Volume II Part 13 (1/2)
Again it appears how reluctant the Roman authorities were to interfere, and how they were impelled rather by the necessity of their position than by their personal belief in the course they had been obliged to take. [Sidenote: The personal sentiments of the Popes.] After all that had pa.s.sed, the Pope, Paul V., admitted Galileo to an audience, at which he professed to him personally the kindest sentiments, and a.s.sured him of safety. When Urban VIII. succeeded to the pontifical chair, Galileo received the distinction of not less than six audiences; the Pope conferred on him several presents, and added the promise of a pension for his son. In a letter to the Duke of Florence his Holiness used the most liberal language, stated how dear to him Galileo was, that he had very lovingly embraced him, and requested the duke to show him every favour.
[Sidenote: Galileo publishes ”The System of the World”.] Whether it was that, under these auspicious circ.u.mstances, Galileo believed he could with impunity break through the engagement he had made, or whether an instinctive hatred of that intellectual despotism and hypocrisy which was weighing upon Europe became irrepressible in his breast, in 1632 he ventured on the publication of his work, ent.i.tled ”The System of the World,” its object being to establish the truth of the Copernican doctrine. It is composed in the dialogue form, three speakers being introduced, two of them true philosophers, the third an objector.
Whatever may have been the personal opinion of the Pope, there can be no doubt that his duty rendered it necessary for him to act. Galileo was therefore again summoned before the Inquisition, the Tuscan amba.s.sador expostulating against the inhumanity of thus dealing with an old man in ill health. But no such considerations were listened to, and Galileo was compelled to appear at Rome, February, 1633, and surrender himself to the Holy Office. The Pope's nephew did all in his power to meet the necessity of the Church and yet to spare the dignity of science. He paid every attention to the personal comfort of the accused. When the time came for Galileo to be put into solitary confinement, he endeavoured to render the imprisonment as light as possible; but, finding it to prey upon the spirits of the aged philosopher, he, on his own responsibility, liberated him, permitting him to reside in the house of the Tuscan amba.s.sador. [Sidenote: Is again condemned by the Inquisition.] The trial being completed, Galileo was directed to appear, on June 22nd, to hear his sentence. Clothed in the penitential garment, he received judgment.
His heretical offences were specified, the pledges he had violated recited; he was declared to have brought upon himself strong suspicions of heresy, and to be liable to the penalties thereof; but from these he might be absolved if, with a sincere heart, he would abjure and curse his heresies. However, that his offences might not altogether go unpunished, and that he might be a warning to others, he was condemned to imprisonment during the pleasure of the Inquisition, his dialogues were prohibited by public edict, and for three years he was directed to recite, once a week, the seven penitential psalms.
[Sidenote: His degradation and punishment.] In his garment of disgrace the aged philosopher was now made to fall upon his knees before the a.s.sembled cardinals, and, with his hand on the Gospels, to make the required abjuration of the heliocentric doctrine, and to give the pledges demanded. He was then committed to the prison of the Inquisition; the persons who had been concerned in the printing of his book were punished; and the sentence and abjuration were formally promulgated, and ordered to be publicly read in the universities. In Florence, the adherents of Galileo were ordered to attend in the Church of Santa Croce to witness his disgrace. After a short imprisonment in the jail of the Inquisition, he was ordered to Arcetri, and confined in his own house. Here severe misfortunes awaited him; his favourite daughter died; he fell into a state of melancholy; an application that he might go to Florence for the sake of medical advice was refused. It became evident that there was an intention to treat him with inexorable severity. After five years of confinement, permission was reluctantly accorded to him to remove to Florence for his health; but still he was forbidden to leave his house, or receive his friends, or even to attend ma.s.s during Pa.s.sion Week without a special order. The Grand-duke tried to abate this excessive severity, directing his amba.s.sador at the court of Rome to plead the venerable age and ill health of the immortal convict, and that it was desirable to permit him to communicate certain scientific discoveries he had made to some other person, such as Father Castelli. Not even that was accorded unless the interview took place in the presence of an official of the Inquisition. Soon after Galileo was remanded to Arcetri. He spent the weary hours in composing his work on Local Motion, his friends causing it to be surrept.i.tiously published in Holland. [Sidenote: The calamities of his old age.] His infirmities and misfortunes now increased. In 1637 he became totally blind. In a letter he plaintively says, referring to this calamity, ”So it pleases G.o.d, it shall therefore please me also.” The exquisite refinement of ecclesiastical vengeance pursued him remorselessly, and now gave him permission to see his friends when sight was no longer possible. It was at this period that an ill.u.s.trious stranger, the author of ”Paradise Lost,” visited him. Shortly after he became totally deaf; but to the last he occupied himself with investigations respecting the force of percussion. [Sidenote: His death; is refused burial.] He died, January, 1642, in the seventy-eighth year of his age, the prisoner of the Inquisition. True to its instincts, that infernal inst.i.tution followed him beyond the grave, disputing his right to make a will, and denying him burial in consecrated ground. The pope also prohibited his friends from raising to him a monument in the church of Santa Croce, in Florence. It was reserved for the nineteenth century to erect a suitable memorial in his honour.
[Sidenote: Steady advance of the Copernican system.] The result of the discoveries of Copernicus and Galileo was thus to bring the earth to her real position of subordination and to give sublimer views of the universe. Moestlin expresses correctly the state of the case when he says, ”What is the earth and the ambient air with respect to the immensity of s.p.a.ce? It is a point, a punctule, or something, if there be any thing, less.” It had been brought down to the condition of one of the members of a family--the solar system. And since it could be no longer regarded as holding all other bodies in submissive attendance upon it, dominating over their movements, there was reason to suppose that it would be found to maintain interconnexions with them in the att.i.tude of an equal or subordinate; in other words, that general relations would be discovered expressive of the manner in which all the planetary members of the solar system sustain their movements round the sun.
[Sidenote: Kepler, his mode of inquiry.] Among those whose minds were thoroughly occupied with this idea, Kepler stands pre-eminently conspicuous. It is not at all surprising, considering the tone of thought of those times, that he regarded his subject with a certain mysticism. They who condemn his manner of thus viewing things do not duly appreciate the mental condition of the generation in which he lived. Whatever may be said on that point, no one can deny him a marvellous patience, and almost superhuman painstaking disposition.
Guess after guess, hypothesis after hypothesis, he submitted to computations of infinite labour, and doubtless he speaks the melancholy truth when he says, ”I considered and reflected till I was almost mad.”
Yet, in the midst of repeated disappointment, he held, with a truly philosophical determination, firmly to the belief that there must be some physical interconnexion among the parts of the solar system, and that it would certainly be displayed by the discovery of laws presiding over the distances, times, and velocities of the planets. In these speculations he was immersed before the publications of Galileo. In his ”Mysterium Cosmographic.u.m” he says, ”In the year 1595 I was brooding with the whole energy of my mind on the subject of the Copernican system.”
[Sidenote: Discovery of Kepler's laws.] In 1609 he published his work ent.i.tled ”On the Motion of Mars.” This was the result of an attempt, upon which he had been engaged since the beginning of the century, to reconcile the motions of that planet to the hypothesis of eccentrics and epicycles. It ended in the abandonment of that hypothesis, and in the discovery of the two great laws now known as the first and second laws of Kepler. They are respectively that the orbits of the planets are elliptical, and that the areas described by a line drawn from the planet to the sun are proportional to the times.
In 1617 he was again rewarded by the discovery which pa.s.ses under the designation of Kepler's third law: it expresses the relation of the mean distances of the planets from the sun with the times of their revolutions--”the squares of the periodic times are in the same proportion as the cubes of the distances.” In his ”Epitome of the Copernican Astronomy,” published 1622, he showed that this law likewise holds good for the satellites of Jupiter as regards their primary.
[Sidenote: His remonstrance with the Church.] Humboldt, referring to the movement of Jupiter's satellites, remarks: ”It was this which led Kepler, in his 'Harmonices Mundi,' to state, with the firm confidence and security of a German spirit of philosophical independence, to those whose opinions bore sway beyond the Alps, 'Eighty years have elapsed during which the doctrines of Copernicus regarding the movement of the earth and the immobility of the sun have been promulgated without hindrance, because it was deemed allowable to dispute concerning natural things and to elucidate the works of G.o.d, and, now that new testimony is discovered in proof of the truth of those doctrines--testimony which was not known to the spiritual judges, ye would prohibit the promulgation of the true system of the structure of the universe.'”
[Sidenote: Rectification of the Copernican theory.] Thus we see that the heliocentric theory, as proposed by Copernicus, was undergoing rectification. The circular movements admitted into it, and which had burdened it with infinite perplexity, though they had hitherto been recommended by an illusive simplicity, were demonstrated to be incorrect. They were replaced by the real ones, the elliptical. Kepler, as was his custom, ingenuously related his trials and disappointments.
Alluding on one occasion to this, he says: ”My first error was that the path of a planet is a perfect circle--an opinion which was a more mischievous thief of my time, in proportion as it was supported by the authority of all philosophers, and apparently agreeable to metaphysics.”
[Sidenote: The philosophical import of these laws.] The philosophical significance of Kepler's discoveries was not recognized by the ecclesiastical party at first. It is chiefly this, that they const.i.tute a most important step to the establishment of the doctrine of the government of the world by law. But it was impossible to receive these laws without seeking for their cause. The result to which that search eventually conducted not only explained their origin, but also showed that, as laws, they must, in the necessity of nature, exist. It may be truly said that the mathematical exposition of their origin const.i.tutes the most splendid monument of the intellectual power of man.
[Sidenote: Necessity for mechanical science.] Before the heliocentric theory could be developed and made to furnish a clear exposition of the solar system, which is obviously the first step to just views of the universe, it was necessary that the science of mechanics should be greatly improved--indeed, it might be said, created; for during those dreary ages following the establishment of Byzantine power, nothing had been done toward the acquisition of correct views either in statics or dynamics. It was impossible that Europe, in her lower states of life, could produce men capable of commencing where Archimedes had left off.
She had to wait for the approach of her Age of Reason for that.
[Sidenote: Leonardo da Vinci.] The man of capacity at last came.
Leonardo da Vinci was born A.D. 1452. The historian Hallam, enumerating some of his works, observes, ”His knowledge was almost preternatural.”
Many of his writings still remain unpublished. Long before Bacon, he laid down the maxim that experience and observation must be the foundation of all reasoning in science; that experiment is the only interpreter of nature, and is essential to the ascertainment of laws.
Unlike Bacon, who was ignorant of mathematics, and even disparaged them, he points out their supreme advantage. Seven years after the voyage of Columbus, this great man--great at once as an artist, mathematician, and engineer--gave a clear exposition of the theory of forces obliquely applied on a lever; a few years later he was well acquainted with the earth's annual motion. He knew the laws of friction, subsequently demonstrated by Amontons, and the principle of virtual velocities; he described the camera obscura before Baptista Porta, understood aerial perspective, the nature of coloured shadows, the use of the iris, and the effects of the duration of visible impressions on the eye. He wrote well on fortification, antic.i.p.ated Castelli on hydraulics, occupied himself with the fall of bodies on the hypothesis of the earth's rotation, treated of the times of descent along inclined planes and circular arcs, and of the nature of machines. He considered, with singular clearness, respiration and combustion, and foreshadowed one of the great hypotheses of geology, the elevation of continents.
[Sidenote: Stevinus continues the movement in Natural Philosophy.] This was the commencement of the movement in Natural Philosophy; it was followed up by the publication of a work on the principles of equilibrium by Stevinus, 1586. In this the author established the fundamental property of the inclined plane, and solved, in a general manner, the cases of forces acting obliquely. Six years later Galileo's treatise on mechanics appeared, a fitting commencement of that career which, even had it not been adorned with such brilliant astronomical discoveries, would alone have conferred the most ill.u.s.trious distinction upon him.
[Sidenote: Discovery of the laws of motion.] The dynamical branch of Mechanics is that which is under most obligation to Galileo. To him is due the establishment of the three laws of motion. They are to the following effect, as given by Newton:
(1.) Every body perseveres in its state of rest or of uniform motion in a right line unless it is compelled to change that state by forces impressed thereon.
(2.) The alteration of motion is ever proportional to the motive force impressed, and is made in the direction of the right line in which that force is impressed.
(3.) To every action there is always opposed an equal reaction, or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
Up to this time it was the general idea that motion can only be maintained by a perpetual application, impression, or expenditure of force. Galileo himself for many years entertained that error, but in 1638 he plainly states in his ”Dialogues on Mechanics” the true law of the uniformity and perpetuity of motion. Such a view necessarily implies a correct and clear appreciation of the nature of resistances. No experimental motion that man can establish is unrestrained. But a perception of the uniformity and perpetuity of motion lies at the very basis of physical astronomy. With difficulty the true idea was attained.
The same may be said as respects rectilinear direction, for many supposed that uniform motion can only take place in a circle.
[Sidenote: Establishment of the first law of motion,] The establishment of the first law of motion was essential to the discovery of the laws of falling bodies, in which the descent is made under the influence of a continually acting force, the velocity increasing in consequence thereof. Galileo saw clearly that, whether a body is moving slowly or swiftly, it will be equally affected by gravity. This principle was with difficulty admitted by some, who were disposed to believe that a swiftly moving body would not be as much affected by a constant force like gravity as one the motion of which is slower. With difficulty, also, was the old Aristotelian error eradicated that a heavy body falls more swiftly than a light one.
[Sidenote: and of the second,] The second law of motion was also established and ill.u.s.trated by Galileo. In his ”Dialogues” he shows that a body projected horizontally must have, from what has been said, a uniform horizontal motion, but that it will also have compounded therewith an accelerated motion downward. Here again we perceive it is necessary to retain a steady conception of this intermingling of forces without deterioration, and, though it may seem simple enough to us, there were some eminent men of those times who did not receive it as true. The special case offered by Galileo is theoretically connected with the paths of military projectiles, though in practice, since they move in a resisting medium, the air, their path is essentially different from the parabola. Curvilinear motions, which necessarily arise from the constant action of a central force, making a body depart from the rectilinear path it must otherwise take, are chiefly of interest, as we shall presently find, in the movements of the celestial bodies.