Galileo Galilei and the Roman Curia / From Authentic Sources

by Karl von Gebler

The spark, however, which was to set fire to the abundant inflammable material, and to turn the scientific and religious world, in which doubt had before been glimmering, into a veritable volcano, the spark which kindled Galileo’s genius and made him for a long time the centre of that period of storm and stress, was the discovery of the telescope.

We will not claim for Galileo, as many of his biographers have erroneously done, priority in the construction of the telescope. We rely far more on Galileo’s own statements than on those of his eulogists, who aim at effect. Galileo relates with perfect simplicity at the beginning of the “Sidereus Nuncius,” published at Venice in 1610, that he had heard about ten months ago that an instrument had been made by a Dutchman, by means of which distant objects were brought nearer and could be seen very plainly. The confirmation of the report by one of his former pupils, a French nobleman, Jean Badovere of Paris, had induced him to reflect upon the means by which such an effect could be produced. By the laws of refraction he soon attained his end. With two glasses fixed at the ends of a leaden tube, both having one side flat and the other side of the one being concave and of the other convex, his primitive telescope, which made objects appear three times nearer and nine times larger, was constructed. But now, having “spared neither expense nor labour,” he had got so far as to construct an instrument which magnified an object nearly a thousand times, and brought it more than thirty times nearer.[37] Although, therefore, it is clear from this that the first idea of the telescope does not belong to Galileo, it is equally clear that he found out how to construct it from his own reflection and experiments. Undoubtedly also the merit of having made great improvements in it belongs to him, which is shown by the fact that at that time, and long afterwards, his telescopes were the most sought after, and that he received numerous orders for them from learned men, princes and governments in distant lands, Holland, the birthplace of the telescope, not excepted.[38] But the idea which first gave to the instrument its scientific importance, the application of it to astronomical observations, belongs not to the original inventor but to the genius of Galileo. This alone would have made his name immortal.[39]

A few days after he had constructed his instrument, imperfect as it doubtless was, he hastened with it to Venice, having received an invitation, to exhibit it to the doge and senate, for he at once recognised its importance, if not to the full extent. We will now let Galileo speak for himself in a letter which he wrote from Venice to his brother-in-law, Benedetto Landucci:—

“You must know then that about two months ago a report was spread here that in Flanders a spy-glass had been presented to Prince Maurice, so ingeniously constructed that it made the most distant objects appear quite near, so that a man could be seen quite plainly at a distance of two miglia. This result seemed to me so extraordinary that it set me thinking; and as it appeared to me that it depended upon the theory of perspective, I reflected on the manner of constructing it, in which I was at length so entirely successful that I made a spy-glass which far surpasses the report of the Flanders one. As the news had reached Venice that I had made such an instrument, six days ago I was summoned before their highnesses the signoria, and exhibited it to them, to the astonishment of the whole senate. Many noblemen and senators, although of a great age, mounted the steps of the highest church towers at Venice, in order to see sails and shipping that were so far off that it was two hours before they were seen steering full sail into the harbour without my spy-glass, for the effect of my instrument is such that it makes an object fifty miglia off appear as large and near as if it were only five.”[40]

Galileo further relates in the same letter that he had presented one of his instruments to the senate, in return for which his professorship at Padua had been conferred on him for life, with an increase of salary to one thousand florins.[41]

On his return to Padua he became eagerly engrossed in telescopic observation of the heavens. The astonishing and sublime discoveries which were disclosed to him must in any case have possessed the deepest interest for the philosopher who was continually seeking to solve nature’s problems, and were all the more so, since they contributed materially to confirm the Copernican theory.

His observations were first directed to the moon, and he discovered that its surface was mountainous, which showed at all events that the earth’s satellite was something like the earth itself, and therefore by no means restored it to the aristocratic position in the universe from which it had been displaced by Copernicus. The milky way, as seen through the telescope, revealed an immense number of small stars. In Orion, instead of the seven heavenly bodies already known, five hundred new stars were seen; the number of the Pleiades, which had been fixed at seven, rose to thirty-six; the planets showed themselves as disks, while the fixed stars appeared as before, as mere bright specks in the firmament.

But the indefatigable observer’s far most important discovery, in its bearing on the Copernican theory, was that of the moons of Jupiter, in January 1610. As they exhibited motions precisely similar to those which Copernicus had assumed for the whole solar system, they strongly fortified his theory. It was placed beyond all doubt that our planet was not the centre of all the heavenly bodies, since Jupiter’s moons revolved round him. The latter was brought, so to speak, by the discovery of his attendants, into relations with the earth which, considering the prevailing views, were humiliating enough, and the more so since Jupiter had four satellites while the earth had only one. There remained, however, the consoling assurance that he and they revolved round our abode!

In honour of the reigning house of his native country, and as an acknowledgment of favours received from it (for since the accession of Cosmo II.[42] Galileo had been in high favour), he called Jupiter’s moons “Medicean stars.” The urgent solicitude of the French court to gain, by Galileo’s aid, a permanent place on the chart of the heavens, is very amusing. Thus, on 20th April, 1610, he received a pressing request, “in case he discovered any other fine star, to call it after the great star of France, Henry IV., then reigning, the most brilliant in the whole universe, and to give it his proper name of Henry rather than that of the family name of Bourbon.” Galileo communicated this flattering request, as he seems to have considered it, with much satisfaction to the secretary of the Tuscan court, Vincenzo Giugni, in a letter from Padua, on 25th June, 1610,[43] as an evidence of the great importance attached to his telescopic discoveries. He added that he did not expect to find any more planets, as he had already made many very close observations.