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Galileo: Telescopes
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In 1609, Galileo was among the first to use a refracting telescope as an instrument to observe stars, planets or moons. In 1610, he used a telescope at close range to magnify the parts of insects,[48] and by 1624 he had perfected[49] a compound microscope. He gave one of these instruments to Cardinal Zollern in May of that year for presentation to the Duke of Bavaria,[50] and in September he sent another to Prince Cesi, the founder of the Academy of Lynxes.[51][52] Illustrations of insects made using one of Galileo's microscopes, and published in 1625, appear to have been the first clear documentation of the use of a compound microscope.[53]
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In 1609 Galileo begins his work with the telescope. Many interpreters have taken this to be an interlude irrelevant to his physics. The Starry Messenger, which describes his early telescopic discoveries, was published in 1610. There are many ways to describe Galileo's findings but for present purposes they are remarkable as the starting point of his effort to dismantle the celestial/terrestrial distinction (Feyerabend 1975). Perhaps the most unequivocal instance of this is Galileo's analogizing the mountains on the moon to mountains in Bohemia. The abandonment of the heaven/earth dichotomy implied that all matter is of the same kind, regardless of whether it is celestial or terrestrial.
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Prior to these discoveries, Galileo had already abandoned the old Ptolemaic astronomy for the Copernican. But, as he confessed in a letter to Kepler in 1597, he had refrained from making himself its advocate, lest like Copernicus himself he should be overwhelmed with ridicule. His telescopic discoveries, the significance of which he immediately perceived, induced him at once to lay aside all reserve and come forward as the avowed and strenuous champion of Copernicanism, and, appealing as these discoveries did to the evidence of sensible phenomena, they not only did more than anything else to recommend the new system to general acceptance, but invested Galileo himself with the credit of being the greatest astronomer of his age, if not the greatest who ever lived. They were ... the cause of his lamentable controversy with ecclesiastical authority, which raises questions of graver import than any others connected with his name. It is necessary, therefore, to understand clearly his exact position in this regard.
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Philosophically, Galileo has been used to exemplify many different themes, usually as a side bar to what the particular writer wished to make the hallmark of the scientific revolution or the nature of good science. Whatever was good about the new science or science in general, it was Galileo who started it. One early 20th Century tradition of Galileo scholarship used to divvy up Galileo's work into three or four parts: (1) his physics, (2) his astronomy, and (3) his methodology, which could include (4) his method of Biblical interpretation and his thoughts about the nature of proof or demonstration. In this tradition, typical treatments dealt with his physical and astronomical discoveries and their background and/or who were Galileo's predecessors. More philosophically, many would ask: how his mathematics relates to his natural philosophy? How did he and his telescopic observations provide evidence in favor of Copernicanism? Was he an experimentalist (Settle 1961, 196, 1983, 1992), a mathematical Platonist (Koyré 1939), an Aristotelian emphasizing experience (Geymonat 1954), precursor of modern positivist science (Drake 1978) or maybe an Archimedean (Machamer 1998c), who might have used a revised Scholastic method of proof (Wallace 1992)?
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Galileo then joined the faculty at the University of Padua and taught geometry, mechanics, and astronomy. It was at Padua where he made many of his amazing discoveries. In 1596, Galileo invented a military compass which could be used to properly aim cannonballs. In 1609, he gained word that a Dutch spectacle-maker had invented a device called a spyglass. The spyglass (later called a telescope) made distant objects appear much closer. Before the Dutch inventor could secure a patent, Galileo quickly constructed his own 3-power telescope, and then a 10-power telescope to present to the Senate in Venice.
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In 1609 Galileo heard that a new instrument had been invented in the Netherlands which made objects in the distance seem close to the observer. Galileo tried to create this using a variety of lenses and he soon succeeded in making a basic telescope using a concave and a convex lens at either end of a lead tube. At the third attempt he produced a telescope that made objects appear 1 000 times larger and over thirty times closer than seen with the naked eye. Although Galileo could see the importance of the telescope's aid to navigation at sea and over land, he was most interested in its use to look at the skies.
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