Galileo Overthrows Ancient Philosophy
Author: Lodge, Sir Oliver
Galileo Overthrows Ancient Philosophy
The Telescope And Its Discoveries, A.D. 1610
When the Copernican system of astronomy was published to the world (1543)
it had to encounter, as all capital theories and discoveries in science have
done, the criticism, and, for some time, the opposition, of men holding other
views. After Copernicus, the next great name in modern science is that of
Tycho Brahe (1546-1601), who rejected the theory of Copernicus in favor of a
modified form of the Ptolemaic system. This was still taught in the schools
when two mighty contemporaries, geniuses of science, rose to overthrow it
These men were Galileo Galilei - commonly known as Galileo - and Kepler,
both astronomers, though Galileo's scientific work covered also a much wider
field. He is regarded to-day as marking a distinct epoch in the progress of
the world, and the following account of his work by the eminent scientist, Sir
Oliver Lodge, expresses no more than a just appreciation of his great services
Galileo exercised a vast influence on the development of human thought. A
man of great and wide culture, a so-called universal genius, it is as an
experimental philosopher that he takes the first rank. In this capacity he
must be placed alongside of Archimedes, and it is pretty certain that between
the two there was no man of magnitude equal to either in experimental
philosophy. It is perhaps too bold a speculation, but I venture to doubt
whether in succeeding generations we find his equal in the domain of purely
experimental science until we come to Faraday. Faraday was no doubt his
superior, but I know of no other of whom the like can unhesitatingly be said.
In mathematical and deductive science, of course, it is quite otherwise.
Kepler, for instance, and many men before and since, have far excelled Galileo
in mathematical skill and power, though at the same time his achievements in
this department are by no means to be despised.
Born at Pisa on the very day that Michelangelo lay dying in Rome, he
inherited from his father a noble name, cultivated tastes, a keen love of
truth, and an impoverished patrimony. Vincenzo de Galilei, a descendant of
the important Bonajuti family, was himself a mathematician and a musician, and
in a book of his still extant he declares himself in favor of free and open
inquiry into scientific matters, unrestrained by the weight of authority and
tradition. In all probability the son imbibed these precepts: certainly he
acted on them.
Vincenzo, having himself experienced the unremunerative character of
scientific work, had a horror of his son's taking to it, especially as in his
boyhood he was always constructing ingenious mechanical toys and exhibiting
other marks of precocity. So the son was destined for business - to be, in
fact, a cloth-dealer. But he was to receive a good education first, and was
sent to an excellent convent school.
Here he made rapid progress, and soon excelled in all branches of
classics and literature. He delighted in poetry, and in later years wrote
several essays on Dante, Tasso, and Ariosto, besides composing some tolerable
poems himself. He played skillfully on several musical instruments,
especially on the lute, of which indeed he became a master, and on which he
solaced himself when quite an old man. Besides this, he seems to have had
some skill as an artist, which was useful afterward in illustrating his
discoveries, and to have had a fine sensibility as an art critic, for we find
several eminent painters of that day acknowledging the value of the opinion of
the young Galileo.
Perceiving all this display of ability, the father wisely came to the
conclusion that the selling of woollen stuffs would hardly satisfy his
aspirations for long, and that it was worth a sacrifice to send him to the
university. So to the university of his native town he went, with the avowed
object of studying medicine, that career seeming the most likely to be
profitable. Old Vincenzo's horror of mathematics or science as a means of
obtaining a livelihood is justified by the fact that while the university
professor of medicine received two thousand scudi a year, the professor of
mathematics had only sixty; that is thirteen pounds a year, or seven and a
half pence a day. So the son had been kept properly ignorant of such
poverty-stricken subjects, and to study medicine he went.
But his natural bent showed itself even here. For praying one day in the
cathedral, like a good Catholic as he was all his life, his attention was
arrested by the great lamp which, after lighting it, the verger had left
swinging to and fro. Galileo proceeded to time its swings by the only watch
he possessed - viz., his own pulse. He noticed that the time of swing
remained, as near as he could tell, the same, notwithstanding the fact that
the swings were getting smaller and smaller.
By subsequent experiment he verified the law, and the isochronism of the
pendulum was discovered. An immensely important practical discovery this, for
upon it all modern clocks are based; and Huyghens soon applied it to the
astronomical clock, which up to that time had been a crude and quite
The best clock which Tycho Brahe could get for his observatory was
inferior to one that may now be purchased for a few shillings; and this change
is owing to the discovery of the pendulum by Galileo. Not that he applied it
to clocks; he was not thinking of astronomy, he was thinking of medicine, and
wanted to count people's pulses. The pendulum served; and "pulsilogies," as
they were called, were thus introduced to and used by medical practitioners.
The Tuscan court came to Pisa for the summer months - for it was then a
seaside place - and among the suite was Ostillio Ricci, a distinguished
mathematician and old friend of the Galileo family. The youth visited him,
and one day, it is said, heard a lesson in Euclid being given by Ricci to the
pages while he stood outside the door entranced. Anyhow, he implored Ricci to
help him into some knowledge of mathematics, and the old man willingly
consented. So he mastered Euclid, and passed on to Archimedes, for whom he
acquired a great veneration.
His father soon heard of this obnoxious proclivity, and did what he could
to divert him back to medicine again. But it was no use. Underneath his
Galen and Hippocrates were secreted copies of Euclid and Archimedes, to be
studied at every available opportunity. Old Vincenzo perceived the bent of
genius to be too strong for him, and at last gave way. With prodigious
rapidity the released philosopher now assimilated the elements of mathematics
and physics, and at twenty-six we find him appointed for three years to the
university chair of mathematics, and enjoying the paternally dreaded stipend
of seven and a half pence a day.
Now it was that he pondered over the laws of falling bodies. He
verified, by experiment, the fact that the velocity acquired by falling down
any slope of given height was independent of the angle of slope. Also, that
the height fallen through was proportional to the square of the time.
Another thing he found experimentally was that all bodies, heavy and
light, fell at the same rate, striking the ground at the same time. Now this
was clean contrary to what he had been taught. The physics of those days were
a simple reproduction of statements in old books. Aristotle had asserted
certain things to be true, and these were universally believed. No one
thought of trying the thing to see if it really were so. The idea of making
an experiment would have savored of impiety, because it seemed to tend toward
scepticism, and cast a doubt on a reverend authority.
Young Galileo, with all the energy and imprudence of youth - what a
blessing that youth has a little imprudence and disregard of consequences in
pursuing a high ideal! - as soon as he perceived that his instructors were
wrong on the subject of falling bodies, instantly informed them of the fact.
Whether he expected them to be pleased or not is a question. Anyhow, they
were not pleased, but were much annoyed by his impertinent arrogance.
It is, perhaps, difficult for us now to appreciate precisely their
position. These doctrines of antiquity, which had come down hoary with age,
and the discovery of which had reawakened learning and quickened intellectual
life, were accepted less as a science or a philosophy than as a religion. Had
they regarded Aristotle as a verbally inspired writer, they could not have
received his statements with more unhesitating conviction. In any dispute as
to a question of fact, such as the one before us concerning the laws of
falling bodies, their method was not to make an experiment, but to turn over
the pages of Aristotle; and he who could quote chapter and verse of this great
writer was held to settle the question and raise it above the reach of
It is very necessary for us to realize this state of things clearly,
because otherwise the attitude of the learned of those days toward every new
discovery seems stupid and almost insane. They had a crystallized system of
truth, perfect, symmetrical; it wanted no novelty, no additions; every
addition or growth was an imperfection, an excrescence, a deformity. Progress
was unnecessary and undesired. The Church had a rigid system of dogma which
must be accepted in its entirety on pain of being treated as a heretic.
Philosophers had a cast-iron system of truth to match - a system founded upon
Aristotle - and so interwoven with the great theological dogmas that to
question one was almost equivalent to casting doubt upon the other.
In such an atmosphere true science was impossible. The life-blood of
science is growth, expansion, freedom, development. Before it could appear it
must throw off these old shackles of centuries. It must burst its old skin,
and emerge, worn with the struggle, weakly and unprotected, but free and able
to grow and to expand. The conflict was inevitable, and it was severe. Is it
over yet? I fear not quite, though so nearly as to disturb science hardly at
all. Then it was different: it was terrible. Honor to the men who bore the
first shock of the battle!
Now, Aristotle had said that bodies fell at rates depending on their
weight. A five-pound weight would fall five times as quick as a one pound
weight; a fifty-pound weight fifty times as quick, and so on. Why he said so
nobody knows. He cannot have tried. He was not above trying experiments,
like his smaller disciples; but probably it never occurred to him to doubt the
fact. It seems so natural that a heavy body should fall quicker than a light
one; and perhaps he thought of a stone and a feather, and was satisfied.
Galileo, however, asserted that the weight did not matter a bit; that
everything fell at the same rate - even a stone and a feather, but for the
resistance of the air - and would reach the ground in the same time. And he
was not content to be pooh-poohed and snubbed. He knew he was right, and he
was determined to make everyone see the facts as he saw them. So one morning,
before the assembled university, he ascended the famous leaning tower, taking
with him a one-hundred-pound shot and a one-pound shot. He balanced them on
the edge of the tower, and let them drop together. Together they fell, and
together they struck the ground. The simultaneous clang of those two weights
sounded the death-knell of the old system of philosophy, and heralded the
birth of the new.
But was the change sudden? Were his opponents convinced? Not a jot.
Though they had seen with their eyes and heard with their ears, the full light
of heaven shining upon them, they went back muttering and discontented to
their musty old volumes and their garrets, there to invent occult reasons for
denying the validity of the observation, and for referring it to some unknown
They saw that if they gave way on this one point they would be letting go
their anchorage, and henceforward would be liable to drift along with the
tide, not knowing whither. They dared not do this. No; they must cling to
the old traditions; they could not cast away their rotting ropes and sail out
on to the free ocean of God's truth in a spirit of fearless faith.
Yet they had received a shock: as by a breath of fresh salt breeze and a
dash of spray in their faces, they had been awakened out of their comfortable
lethargy. They felt the approach of a new era. Yes, it was a shock, and they
hated the young Galileo for giving it them - hated him with the sullen hatred
of men who fight for a lost and dying cause.
We need scarcely blame these men; at least we need not blame them
overmuch. To say that they acted as they did is to say that they were human,
were narrow-minded, and were the apostles of a lost cause. But they could not
know this; they had no experience of the past to guide them; the conditions
under which they found themselves were novel, and had to be met for the first
time. Conduct which was excusable then would be unpardonable now, in the
light of all this experience to guide us. Are there any now who practically
repeat their error, and resist new truth? who cling to any old anchorage of
dogma, and refuse to rise with the tide of advancing knowledge? There may be
some even now.
Well, the unpopularity of Galileo smouldered for a time, until, by
another noble imprudence, he managed to offend a semiroyal personage, Giovanni
de' Medici, by giving his real opinion, when consulted, about a machine which
De' Medici had invented for cleaning out the harbor of Leghorn. He said it was
as useless as it in fact turned out to be. Through the influence of the
mortified inventor he lost favor at court; and his enemies took advantage of
the fact to render his chair untenable. He resigned before his three years
were up, and retired to Florence.
His father at this time died, and the family were left in narrow
circumstances. He had a brother and three sisters to provide for. He was
offered a professorship at Padua for six years by the Senate of Venice, and
willingly accepted it. Now began a very successful career. His introductory
address was marked by brilliant eloquence, and his lectures soon acquired
fame. He wrote for his pupils on the laws of motion, on fortifications, on
sun-dials, on mechanics, and on the celestial globe: some of these papers are
now lost, others have been printed during the present century.
Kepler sent him a copy of his new book, Mysterium Cosmographicum, and
Galileo, in thanking him for it, writes him the following letter:
"I count myself happy, in the search after truth, to have so great an
ally as yourself, and one who is so great a friend of the truth itself. It is
really pitiful that there are so few who seek truth, and who do not pursue a
perverse method of philosophizing. But this is not the place to mourn over
the miseries of our times, but to congratulate you on your splendid
discoveries in confirmation of truth. I shall read your book to the end, sure
of finding much that is excellent in it. I shall do so with the more
pleasure, because I have been for many years an adherent of the Copernican
system, and it explains to me the causes of many of the appearances of nature
which are quite unintelligible on the commonly accepted hypothesis. I have
collected many arguments for the purpose of refuting the latter; but I do not
venture to bring them to the light of publicity, for fear of sharing the fate
of our master, Copernicus, who, although he has earned immortal fame with
some, yet with very many (so great is the number of fools) has become an
object of ridicule and scorn. I should certainly venture to publish my
speculations if there were more people like you. But this not being the case,
I refrain from such an undertaking."
Kepler urged him to publish his arguments in favor of the Copernican
theory, but he hesitated for the present, knowing that his declaration would
be received with ridicule and opposition, and thinking it wiser to get rather
more firmly seated in his chair before encountering the storm of controversy.
The six years passed away, and the Venetian Senate, anxious not to lose so
bright an ornament, renewed his appointment for another six years at a largely
Soon after this appeared a new star - the stella nova of 1604 - not the
one Tycho had seen - that was in 1572 - but the same that Kepler was so much
interested in. Galileo gave a course of three lectures upon it to a great
audience. At the first the theatre was overcrowded, so he had to adjourn to a
hall holding one thousand persons. At the next he had to lecture in the open
air. He took occasion to rebuke his hearers for thronging to hear about an
ephemeral novelty, while for the much more wonderful and important truths
about the permanent stars and facts of nature they had but deaf ears.
But the main point he brought out concerning the new star was that it
upset the received Aristotelian doctrine of the immutability of the heavens.
According to that doctrine the heavens were unchangeable, perfect, subject
neither to growth not to decay. Here was a body, not a meteor but a real
distant star, which had not been visible and which would shortly fade away
again, but which meanwhile was brighter than Jupiter.
The staff of petrified professorial wisdom were annoyed at the appearance
of the star, still more at Galileo's calling public attention to it; and
controversy began at Padua. However, he accepted it, and now boldly threw
down the gauntlet in favor of the Copernican theory, utterly repudiating the
old Ptolemaic system, which up to that time he had taught in the schools
according to established custom.
The earth no longer the only world to which all else in the firmament
were obsequious attendants, but a mere insignificant speck among the host of
heaven! Man no longer the centre and cynosure of creation, but, as it were,
an insect crawling on the surface of this little speck! All this not set down
in crabbed Latin in dry folios for a few learned monks, as in Copernicus'
time, but promulgated and argued in rich Italian, illustrated by analogy, by
experiment, and with cultured wit; taught not to a few scholars here and there
in musty libraries, but proclaimed in the vernacular to the whole populace
with all the energy and enthusiasm of a recent convert and a master of
language! Had a bombshell been exploded among the fossilized professors it
had been less disturbing.
But there was worse in store for them. A Dutch optician, Hans Lippershey
by name, of Middleburg, had in his shop a curious toy, rigged up, it is said,
by an apprentice, and made out of a couple of spectacle lenses, whereby, if
one looked through it, the weather-cock of a neighboring church spire was seen
nearer and upside down. The tale goes that the Marquis Spinola, happening to
call at the shop, was struck with the toy and bought it. He showed it to
Prince Maurice of Nassau, who thought of using it for military reconnoitring.
All this is trivial. What is important is that some faint and inaccurate echo
of this news found its way to Padua and into the ears of Galileo.
The seed fell on good soil. All that night he sat up and pondered. He
knew about lenses and magnifying-glasses. He had read Kepler's theory of the
eye, and had himself lectured on optics. Could he not hit on the device and
make an instrument capable of bringing the heavenly bodies nearer? Who knew
what marvels he might not so perceive! By morning he had some schemes ready
to try, and one of them was successful. Singularly enough it was not the same
plan as the Dutch optician's: it was another mode of achieving the same end.
He took an old small organ-pipe, jammed a suitably chosen spectacle glass into
either end, one convex, the other concave, and, behold! he had the half of a
wretchedly bad opera-glass capable of magnifying three times. It was better
than the Dutchman's, however: it did not invert.
Such a thing as Galileo made may now be bought at a toy-shop for I
suppose half a crown, and yet what a potentiality lay in that "glazed optic
tube," as Milton called it. Away he went with it to Venice and showed it to
the Seigniory, to their great astonishment. "Many noblemen and senators,"
says Galileo, "though of advanced age, mounted to the top of one of the
highest towers to watch the ships, which were visible through my glass two
hours before they were seen entering the harbor, for it makes a thing fifty
miles off as near and clear as if it were only five." Among the people, too,
the instrument excited the greatest astonishment and interest, so that he was
nearly mobbed. The Senate hinted to him that a present of the instrument
would not be unacceptable, so Galileo took the hint and made another for them.
They immediately doubled his salary at Padua, making it one thousand florins,
and confirmed him in the enjoyment of it for life.
He now eagerly began the construction of a larger and better instrument.
Grinding the lenses with his own hands with consummate skill, he succeeded in
making a telescope magnifying thirty times. Thus equipped he was ready to
begin a survey of the heavens. The first object he carefully examined was
naturally the moon. He found there everything at first sight very like the
earth, mountains and valleys, craters and plains, rocks, and apparently seas.
You may imagine the hostility excited among the Aristotelian philosophers,
especially, no doubt, those he had left behind at Pisa, on the ground of his
spoiling the pure, smooth, crystalline, celestial face of the moon as they had
thought it, and making it harsh and rugged, and like so vile and ignoble a
body as the earth.
He went further, however, into heterodoxy than this: he not only made the
moon like the earth, but he made the earth shine like the moon. The
visibility of "the old moon in the new moon's arms" he explained by
earth-shine. Leonardo had given the same explanation a century before. Now,
one of the many stock arguments against Copernican theory of the earth being a
planet like the rest was that the earth was dull and dark and did not shine.
Galileo argued that it shone just as much as the moon does, and in fact rather
more - especially if it be covered with clouds. One reason of the peculiar
brilliancy of Venus is that she is a very cloudy planet. ^1 Seen from the moon
the earth would look exactly as the moon does to us, only a little brighter
and sixteen times as big - four times the diameter.
[Footnote 1: It is of course the "silver lining" of clouds that outside
Wherever, Galileo turned his telescope new stars appeared. The Milky
Way, which had so puzzled the ancients, was found to be composed of stars.
Stars that appeared single to the eye were some of them found to be double;
and at intervals were found hazy nebulous wisps, some of which seemed to be
star clusters, while others seemed only a fleecy cloud.
Now we come to his most brilliant, at least his most sensational,
discovery. Examining Jupiter minutely on January 7, 1610, he noticed three
little stars near it, which he noted down as fixing its then position. On the
following night Jupiter had moved to the other side of the three stars. This
was natural enough, but was it moving the right way? On examination it
appeared not. Was it possible the tables were wrong? The next evening was
cloudy, and he had to curb his feverish impatience. On the 10th there were
only two, and those on the other side. On the 11th two again, but one bigger
than the other. On the 12th the three reappeared, and on the 13th there were
four. No more appeared. Jupiter, then, had moons like the earth - four of
them in fact! - and they revolved round him in periods which were soon
The news of the discovery soon spread and excited the greatest interest
and astonishment. Many of course refused to believe it. Some there were who,
having been shown them, refused to believe their eyes, and asserted that
although the telescope acted well enough for terrestrial objects, it was
altogether false and illusory when applied to the heavens. Others took the
safer ground of refusing to look through the glass. One of these who would
not look at the satellites happened to die soon afterward. "I hope," says
Galileo, "that he saw them on his way to heaven."
The way in which Kepler received the news is characteristic, though by
adding four to the supposed number of planets it might have seemed to upset
his notions about the five regular solids.
He says: "I was sitting idle at home thinking of you, most excellent
Galileo, and your letters, when the news was brought me of the discovery of
four planets by the help of the double eyeglass. Wachenfels stopped his
carriage at my door to tell me, when such a fit of wonder seized me at a
report which seemed so very absurd, and I was thrown into such agitation at
seeing an old dispute between us decided in this way, that between his joy, my
coloring, and the laughter of us both, confounded as we were by such a
novelty, we were hardly capable, he of speaking, or I of listening.
"On our separating, I immediately fell to thinking how there could be any
addition to the number of planets without overturning my Mysterium
Cosmographicon, published thirteen years ago, according to which Euclid's five
regular solids do not allow more than six planets round the sun. But I am so
far from disbelieving the existence of the four circumjovial planets that I
long for a telescope to anticipate you if possible in discovering two round
Mars - as the proportion seems to me to require - six or eight round Saturn,
and one each round Mercury and Venus."
As an illustration of the opposite school I will take the following
extract from Francesco Sizzi, a Florentine astronomer, who argues against the
"There are seven windows in the head - two nostrils, two eyes, two ears,
and a mouth; so in the heavens there are two favorable stars, two
unpropitious, two luminaries, and Mercury alone undecided and indifferent.
From which and many other similar phenomena of nature, such as the seven
metals, etc., which it were tedious to enumerate, we gather that the number of
planets is necessarily seven.
"Moreover, the satellites are invisible to the naked eye, and therefore
can have no influence on the earth, and therefore would be useless, and
therefore do not exist.
"Besides, the Jews and other ancient nations as well as modern Europeans
have adopted the division of the week into seven days, and have named them
from the seven planets: now if we increase the number of the planets this
whole system falls to the ground."
To these arguments Galileo replied that whatever their force might be as
a reason for believing beforehand that no more than seven planets would be
discovered, they hardly seemed of sufficient weight to destroy the new ones
when actually seen. Writing to Kepler at this time, Galileo ejaculates:
"Oh, my dear Kepler, how I wish that we could have one hearty laugh
together! Here, at Padua, is the principal professor of philosophy whom I
have repeatedly and urgently requested to look at the moon and planets through
my glass, which he pertinaciously refuses to do. Why are you not here? What
shouts of laughter we should have at this glorious folly! And to hear the
professor of philosophy at Pisa laboring before the Grand Duke with logical
arguments, as if with magical incantations, to charm the new planets out of
A young German protege of Kepler, Martin Horkey, was travelling in Italy,
and meeting Galileo at Bologna was favored with a view through his telescope.
But supposing that Kepler must necessarily be jealous of such great
discoveries, and thinking to please him, he writes: "I cannot tell what to
think about these observations. They are stupendous, they are wonderful, but
whether they are true or false I cannot tell." He concludes, "I will never
concede his four new planets to that Italian from Padua, though I die for it."
So he published a pamphlet asserting that reflected rays and optical illusions
were the sole cause of the appearance, and that the only use of the imaginary
planets was to gratify Galileo's thirst for gold and notoriety.
When after this performance he paid a visit to his old instructor Kepler
he got a reception which astonished him. However, he pleaded so hard to be
forgiven that Kepler restored him to partial favor, on this condition, that he
was to look again at the satellites, and this time to see them and own that
they were there.
By degrees the enemies of Galileo were compelled to confess to the truth
of the discovery, and the next step was to outdo him. Scheiner counted five,
Rheiter nine, and others went as high as twelve. Some of these were
imaginary, some were fixed stars, and four satellites only are known to this
[Footnote 1: A fifth satellite of Jupiter has been recently discovered; and
Kepler's guess at two moons for Mars has also been justified.]
Here, close to the summit of his greatness, we must leave him for a time.
A few steps more and he will be on the brow of the hill; a short piece of
table-land, and then the descent begins.
In dealing with these historic events will you allow me to repudiate once
for all the slightest sectarian bias or meaning? I have nothing to do with
Catholic or Protestant as such. I have nothing to do with the Church of Rome
as such. I am dealing with the history of science. But historically at one
period science and the Church came into conflict. It was not specially one
church rather than another - it was the Church in general, the only one that
then existed in those countries. Historically, I say, they came into
conflict, and historically the Church was the conqueror. It got its way; and
science, in the persons of Bruno, Galileo, and several others, was vanquished.
Such being the facts, there is no help but to mention them in dealing with the
history of science. Doubtless now the Church regards it as an unhappy
victory, and gladly would ignore this painful struggle. This, however, is
impossible. With their creed the churchmen of that day could act in no other
way. They were bound to prosecute heresy, and they were bound to conquer in
the struggle or be themselves shattered.
But let me insist on the fact that no one accuses the ecclesiastical
courts of crime or evil motives. They attacked heresy after their manner, as
the civil courts attacked witchcraft after their manner. Both erred
grievously, but both acted with the best intentions.
We must remember, moreover, that his doctrines were scientifically
heterodox, and the university professors of that day were probably quite as
ready so condemn them as the Church was. To realize the position we must
think of some subjects which to-day are scientifically heterodox, and of the
customary attitude adopted toward them by persons of widely differing creeds.
If it be contended now, as it is, that the ecclesiastics treated Galileo
well, I admit it freely: they treated him as well as they possibly could. They
overcame him, and he recanted; but if he had not recanted, if he had persisted
in his heresy, they would - well, they would still have treated his soul well,
but they would have set fire to his body. Their mistake consisted not in
cruelty, but in supposing themselves the arbiters of eternal truth; and by no
amount of slurring and glossing over facts can they evade the responsibility
assumed by them on account of this mistaken attitude.
We left Galileo standing at his telescope and beginning his survey of the
heavens. We followed him indeed through a few of his first great discoveries
- the discovery of the mountains and other variety of surface in the moon, of
the nebulae and a multitude of faint stars, and lastly of the four satellites
This latter discovery made an immense sensation, and contributed its
share to his removal from Padua, which quickly followed it. Before the end of
the year 1610 Galileo had made another discovery - this time on Saturn. But to
guard against the host of plagiarists and impostors he published it in the
form of an anagram, which, at the request of the Emperor Rudolph - a request
probably inspired by Kepler - he interpreted; it ran thus: The farthest planet
Very soon after he found that Venus was changing from a full-moon to a
half-moon appearance. He announced this also by an anagram, and waited till
it should become a crescent, which it did. This was a dreadful blow to the
anti-Copernicans, for it removed the last lingering difficulty to the
reception of the Copernican doctrine. Copernicus had predicted, indeed, a
hundred years before, that, if ever our powers of sight were sufficiently
enhanced, Venus and Mercury would be seen to have phases like the moon. And
now Galileo with his telescope verifies the prediction to the letter.
Here was a triumph for the grand old monk, and a bitter morsel for his
Castelli writes, "This must now convince the most obstinate." But
Galileo, with more experience, replies: "You almost make me laugh by saying
that these clear observations are sufficient to convince the most obstinate;
it seems you have yet to learn that long ago the observations were enough to
convince those who are capable of reasoning and those who wish to learn the
truth; but that to convince the obstinate and those who care for nothing
beyond the vain applause of the senseless vulgar, not even the testimony of
the stars would suffice, were they to descend on earth to speak for
themselves. Let us, then, endeavor to procure some knowledge for ourselves,
and rest contended with this sole satisfaction; but of advancing in popular
opinion, or of gaining the assent of the book-philosophers, let us abandon
both the hope and the desire."
What a year's work it had been! In twelve months observational astronomy
had made such a bound as it has never made before or since ^1. Why did not
others made any of these observations? Because no one could make telescopes
like Galileo. He gathered pupils round him, however, and taught them how to
work the lenses, so that gradually these instruments penetrated Europe, and
astronomers everywhere verified his splendid discoveries.
[Footnote 1: The next year Galileo discovered also the spots upon the sun and
estimated roughly its time of rotation.]