"Oh, my dear Kepler, how I wish that we could have one hearty laugh together! Here, at Padua, is the princ.i.p.al professor of philosophy whom I have repeatedly and urgently requested to look at the moon and planets through my gla.s.s, 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 labouring before the grand duke with logical arguments, as if with magical incantations, to charm the new planets out of the sky."
A young German _protege_ of Kepler, Martin Horkey, was travelling in Italy, and meeting Galileo at Bologna was favoured 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 a.s.serting 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 favour, 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 day.[10]
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.
LECTURE V
GALILEO AND THE INQUISITION
One sinister event occurred while Galileo was at Padua, some time before the era we have now arrived at, before the invention of the telescope--two years indeed after he had first gone to Padua; an event not directly concerning Galileo, but which I must mention because it must have shadowed his life both at the time and long afterwards. It was the execution of Giordano Bruno for heresy. This eminent philosopher had travelled largely, had lived some time in England, had acquired new and heterodox views on a variety of subjects, and did not hesitate to propound them even after he had returned to Italy.
The Copernican doctrine of the motion of the earth was one of his obnoxious heresies. Being persecuted to some extent by the Church, Bruno took refuge in Venice--a free republic almost independent of the Papacy--where he felt himself safe. Galileo was at Padua hard by: the University of Padua was under the government of the Senate of Venice: the two men must in all probability have met.
Well, the Inquisition at Rome sent messengers to Venice with a demand for the extradition of Bruno--they wanted him at Rome to try him for heresy.
In a moment of miserable weakness the Venetian republic gave him up, and Bruno was taken to Rome. There he was tried, and cast into the dungeons for six years, and because he entirely refused to recant, was at length delivered over to the secular arm and burned at the stake on 16th February, Anno Domini 1600.
This event could not but have cast a gloom over the mind of lovers and expounders of truth, and the lesson probably sank deep into Galileo"s soul.
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 to condemn them as the Church was. To realise the position we must think of some subjects which _to-day_ are scientifically heterodox, and of the customary att.i.tude adopted towards 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 a.s.sumed by them on account of this mistaken att.i.tude.
I am not here attacking the dogma of Papal Infallibility: it is historically, I believe, quite unaffected by the controversy respecting the motion of the earth, no Papal edict _ex cathedra_ having been promulgated on the subject.
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 mult.i.tude of faint stars, and lastly of the four satellites of Jupiter.
This latter discovery made an immense sensation, and contributed its share to his removal from Padua, which quickly followed it, as I shall shortly narrate; but first I think it will be best to continue our survey of his astronomical discoveries without regard to the place whence they were made.
Before the end of the year 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 furthest planet is triple.
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.
[Ill.u.s.tration: FIG. 46.--Old drawings of Saturn by different observers, with the imperfect instruments of that day. The first is Galileo"s idea of what he saw.]
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 opponents.
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, endeavour to procure some knowledge for ourselves, and rest contented with this sole satisfaction; but of advancing in popular opinion, or of gaining the a.s.sent of the book-philosophers, let us abandon both the hope and the desire."
[Ill.u.s.tration: FIG. 47.--Phases of Venus. Showing also its apparent variations in size by reason of its varying distance from the earth.
When fully illuminated it is necessarily most distant. It looks brightest to us when a broad crescent.]
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.
Why did not others make 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.
But still he worked on, and by March in the very next year, he saw something still more hateful to the Aristotelian philosophers, viz.
spots on the sun.
[Ill.u.s.tration: FIG. 48.]
If anything was pure and perfect it was the sun, they said. Was this impostor going to blacken its face too?
Well, there they were. They slowly formed and changed, and by moving all together showed him that the sun rotated about once a month.
Before taking leave of Galileo"s astronomical researches, I must mention an observation made at the end of 1612, that the apparent triplicity of Saturn (Fig. 46) had vanished.
[Ill.u.s.tration: FIG. 49.--A portion of the sun"s disk as seen in a powerful modern telescope.]
"Looking on Saturn within these few days, I found it solitary, without the a.s.sistance of its accustomed stars, and in short perfectly round and defined, like Jupiter, and such it still remains. Now what can be said of so strange a metamorphosis? Are perhaps the two smaller stars consumed like spots on the sun? Have they suddenly vanished and fled? Or has Saturn devoured his own children? Or was the appearance indeed fraud and illusion, with which the gla.s.ses have so long time mocked me and so many others who have so often observed with me? Now perhaps the time is come to revive the withering hopes of those, who, guided by more profound contemplations, have fathomed all the fallacies of the new observations and recognized their impossibility! I cannot resolve what to say in a chance so strange, so new, so unexpected. The shortness of time, the unexampled occurrence, the weakness of my intellect, the terror of being mistaken, have greatly confounded me."
However, he plucked up courage, and conjectured that the two attendants would reappear, by revolving round the planet.
[Ill.u.s.tration: FIG. 50.--Saturn and his rings, as seen under the most favourable circ.u.mstances.]
The real reason of their disappearance is well known to us now. The plane of Saturn"s rings oscillates slowly about our line of sight, and so we sometimes see them edgeways and sometimes with a moderate amount of obliquity. The rings are so thin that, when turned precisely edgeways, they become invisible. The two imaginary attendants were the most conspicuous portions of the ring, subsequently called _ansae_.
I have thought it better not to interrupt this catalogue of brilliant discoveries by any biographical details; but we must now retrace our steps to the years 1609 and 1610, the era of the invention of the telescope.
By this time Galileo had been eighteen years at Padua, and like many another man in like case, was getting rather tired of continual lecturing. Moreover, he felt so full of ideas that he longed to have a better opportunity of following them up, and more time for thinking them out.
Now in the holidays he had been accustomed to return to his family home at Pisa, and there to come a good deal into contact with the Grand-Ducal House of Tuscany. Young Cosmo di Medici became in fact his pupil, and arrived at man"s estate with the highest opinion of the philosopher.