical discoveries related to the
libration of the moon. I think that the detection of this phenomenon
shows his acuteness of observation more remarkably than does any one
of his other achievements with the telescope. It is well known that
the moon constantly keeps the same face turned towards the earth.
When, however, careful measurements have been made with regard to the
spots and marks on the lunar surface, it is found that there is a
slight periodic variation which permits us to see now a little to the
east or to the west, now a little to the north or to the south of
the average lunar disc.
But the circumstances which make the career of Galileo so especially
interesting from the biographer's point of view, are hardly so much
the triumphs that he won as the sufferings that he endured. The
sufferings and the triumphs were, however, closely connected, and it
is fitting that we should give due consideration to what was perhaps
the greatest drama in the history of science.
On the appearance of the immortal work of Copernicus, in which it was
taught that the earth rotated on its axis, and that the earth, like
the other planets, revolved round the sun, orthodoxy stood aghast.
The Holy Roman Church submitted this treatise, which bore the name
"De Revolutionibus Orbium Coelestium," to the Congregation of the
Index. After due examination it was condemned as heretical in 1615.
Galileo was suspected, on no doubt excellent grounds, of entertaining
the objectionable views of Copernicus. He was accordingly privately
summoned before Cardinal Bellarmine on 26th February 1616, and duly
admonished that he was on no account to teach or to defend the
obnoxious doctrines. Galileo was much distressed by this
intimation. He felt it a serious matter to be deprived of the
privilege of discoursing with his friends about the Copernican
system, and of instructing his disciples in the principles of the
great theory of whose truth he was perfectly convinced. It pained
him, however, still more to think, devout Catholic as he was, that
such suspicions of his fervent allegiance to his Church should ever
have existed, as were implied by the words and monitions of Cardinal
Bellarmine.
In 1616, Galileo had an interview with Pope Paul V., who received the
great astronomer very graciously, and walked up and down with him in
conversation for three-quarters of an hour. Galileo complained to
his Holiness of the attempts made by his enemies to embarrass him
with the authorities of the Church, but the Pope bade him be
comforted. His Holiness had himself no doubts of Galileo's
orthodoxy, and he assured him that the Congregation of the Index
should give Galileo no further trouble so long as Paul V. was in the
chair of St. Peter.
On the death of Paul V. in 1623, Maffeo Barberini was elected Pope,
as Urban VIII. This new Pope, while a cardinal, had been an intimate
friend of Galileo's, and had indeed written Latin verses in praise of
the great astronomer and his discoveries. It was therefore not
unnatural for Galileo to think that the time had arrived when, with
the use of due circumspection, he might continue his studies and his
writings, without fear of incurring the displeasure of the Church.
Indeed, in 1624, one of Galileo's friends writing from Rome, urges
Galileo to visit the city again, and added that--
"Under the auspices of this most excellent, learned, and benignant
Pontiff, science must flourish. Your arrival will be welcome to his
Holiness. He asked me if you were coming, and when, and in short, he
seems to love and esteem you more than ever."
The visit was duly paid, and when Galileo returned to Florence, the
Pope wrote a letter from which the following is an extract,
commanding the philosopher to the good offices of the young
Ferdinand, who had shortly before succeeded his father in the Grand
Duchy of Tuscany.
"We find in Galileo not only literary distinction, but also the love
of piety, and he is also strong in those qualities by which the
pontifical good-will is easily obtained. And now, when he has been
brought to this city to congratulate us on our elevation, we have
very lovingly embraced him; nor can we suffer him to return to the
country whither your liberality calls him, without an ample provision
of pontifical love. And that you may know how dear he is to us, we
have willed to give him this honourable testimonial of virtue and
piety. And we further signify that every benefit which you shall
confer upon him, imitating or even surpassing your father's
liberality, will conduce to our gratification."
The favourable reception which had been accorded to him by Pope Urban
VIII. seems to have led Galileo to expect that there might be some
corresponding change in the attitude of the Papal authorities on the
great question of the stability of the earth. He accordingly
proceeded with the preparation of the chief work of his life, "The
Dialogue of the two Systems." It was submitted for inspection by the
constituted authorities. The Pope himself thought that, if a few
conditions which he laid down were duly complied with, there could be
no objection to the publication of the work. In the first place, the
title of the book was to be so carefully worded as to show plainly
that the Copernican doctrine was merely to be regarded as an
hypothesis, and not as a scientific fact. Galileo was also
instructed to conclude the book with special arguments which had been
supplied by the Pope himself, and which appeared to his Holiness to
be quite conclusive against the new doctrine of Copernicus.