In popular imagination the name of Galileo is connected with the invention of the telescope. His last year in Padua was, indeed, filled with events linked to the construction of this instrument, public demonstrations in the presence of the Venetian nobility and even of the Doge, together with enquiries from well-known figures all over Europe. There were however also the assertions of various people who claimed to have invented it themselves, as well as bitter, insinuating comments. The telescope, in fact, already existed before Galileo built his first version, probably in 1609, nor did he ever make any particular claim to be its inventor. But it was only through his inventive genius that it was perfected and made more powerful, emerging from the world of mere curiosities, and leaving behind the cabinet of wonders, or in Galileo's own words, 'the little studio of some curious little man', on the same level as 'a petrified crab, a dried chameleon, a fly or a spider preserved in a piece of amber' or those 'little things which for their age, rarity or whatever were considered extraordinary.' The telescope became in all respects a scientific instrument. And this was not all. In the hands of Galileo, the 'eyepiece' or 'giant reed' as it was then called, ceased to be aimed only at 'the church of Santa Giustina in Padua' or toward 'those who went in and out of the church of San Giacomo di Murano', as described by the Venetian senator Antonio Priuli, amazed at the first demonstration. It was instead pointed at the sky. Tenaciously and methodically, Galileo began to observe the aspect and movements of the heavenly bodies, hitherto seen only by the naked eye, with unimaginable results that were to provoke a cataclysm in the conception of the cosmos, the world and mankind.

 

In 1610 The Starry Messenger was published in Venice. This starry messenger bore amazing news in the astronomical field, reporting in detail the results of the telescopic observations conducted daily and recorded in full detail. Galileo had studied the Moon and had failed to find the 'even, smooth, clean' surface, 'uniform and exactly spherical', that was commonly believed to distinguish the celestial bodies, finding its surface instead 'uneven, rough, full of cavities and protrusions, no less than the face of the Earth itself, from which it differs in regard to chains of mountains and the depth of valleys.' Aiming the telescope at Jupiter, he had seen four satellites orbiting around it. He had found in cosmic space myriads of stars, invisible to the naked eye, which constituted the nebulae and the Milky Way. Galileo himself described these discoveries as 'so many and with so many important consequences, that, considering what they add and what is necessarily changed in the science of the celestial movement', it could be said 'that in great part this science has been given new life and drawn out of the shadows.' But what were these 'important consequences'? What 'shadows' would be swept away? It is clear that the results of these observations corroborated the thesis of a Copernican universe as opposed to the Aristotelian-Ptolemaic structure universally accepted up to that point. The idea of a Moon similar to the Earth refuted the Aristotelian theory of the different nature of the celestial bodies. Furthermore, conceiving of the Moon as a satellite orbiting around a centre, which was the Earth, suggested that the latter, being made of the same substance, might behave in the same way, orbiting in turn around a centre of its own. The observation of an enormous quantity of stars never before seen cast doubt on the small size of the Ptolemaic universe and, without denying its finite nature, substituted for the restricted covering of the sky a great sidereal space of Copernican origin. It had also become obvious that the 'four stars moving around Jupiter... were tracing a circle around the Sun', all of them moving 'together with Jupiter.' They were, that is, Jupiter's satellites, and revolved contemporaneously with the planet, a phenomenon whose impossibility had always been viewed by the Ptolemaics as proof of an earth-centred system. Once it had been demonstrated that this was by no means impossible, the same thing could be true of the Earth, which might very well revolve around the Sun, accompanied by its satellite the Moon. Among all these discoveries, that of Jupiter's satellites was thus the one with the greatest impact. And it was not by chance that Galileo, who had long been seeking the protection of a prince in order to continue his studies without having to teach, named them the Medicean Stars, dedicating them to the House of Medici and to Cosimo II in particular, his former pupil, who had now become the Grand Duke of Tuscany.

 

The publication of The Starry Messenger provoked an explosion among the more or less orthodox scientists and Aristotelians, in an atmosphere of malice, denial, envy, false refutation and spiteful gossip (as well, it should be said, as some enthusiastic praise). Galileo's colleague, Cesare Cremonini, though inclined to be friendly, had no wish to put the telescope to his eye. He was a priest in the tradition of that Aristotelian rationalism which, some centuries previously, had been unprejudiced and independent, but was by now in decay. His outlook brought him into trouble with the Inquisition, without however preventing him from denouncing in his turn Bernardino Telesio's De rerum natura [On the Nature of Things]. As regards the telescope, he proclaimed, between a sneer and a reprimand, that to 'look through those lenses ... confounded his very mind.' This brought to an end his contribution to the debate on new scientific developments. The Bohemian doctor and astrologer, Martin Horky, was not much better, although he did publish a pamphlet. He denied the existence of Jupiter's satellites, strong in the assumption that no-one had ever seen them, and attributed Galileo's false discovery of them to kaleidoscopic effects of the lenses and above all to his thirst for money. Having gone beyond the limit of decency, he was dismissed by those who had supported him in the polemic and was advised to leave Italy by Kepler to whom he had turned in search of protection. Another suggestion was that the planets, each of which wore a particular colour, were already seven, a number whose sacredness no-one could doubt: seven, like the metals existing in nature, seven, like the vital parts of the human organism. How could these four extraneous bodies be allowed to discompose perfection?

 

Unassailable arguments aside, Galileo's opponents could do little in the face of the evidence, especially when Kepler, using a telescope given him by Galileo himself, confirmed the sighting of Jupiter's satellites. The Medicean Stars had the desired effect, and the Grand Duke of Tuscany summoned Galileo to Florence, as Chief Mathematician to the University of Pisa and to the Grand Duke himself. Galileo expressly requested that he might also be given the title of Philosopher, 'professing ... to have spent more years studying philosophy than months studying pure mathematics.' The salary was excellent, the prestige enormous, and there was no obligation to teach. The discontent and protests of Galileo's Paduan friends against his leaving were of no avail.