Difference between revisions of "The Galileo Affair"

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:; 1687 -- G+54 (54 years after the 1633 condemnation)
:; 1687 -- G+54 (54 years after the 1633 condemnation)

:: Newton's Philosophiae Naturalis Principia Mathematica shows how the concept of gravity, coupled with Galileo's laws of motion, explains Kepler's ellipses.  Newton's laws of motion:
:: Newton's ''Philosophiae Naturalis Principia Mathematica'' shows how the concept of gravity, coupled with Galileo's laws of motion, explains Kepler's ellipses.   
::; Newton's laws of motion:
::: 1. Every body in motion or at rest tends to stay in motion or at rest unless a force acts on it.
::: 1. Every body in motion or at rest tends to stay in motion or at rest unless a force acts on it.
::: 2. Force is measured as mass times acceleration (F = ma); the force of gravity is G * m<sub>1</sub> * m<sub>2</sub> / d<sup>2</sup>).   
::: 2. Force is measured as mass times acceleration (F = ma); the force of gravity is G * m<sub>1</sub> * m<sub>2</sub> / d<sup>2</sup>).   

Latest revision as of 16:25, 4 June 2022

The short story
Galileo did not prove the truth of heliocentrism; he asserted it as an article of faith. His appeal to tidal motion did NOT establish heliocentrism; it showed that the moon moves around the earth, not that the earth moves around the sun. He rejected Kepler's laws of planetary motion and clung to the cycles and epicycles required by the Greek assumptions of perfect circular motion and uniform velocity. He added nothing to Copernicus' derivation of the relative size and period of planetary orbits. He failed to apply his laws of motion to planetary motion; Newton did that after Galileo was dead. The astronomical observations that supported heliocentrism were not made until 98 to 218 years after the second trial of Galileo in 1633. Galileo treated as a fact what was NOT an established fact in his day, he insulted the Pope, who had been a personal benefactor of his, and he commented on the Scriptures without any scientific need to do so. Galileo asked for trouble, and he got it.
Anti-Catholics systematically misrepresent the controversy AS IF Galileo had adopted the Kepler-Newton understanding of our own day or AS IF he had made observations that clinched the argument in his favor. Nothing could be further from the truth.
Scientists are qualified to do science. They are not qualified by their scientific credentials to do history. You might exercise a little bit of critical thinking when you come up against their historical claims. "Doubt everything," especially when a scientist stops doing science and dabbles in other disciplines like history, philosophy, politics, ethics, and religion.
"Galileo: Rude, Arrogant, and Almost Entirely Wrong"
This was a "Theology on Tap" presentation in 2009.

Some Great Moments in Astronomy

Classical Era: Greek & Roman Civilization (6th BC to ~5th AD)

~340 BC
Aristotle (384-322 BC) theorized that above the moon, all is perfect and unchanging. [Galileo demolished this assumption by observing the mountains of the moon, the phases of Venus, and the phases of Jupiter's moons.]
50 BC
Ptolemy created a geocentric (earth-centered) system of cycles and epicycles to account for retrograde motion of the planets. His system is also consistent with the fact that the motions of the earth cannot be detected by unaided and untrained senses. Ptolemy was rediscovered around 1175.
46 BC
Julius Caesar introduced the Julian calendar, replacing one based on the moon. It provided for one leap year every four years, without exception. Julius named "July" after himself. His successor, Augustus, named August after himself and stole a day from February so that his month (August) would have as many days as Julius' month (July).
The Julian calendar created too many leap years. It was later revised so that we have a leap year every fourth year, except when the year is evenly divisible by 100--except when the year is evenly divisible by 400. So, for example, 1700, 1800, and 1900 were not leap years, but 2000 was a leap year. This means three fewer leap years every 400 years than in the Julian system.

Dark Ages (Early Middle Ages): After the Fall of Rome (~5th to 10th AD)

The inspiration for doing astronomy (studying the laws of the stars) was inspired by astrology (belief that the stars control our destiny). Astrology was a leftover of polytheism and animism.

Middle Ages: Reason inspired by Greek Philosophy (11th to 13th AD)

Observation of the motion of the stars and planets improved during the middle ages. Mechanical clocks driven by weights and controlled by escapement mechanisms developed in the 14th century.

Renaissance: Re-birth of Greco-Roman Civilization (14th to 16th AD)

Beginning of Protestant Reformation by Martin Luther. One of the primary characteristics of the Reformation was argument about proper methods of interpreting the Scriptures (hermeneutics and exegesis) and, in particular, the relationship between Tradition and the Scriptures. Galileo got in trouble, in part, for what he taught about the Scriptures.
Nicholas Copernicus, a Polish Canon (a Catholic cleric), published On the Revolution of the Celestial Orbs. Copernicus was a celibate member of a Catholic religious community--he was once nominated to be bishop. It's not clear whether he was a priest at the time of his nomination or whether he ever was ordained a priest at all. His book was dedicated to and received by Pope Pius III. In his heliocentric (sun-centered) theory, Copernicus maintained the classical assumptions of perfect circular motion and uniform speed; he needed eight more epicycles than the Ptolemaic system (geo-centric, earth-centered system) to make his system work, and it was less accurate in its predictions than the Ptolemaic system. He had no new evidence to show his system was better.
The glory of Copernicus was that he showed that if we assume that the sun is at the center of planetary motion (helicentrism) rather than the earth (geocentrism), then it is possible to use trigonometry to derive the size and period of the planetary orbits from the astronomical data that had already been collected.
Copernicus made no new observations to support heliocentrism. He used data that was already available. What he did was to see the meaning of the heliocentric hypothesis and to show what the consequences would be of assuming the truth of heliocentrism.
Tycho Brahe took astronomical observation to new levels of precision. His 25 years of data on Mars gave Kepler the raw material to work out the three laws of planetary motion. Tycho's observations preceded the invention of the telescope! Tycho, a Lutheran, believed that the other planets orbited the sun but that the sun orbited the earth. From the same data that he left to Kepler, Tycho drew a wrong conclusion.
Science is not just observation, but thinking rightly about observation.
Birth of Galileo Galilei. Died in 1642.
Pope Gregory (with help from a Jesuit astronomer) reformed the Julian calendar system on October 15. The Gregorian Calendar is the predominant calendar system in use in the United States today. The Gregorian system assumes that the year is 365.2425 days long, which overstates the facts by about twenty-six seconds on average. The Gregorian Calendar is what gave us our system of leap years: add a day every four years, except for every hundred years, unless the hundredth year is divisible by 400. The purpose of the reform was to keep the date of Easter within springtime (Passover is a spring festival). To get back on schedule, 10 days were dropped between October 4 and October 15. Because of the inaccuracy of the Gregorian assumptions, the system will have to be corrected again between 4,000 and 14,000 AD (depending on which method of making corrections is adopted).
Johannes Kepler (1571-1630) published what we now know to be an absurd theory of planetary motion based on five Platonic solids (cube, tetrahedron, dodecahedron, octahedron, icosahedron). His scheme was only off by about 5% from observed motion of the planets. Trying to make his theory fit the facts later led him to abandon it. It took him six years to work out the elliptical orbits; he threw out his first, valid proof of elliptical motion because it was just too hard for him to break with tradition; then he proved the same thing using a different method and forced himself to accept the results. He also had to give up the assumption that each planet moves at a uniform speed; they speed up as they come closest to the sun and slow down as they move further away. What a mind--what a man!
The telescope was invented in Holland. Galileo improved the design and made the first great telescopic discoveries that shattered the Aristotelian cosmology: the moon was imperfect; the sun had spots and rotated on its axis; Venus showed phases; Jupiter had four moons that orbited Jupiter, not the earth--providing a tiny model of the heliocentric system.
Kepler published first two laws of planetary motion: the planets move in elliptical orbits; as the planet moves, a radius drawn from it to the center of the ellipse sweeps out equal area in equal time.
Kepler asked why the sky is dark at night. His answer: we live in a finite universe. Contemporary answer: because the universe had a beginning, it expands rapidly, and stars die out.
Galileo published his telescopic discoveries in The Starry Messenger. These observations proved that Aristotle's belief in the unchangeable perfection of the realm beyond the moon was false.
Galileo started doing Scripture studies in Letter to Castelli. There are four controversial passages:
  • Joshua 10:12: "'Sun, stand thou still at Gibeon' ... and the sun stood still."
  • Ps 93:1: "The world is established; it shall never be moved."
  • Ps 104:5: "Thou didst set the earth on its foundations, so that it should never be shaken."
  • Ecclesiastes 1:5: "The sun rises and the sun goes down, and hastens to the place where it rises."
"[Galileo] pointed out correctly that both St. Augustine (354-430 AD) and St. Thomas Aquinas (1225-1274) taught that the sacred writers in no way meant to teach a system of astronomy. St. Augustine wrote that 'One does not read in the Gospel that the Lord said: I will send you the Paraclete who will teach you about the course of the sun and moon. For He willed to make them Christians, not mathematicians'" (George Sim Johnston).
Cardinal Bellarmine (a Jesuit) asked Galileo to treat the Copernican system hypothetically and not to teach that the Scriptures are known to be false concerning the movement of the earth. "In April 1615, he wrote a letter which amounted to an unofficial statement of the Church's position. He pointed out that:
1. it was perfectly acceptable to maintain Copernicanism as a working hypothesis; and
2. if there were 'real proof' that the earth circles around the sun, 'then we should have to proceed with great circumspection in explaining passages of Scripture which appear to teach the contrary...'" (Johnston).
Kepler began publishing the first full-fledged Copernican textbook based on elliptical orbits and varying speeds (slowest at the furthest distance from the sun, fastest at the closest distance); publication was completed in 1621. Galileo rejected Kepler's work and continued to affirm the classical, Platonic, unscientific, false assumption that the planets orbit in perfect circles at uniform speed; because of this assumption, Galileo, like Copernicus before him, had to rely on the same system of cycles and epicycles employed in the Ptolemaic (geocentric) model.
In his Dialogue on the Two Chief World Systems, Galileo mocked Pope Urban VIII, who had asked Galileo to represent his view of science in the book. Galileo included the pope's point of view only in the mouth of Simplicio, the dunderhead who is always proven wrong by the character who represents Galileo. Up until this point, Urban had always treated Galileo favorably. Now the Pope wanted revenge. This was sinful and stupid. But it was a personal sin of the Pope and NOT of the Church.
The Pope pushed through a condemnation of Galileo based on a statement which differed from what Galileo had been instructed to do in 1616; it's not clear whether the more stringent statement was a forgery or a letter that had never been delivered to Galileo. Galileo spent the rest of his life under "house arrest," living in Florence.
The group that the Pope used to get revenge on Galileo did not have the authority to make an ex cathedra (infallible) pronouncement, and it was definitely NOT a council of the Church; their commitment to the geocentric system represented the opinion of this committee, not a dogma of the Church. The church allowed Copernicanism to be taught as a working hypothesis, not as a known fact.
This is exactly what the state of affairs was in science at the time. Heliocentrism had not been proven to be true. It was an act of faith on the part of Copernicus and Galileo to believe in heliocentrism. The scientific evidence supporting that act of faith did was not available until 95 to 218 years after Galileo was condemned. See below for more details.
Galileo's great blunder was was that he treated heliocentrism as a FACT when it had not yet been established as a FACT.
Galileo published Two New Sciences on laws of motion and mechanics. Galileo's work on motion laid the groundwork for Newton's Philosophiae Naturalis Principia Mathematica (1687). Using Galileo's laws of motion in conjunction with his own law of gravity, Newton showed that gravity perfectly explained the elliptical orbits and varying speeds of planetary motion deduced by Kepler from Tycho's data.
Galileo died.

Enlightenment: The Age of "Pure Reason" (17th-19th AD)

Newton was born. Died in 1727.
Christian Huygens invented the pendulum clock--the first clock that could count seconds.
1687 -- G+54 (54 years after the 1633 condemnation)
Newton's Philosophiae Naturalis Principia Mathematica shows how the concept of gravity, coupled with Galileo's laws of motion, explains Kepler's ellipses.
Newton's laws of motion
1. Every body in motion or at rest tends to stay in motion or at rest unless a force acts on it.
2. Force is measured as mass times acceleration (F = ma); the force of gravity is G * m1 * m2 / d2).
3. For every action there is an equal and opposite reaction.
1728 -- G+95
First evidence of the motion of the earth gleaned by Bradley's work on the slant of light falling from the stars.
1741 -- G+108
Benedict XIV told the Holy Office to grant an imprimatur to the first edition of the Complete Works of Galileo. This means that Catholics were permitted to read and discuss Galileo's theories.
1820 -- G+187
Based on Italian evidence of rotation and orbit (1792-1806), Catholics were allowed to teach Copernicanism as a fact rather than as a working hypothesis (theory).
1838 -- G+205
Measurement of stellar parallax by Friedrich Bessel confirms that the earth orbits around the sun. This was the proof of heliocentrism that everyone asked for in the 17th century!
Stellar parallax is the apparent motion of the stars caused by the real motion of the earth toward and away from the stars as the earth orbits the sun. When the earth is close to a star, the angle from the observer to the star will be broader than when the same observation is made from further away. The stars are so far away from the earth that the difference in viewing angle is very, very small. Extremely precise clocks and telescopes were necessary to demonstrate the difference in the viewing angle caused by the motion of the earth in its orbit around the sun.
1851 -- G+218
Léon Foucault used a pendulum to demonstrate the motion of the earth around its axis.

Modernity and Post-Modernity (20th to 21st AD)

Einstein introduces the cosmological constant (?) in applying general relativity to understanding the cosmos. Without the constant, his theory predicts that the entire universe would collapse into itself. He set the value of the constant to produce a static universe. At that time, scientists thought that our galaxy, the Milky Way, was the only galaxy that existed. Later, Einstein called this supposition of an anti-gravity force his "greatest mistake." After 1998, astronomers seem to have found evidence for it!
First confirmation of Einstein's theories via observations of a star close to the sun during an eclipse.
Edwin Hubble (1889 - 1953) identifies first galaxy outside the Milky Way via cepheid standard.
Hubble's Law: galaxies move away from each other; the farther apart the galaxies are, the greater the rate at which they move apart. The Hubble Telescope was designed to measure Hubble's constant. Hubbles observation of an expanding universe contradicted Einstein's theory of a static universe, so it seemed as though Einstein's anti-gravity cosmological constant (?) was no longer needed.
Fred Hoyle introduced the steady-state theory of the cosmos and coined Big Bang as a term of derision for the alternative that he rejected. He theorized that matter/energy/space/time is continuously being created between galaxies. No observations have confirmed his theory.
Arno Penzias and Robert Wilson stumble across cosmic background radiation, fulfilling a key prediction of the Big Bang theory. They realized that "static" picked up by their radio-telescope was, in fact, a remnant of the primordial explosion that created all the stars and galaxies in our universe.
The Cosmic Background Explorer (COBE) detects tiny temperature variations in the cosmic background radiation (30 millionths of a degree C or so). Without the irregularities in the original fireball, there would be no stars or galaxies; and without them, we wouldn't be here, either.
Super-Kamiokande determined that neutrinos have mass and can change type over time.
"By observing the redshift and the brightness of 58 supernova, two teams of astronomers - one led by Saul Perlmutter from the Lawrence Berkeley National Laboratory, the other by Alex Filippenko of the University of California at Berkeley - have found that the remnants of nearly all type 1a supernovae are at least 15 % further away than the standard model of the Universe predicts. This implies that the Universe is 'open' and will expand forever. It also suggests that a bizarre quantum force is affecting the expansion rate" <http://physicsweb.org/articles/news/2/11/3/1>.
Wilkinson Microwave Anisotropy Probe (WMAP) launched. This is an improved version of COBE. As of 2003, WMAP has produced the most detailed picture of the early universe at 380,000 years old, supported the Big Bang and Inflationary models, shown that the first stars began to shine after 200 million years, dated the universe to 13.7 billion years old (± 1%), supported the idea that 74% of the universe is dark energy, 23% is cold dark matter, and only about 4% is normal stuff (made out of the elements found in the periodic table), determined (as best it could) that the geometry of space is flat rather than open or closed, which suggests that the universe will therefore continue to expand indefinitely <http://map.gsfc.nasa.gov/m_mm/mr_limits.html>.
Hubble Space Telescope confirms that the rate of expansion of space seems to accelerate over time. That destroyed the possibility of an infinite series of Big Bangs followed by Big Crunches (what I call the PaddleBall model). Gravity is too weak to counteract the force that is causing space to expand.

Faith can never conflict with reason

Excerpts taken from Pope John Paul II, L'Osservatore Romano, 4 Nov 1992.[1]

In 1979 Pope John Paul II expressed the wish that the Pontifical Academy of Sciences would conduct an indepth study of the celebrated and controversial "Galileo case". A Commission of scholars for this purpose was established in 1981 and on Saturday morning, 31 October 1992, they presented their conclusions to the Pope. A summary of these conclusions was given by Cardinal Paul Poupard. Receiving them in the Sala Regia of the Apostolic Palace, the Holy Father took the occasion to thank the members of the Commission for their work and to speak to the Pontifical Academy of Sciences on the distinct but complementary roles that faith and science fulfill in human life. Also present were members of the Diplomatic Corps accredited to the Holy See and high-ranking officials of the Roman Curia.

The following English translation of the Holy Father's address, which was given in French, appeared in L'Osservatore Romano N. 44 (1264) - 4 November 1992.

[emphasis added in bold; indented comments in italics]

I. [Remarks on Complexity]

2. In the first place, I wish to congratulate the Pontifical Academy of Sciences for having chosen to deal, in its plenary session, with a problem of great importance and great relevance today: the problem of the emergence of complexity in mathematics, physics, chemistry and biology.

The emergence of the subject of complexity probably marks in the history of the natural sciences a stage as important as the stage which bears relation to the name of Galileo, when a univocal model of order seemed to be obvious. Complexity indicates precisely that, in order to account for the rich variety of reality, we must have recourse to a number of different models.

The Pope is using "complexity" as a synonym for "evolutionary theory." The great debate in biology and in the philosophy of biology is whether complexity can arise strictly from accidental causes (Darwin) or requires Intelligent Design (Demske, Behe, et al.).

This realization poses a question which concerns scientists, philosophers and theologians: how are we to reconcile the explanation of the world--beginning with the level of elementary entities and phenomena--with the recognition of the fact that "the whole is more than the sum of its parts"?

In his effort to establish a rigorous description and formalization of the data of experience, the scientist is led to have recourse to metascientific concepts, the use of which is, as it were, demanded by the logic of his procedure. It is useful to state exactly the nature of these concepts in order to avoid proceeding to undue extrapolations which link strictly scientific discoveries to a vision of the world, or to ideological or philosophical affirmations, which are in no way corollaries of it. Here one sees the importance of philosophy which considers phenomena just as much as their interpretation.

As in the Galileo affair, today's scientists often drift out of the field of their competence into philosophical and theological speculation.

3. Let us think, for example, of the working out of new theories at the scientific level in order to take account of the emergence of living beings. In a correct method, one could not interpret them immediately and in the exclusive framework of science. In particular, when it is a question of the living being which is man, and of his brain, it cannot be said that these theories of themselves constitute an affirmation or a denial of the spiritual soul, or that they provide a proof of the doctrine of creation, or that, on the contrary, they render it useless.

A further work of interpretation is needed. This is precisely the object of philosophy, which is the study of the global meaning of the data of experience, and therefore also of the phenomena gathered and analyzed by the sciences.

When a biologist says, "My theory of evolution means that there is no God," the biologist has ceased doing biology and has begun to do philosophy and theology.

Contemporary culture demands a constant effort to synthesize knowledge and to integrate learning. Of course, the successes which we see are due to the specialization of research. But unless this is balanced by a reflection concerned with articulating the various branches of knowledge, there is a great risk that we shall have a "shattered culture", which would in fact be the negation of true culture. A true culture cannot be conceived of without humanism and wisdom.

Many scientists are possessed by the conviction that the methods of science can be used to answer all questions, both about the physical world and about the metaphysical world. Their philosophy of science must be evaluated by the standards of philosophy. Metaphysical propositions cannot be tested empirically.

II. [Study Commission on Galileo Affair]

4. I was moved by similar concerns on 10 November 1979, at the time of the first centenary of the birth of Albert Einstein, when I expressed the hope before this same Academy that "theologians, scholars and historians, animated by a spirit of sincere collaboration, will study the Galileo case more deeply and, in frank recognition of wrongs from whatever side they come, dispel the mistrust that still opposes, in many minds, a fruitful concord between science and faith."[2] A Study Commission was constituted for this purpose on 3 July 1981. The very year when we are celebrating the 350th anniversary of Galileo's death, the Commission is presenting today, at the conclusion of its work, a number of publications which I value highly. I would like to express my sincere gratitude to Cardinal Poupard, who was entrusted with coordinating the Commission's research in its concluding phase. To all the experts who in any way took part in the proceedings of the four groups that guided this multidisciplinary study, I express my profound satisfaction and my deep gratitude. The work that has been carried out for more than 10 years responds to a guideline suggested by the Second Vatican Council and enables us to shed more light on several important aspects of the question. In the future, it will be impossible to ignore the Commission's conclusions.

One might perhaps be surprised that at the end of the Academy's study week on the theme of the emergence of complexity in the various sciences, I am returning to the Galileo case. Has not this case long been shelved and have not the errors committed been recognized?

That is certainly true. However, the underlying problems of this case concern both the nature of science and the message of faith. It is therefore not to be excluded that one day we shall find ourselves in a similar situation, one which will require both sides to have an informed awareness of the field and of the limits of their own competencies. The approach provided by the theme of complexity could provide an illustration of this.

5. A twofold question is at the heart of the debate of which Galileo was the center.

The first is of the epistemological order and concerns biblical hermeneutics. In this regard, two points must again be raised. In the first place, like most of his adversaries, Galileo made no distinction between the scientific approach to natural phenomena and a reflection on nature, of the philosophical order, which that approach generally calls for. That is why he rejected the suggestion made to him to present the Copernican system as a hypothesis, inasmuch as it had not been confirmed by irrefutable proof. Such therefore, was an exigency of the experimental method of which he was the inspired founder.

Galileo made two mistakes: 1) he crossed the boundary from natural science into a philosophy of science, and 2) he failed to meet the standards of proof required for making scientific claims. He was both a bad philosopher and a bad scientist.

Secondly, the geocentric representation of the world was commonly admitted in the culture of the time as fully agreeing with the teaching of the Bible of which certain expressions, taken literally seemed to affirm geocentrism. The problem posed by theologians of that age was, therefore, that of the compatibility between heliocentrism and Scripture.

Thus the new science, with its methods and the freedom of research which they implied, obliged theologians to examine their own criteria of scriptural interpretation. Most of them did not know how to do so.

The theologians similarly crossed the line from their specialty into the field of science, as if the Scriptures were intended by God to teach scientific truths.

Paradoxically, Galileo, a sincere believer, showed himself to be more perceptive in this regard than the theologians who opposed him. "If Scripture cannot err", he wrote to Benedetto Castelli, "certain of its interpreters and commentators can and do so in many ways".[3] We also know of his letter to Christine de Lorraine (1615) which is like a short treatise on biblical hermeneutics.[4]

6. From this we can now draw our first conclusion. The birth of a new way of approaching the study of natural phenomena demands a clarification on the part of all disciplines of knowledge. It obliges them to define more clearly their own field, their approach, their methods, as well as the precise import of their conclusions. In other words, this new way requires each discipline to become more rigorously aware of its own nature.

The upset caused by the Copernican system thus demanded epistemological reflection on the biblical sciences, an effort which later would produce abundant fruit in modern exegetical works and which has found sanction and a new stimulus in the Dogmatic Constitution Dei Verbum of the Second Vatican Council.

7. The crisis that I have just recalled is not the only factor to have had repercussions on biblical interpretation. Here we are concerned with the second aspect of the problem, its pastoral dimension.

By virtue of her own mission, the Church has the duty to be attentive to the pastoral consequences of her teaching. Before all else, let it be clear that this teaching must correspond to the truth. But it is a question of knowing how to judge a new scientific datum when it seems to contradict the truths of faith. The pastoral judgement which the Copernican theory required was difficult to make, in so far as geocentrism seemed to be a part of scriptural teaching itself. It would have been necessary all at once to overcome habits of thought and to devise a way of teaching capable of enlightening the people of God. Let us say, in a general way, that the pastor ought to show a genuine boldness, avoiding the double trap of a hesitant attitude and of hasty judgement, both of which can cause considerable harm.

The Church's pastoral concern is the salvation of souls. The Church must make judgments here and now about the scope of her own teachings so that the questions of the faithful can be answered faithfully. We cannot postpone pastoral teaching for decades or centuries until science answers its own proper scientific questions. At the same time, we must not trespass on the proper domain of science, substituting spiritual truths for scientific research.

8. Another crisis, similar to the one we are speaking of, can be mentioned here. In the last century and at the beginning of our own, advances in the historical sciences made it possible to acquire a new understanding of the Bible and of the biblical world. The rationalist context in which these data were most often presented seemed to make them dangerous to the Christian faith. Certain people, in their concern to defend the faith, thought it necessary to reject firmly-based historical conclusions. That was a hasty and unhappy decision. The work of a pioneer like Fr Lagrange was able to make the necessary discernment on the basis of dependable criteria.

Biblical criticism has shown that the Scriptures cannot be used naively as a historical textbook. The defense of the Scriptures by some Church theologians, including papal commissions, brought unnecessary shame on the Church.

It is necessary to repeat here what I said above. It is a duty for theologians to keep themselves regularly informed of scientific advances in order to examine if such be necessary, whether or not there are reasons for taking them into account in their reflection or for introducing changes in their teaching.

9. If contemporary culture is marked by a tendency to scientism, the cultural horizon of Galileo's age was uniform and carried the imprint of a particular philosophical formation. This unitary character of culture, which in itself is positive and desirable even in our own day, was one of the reasons for Galileo's condemnation. The majority of theologians did not recognize the formal distinction between Sacred Scripture and its interpretation, and this led them unduly to transpose into the realm of the doctrine of the faith a question which in fact pertained to scientific investigation.

Scientism is the philosophical conviction that the methods of science can answer all questions. If it is true that "there are no metaphysical realities," then scientism is true. But the proposition that "there are no metaphysical realities" is not a finding of science but a philosophical assumption that may be contested on philosophical grounds.

In fact, as Cardinal Poupard has recalled, Robert Bellarmine, who had seen what was truly at stake in the debate personally felt that, in the face of possible scientific proofs that the earth orbited round the sun, one should "interpret with great circumspection" every biblical passage which seems to affirm that the earth is immobile and "say that we do not understand, rather than affirm that what has been demonstrated is false".[5] Before Bellarmine, this same wisdom and same respect for the divine Word guided St Augustine when he wrote: "If it happens that the authority of Sacred Scripture is set in opposition to clear and certain reasoning, this must mean that the person who interprets Scripture does not understand it correctly. It is not the meaning of Scripture which is opposed to the truth but the meaning which he has wanted to give to it. That which is opposed to Scripture is not what is in Scripture but what he has placed there himself, believing that this is what Scripture meant".[6] A century ago, Pope Leo XIII echoed this advice in his Encyclical Providentissimus Deus: "Truth cannot contradict truth and we may be sure that some mistake has been made either in the interpretation of the sacred words, or in the polemical discussion itself".[7]

Hermeneutics is a discipline in philosophy and theology which focuses on the question of how we place the right interpretation on a text, whether it is sacred or profane.

Cardinal Poupard has also reminded us that the sentence of 1633 was not irreformable, and that the debate which had not ceased to evolve thereafter, was closed in 1820 with the imprimatur given to the work of Canon Settele.[8]

10. From the beginning of the Age of Enlightenment down to our own day, the Galileo case has been a sort of "myth", in which the image fabricated out of the events was quite far removed from reality. In this perspective, the Galileo case was the symbol of the Church's supposed rejection of scientific progress, or of "dogmatic" obscurantism opposed to the free search for truth. This myth has played a considerable cultural role. It has helped to anchor a number of scientists of good faith in the idea that there was an incompatibility between the spirit of science and its rules of research on the one hand and the Christian faith on the other. A tragic mutual incomprehension has been interpreted as the reflection of a fundamental opposition between science and faith. The clarifications furnished by recent historical studies enable us to state that this sad misunderstanding now belongs to the past.

The Pope was too optimistic in this passage. The work of overturning the Galileo myth depends on teaching scientists to recognize philosophical and historical truths. But they are culturally conditioned to give inflated value to their own methods at the expense of other modes of knowing, and it is an uphill struggle that is far from over.

11. From the Galileo affair we can learn a lesson which remains valid in relation to similar situations which occur today and which may occur in the future.

In Galileo's time, to depict the world as lacking an absolute physical reference point was, so to speak, inconceivable. And since the cosmos, as it was then known, was contained within the solar system alone, this reference point could only be situated in the earth or in the sun. Today, after Einstein and within the perspective of contemporary cosmology neither of these two reference points has the importance they once had. This observation, it goes without saying, is not directed against the validity of Galileo's position in the debate; it is only meant to show that often, beyond two partial and contrasting perceptions, there exists a wider perception which includes them and goes beyond both of them.

12. Another lesson which we can draw is that the different branches of knowledge call for different methods. Thanks to his intuition as a brilliant physicist and by relying on different arguments, Galileo, who practically invented the experimental method, understood why only the sun could function as the center of the world, as it was then known, that is to say, as a planetary system.

The Pope is wrong. It was Newton, not Galileo, who applied Galileo's brilliant experiments on motion to the motion of the planets and who, through his understanding of gravity, "understood why only the sun could function as the center" of the planetary system.

The error of the theologians of the time, when they maintained the centrality of the earth, was to think that our understanding of the physical world's structure was, in some way, imposed by the literal sense of Sacred Scripture. Let us recall the celebrated saying attributed to Baronius: "Spiritui Sancto mentem fuisse nos docere quomodo ad coelum eatur, non quomodo coelum gradiatur".

"The Holy Spirit did not intend to teach us how the heavens go, but how to go to Heaven."

In fact, the Bible does not concern itself with the details of the physical world, the understanding of which is the competence of human experience and reasoning. There exist two realms of knowledge, one which has its source in Revelation and one which reason can discover by its own power. To the latter belong especially the experimental sciences and philosophy. The distinction between the two realms of knowledge ought not to be understood as opposition. The two realms are not altogether foreign to each other, they have points of contact. The methodologies proper to each make it possible to bring out different aspects of reality.

III. [Science and the Church]

13. Your Academy conducts its work with this outlook. Its principal task is to promote the advancement of knowledge with respect for the legitimate freedom of science[9] which the Apostolic See expressly acknowledges in the statutes of your institution.

What is important in a scientific or philosophic theory is above all that it should be true or, at least, seriously and solidly grounded. And the purpose of your Academy is precisely to discern and to make known, in the present state of science and within its proper limits, what can be regarded as an acquired truth or at least as enjoying such a degree of probability that it would be imprudent and unreasonable to reject it. In this way unnecessary conflicts can be avoided.

The seriousness of scientific knowledge will thus be the best contribution that the Academy can make to the exact formulation and solution of the serious problems to which the Church, by virtue of her specific mission, is obliged to pay close attention--problems no longer related merely to astronomy, physics and mathematics, but also to relatively new disciplines such as biology and biogenetics. Many recent scientific discoveries and their possible applications affect man more directly than ever before, his thought and action, to the point of seeming to threaten the very basis of what is human.

14. Humanity has before it two modes of development. The first involves culture, scientific research and technology that is to say whatever falls within the horizontal aspect of man and creation which is growing at an impressive rate. In order that this progress should not remain completely external to man, it presupposes a simultaneous raising of conscience, as well as its actuation. The second mode of development involves what is deepest in the human being, when transcending the world and transcending himself, man turns to the One who is the Creator of all. It is only this vertical direction which can give full meaning to man's being and action, because it situates him in relation to his origin and his end. In this twofold direction, horizontal and vertical, man realizes himself fully as a spiritual being and as homo sapiens. But we see that development is not uniform and linear, and that progress is not always well ordered. This reveals the disorder which affects the human condition. The scientist who is conscious of this twofold development and takes it into account contributes to the restoration of harmony.

Those who engage in scientific and technological research admit as the premise of its progress, that the world is not a chaos but a "cosmos"--that is to say, that there exist order and natural laws which can be grasped and examined, and which, for this reason, have a certain affinity with the spirit. Einstein used to say: "What is eternally incomprehensible in the world is that it is comprehensible."[10] This intelligibility, attested to by the marvelous discoveries of science and technology, leads us, in the last analysis, to that transcendent and primordial Thought imprinted on all things.

Setup for live presentations of the slideshow

Before going to class

- Make sure Cybersky is on laptop.
- Update drive H with modified slideshow files.
- Run Windows update several times. It is a bandwidth hog in the classroom!

Before the slideshow begins

- Run Cybersky. Load cyberskymap in this folder.
- Run PowerPoint. Make sure slide 15 is animated and projects OK.
- Slide 15 backup: retro-motion gif.html
- Ptolemaic simulator.
- Homer Simpson demonstration.
- Check slide link to Ptolemaic orbital simulator.
- Check slide link to third law simulator.


  1. Taken from the Caltech Newman Center website. I have added three headings where the original text merely has roman numerals (I, II, III).
  2. AAS 71 (1979), pp. 1464-1465.
  3. Letter of 21 November 1613, in Edizione nazionale delle Opere di Galileo Galilei, dir. A. Favaro, edition of 1968, vol. V, p. 282.
  4. Letter to Christine de Lorraine, 1615, in Edizione nazionale delle Opere di Galileo Galilei, dir. A. Favaro, edition of 1968, vol. V, pp. 307-348.
  5. Letter to Fr A. Foscarini 12 April 1615, cf. Edizione nazionale delle Opere di Galileo Galilei, dir. A. Favaro, vol. XII, p. 172.
  6. Saint Augustine, Epistula 143, n. 7 PL 33, col. 588.
  7. Leonis XIII Pont. Max. Acta, vol. XIII (-1894), p. 361.
  8. Cf. Pontificia Academia Scientiarum Copernico, Galilei e la Chiesa. Fine della controversia (1820). Gli atti del Sant'Ufficio, a cura di W. Brandmuller e E. J. Griepl, Firenze, Olschki, 1992.
  9. Cf. Second Vatican Ecumenical Council, Pastoral Constitution "Gaudium et spes," n. 36, par. 2.
  10. In The Journal of the Franklin Institute, vol. 221, n. 3, March 1936.