Pope Benedict and the astronomers…

And then I wrote… On occasion I’ve quoted various posts I had up at my long-departed LiveJournal site. This one, from December, 2008, features not only such a post but the English version of an article that eventually was published in Italian in L’Osservatore Romano

At his weekly “Angelus” prayer and public address at noon on Sunday, Pope Benedict XVI had a nice call out to us astronomers. I haven’t seen an official English translation yet, but here’s my translation of his comments.

…This mystery of salvation has a cosmic dimension: Christ is the Sun which, with its light, “transfigures and illuminates the universe in waiting.” The setting of the feast of Christmas is tied to the winter solstice, when the days in the northern hemisphere begin to get longer. And incidentally, perhaps not everyone realizes that St. Peter’s Square is also a meridian: the great Obelisk throws its shadow along a line that runs across the pavement up to the fountain under this window, and at this season the shadow is the longest of the year. This reminds us of the function of astronomy in indicating the times of prayer: the Angleus, for example, is recited in the mornings, at noon, and in the evening; and with a meridian, which in times past served to indicate the true moment of noon, you can regulate your clocks.

At an audience when we were able to snag seats close to the Pope, I was able to take this view of St. Peter’s Square. Notice the Egyptian obelisk, topped by a cross, that works like a giant sundial.

And because today, in fact, the 21st of December, at this very hour, is the occurrence of the winter solstice, I would like to take this opportunity to salute all those who are taking part in the various initiatives of the International Year of Astronomy, 2009, honoring the 400th anniversary of the first telescopic observations by Galileo Galilei. Among my predecessors of venerated memory were those who were highly proficient in this science, such as Sylvester II who taught it, Gregory XIII to whom we owe our calendar, and Saint Pius X, who used to enjoy making sundials. If the heavens, which according to the beautiful words of the psalmist, “declare the glory of God” (Psalm 19, v. 2); so likewise the laws of nature, which over the years so many men and women of science have come to know ever better, are a great stimulus for a grateful contemplation of the works of The Lord.

Who were the people mentioned by Pope Benedict? And how do they fit into the history of the Church and the history of Astronomy?

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Pope Sylvester II’s scholarship was well ahead of his time, and in popular lore he was thought to be a wizard and magician! Born Gerbert d’Aurillac in France, he entered the monastery of St. Gerald of Aurillac in Spain, where he first came in contact with Arabic learning: especially the Arabic scholars of mathematics and astronomy in Cordoba (then under Arabic control). He later taught at the Cathedral School of Rheims, where he also served briefly as bishop. Later he was a tutor to the Holy Roman Emperor Otto III, and served as archbishop of Ravenna, before being elected Pope in 999. He served until his death in 1003.

An armillary sphere at the Galileo Museum in Florence; I once had a set of these (made of cardboard) for my astronomy undergrads to use, to see how stars and planets move across the sky over the seasons. They look complicated but once you understand them they’re easy to use!

He was influential in the development of the medieval university curriculum, but is probably most famous for introducing to Europe the use of Arabic numbers and the abacus. In the realm of astronomy, he introduced the armillary sphere, an early device used to demonstrate the positions of the Sun and planets during the year; notably for the history of astronomy and this 400th anniversary of Galileo’s telescope [in 2009], it is notable that Gerbert used sighting tubes (but without lenses) attached to his astrolabe to help align the instrument to the proper stars.

Pope Gregory XIII is, of course, most famous for his reform of the calendar. Astronomy, which involves studying the Sun, the Moon, and other heavenly bodies, was originally tied to making calendars. Knowing the days when the seasons change is important to any culture based on agriculture. But for the early Church, the first day of spring had another importance: it was used in calculating the date of Easter.

The Council of Nicea, in 325, wanted Easter to be modeled after the first Easter, which was the first Sunday after Passover. The Jewish feast of Passover was established in the Mosaic law as the first full Moon of Spring. Thus, in order to know when Easter would occur, one needed to be able to know exactly when Spring began. The Council of Nicea established a mathematical rule for calculating Easter, based on the civil calendar or Rome. 

However, when Julius Caesar introduced the calendar year of 365.25 days – exactly one leap year every four years – it was already known that this length was slightly too long. Compared to the actual motion of the seasons, this produced an error of one day in about 133 years. This small difference accumulated with the passage of time, however, and by the Middle Ages it was evident that the spring equinox no longer coincided with the official equinox of 21 March. In addition, the calculation of the date of Easter was also slipping away from the actual times intended by the Council of Nicea.

Church councils, particularly those held in Constance (1414-1418) and Trent (1545-1563), requested that the Popes work towards a finding a correction to the calendar. But no one had yet presented a reform that was valid and simple, unambiguous, and fully in accord with the Council of Nicea until Pietro Pitati, in a treatise published in Verona in 1560, and Aloysius (Luigi) Lilio (1510-1552), a professor of medicine at the University of Perugia, came up with a solution that was relatively easy to calculate. A Calendar Commission was named to prepare a description of the proposal, called the Compendium, and in 1577 it was sent to all the civil authorities of Europe, including universities and academies. After going through all the responses, the calendar commission then prepared the Papal Bull, Inter Gravissimas (1582), in which Pope Greogry XIII decreed the adoption of the new calendar.

Tower of the Winds Meridian. Photo by Fr. Manny Carreira SJ, adjunct of the Vatican Observatory and extraordinary photographer, who sadly died this past year. I was there when he added the beam of light via darkroom trickery; the only time I ever saw color photos printed in a darkroom!

The Julian rule for leap years was somewhat modified; an improved formula for the calculation of Easter was presented; and, for one time only, 10 days were eliminated to move the equinox back to March 21, bringing it back into accord with the official date in use since the Council of Nicea. This was the great merit of the Gregorian reform: with a minimum of adjustment and with clear rules, it preserved the intent of the Council. And because it relied on a Council that had sat before the schism between East and West, it was hoped that this reform could avoid further conflict with the Orthodox Church.

An important member of this commission for the reform of the calendar was Fr. Christoph Clavius SJ, a professor of mathematics at the Roman College, known for his publications in geometry, arithmetic, and astronomy. It is difficult to know for sure his full role in the commission, but it is enough to note that he was the one instructed by the Pope to describe and defend the new calendar, Explanatio Romani Calendarii, published in Rome in 1603.

Finally, the calendar was in line with the seasons. But how could they be sure? How did they actually determine the beginning of each season?

Seasons depend on the position of the sun in the sky. When the sun is high, and shines directly on the ground, the days are warm; when it only just creeps above the horizon, shining at an oblique angle, the days are colder. The easiest way to measure the actual seasons of the year is to measure the position of the sun. For that, one uses a “meridian.”

The idea of a meridian line is quite simple: one can measure the position of the sun in the sky by measuring the shadow cast by a “gnomon” – a pole of known length, like the obelisk in St. Peter’s Square – at exactly noon, the time of day when the sun is at its highest in the sky. Thus all one needs is a sufficiently well-measured gnomon, and a line oriented exactly north-south against which the shadow can be measured. The bigger the obelisk, the more precisely the shadow can be measured. When the sun is lowest in the sky – the winter solstice – our calendars mark as the first day of winter, and likewise the shortest noon shadow is found on the first day of summer, the summer solstice. Shadows of a length exactly halfway between these extremes are found on the equinoxes, the first days of spring and fall.

But another, more elegant way of measuring the position of the Sun is to find a dark room and put a hole in the south-facing wall. Then one can follow the spot of sunlight coming through the hole as it crosses the walls and floor of the room. Again, the bigger the room, the more precisely one can measure the position of the Sun.

In his book The Sun in the Church (Harvard University Press, 1999), the historian of science J. L. Heilbron (of Berkeley and Oxford Universities) notes that “the most convenient of such buildings [with dark interiors] were cathedrals; they came large and dark, and needed only a hole in the roof and on rod in the floor to serve as solar observatories.” In the 17th century, such meridian lines were constructed in cathedrals in Bologna, Florence, Paris, and Rome. They served not only to determine the days of the seasons, however. For one thing, the height of the Sun could be directly connected to the latitude of the church; these devices allowed surveyors to make the first accurate maps of Europe. But in addition, as Heilbron notes, the small holes in big rooms actually acted like pinhole lenses, creating images of the Sun that could be studied to see how the Sun’s size changed during the year, which was an indirect confirmation of the Keplerian system of elliptical orbits.

The meridian line in St. Peter’s Square was set up in 1817 by Mgr. Filippo Luigi Gilii. He was the one who, in 1797, re-established a “Specula Vaticana” in the Tower of the Winds. This line in the square was inspired no doubt by the meridian line put on the floor of the Tower of the Winds by its designer, Ignacio Danti, in 1582. Unfortunately, Gilii’s work did not continue after his death, and the Specola lay dormant until it was refounded by Pope Leo XIII in 1891.

Finally, we come to Pope Pius X, mentioned with great approval by Pope Benedict. Where Leo XIII re-established the Vatican Observatory, it was under Pope Pius X that it finally came into its own.

In November of 1904, Pope Pius X appointed the archbishop of Pisa, Pietro Maffi, to reorganize the Specola and search for a new director. After more than a year of very delicate negotiations, in February 1906 the decision was finally made: the new director would be the Jesuit priest Johan Hagen (born in Austria, but by then an American citizen and director of the Georgetown Observatory in Washington). 

At the suggestion of Monsignor Maffi, Pius X in 1906 very graciously put at the disposal of his astronomers his personal Villa (today the headquarters of the technical division of the Vatican Radio.) In the meridian room on the topmost floor of the little villa, the meridian telescope or the transit instrument for measuring sidereal time was placed. (Later on this instrument went out of use when a radio receiver for time signals to control the clocks was installed.) And the heliograph, a telescope that was the modern descendent of the meridian lines of times past, was placed on the terrace which today is the monastery of the cloistered nuns, Mater Ecclesiae [and the current residence of the Pope Emeritus!]

This gold medal was issued by Pope Pius X to honor the Vatican Observatory

On 17 November 1910, Pius X granted a special audience to the staff of the Specola to officially celebrate the new headquarters. The following year, as a commemoration of the eighth year of the pontificate of Pius X, the historical medal which was customarily coined each year in gold, silver and bronze and distributed to the members of the Papal Court and Ecclesiastical Dignitaries on the Feast of the Apostles Peter and Paul, had inscribed on one side the allegorical figure of Astronomy speaking the words: Ampliorem. in. Hortis. Vat. Mihi. Sedem. Adornavit (“He has prepared for me a more ample seat in the Vatican Gardens”). Today near the entrance to the chapel of the Vatican Radio in the little villa of Leo XIII one can still see a plaque recalling the new housing of the Specola.

Astronomy has long featured in Christian theology. Indeed, astronomy was one of the seven subjects of the medieval university that all scholars were expected to master before they could begin their studies of philosophy and theology.

Since the establishment of the modern Vatican Observatory, many Popes have had important things to say about the love the Church has for the study of the heavens. Much of the Church’s interest has had an overt apologetic slant, using science to support its philosophical ideas or using its support of science to refute those who would accuse the Church of opposing progress and fearing newly-discovered truths. 

But through the writings of the more recent Popes one begins to see developing a second realization: that, as the Psalmist knew, the Heavens themselves do proclaim the greatness of the Creator. The simple act of seeking truth in the natural sciences is in and of itself a religious act, independent of any apologetic agenda.

In refounding the modern Specola Vaticana, Pope Leo XIII in 1891 wrote that he was motivated “…that everyone might see clearly that the Church and her Pastors are not opposed to true and solid science… but that they embrace it, encourage it, and promote it.”

At the dedication of the new Specola headquarters in Castel Gandolfo in 1935, Pope Pius XI noted about the study of the sky, “… from no part of Creation does there arise a more eloquent or stronger invitation to prayer and to adoration.”

Pope Pius XII at the finder of our Schmidt telescope, which he paid for personally.

In his first address as Pope to the Pontifical Academy of Sciences, in 1939, Pope Pius XII eloquently stated, “Man ascends to God by climbing the ladder of the Universe.” Speaking to that same group in 1951, he noted that “the more true science advances, the more it discovers God, almost as though He were standing, vigilant and waiting, behind every door which science opens.”

Pope Pius XII’s most beautiful hymn to the glory of God visible through astronomy was his address to the General Assembly of the International Astronomical Union, held in Rome in 1952: “[In studying astronomy] the human spirit has surpassed all the limits of the body’s senses… and succeeded in seizing the immense Universe… What a happy and sublime encounter over the contemplation of the cosmos is that of the human spirit with the Spirit of the Creator!”

Pope John Paul II outlined his hopes for the relationship between science and religion in a letter to the director of the Vatican Observatory, George Coyne, in 1987 for publication with the proceedings of a conference held by the Pontifical Academy of Sciences on the occasion of the 300th anniversary of the Publication of Newton’s Principia. In it he wrote, “Both religion and science must preserve their autonomy and their distinctiveness. Religion is not founded on science nor is science an extension of religion. Each should possess its own principles, its pattern of procedures, its diversities of interpretation and its own conclusions… Science can purify religion from error and superstition; religion can purify science from idolatry and false absolutes.”

It is interesting to note how astronomy has historically connected different cultures, including cultures that were otherwise in conflict. See how Sylvester II looked with favor on the learning of the Arabs even as Christians and Arabs were warring over control of Spain; and how the adoption of the Gregorian reform of the calendar was motivated to a large degree in finding a solution that would be acceptable to the Eastern churches.