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Galileo Galilei (1564 – 1642) was an Italian scientist who was a major figure in the Scientific Revolution. He was a pioneer in the modern combination of mathematical theory with systematic experiment in science.

His work in physics included experimentation to establish the behavior of falling bodies, as well as the first modern theoretical work on inertia (for which he was given credit by Newton) and relativity of motion (for which he was credited by Einstein).

He was one of the first astronomers to use a telescope, and the discoverer or co-discoverer of several phenomena that contradicted the accepted ideas of the heavens. His support of the Copernican idea that the Earth rotates around the Sun led to a trial before the Inquisitonon a suspicion of heresy.

2004-01-13 00.38

Experimental science

In the pantheon of the scientific revolution Galileo occupies a high position because of his pioneering use of quantitative experiments with results analyzed mathematically. There was no tradition of such methods in European thought at that time; the great experimentalist who immediately preceded Galileo, William Gilbert, did not use a quantitative approach. (However, Galileo's father, Vincenzo Galilei, had performed experiments in which he discovered what may be the oldest known non-linear relation in physics, between the tension and the pitch of a stretched string.)

In the 20th century the reality of Galileo's experiments was challenged by some authorities, in particular the distinguished French historian of science Alexandre Koyré. The experiments reported in Two New Sciences to determine the law of acceleration of falling bodies, for instance, required accurate measurements of time, which appeared to have been impossible with the technology of 1600. According to Koyré, the law was arrived at deductively, and the experiments were merely illustrative thought experiments.

Later research, however, has validated the experiments. The experiments on falling bodies (actually rolling balls) were replicated using the methods described by Galileo (Settle, 1961), and the precision of the results was consistent with Galileo's report. Later research into Galileo's unpublished working papers from as early as 1604 clearly showed the reality of the experiments and even indicated the particular results that led to the time-squared law (Drake, 1973).

Astronomy

Where's the rest of the astronomy? This can't be all I put in.

2003-07-19 15:06

NB: Some of this is not my material! (wrong, it is 07-18)
In 1610 Galileo discovered Jupiter's four largest [[natural satellite|satellite]]s (moons): Io, Europa, Ganymede, and Callisto. He determined that these moons were orbiting the planet since they would occasionally disappear; something he attributed to their movement behind Jupiter. He made additional observations of them in 1620. (Later astronomers overruled Galileo's naming of these objects, changing his Medicean stars to Galilean satellites.) The demonstration that a planet had smaller planets orbiting it was problematic for the orderly, comprehensive picture of the geocentric model of the universe, in which everything circled around the Earth.

This looks wrong:
Galileo noted that Venus exhibited a full set of phases like the Moon. Because the apparent brightness of Venus is nearly constant, Galileo reasoned that Venus could not be circling the Earth at a constant distance. By contrast, the [[heliocentric model]] of the solar system developed by Copernicus would neatly account for the steady brightness by reason of the much greater distance from the Earth at the time of "full Venus".

Galileo made the first European observations of sunspots, although there is evidence that Chinese astronomers had done so before him. The very existence of sunspots showed another difficulty with the perfection of the heavens as assumed in the older philosophy. And the annual variations in their motions, first noticed by Francesco Sizzi, presented great difficulties for either the geocentric system or that of Tycho Brahe.

2004-05-09 21:30

A dispute over priority in the discovery of sunspots led to a long and bitter feud with Christoph Scheiner; in fact, there can be little doubt that both of them were beaten by David Fabricius and his son Johannes.

Physics

2005-06-04 18.33

In his 1632 Dialogue Galileo presented a physical theory to account for tides, based on the motion of the Earth. If correct, this would have been a strong argument for the reality of the Earth's motion. (The original title fo the book, in fact, described it as a dialogue on the tides; the reference to tides was removed by order of the Inquisition.) His theory gave the first insight into the importance of the shapes of ocean basins in the size and timing of tides; he correctly accounted, for instance, for the negligible tides halfway along the [[Adriatic Sea]] compared to those at the ends. As a general account of the cause of tides, however, his theory was a failure.

Mathematics

While Galileo's application of mathematics to experimental physics was innovative, his mathematical methods were the standard ones of the day. The analyses and proofs relied heavily on the Eudoxian theory of proportion, as set forth in the fifth book of Euclid's Elements. This theory had become available only a century before, thanks to accurate translations by Tartaglia and others; but by the end of Galileo's life it was being superseded by the algebraic methods of Descartes, which a modern finds incomparably easier to follow.

Galileo produced one piece of original and even prophetic work in mathematics: Galileo's paradox, which shows that there are as many odd numbers as there are whole numbers including both even and odd. Such seeming contradictions were brought under control 250 years later in the work of Georg Cantor.

Technology

200x Technology

Galileo made a few contributions to what we now call technology as distinct from pure physics, and suggested others. This is not the same distinction as made by Aristotle, who would have considered all Galileo's physics as techne or useful knowledge, as opposed to episteme, or philosophical investigation into the causes of things.

In 1595 - 1598 Galileo devised and improved a "Geometric and Military Compass" suitable for use by gunners and surveyors. This expanded on earlier instruments designed by [[Niccolo Fontana Tartaglia|Tartaglia]] and Guidobaldo. For gunners, it offered, in addition to a new and safer way of elevating cannon accurately, a way of quickly computing the charge of gunpowder for cannonballs of different sizes and materials. As a geometric instrument it enabled the construction of any regular polygon, computation of the area of any polygon or circular sector, and a variety of other calculations.

About 1606 - 1607 (or possiblyearlier) Galileo made a thermometer, using the expansion and contraction of air in a bulb to move water in an attached tube.

In 1610 he used a telescope as a compound microscope, and he made improved microscopes in 1623 and after. This appears to be the first clearly documented use of the compound microscope.

..................

In his last year, when totally blind, he designed an escapement mechanism for a pendulum clock. The first fully operational pendulum clock was made by Huygens in the 1650s.

Galileo wrote several books which were circulated outside of Italy. In fact, his final book, the Two New Sciences, was published by Elzevir in the Netherlands and was not publicly circulated in Italy, where the Inquisition's ban against publishing anything whatever by Galileo was in force.

Relations with the Church

During the second half of his life Galileo, a practicing Catholic, had many problems with important figures in the Catholic Church, including a sainted Cardinal, members of the Inquisition, and two Popes. There were periods in which peace and good will prevailed, and Galileo had at all times many friends and supporters in the Church; but the outcome was a conflict that became legendary. Nearly every aspect of this conflict has been and remains the subject of controversy, often bitter. A relatively brief summary of the events and their historical background will be given here, followed by a more extensive treatment in several sections.

The heliocentric idea—that the Earth moves around the Sun, rather than the reverse—contradicts what is perfectly obvious to anyone who looks at the skies. Where the idea existed at all, it was often treated as irreligious; the Greek philosopher [[Aristarchus], as a result of his advocacy of the idea, was accused of atheism. In Christian Europe the problem was aggravated by the contradiction between heliocentrism and some passages in the Bible; moreover, heliocentrism was against the teachings of Aristotle, whose work was dominant among the learned and was the official basis of Catholic philosophy. When Copernicus first published his heliocentric system in 1542, it was considered a fairly obscure matter and raised little trouble; but in the next century it became the source of much conflict.

After 1610 the discoveries that Galileo and others made using the telescope demonstrated that many of the accepted ideas of astronomy were factually wrong. These findings made heliocentrism more plausible and in some ways provided direct support for it, though not rigorous proof. Galileo began publicly arguing for heliocentrism at this time and was promptly attacked on religious grounds—by philosophers as well as clerics. (There was also scientific controversy, which is mostly irrelevant here. On both scientific and religious grounds Galileo had many supporters, both within and outside the Church.) Hostile responses ranged from a fiery sermon on the text, "Ye men of Galilee, why stand ye gazing up into heaven?" to direct complaints to the Inquisition. Such attacks were serious, potentially backed by the power of the Church to enforce doctrine.

In 1616 Galileo went to Rome to argue against the banning of Copernican teachings. This mission (often called the first trial of Galileo, although it was not a trial in any formal sense) was a failure. In the end, the heliocentric works of Copernicus and others were temporarily suppressed pending theological "corrections"; a book by the priest Paolo Antonio Foscarini, arguing that heliocentrism was not in conflict with Christianity, was formally banned; and Galileo was directly ordered not to "hold or defend" the Copernican ideas.

Until 1624 Galileo avoided any dangerous public involvement with heliocentrism. In that year the new Pope, Urban VIII, who was an admirer of Galileo's work, approved his writing a book about the theory, on condition that it would not argue that Copernican ideas were true, but merely give both sides.

In 1630 Galileo completed the book, the Dialogue Concerning the Two Chief World Systems, and submitted it to the Congregation of the Index for approval to publish. The process was long and difficult and required changes to the book before the license could be issued. When finally published in 1632, the book immediately encountered determined opposition. Galileo was ordered to go to Rome to be questioned by the authorities. In 1633 he was tried by the Inquisition on "grave suspicion of heresy" and on charges that he had disobeyed the orders given him in 1616. He was convicted, forced to recant his ideas, and placed under permanent house arrest. (The story of his saying "But it does move!" refers to this proceeding.) His Dialogue was banned, and somewhat later all his works were banned.

The ban on heliocentric books began to be relaxeded in 1741, and was finally completely removed in 1822. In 1994 Pope John Paul II issued a formal statement that cleared Galileo of the taint of heresy. The Pope's position, though widely accepted and welcomed, is now the occasion for some controversy, even within the Church.

An understanding of the controversies, if it is even possible, requires attention not only to the politics of religious organizations but to those of academic philosophy. Before Galileo had trouble with the Jesuits and before the Dominican friar Caccini denounced him from the pulpit, his employer heard him accused of contradicting Scripture by a professor of philosophy, Cosimo Boscaglia, who was neither a theologian nor a priest. The first to defend Galileo was a Benedictine abbot, Benedetto Castelli, who was also a professor ot mathematics and a former student of Galileo's. It was this exchange that led Galileo to write the Letter to Grand Duchess Christina. (Castelli remained Galileo's friend, visiting him at Arcetri near the end of Galileo's life, after months of effort to get permission from the Inquisition to do so.)

2005-12-08 17.59

Not long after Galileo began publishing his astronomical work in The Starry Messenger, his Copernican ideas came under attack as a possible heresy, violating the Biblical picture of the Earth as the center of the universe (as well as the accepted philosophical teachings of the time).

By 1616 the attacks seemed to Galileo to have become dangerous, and he went to Rome to try to persuade the Church authorities not to ban the new teachings. The mission was a failure: in the end, [[Robert Bellarmine|Cardinal Bellarmine]], acting on orders from the Pope, delivered him an order not hold or defend the idea that the Earth moves and the Sun stands still at the center.

For the next several years Galileo stayed well away from the controversy. Toward 1630, however, he revived his project of writing a book on the subject, encouraged by the election of Pope Urban VII. The book, Dialogue Concerning the Two Chief World Systems, was published in 1632, with formal authorization from the Inquisition; there is dispute, however, concerning this license.

2005-09-06 13.39

The real meaning of the requirement for better proof became clear in the 1630s, when Galileo was condemned by the Inquisition because of his book Dialogue Concerning the Two Chief World Systems. That book contained what Galileo considered to be a physical proof of the Earth's motion, based on the tides; had it been correct (which it was not), it would have satisfied Bellarmine's condition—or rather, Bellarmine's position would have required the Inquisition to decide whether or not this scientific argument was correct. In the event, there was no such assessment, and Galileo was condemned simply for publishing.

2005-12-08 17.59

Galileo was ordered to Rome to stand trial on suspicion of heresy in 1633. The sentence of the Inquisition was in three essential parts:

• Galileo was required to recant his heliocentric

ideas, which were condemned as "formally heretical";.

• He was ordered imprisoned; the sentence was later commuted to house

arrest.

• His offending Dialogue was banned; and in an action not announced

at the trial, publication of any of his works was forbidden, including any he might write in the future.

After a period with the friendly Archbishop Piccolomini in Siena, Galileo was allowed to return to his villa at Arcetri near Florence, where he spent the remainder of his life under house arrest.

200x Eppur

The tale that Galileo, rising from his knees after recanting, said "Eppur si muove!" (But it does move!) cannot possibly be true; to say any such thing in the offices of the Inquisition would have been a ticket to follow Bruno to the stake. But the widespread belief that the whole incident is an 18th-century invention is also false. A Spanish painting, dated 1643 or possibly 1645, shows Galileo writing the phrase on the wall of a dungeon. Thus we have two versions of the story, neither of which is true; but the painting shows that some story of "Eppur si muove" was circulating in Galileo's time. In the months immediately after his condemnation, Galileo resided with Archbishop Ascanio Piccolomini of Siena, a learned man and a sympathetic host; the fact that Piccolomini's brother was a military attaché in Madrid, where the painting was made some years later, suggests some family tale that later became a garbled oral tradition.

2003-07-16 18.03

When Galileo was tried in 1633, the Inquisition was proceeding on the premise that he had been ordered not to teach it at all, based on a paper in the records from 1616; but Galileo produced a letter from Cardinal Bellarmine that showed only the "hold or defend" order. The latter is in Bellarmine's own hand and of unquestioned authenticity; the former is unsigned, violating the Inquisition's own rule that the record of such an admonition had to be signed by all parties and notarized. Leaving aside technical rules of evidence, what can one conclude as to the real events? There are two schools: according to Stillman Drake, the order not to teach was delivered unofficially and improperly; Bellarmine would not allow a formal record to be made, and assured Galileo in writing that the only order in effect was not to "defend or hold". According to Giorgio di Santillana, however, the unsigned minute was simply a fabrication by the Inquisition.

...

After the release of this report, the Pope said further that "... Galileo, a sincere believer, showed himself to be more perceptive in this regard [the relation of scientific and Biblical truths] than the theologians who opposed him."

2005-07-31 17.01

There is evidence of an organized and secretive opposition to Galileo among some academic philosophers. This included professors against whom Galileo, who was not officially a philosoper at all, had successfully argued for the theory of buoyancy developed by Archimedes, as against that of Aristotle, which had been taught in the academies. Moreover, the new telesopic discoveries in astronomy were, even without arguments on heliocentrism, upsetting the established comprehensive theory of the heavens, again due to Aristotle. The Jesuit astronomers, after a period of disbelief when good telescopes were almost unobtainable, had soon enough agreed on the validity of Galileo's discoveries; by contrast, some professors of the secular academic world refused for a time to look through the telescope. Caccini's attack, if not actually inspired by the philosophers, was welcomed by them and had their support.

2004-05-09 21:30

When the ambassador reported Galileo's arrival and asked how long the proceedings would be, the Pope replied that the Holy Office proceeded slowly, and was still in the process of preparing for the formal proceedings. In the event, having responded to the urgent demands of the Inquisition that he must report to Rome immediately, Galileo was laft to wait for two months before proceedings would begin.

.................. disjoint
Publication was another matter. His Dialogue had been put on the Index Librorum Prohibitorum, a black list of banned books, where it stayed until 1822[2]. Though the official sentence passed on Galileo mentioned no other works, Galileo found out two years later that publication of anything he might ever write had been quietly banned. The ban was effective in France, Poland, and German states, but not in the Netherlands.

The longer narrative

2005-12-08 21.23 Galileo Affair

In 1610 Galileo published his [[Sidereus Nuncius|Starry Messenger]], describing the surprising observations that he had made with the new telescope. These and other discoveries exposed major difficulties with the understanding of the heavens that had been held since antiquity, and raised new interest in radical teachings such as the heliocentric theory of Copernicus. In reaction, many maintained that the motion of the Earth and immobility of the Sun were heretical, as they contradicted the accounsts given in the Bible as understood at that time. This article treats of Galileo's part in the controversies over theology, astronomy, and philosophy, culminating in his trial and sentencing in 1633 on a grave suspicion of heresy.

Opening of the controversy

Galileo began his telescopic observations in the latter part of 1609, and by March of 1610 was able to publish a small book, The Starry Messenger (Siderius Nuncius), relating some discoveries that had not been dreamed of in the philosophy of the time: mountains on the Moon, lesser moons in orbit around Jupiter, and the resolution of what had been thought cloudy masses in the sky (nebulae) into collections of stars too faint to see individually. Other observations followed, including the phases of Venus, which were impossible under the old Ptolemaic astronomy.

2005-12-09 16.39 Affair

Not all the claims were completely accepted: Christopher Clavius, the most distinguished astronomer of his age, never was reconciled to the idea of mountains on the Moon. And outside the Collegium many still disputed the reality of the observations. Tales of savants who refused even to look through he telescope are not without basis, although the few documented instances involve philosophers, and not (as commonly related) bishops.

Not all relations with the Jesuits were good. Galileo became involved in a dispute over priority in the discovery of sunspots with Christoph Scheiner, a prominent Jesuit. This became a bitter lifelong feud. Oddly, neither of them was right; there can be little doubt that the first observations were by David Fabricius and his son Johannes.

At this time also, Galileo engaged in a dispute over the reasons that objects float or sink in water, taking the part of Archimedes against Aristotle, the favorite of the academics. The debate was unfriendly, and Galileo's blunt and sometimes sarcastic style, though not extraordinary in academic debates of the time, made him enemies. There is reason to believe that a group of professors of philosphy worked quietly and successfully to raise opposition to him in the Church, where accusations of heresy were more deadly than anything that could be done in universities.

One of the first suggestions of heresy that Galileo had to deal with came in 1613 from a professor of philosophy, Cosimo Boscaglia, who was neither a theologian nor a priest. In conversation with Galileo's patron, Cosimo II de' Medici, Boscaglia gave the opinion that the telescopic discveries were valid, but the motion of the Earth was obviously contrary to Scripture. Galileo was defended on the spot by a Benedictine abbot, Benedetto Castelli, who was also a professor of mathematics and a former student of Galileo's. It was this exchange, reported to Galileo by Castelli, that led Galileo to write the Letter to Grand Duchess Christina. (Castelli remained Galileo's friend, visiting him at Arcetri near the end of Galileo's life, after months of effort to get permission from the Inquisition to do so.)

The first dangerous attack appears to have been that by [[Tommaso Caccini]], a Dominican friar, who preached a sermon in Florence at the end of 1614, denouncing Galileo, his associates, and mathematicians in general (a category that included astronomers). The biblical text for the sermon on that day was Joshua 10, in which Joshua makes the Sun stand still; this was the story that Castelli had had to interpret for the Medici family the year before. It is said, though it is not verifiable, that Caccini used the passage "Ye men of Galilee, why stand ye gazing up into heaven?" (Acts 1:11).

2005-12-20 01.49 Affair

At this time also, Galileo engaged in a dispute over the reasons that objects float or sink in water, taking the part of Archimedes against Aristotle, the favorite of the academics. The debate was unfriendly, and Galileo's blunt and sometimes sarcastic style, though not extraordinary in academic debates of the time, made him enemies. Galileo's friends reported to him that a group of professors of philosophy were working quietly to raise opposition to him in the Church, where accusations of heresy were more deadly than anything that could be done to a dissenter in a university; their success is indicated by the sermon of Caccini, described later.

First meetings with theological authorities

2005-12-20 01.49 Affair

In February of 1616, in response to Galileo's presentation of his case in Rome and to the attacks on him by Caccini and others, the Inquisition asked a commission of theologians, known as the Qualifiers, about the propositions that the Sun is at the center of the planets' motions and does not move, and that the Earth is not at the center and does move. On February 24 the Qualifiers delivered [http://astro.wcupa.edu/mgagne/ess362/resources/finocchiaro.html their unanimous report]: the idea that the Sun is stationary is "foolish and absurd in philosophy, and formally heretical since it explicitly contradicts many places the sense of Holy Scripture..."; while the Earth's movement "receives the same judgement in philosophy and ... in regard to theological truth it is at least erroneous in faith."

At a meeting of the cardinals of the Inquisition on the following day, Pope Paul V instructed Bellarmine to deliver this result to Galileo, and to order him to abandon the Copernican opinions; should Galileo resist the decree, stronger action would be taken. On February 26 Galileo was called to Bellarmine's residence, and accepted the orders. (Drake 1978, p. 253)

Galileo met again with Bellarmine, apparently on friendly terms; and on March 11 he met with the Pope, who assured him that he was safe from persecution so long as he, the Pope, should live. Nonetheless, Galileo's friends Sagredo and Castelli reported that there were rumors that Galileo had been forced to recant and do penance. To protect his good name, Galileo requested a letter from Bellarmine stating the truth of the matter. This letter assumed great importance in 1633, as did the question whether Galileo had been ordered not to "hold or defend" Copernican ideas (which would have allowed their hypothetical treatment) or not to teach them in any way.

In the end, the mission was a failure. Galileo did not persuade the Church to stay out of the controversy, but instead saw heliocentrism formally declared an idea that could not be held as truth. It was even termed heretical by the Qualifiers, though this position was not binding on the Church. Foscarini's book was banned; Copernicus' De Revolutionibus, though not formally banned, was removed from circulation pending revisions, and in fact was not fully cleared until the 19th century. Though Galileo was personally safe, and his works had not been banned, he was effectively barred from much serious work in astronomy.

.....
By 1616 the attacks seemed to Galileo to have become dangerous, and he went to Rome to try to persuade the Church authorities not to ban the new teachings. The mission was a failure: in the end, [[Robert Bellarmine|Cardinal Bellarmine]], acting on orders from the Pope, delivered him an order not hold or defend the idea that the Earth moves and the Sun stands still at the center.

2005-12-12 19.30 Affair

In 1615 the question of heliocentrism had been raised with [[Robert Bellarmine|Cardinal Bellarmine]], in the case of Paolo Antonio Foscarini, a Carmelite father. Foscarini had published a book, Lettera ... sopra l'opinione ... del Copernico, which took the dangerous step of attempting to reconcile Copernicus with the biblical passages that seemed to be in contradiction. Bellarmine at first expressed the opinion that Copernicus would not be banned, but would at most require some editing to assure that the heliocentric idea was purely hypothetical. This, in the language of the time, did not mean that it was a new idea, possibly true, and requiring experimental test; rather, it referred to a device or trick that was not considered to be true, but was convenient for calculations.

When Foscarini sent his book to Bellarmine, the latter sent a reply to both Foscarini and Galileo. In this he stated that the heliocentric ideas were "a very dangerous thing, not only by irritating all the philosophers and scholastic theologians, but also by injuring our holy faith and rendering the Holy Scriptures false." Moreover, while the matter was not inherently a matter of faith, it became one "on the part of the ones who have spoken", namely "the holy Fathers and all the Latin and Greek commentators." He conceded that if there were positive proof, "then it would be necessary to proceed with great caution in explaining the passages of Scripture which seemed contrary, and we would rather have to say that we did not understand them than to say that something was false which has been demonstrated." He did not, however, consider this to be a serious possibility. His final argument was that the motion of the Sun could not be a mere appearance, as the shore appears to recede whan one sails away from it, because no one perceives the latter as a mere appearance.

The mission was a failure: in the end, Bellarmine, acting on orders from the Pope, delivered him an order not to hold or defend the idea that the Earth moves and the Sun stands still at the center.

2005-12-21 19.48 Affair

In sum, he found no problem with heliocentrism so long as it was treated purely as hypothesis and not as a fact that one undertakes to prove (unless one comes up with conclusive proof).

..........
If the Inquisition had issued the order not to teach heliocentrism at all, it would have been ignoring Bellarmine's position, which was in any case effectively ignored in the proceedings in 1633.

........
In the end, the mission was a failure. Galileo did not persuade the Church to stay out of the controversy, but instead saw heliocentrism formally declared an idea that could not be held as truth. It was even termed heretical by the Qualifiers, though this position was not binding on the Church. Foscarini's book was banned; Copernicus' De Revolutionibus, though not formally banned, was removed from circulation pending revisions, and in fact was not fully cleared until the 19th century. Though Galileo was personally safe, and his works had not been banned, there was now much doubt (felt by other astronomers as far away as Germany) whether it was possible to do serious work in Copernican astronomy.

The Dialogue

For the next several years Galileo stayed well away from the controversy. Toward 1630, however, he revived his project of writing a book on the subject, encouraged by the election of Pope Urban VII. The book, Dialogue Concerning the Two Chief World Systems, was published in 1632, with formal authorization from the Inquisition; there is dispute, however, concerning this license.

Galileo was ordered to Rome to stand trial on suspicion of heresy in 1633. The sentence of the Inquisition was in three essential parts:

• Galileo was required to recant his heliocentricideas, which were condemned as "formally heretical";
• He was ordered imprisoned; the sentence was later commuted to house arrest.
• His offending Dialogue was banned; and in an action not announced at the trial, publication of any of his works was forbidden, including any

he might write in the future.

After a period with the friendly Archbishop Piccolomini in Siena, Galileo was allowed to return to his villa at Arcetri near Florence, where he spent the remainder of his life under house arrest.