British Broadcasting Corporation Home. Galileo Galilei was born on 15 February near Pisa, the son of a musician. He began to study medicine at the University of Pisa but changed to philosophy and mathematics. In , he became professor of mathematics at Pisa. In , he moved to become mathematics professor at the University of Padua, a position he held until During this time he worked on a variety of experiments, including the speed at which different objects fall, mechanics and pendulums.
In , Galileo heard about the invention of the telescope in Holland. Without having seen an example, he constructed a superior version and made many astronomical discoveries. These included mountains and valleys on the surface of the moon, sunspots, the four largest moons of the planet Jupiter and the phases of the planet Venus.
His work on astronomy made him famous and he was appointed court mathematician in Florence. Yet he also introduces, in places, an intrinsic tendency for rectilinear motion.
For example, Galileo recognizes that a stone whirled circularly in a sling would fly off along the rectilinear tangent if released Galilei , —94; see Hooper Further, in Day Four, when he is giving his mechanical explanation of the tides, he nuances his matter theory by attributing to water an additional power of retaining an impetus for motion such that it can generate a reciprocal movement once it is sloshed against a side of a basin.
We saw it first in the De Motu around , where Galileo discusses submerged and floating bodies, but he learned much more in his dispute over floating bodies which produced the Discourse on Floating Bodies in In fact, a large part of that debate turned on the exact nature of water as matter, and what kind of mathematical proportionality could be used to correctly describe it and bodies moving in it see Palmieri ; The second science, discussed in the last two Days, deals with the principles of local motion and has been much commented upon in the Galilean literature.
But the first science, discussed in the first two Days, has been misunderstood and infrequently discussed. It has misleadingly been called the science of the strength of materials, and so seems to have found a place in history of engineering, since such a course is still taught today. However, this science is not about the strength of materials per se. Galileo realizes that, before he can work out a science of the motion of matter, he must have some way of showing that the nature of matter may be mathematically characterized.
So it is in Day One that Galileo begins to discuss how to describe mathematically or geometrically the causes of the breaking of beams. But this requires a way to reconcile mathematical description with the physical constitution of material bodies. In this vein, Galileo rejects using finite atoms as a basis for physical discussion, since they are not representable by continuously divisible mathematical magnitudes. Instead, he treats matter as composed of infinitely many indivisible—which is to say, mathematical—points.
This allows him to give mathematical accounts for various properties of matter. Among these are the density of matter, its coherence in material bodies, and the properties of the resisting media in which bodies move. The Second Day lays out the mathematical principles concerning how bodies break. Galileo does all this by reducing the problems of matter to problems of how a lever and a balance function, which renders them mathematically tractable via the law of the lever.
He had begun this back in , though this time he believes he is getting it right, showing mathematically how bits of matter solidify and stick together, and how they break into bits. On the one hand, if Aristotle is correct, the faster fall of the heavier body will be retarded by the slower motion of the lighter body, so that the conjoined body will fall slower than the original heavy body.
And yet, the conjoined body is heavier than either original body, so it should also fall faster. Hence, there is a contradiction in the Aristotelian position Gendler ; Palmieri ; Brown and Fehige This is now the motion of all matter, not just sublunary stuff, and the treatment takes the categories of time and acceleration as basic.
In the projected Fifth Day, Galileo would have treated the power of moving matter to act by impact, which he calls the force of percussion. Ultimately, Galileo was unable to give mathematical principles of this kind of interaction, but this problem subsequently became an important locus of interest. He offered a new science of matter, a new physical cosmography, and a new science of local motion.
It is in this way that Galileo developed the categories of the mechanical new science, the science of matter and motion. His new categories utilized some of the basic principles of traditional mechanics, to which he added the category of time and so emphasized acceleration. But throughout, he was working out the details about the nature of matter so that it could be understood as uniform and universal, and treated in a way that allowed for coherent discussion of the principles of motion.
It was due to Galileo that a unified matter became accepted and its nature became one of the problems for the new science that followed. After him, matter really mattered. The end of the affair is simply stated. In late , in the aftermath of the publication of the Dialogue Concerning the Two Chief World Systems , Galileo was ordered to appear in Rome to be examined by the Congregation of the Holy Office; i.
In January , a very ill Galileo made an arduous journey to Rome. From April, Galileo was called four times to hearings; the last was on June The next day, June 22, , Galileo was taken to the church of Santa Maria sopra Minerva, and ordered to kneel while his condemnation was read.
I have been judged vehemently suspect of heresy, that is, of having held and believed that the sun in the center of the universe and immoveable, and that the Earth is not at the center of same, and that it does move. Wishing however, to remove from the minds of your Eminences and all faithful Christians this vehement suspicion reasonably conceived against me, I abjure with a sincere heart and unfeigned faith, I curse and detest the said errors and heresies, and generally all and every error, heresy, and sect contrary to the Holy Catholic Church.
Quoted in Shea and Artigas , When he later finished his last book, the Two New Sciences which does not mention Copernicanism at all , it had to be printed in Holland, and Galileo professed amazement at how it could have been published. The details and interpretations of these proceedings have long been debated, and it seems that each year we learn more about what actually happened.
One point of controversy is the legitimacy of the charges against Galileo, both in terms of their content and the judicial procedure. Galileo was charged with teaching and defending the Copernican doctrine that holds the sun is at the center of the universe and the Earth moves.
The status of this doctrine was cloudy. In , an internal commission of the Inquisition had determined that it was heretical, but this was not publicly proclaimed. In , at the same time that the Inquisition was evaluating Copernicanism, they were also investigating Galileo personally—a separate proceeding of which Galileo himself was not likely aware. To confound issues further, the case against Galileo transpired in a fraught political context.
Galileo was a creature of the powerful Medici and a personal friend of Pope Urban VIII, connections that significantly modulated developments Biagioli The legitimacy of the underlying condemnation of Copernicus on theological and rational grounds is even more problematic. Galileo had addressed this problem in , when he wrote his Letter to Castelli and then the Letter to the Grand Duchess Christina.
In these texts, Galileo argues that there are two truths: one derived from Scripture, the other from the created natural world. Since both are expressions of the divine will, they cannot contradict one another. However, Scripture and Creation both require interpretation in order to glean the truths they contain—Scripture because it is a historical document written for common people, and thus accommodated to their understanding so as to lead them towards true religion; Creation because the divine act must be distilled from sense experience through scientific enquiry.
While the truths are necessarily compatible, biblical and natural interpretations can go awry, and are subject to correction. Cardinal Bellarmine was willing to countenance scientific truth if it could be proven or demonstrated McMullin But Bellarmine held that the planetary theories of Ptolemy and Copernicus and presumably Tycho Brahe are only mathematical hypotheses; since they are just calculating devices, they are not susceptible to physical proof.
This is a sort of instrumentalist, anti-realist position Machamer ; Duhem There are any number of ways to argue for some sort of instrumentalism. Duhem himself argued that science is not metaphysics, and so only deals with useful conjectures that enable us to systematize phenomena. Subtler versions of this position, without an Aquinian metaphysical bias, have been argued subsequently and more fully by Van Fraassen and others.
Galileo would be led to such a view by his concern with matter theory, which minimized the kinds of motion ascribed uniformly to all bodies. Of course, when put this way, we are faced with the question of what constitutes identity conditions for a theory. The other aspect of all this that has been hotly debated is what constitutes proof or demonstration of a scientific claim.
Galileo believed he had a proof of terrestrial motion. How could the moon cause the tides to ebb and flow without any connection to the seas? Such an explanation would be an invocation of magic or occult powers. Thus, for Galileo, the only conceivable or maybe plausible physical cause for the regular reciprocation of the tides is the combination of the diurnal and annual motions of the Earth.
Briefly, as the Earth rotates around its axis, some parts of its surface are moving along with the annual revolution around the sun and some parts are moving in the contrary direction.
Hence the tides. Local differences in tidal flows are due to the differences in the physical conformations of the basins in which they occur for background and more detail, see Palmieri One can see why Galileo thinks he has some sort of proof for the motion of the Earth, and therefore for Copernicanism.
Yet one can also see why Bellarmine and the instrumentalists would not have been impressed. Third, the argument does not touch upon the central position of the sun or arrangement of the planets as calculated by Copernicus. Nevertheless, when the tidal argument is added to the earlier telescopic observations that show the improbabilities of the older celestial picture—the fact that Venus has phases like the moon and so must revolve around the sun; the principle of the relativity of perceived motion which neutralizes the physical arguments against a moving Earth; and so on—it was enough for Galileo to believe that he had the necessary proof to convince the doubters.
But this could occur only after Galileo had changed the acceptable parameters for gaining knowledge and theorizing about the world. Copernicus, Nicolaus natural philosophy: in the Renaissance religion: and science. Brief Biography 2. Introduction and Background 3.
Brief Biography Galileo was born in Pisa on February 15, Fredette, Raymond trans. Drake, Stillman trans. Van Helden, Albert trans. Hessler eds. Barker, Peter trans. Shea, William R. Reeves, Eileen, and Van Helden, Albert trans. Crew, Henry, and de Salvio, Alfonso trans. This inferior translation, first published in , has been reprinted numerous times and is widely available. Collections of primary sources in English: Drake, Stillman ed. Finocchiaro, Maurice A. Secondary Sources Adams, Marcus P.
Sullivan eds. Zalta ed. Bolton trans. Carugo, Adriano, and Alistair C. Coyne, George V. McMullin ed. Crombie, Alistair C. Bonelli and W. He publishes the results in the book, "Sidereus Nuncius. He leaves his position at Padua to become the first philosopher and mathematician to the grand duke of Tuscany.
The Duke allowed Galileo more time to work on his projects. He visits Rome to demonstrate the telescope. After being so warmly accepted at Rome, Galileo writes three letters to formally take his position on the heliocentric theory of the universe.
His main reason for believing Kepler and Copernicus were his observations of sunspots moving around the sun. Rome and Galileo spend three long years in conflict. Because Galileo choose to write his letters in Italian, they enjoyed a larger audience than the religious and scientific communities. The Aristotelian Scholars saw the attacks on Aristotelian Philosophy to be attacks upon themselves. The Aristotelian Scholars united against Galileo.
The Church, swayed by the Aristotelian Scholars declared that Galileo was contradicting scripture,. March 5, The Catholic Church formally declares the writings of Galileo banned, and warns Galileo not to "hold or defend his doctrines.
He retires to his home in Bellosguardo near Florence. Galileo writes his "Assayer He again travels to Rome hoping to appeal the decree.
The Pope does not repeal the decree, but he does allow Galileo to write on both sides of the issue, noncomentally, and equally supportive of both sides of the issue, and without making any definite conclusions. Galileo publishes his great work, Dialogo sopra I due massimi sistemi del mondo, tolemaico e copernicano Dialogue Concerning the Two Chief World Systems--Ptolemaic and Copernican IN compliance with the Pope, the work is set as a conversation between two men discussing the Ptolemaic and Copernican systems.
Simply put, all hell brakes loose in Galileo's world.
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