They had predecessors. But no one needed them for the reasons that he did, namely that they were necessitated by a unified cosmological matter. One key effect of these principles is that the diurnal terrestrial rotation asserted by the Copernican system is unobservable. We only notice departures from shared rotation, such as bodies falling or rising. This blunted standard objections to Copernicanism on the grounds that there is no evidence of terrestrial motion.
Having dispelled these arguments against the Copernican system, Galileo then dramatically argues in its favor. In Day Three of the Dialogue. The resulting diagram neatly corresponds to the Copernican model. In the Dialogue , things are more complicated than we have just sketched. Galileo, as noted, argues for circular natural motion.
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. It was concerned with the story that Archimedes had found a way of discovering if a crown made for King Hiero of Syracuse was in fact of pure gold, as it was supposed to be, or had been adulterated with a cheaper metal.
This he had done, according to the story, by finding the weight of water displaced from a full bowl. Galileo could not believe that a genius such as Archimedes would have used such a crude method.
So Galileo set out to devise a method of considerable precision. He made for himself a special balance with which he could measure the exact proportions of two metals in a mixture or alloy. He realised that fine-enough markings would be too difficult to read so he wound along a part of one arm of the balance a tight spiral of very fine brass wire, extending from where the suspended weight would balance metal A suspended in water to where it would balance metal B suspended in water.
He then balanced the immersed mixture by sliding the weight along. Thus, with his fine musical ear, he could count the number of turns, and therefore the distance.
So he was able to state the proportion of A to B in the mixture. This tiny essay, which he called La Bilancetta , is enchanting.
There is first of all his outstanding and delicate manual skill. More important, there is always his insistence on accurate measurements and also repeatable measurements. And there is the use of mathematics, in this case the principle of the lever, which he was to use many a time in later work. Moreover his mathematical basis was Euclid and Archimedes. Across his work Galileo was original in dynamics, hydrostatics, mechanics and the strength of materials, optics and astronomy.
He was interested only in what he could see or hear or touch and, above everything, measure. In came the most sensational discovery of his life. And he succeeded in making a telescope of the sort familiar to everyone today who has seen an elementary book on optics.
It astonished and delighted everyone, and when he succeeded in making one of eight magnifications and then even of 20 grinding his own lenses! He saw mountains on the Moon very anti-Aristotle this , then satellites orbiting Jupiter, which he mapped with such accuracy that his orbital times are hardly different from those calculated today.
That he saw sunspots and described their variations. Finally he observed that Venus showed phases very like those of the Moon, an observation that clinched the Copernican argument. In he published The Starry Messenger.
He presented telescopes to the Doge of Venice and had ageing councillors climbing bell towers to see merchant ships out at sea and to his former pupil and friend Cosimo II, Grand Duke of Tuscany. He became famous all over Europe. He was the equivalent in science of a Nobel prize winner today. When he left Padua and Venice, he returned to his home near Florence and completed his book on hydrostatics, in which it is interesting to see that he was nonplussed by the fact that a thin flake of ebony, though denser than water would nonetheless float.
This pleased his Peripatetic opponents who asserted with Aristotle that sinking or floating was merely a matter of shape. Galileo did have the insight to perceive that the effect was probably the same as that when a drop of water would remain on a cabbage leaf.
Of course surface tension was an unknown phenomenon. A year later he published his three letters on sunspots. He was by now a very powerful man and had created jealousy and resentment. He had so many appreciative friends in high places, including former pupils, that he probably considered himself safe.
Most of his enemies worked quietly like rats in a cellar, but some did not. There was, for example, the hateful person Christopher Scheiner, a Jesuit, who claimed priority in seeing sunspots and of course gave an Aristotelian explanation of them. In , Galileo heard about the invention of the spyglass, a device which made distant objects appear closer. Galileo used his mathematics knowledge and technical skills to improve upon the spyglass and build a telescope.
Later that same year, he became the first person to look at the Moon through a telescope and make his first astronomy discovery. He found that the Moon was not smooth, but mountainous and pitted - just like the Earth! He subsequently used his newly invented telescope to discover four of the moons circling Jupiter, to study Saturn, to observe the phases of Venus, and to study sunspots on the Sun. Galileo's observations strengthened his belief in Copernicus' theory that Earth and all other planets revolve around the Sun.
Most people in Galileo's time believed that the Earth was the center of the universe and that the Sun and planets revolved around it. The Catholic Church, which was very powerful and influential in Galileo's day, strongly supported the theory of a geocentric, or Earth-centered, universe.
After Galileo began publishing papers about his astronomy discoveries and his belief in a heliocentric , or Sun-centered, Universe, he was called to Rome to answer charges brought against him by the Inquisition the legal body of the Catholic Church. Early in , Galileo was accused of being a heretic, a person who opposed Church teachings.
Heresy was a crime for which people were sometimes sentenced to death. Galileo was cleared of charges of heresy, but was told that he should no longer publicly state his belief that Earth moved around the Sun.
0コメント