Before Galileo there was no astronomy. It was he who applied the methods of science to the heavens, who dared to look with a telescope at the abodes of the gods. Thus he discovered what no human being had ever observed before.
On March 12, 1610, a 58-page monographic magazine was published in Venice, with numerous woodcut illustrations, dedicated to recounting the wonders that Galileo had discovered in the heavens during that winter. As was usual at the time, the cover featured a long headline: “Sidereus Nuncius Magna, longeque admirabilia …” This important publication is universally known by its first two words, the most appropriate translation of which is “Sidereal news”, or news of the stars.
The complete text of the initial page of the Sidereus Nuncius reads as follows:? Sidereal news that reveals important and very admirable visions and exposes to the eyes of all, but especially philosophers and astronomers, the things that were observed by Galileo Galilei, Florentine patrician Official mathematician of the University of Padua, with the help of a spyglass recently designed by him, on the face of the Moon, innumerable fixed stars, the Milky Way and nebular stars. But especially on four planets that revolve around the star of Jupiter with different intervals and periods at surprising speed; which, unknown to all to this day, the author recently discovered and decided to call Medicean Stars.
The origins of the telescope
The spyglass is the result of combining two lenses, one plano-concave and the other plano-convex, in a tube. One of the lenses is placed near the eye (the eyepiece ) and the other, at the end of the tube that points towards the object (the objective ). At the end of September 1608 the Dutchman Hans Lipperhey had designed an “artifice by means of which all things that are at a great distance can be seen as if they were close.” Galileo learned of the existence of these instruments in July 1609 , and began to build one with a lead tube, testing different lenses. Modifying the cuts of these, and polishing them himself, he obtained a device that brought objects much closer. On August 4 he already had a good spyglass, but he continued working on it until the 20th, when he set out to present it to the Doge and present it to the Republic of Venice. Over time, he significantly increased the power of the lenses – according to his own testimony up to 60 times – and made this toy a powerful instrument for astronomical research. Prince Federico Cesi, one of the four founders of the Academy of Lynxes , was the one who in 1611 used the word telescope for the first time to designate it. Although he had not invented it, with the discoveries made after the autumn of 1609, Galileo had turned it into an instrument of scientific revolution.
In 1609 Galileo was 45 years old and lived in Padua, teaching at the university, running a student boarding house where? According to them? there was “a good bed and a good table” and spending much of his time on subjects of experimental physics, astronomy and mathematics. When he heard about a new instrument that allowed him to see distant objects up close, he did not wait to build one. His first spyglass would have no more than three magnifications, but he soon managed to improve it. For three weeks he observed our satellite in detail, and left at least eight pictures of the first big surprise: The Moon had mountains!
That discovery would have a great impact. Everyone believed, following Aristotle, that the Sun and the Moon were perfect, as befits heavenly bodies. According to Aristotelian cosmology, while the things of our world were made up of the four elements -Earth, Water, Air, Fire- and were imperfect and changing, everything from the Moon up was made up of a fifth element, the Ether. or Quintessence, and was by nature perfect and unchanging. However, the Moon that the telescope revealed to Galileo’s eyes was not smooth and uniform, but just like the Earth, with valleys and mountains . Astronomical observations followed one another in a systematic way, also discovering, among other things, that the sky has many more stars than those observed with the naked eye and that the Milky Way is a conglomeration of innumerable stars.
The discovery that Galileo considered the most important concerns the satellites of Jupiter . The date, historical for science, is January 7, 1610. That day, early in the evening, he observed three stars, small and bright, in the vicinity of Jupiter that he had not seen with other less powerful telescopes. . Although he thought they were fixed stars, they caught his attention because they were in a straight line. In successive days he observed, with great admiration, that their position varied with respect to Jupiter, that is, that they were not fixed stars, but wandering. Galileo would speak of the discovery of “four planets” that revolve around that star with great speed.
Seeing that there were things in the sky revolving around Jupiter fitted well with Copernicus’ ideas that we are not the center. In addition, Galileo had seen the light that the Earth reflects on the Moon, and concluded that it shone, like the planets. Those discoveries, along with others he made that same year, would serve to convince him that the heliocentric system was a reality. Galileo matured that idea for more than twenty years and, committed to his intellectual freedom, he would defend it publicly, which earned him the punishment of the Inquisition.
By Ramón Núñez (No. 235, December 2000)
