The Essential Galileo

by Galilei, Galileo, Finocchiaro, Maurice A.

  February: Dominican friar Niccolò Lorini sends a formal complaint against Galileo to Cardinal Paolo Sfondrati (member of the Inquisition and prefect of the Index), enclosing Galileo’s “Letter to Castelli” as incriminating evidence.

  March: Caccini gives a deposition to the Inquisition in Rome, charging Galileo with suspicion of heresy, based on the content of his “Letter to Castelli” and his book on Sunspots.

  April: Cardinal Robert Bellarmine, influential theologian and member of the Congregations of the Inquisition and of the Index, replies to Foscarini’s private request for an opinion on his Letter on the Earth’s Motion; Bellarmine’s letter explicitly states that his remarks apply to Galileo as well as to Foscarini.

  Spring and summer: Galileo expands his “Letter to Castelli” into the Letter to the Grand Duchess Christina and writes his “Considerations on the Copernican Opinion” in response to Bellarmine’s letter to Foscarini.

  December: After a long delay due to illness, Galileo goes to Rome to defend himself and the Copernican doctrine from the charge of heresy.

  1616 8 January: At the request of Cardinal Alessandro Orsini, Galileo writes his “Discourse on the Tides,” containing a physical argument for the earth’s motion based on its ability to explain the existence of tides; this argument will later be expanded and included in the Dialogue.

  24 February: A committee of eleven consultants reports to the Roman Inquisition their unanimous opinion that the heliocentric and heliostatic thesis is philosophically absurd and formally heretical; and that the geokinetic thesis is philosophically absurd and theologically erroneous.

  25 February: At an Inquisition meeting, Pope Paul V orders Cardinal Robert Bellarmine to warn Galileo to abandon his Copernican views.

  26 February: Bellarmine calls Galileo to his house and gives him the warning.

  3 March: Bellarmine reports to the Inquisition that Galileo has acquiesced.

  5 March: The Congregation of the Index publishes a decree declaring the earth’s motion physically false and contrary to Scripture, prohibiting and condemning Foscarini’s book, suspending until corrected Copernicus’ book, and ordering analogous censures for analogous works; Galileo is not mentioned at all.

  26 May: Bellarmine writes a certificate for Galileo, denying rumors that he has been tried and condemned, and clarifying that he has been warned not to hold or defend the earth’s motion.

  June: Galileo returns to Florence.

  1619 June: Mario Guiducci, a disciple of Galileo, publishes a booklet entitled Discourse on the Comets; it contains two lectures he (Guiducci) had given about the three comets that had appeared the previous year and had sparked wide discussion; although Galileo collaborated in its writing, the book is published under Guiducci’s name.

  October: Using a pseudonym, Orazio Grassi, a Jesuit professor of mathematics at the Roman College, publishes a book (Astronomical and Philosophical Balance) highly critical of Galileo’s (and Guiducci’s) view of comets; Grassi argues, among other things, that their view of comets is committed to Copernicanism and thus violates the anti Copernican decree.

  1620 May: The Congregation of the Index issues a decree containing the corrections of Copernicus’ book On the Revolutions, promised in the Decree of 5 March 1616.

  August: Florentine Cardinal Maffeo Barberini sends Galileo a Latin poem entitled Dangerous Adulation, which he has written in praise of Galileo.

  1621 January: Pope Paul V dies; Alessandro Ludovisi is then elected Pope Gregory XV.

  February: Grand Duke Cosimo II dies prematurely and is succeeded by his son Ferdinando II; but due to the latter’s young age (10 years), Tuscany is governed by a regency council until 1627.

  September: Cardinal Bellarmine dies.

  1623 July: Pope Gregory XV dies.

  August: Cardinal Maffeo Barberini is elected Pope Urban VIII.

  October: Galileo’s The Assayer is published in Rome, sponsored by the Lincean Academy and dedicated to the new pope; it contains a discussion of comets and is highly critical of Grassi’s views.

  1624 Spring: Galileo visits Rome to pay homage to his old patron, now Pope Urban VIII; he stays for six weeks, receiving weekly audiences from the pope and warm treatment from other Church officials.

  Fall: Galileo begins working on a book that discusses the system of the world and ties together all his discoveries and ideas on the subject (except for questions of biblical interpretation).

  1625 Sometime in 1625, or perhaps in 1624, a complaint is sent to a Church official, charging that the atomistic theory of matter in Galileo’s The Assayer conflicts with the Catholic doctrine of the Eucharist; but the identities of the writer and the recipient are unknown, nor is it known whether the Inquisition conducted an investigation.

  April: After investigating another complaint, that Galileo’s The Assayer contains too much praise for Copernicanism, the Inquisition concludes the case with a clear and strong exoneration.

  1626 Grassi, again using a pseudonym, publishes in Paris a book (Comparison of the Weights of the Assayer and the Balance) against Galileo’s The Assayer; it argues that Galileo’s physics implies a denial of the Catholic doctrine of the Eucharist, and more generally the other alleged impieties of the atomists. Galileo feels no need to reply.

  1630 Spring: Galileo completes work on the book he had been writing since 1624; he goes to Rome to obtain the imprimatur from Church authorities, and to arrange for its publication by the Lincean Academy.

  June: Scheiner publishes a massive book on sunspots, filled with valuable observations and interesting speculations; it also has a long beginning section that violently attacks Galileo, especially his claim of priority in the discovery of sunspots. Galileo will include a brief reply and criticism in the Dialogue.

  August: Prince Federico Cesi, founder and head of the Lincean Academy, dies

  1632 February: Printing is completed in Florence for Galileo’s Dialogue

  on the Two Chief World Systems, Ptolemaic and Copernican. Summer: The Dialogue is received with great enthusiasm and praise in many quarters; but a number of questions, rumors, complaints, and criticisms emerge in Rome concerning its content, form, and manner of publication; these lead the pope to prohibit the sale of the book and to appoint a special commission to investigate the matter.

  September: At a meeting of the Inquisition presided by the pope, the special commission’s report is discussed and the pope decides to forward the case to the Inquisition and to summon Galileo to Rome to stand trial.

  1633 13 February: Galileo arrives in Rome and is lodged at the Tuscan embassy (Palazzo Firenze).

  Spring: The Inquisition trial proceedings begin, go through several stages, and are concluded.

  22 June: Galileo is convicted of “vehement suspicion of heresy”; the punishments include a formal abjuration, the prohibition of the Dialogue, imprisonment at the pleasure of the Inquisition, and some religious penances; he recites the abjuration at the convent of Santa Maria sopra Minerva.

  23 June: Galileo’s prison sentence is commuted to house arrest at Villa Medici, a sumptuous palace in Rome owned by the grand duke of Tuscany.

  30 June: His prison sentence is again commuted to house arrest in Siena, at the residence of the archbishop, who was a good friend of Galileo’s.

  July–November: In Siena, Galileo starts writing a book on topics he had researched earlier, the strength of materials and the motion of falling bodies.

  1 December: Galileo’s prison sentence is commuted once again, now to house arrest at his villa in Arcetri near Florence.

  1634 In Paris, Marin Mersenne publishes a French translation of Galileo’s unpublished manuscript on Mechanics.

  1635 A Latin translation of Galileo’s Dialogue is published in Strasbourg, with the title Systema cosmicum and under the editorship of a friend of Galileo’s, a French lawyer named Elia Diodati; it includes an appendix with a Latin translation of Foscarini’s Letter on the Earth’s Motion (banned and condemned by the Index’s d
ecree of 1616).

  1636 Again in Strasbourg and under the editorship of Diodati, Galileo’s Letter to the Grand Duchess Christina is published for the first time, in an edition that contains the original Italian text and a Latin translation. It is revealingly entitled: New and Old Doctrine of the Most Holy Fathers and Esteemed Theologians on Preventing the Reckless Use of the Testimony of the Sacred Scripture in Purely Natural Conclusions That Can Be Established by Sense Experience and Necessary Demonstrations.

  1637 Galileo becomes completely blind.

  1638 July: Galileo’s Two New Sciences is published in Leiden, Holland; in the preface he speaks as if the book had been published without his knowledge (which was not the case).

  1639 Mersenne publishes in Paris a French translation of Galileo’s latest book, under the title The New Thoughts of Galileo, Mathematician and Engineer to the Duke of Florence. Vincenzio Viviani begins studying with Galileo and assisting him in his correspondence; for this he receives a modest salary from the grand duke.

  1640 With his approval, Galileo’s Operations of the Geometric and Military Compass is reprinted in Padua.

  1641 The Latin translation of Galileo’s Dialogue is reprinted in Lyons. Evangelista Torricelli begins living at Galileo’s house and serving as his research assistant.

  1642 8 January: Galileo dies at Arcetri.

  9 January: Galileo is quietly buried at the Church of Santa Croce in Florence, in an unmarked grave located in an out-of- the-way room behind the sacristy and under the bell tower.

  1687 Isaac Newton publishes his Mathematical Principles of Natural Philosophy, providing a compelling indirect proof of the earth’s motion based on a systematization of the general laws of motion and the formulation of the law of universal gravitation.

  1729 English astronomer James Bradley discovers the aberration of starlight, providing direct observational evidence that the earth has translational motion.

  1737 Galileo’s body is exhumed from the original grave in Santa Croce and moved to a mausoleum in the church’s main aisle, across from Michelangelo’s tomb.

  1744 With Church approval, a four-volume collection of Galileo’s works is published in Padua; the fourth volume contains the Dialogue, preceded by the Inquisition’s sentence and Galileo’s abjuration of 1633.

  1758 The new edition of the Catholic Index of Prohibited Books no longer lists the entry “all books teaching the earth’s motion and the sun’s immobility”; but it continues to include the three previously prohibited books by Copernicus, Foscarini, and Galileo.

  1789 Italian priest and astronomer Giambattista Guglielmini begins to provide direct confirmation of terrestrial rotation by means of experiments detecting an easterly deviation of falling bodies.

  1835 The new edition of the Index for the first time omits from the list Galileo’s Dialogue, as well as the books by Copernicus and Foscarini.

  1838 German astronomer and mathematician Friedrich Bessel observes that fixed stars exhibit an annual shift in apparent position, called annual stellar parallax; this provides direct evidence that the earth revolves annually around the sun.

  1851 Léon Foucault in Paris invents a pendulum that demonstrates the earth’s rotation; the experiment is repeated in many other places.

  1893 In the encyclical letter Providentissimus Deus, Pope Leo XIII puts forth a view of the relationship between biblical interpretation and scientific investigation that corresponds to the one advanced by Galileo in the Letter to the Grand Duchess Christina; but Galileo is not even mentioned.

  1942 The tercentennial of Galileo’s death provides the occasion for a first partial and informal rehabilitation. In 1941–46, this was done by several clergymen who held the top positions at the Pontifical Academy of Sciences, the Catholic University of Milan, the Pontifical Lateran University in Rome, and the Vatican Radio. They publish accounts of Galileo as a Catholic hero who upheld the harmony between science and religion; who had the courage to advocate the truth even against the Catholic authorities of his time; and who had the piety to retract his views outwardly when the 1633 trial proceedings made his obedience necessary.

  1979 Pope John Paul II begins a further informal rehabilitation of Galileo that was not concluded until 1992. In two speeches to the Pontifical Academy of Sciences, and in other statements and actions, the pope admits that Galileo’s trial was not merely an error but also an injustice; that Galileo was theologically right about scriptural interpretation, as against his ecclesiastical opponents; that even pastorally speaking, his desire to disseminate novelties was as reasonable as his opponents’ inclination to resist them; and that he provides an instructive example of the harmony between science and religion.

  Glossary of Terms and Names

  This glossary includes terms and names which appear in more than one section, and whose meaning is relatively peculiar, unusual, or obscure; such words are not explained in the notes. When such a word occurs in only one section, it is usually explained in a note and not here. Words whose meanings are generally known or commonly included in small desk-top dictionaries are not included here or in the notes.

  Academician. A term referring to Galileo, used by him in some of his books written in dialogue form. It is meant to remind readers that he was a member of the Lincean Academy.

  ad hominem. In the 17th century, this expression referred to an argument designed to examine the correctness of a controversial view by showing that it implies consequences not acceptable to those who hold that view. This Galilean meaning should not be confused with the most common modern meaning, referring to the fallacy of criticizing a controversial view by questioning the motives, character, or circumstances of those who hold that view, instead of criticizing the reasons and evidence they offer.

  annual motion. In the geostatic worldview, this was the orbital revolution of the sun around the central motionless earth, in an eastward direction relative to the fixed stars and taking one year to complete. In the Copernican system, the annual motion is simply the earth’s orbital revolution around the sun, also in an eastward direction and lasting one year.

  apogee. In the orbit of a heavenly body, this is the point farthest from the earth.

  Aristarchus of Samos (c. 310–250 B.C.). Greek astronomer who elaborated the theory that the earth moves around the sun.

  Bellarmine, Robert (1542–1621). Jesuit theologian, perhaps the most influential Catholic churchman of his time, and now a saint. Besides being a cardinal, he also served as a professor at the Roman College (the Jesuit university in Rome), an archbishop, the pope’s theologian, a consultant to the Inquisition, and a member of both the Congregation of the Inquisition and the Congregation of the Index.

  Brahe, Tycho. See Tycho Brahe.

  Caccini, Tommaso (1574–1648). A Dominican friar from Florence who held various administrative positions in his order and earned various academic degrees and positions in theology. He accused Galileo of heresy in a sermon in 1614 and testified against him with the Inquisition in 1615.

  Castelli, Benedetto (1578–1643). Benedictine monk, student of Galileo at the University of Padua, his successor at the University of Pisa, and friend and collaborator; also an important figure in his own right, mainly for his contributions to the science of hydraulics, and as the teacher of many outstanding Italian scientists of the period.

  comet. A large heavenly body appearing as a luminous mass to which is attached a long tail, and visible for only brief periods ranging from a few days to several months. Though comets had been observed since antiquity, in Galileo’s time their nature and origin remained controversial; the main issue was whether they were heavenly bodies or atmospheric phenomena. Nowadays, comets are known to be bodies of great volume but very small mass, to consist mostly of ice, and to follow definite (elliptical or parabolic) orbits around the sun; furthermore, the periodic recurrence of some of them can be predicted with great accuracy; but many more details remain controversial or unknown.

  conjunction. A configuration in
the apparent position of two heavenly bodies when they appear to be on the same side of the earth, namely, close to each other or separated by only a few degrees on the celestial sphere. For example, a new or thinly crescent moon occurs when it and the sun are in conjunction.

  cubit. An ancient unit of distance corresponding to the length of a forearm, and thus approximately one and one-half to two feet. This is the term used to translate Galileo’s term braccio.

  declination. The angular distance of a star from the celestial equator as seen from the earth. The analogue for the celestial sphere of what latitude is for the earth’s surface.

  direct motion. Apparent motion which planets exhibit most of the time in their journeys against the background of the fixed stars; its direction is eastward, namely it follows the order of the constellations of the zodiac. Used primarily in contexts where one wants to contrast direct motion to retrograde motion, whose direction is opposite (namely, westward).

  diurnal motion. At the level of observation, diurnal motion is the apparent motion of all heavenly bodies around the earth, occurring every day in a westward direction. In the geostatic worldview, such apparent motion corresponds to reality. In the Copernican system, the diurnal motion is simply the earth’s daily rotation around its own axis, in an eastward direction.

  eccentric. An eccentric is a circular orbit of one heavenly body around another such that the second body is not located at the geometrical center of the orbit but off that center. This device enables the distance between the two bodies to vary.

  eclipse. An eclipse occurs when the sun or moon becomes partially or completely invisible due to their relative position vis-à-vis the earth. In a lunar eclipse, the moon is eclipsed; that is, the earth is directly between the sun and the moon, and the moon is in the earth’s cone-shaped shadow. In a solar eclipse, the sun is eclipsed; that is, the moon is directly between the sun and the earth, and the earth is in the moon’s cone-shaped shadow.

  ecliptic. A term used to denote the annual orbit of the sun around the earth (in the geostatic system) or of the earth around the sun (in the Copernican system). The term also denotes both the plane on which the annual orbit lies and the circle resulting from projecting the annual orbit onto the celestial sphere.