Honors in Rome - Summer 2008
Time is a fickle and fleeting idea, but it is also one that often drives the decisions of important institutions. In this particular instance, time was of the utmost significance to the Catholic Church. The Church wanted to be sure that they celebrated Easter on the correct date, which was very difficult because of the discrepancies that manifested over centuries of compounding incorrect calculations. The focus here is on achieving the beginning of the end of this problem, which finally occurs by the building of a scientific instrument within a pre-existing church. This apparatus is known as a meridiana line, which is used to determine local noon, and if made correctly, it is a more accurate time indicator than clocks. Thus, the Church commissioned one to be built in
The Baths of Diocletian, completed in AD 306 under the reign of Emperor Diocletian, had been sitting in Rome for centuries when it was decided to use them as the site for Santa Maria degli Angeli e dei Martiri. This conversion occurred in 1541, when a Sicilian priest, Antonio del Duca, had a vision that would revive the reverence of the Baths as an important
Another attractive feature of using the Baths as the site of the church was the fact that they were pagan in origin. The construction of
The Sicilian priest also had a plan for how the church should be built. He wanted the great hall of the Baths to be the nave of the church, with a northwest entrance which would open onto the Via Pia. This would have placed the alter on the opposite, southeast end (Ackerman 125). Del Duca’s plan was originally adopted in 1550, and work began on incorporating his vision into the design of the church. However, in the midst of planning, the Carthusians gained control of
Michelangelo’s plan was the complete opposite of del Duca’s. His overarching plan was to preserve the original facades and structure of the Baths of Diocletian. Due to this technique, he chose to place the entrance of the church in the rotunda and construct the alter across the great hall in the passage to the frigidarium. This, according to Michelangelo, was the logical place to build the church because the frigidarium was the only room that was large enough and sufficiently devoid of ruins to erect the cloister with the minimum destruction of the site. This plan was well-suited to the Carthusians because it isolated the chancel from the main hall, which would contain the public alters, and thus provided them with the maximum amount of privacy. Michelangelo also was able to build a choir that was isolated from the church because he pursued minimum demolition of existing features of the Baths (Ackerman 126). Michelangelo’s design of the church also allowed the church to be constructed with the maximum amount of symmetry. This architectural practice was a hallmark of Renaissance architecture and thus held more public appeal. In fact, he managed to make every aspect of the church symmetric with respect to the line that connected the main alter and the entrance. Further, he designed the church in the shape of a Greek cross, which bespoke of strong Catholic influence, which the papacy endorsed in its Counter-Reformative struggle against the Protestants.
For many centuries before the building of
Unfortunately, reconciling these two calendrical systems with each other to calculate the date of the vernal equinox was very difficult and given to inconsistencies and miscalculations. The Church was very unhappy with the rather gross inconsistencies surrounding the celebration of Easter, because it meant that not only was the correct day not being observed, but also that the power of the Church was not absolute. Their next move was to adopt the Julian solar year of 365.25 days, instead of the odd amalgamation of lunar and solar calendrical systems that was currently used. This caused its own difficulties, as it was tricky to calculate average values of successive vernal equinoxes as well as the average length of a lunar cycle, and so determining when the correct observance of Easter should occur was still a problem. These values were first calculated in the sixth century, and went largely uncontested until the twelfth century, when it was noticed that the vernal equinoxes were not coinciding with their predicted dates.
After this, many different theories attempted to align the calendar into a unified system; all of these agreed that the major issue was the fractional day that the solar year left (365.2422 days). That fraction of a day was always rounded, which led to a compensatory cycle of extra days every few hundred years. However, depending on whether it was rounded up by 0.008 or 0.0075 to one quarter of a day varied both what year was to have days added to it as well as how many days were to be added. Several systems were constructed to deal with this. Unfortunately, by the end of all the mathematics, every system ended up with errors due to rounding or miscalculation. Added on to this difficulty was the emergence of varying church calendars, such as how
The papacy did not like this idea at all, as it would detract from the correct observance of this very sacred holiday. However, it did decide that the vernal equinox should be fixed in the calendar. Previously, the equinox had been set as March 25 on the Julian calendar, but by this time that day was completely incorrect in relation to the actual equinox. Fortunately, in 1568, Pope Gregory XIII decided that the entire calendar should once again be completely reworked. This time the papacy was slightly luckier, as Luigi Giglio, a doctor from southern
Unfortunately, this calendar was not universally accepted, and by 1660,
To reconcile this, a meridiana, which is a very accurate time-measuring instrument, was necessary. The Church found a man who could bring about this change in Francesco Bianchini, and an ideal site for his measuring instrument in the
When Francesco graduated from the university, he began to pursue an ecclesiastical life. His first step was to befriend Cardinal Pietro Ottoboni, who put Bianchini in charge of his personal library, which gave him another opportunity to further his education. This patronage also helped him join Ciampini’s academy, which was a discussion group of “laymen and ecclesiastical scholars” that discussed “contemporary polite subjects” held in Ottoboni’s palace (Heilbron 150). Through this, Bianchini became acquainted with the most influential scientists of the time, including Campini, Cassini, and Leibniz.
Bianchini lucked out again when Ottoboni was named Pope Alexander VIII in 1689. The new pope showered him with gifts and positions, which he gladly accepted. The next two successors to the head of the Catholic Church, Innocent XII and Clement XI, were just as generous with their patronage. Further, Pope Clement XI was the best friend of Ottoboni, so Bianchini had even further access to the highest echelons of Catholic power. Thus, when Clement XI decreed that the calendrical problems should be absolutely resolved, Francesco was the obvious choice for the scientist to lead this latest attempt, and was given the position of secretary to the new commission of the calendar, as well as chosen to build the meridiana.
Next, the church in which the meridiana was to be placed had to be selected. A meridiana already existed in
The Placement of the two Meridianae
Many meridiane had been made in churches all over
Bianchini was soon satisfied with the placement of his line, and began preparations for its actual construction. He used the same technique as Cassini had tried in San Petronio, as it was remarkably accurate. The first step of this method was to dig a ditch where the line was to be placed and insert a wooden canal into it, which was then filled with water to use as a level. The hole in the wall of the church was then checked to see if it was parallel to the ground, and then the diameter of this opening was made to be one-thousandth of its distance above the ground. The other aspect of these measurements was making sure that the meridiana was correctly aligned to the hole and passed directly under it. This was achieved by hanging a weighted string from the hole, and then damping its motion in water to correct for any disturbing motions. (Heilbron 90-91) The final step was then to pour metal into the canal, making sure it was of uniform height and width to maintain the maximum amount of accuracy.
Bianchini actually afforded
Precessing Star Tracks
Both the northern and the southern meridiane were rather extravagantly decorated. The hole for the southern meridiana had been surrounded by Pope Clement XI’s coat of arms, as a showing of papal power as well as a ploy by Bianchini for more papal favor. This coat of arms actually opened, and the larger hole left in the wall allowed for observation of both the sun and the moon for the times surrounding its highest ascent. Surrounding both lines, brass stars had been imbedded in the ground to mark the diurnal motions of various stars that had been observed for centuries (Heilbron 158). By each marker, the name of the star it tracks is recorded, as well as that star’s right ascension, or celestial longitude.
The Transit of the Sun across the Meridiana
By October 6, 1702, Bianchini’s meridiane was close to completion, and Pope Clement XI came to view the sun’s transit across the southern meridiana. Many others also witnessed this event, and it was noted that Bianchini had “[constructed] a line that contemporary connoisseurs rated the most beautiful, ornate, and versatile of all meridiane” (Heilbron 153). This instrument allowed Bianchini to calculate the latitude of
Ackerman, James S. The Architecture of Michelangelo.
Heilbron, J. L. The Sun in the Church: Cathedrals as Solar Observatories.
Sestieri, Anna Maria Bietti, et al. Museo Nationale Romano: The Baths of Diocletian.