The Calendar (31 page)
*Nicholas of Cusa was also the author of two of the earliest scale maps of land areas, including attempts at the longitude and latitude of Europe. And he repeated the idea that the earth rotates, as suggested by Aristarchus, Aryabhata and others.
By the mid-1400s Europe was beginning to recover from the disastrous effects of the plague. Politics remained unsettled, with more campaigns and skirmishes. Byzantium fell in 1453, when the Turks breached the once invincible walls of Constantine’s ancient city using a newly arrived invention, the cannon.
As the fifteenth century waned the Church finally began to put its house in order, turning to serious debates over its role in a Europe that was quickly becoming more secular, and over an outdated medieval dogma being challenged by the new philosophy of the nascent Renaissance. Humanism, a movement that emphasized human welfare, values and dignity stood in opposition to the medieval emphasis on spiritualism, pageantry and the absolutism of the Church and papacy. At the same time, the awe felt by earlier generations of intellectuals for texts by Ptolemy, Aristotle, Euclid and other ancient masters, who previously had been the last word on science and philosophy, were beginning to give way to a new curiosity to use this knowledge as a basis to explore the world and to test the old ideas.
This was mirrored across the social spectrum as Europe’s economy revived between 1460 and 1500, and the Europeans began to expand their thinking and influence in the world. In commerce, European ships sought markets farther afield than ever, with explorers heading off in all directions. In 1470 Portuguese sailors discovered the Gold Coast while tracing the coast of Africa in newly invented caravels. In 1486 they found Angola. Six years later Ferdinand and Isabella of Spain bankrolled Christopher Columbus to trek across the Ocean Sea. That same year the Spanish defeated the last of the Arabs occupying Iberia.
In warfare, engineers invented or borrowed and improved upon new methods for making armour and battlements. They learned to use cannon and gunpowder, borrowed from the Turks and Arabs, who had borrowed them from the Chinese. At the same time tinkerers, scientists and entrepreneurs became both more common and more bold, in the spirit of Roger Bacon. The resulting inventions included the printing press, in about 1470, perhaps the most important creation of this era.
Among other things, the printing press allowed calendars to be mass-produced, bringing for the first time a standardized, easy-to-read rendering of days, weeks, months and holidays to people other than astronomers, ecclesiastics, kings and tax collectors. The earliest printed calendars used symbols so that illiterates could count the days, and employed illustrations of saints and pictures to represent feast days. In the calendar, a ‘Farmer’s Calendar’ printed in Zurich for the leap year 1544, the days are depicted with black triangles, except for Sunday, which is red. Other symbols list the passing progression of the zodiac; kalends, nones and ides; phases of the moon; and saints’ days. Easter is marked on 13 April with a cross.
Toward the end of the century, Leonardo da Vinci and other Renaissance inventors were at work. So were a new generation of artists--Leonardo once again, Michelangelo and Raphael, to name only three--who applied the science of the ancients to a new visual sense of perspective, beauty and symmetry in composition that blended reality and a classic Greek sensibility for perfection and beauty in paintings and sculptures.
Meanwhile the calendar at the turn of the sixteenth century had drifted away from the true seasons of the earth by over twelve days since Caesar, and over nine days since the Council of Nicaea. In 1500 no one could measure this error exactly, but every intellectual acquainted with mathematics, astronomy or theology knew about it. But how to fix it? And who decided?
These questions popped up at yet another Church-wide council begun at the height of the Renaissance in Italy. In 1512, Pope Julius II convened the Fifth Lateran Council (1512-1517) at the Lateran Palace in Rome, presided over by Julius and his successor, Leo X. Again, calendar reform was not a major agenda item in a meeting called to settle issues such as how much power the pope wielded over kings, and the raising of a Christian army to combat the Turks--whose troops after taking Byzantium had surged into Europe to seize Greece and much of the Balkans.
Calls for calendar reform had been increasing, however, even as the difficulties of how to accomplish this became more complicated. For instance, should the proper date for the equinox be based on the year of Caesar’s reform, the time of Christ, the Council of Nicaea or the creation of the world? What was the correct meridian on which to base the Easter calculation: Rome? Jerusalem? And what happens when the equinox falls at the end of the day in Rome and lands on the next day in the Holy Land?
A number of astronomers tried to deal with these questions by improving the charts measuring the equinoxes to make them more accurate. None got it right, though. Indeed, as the new charts circulated, the glaring errors in the calendar became more widely known, and a persistent source of embarrassment for the Church. The wide dissemination of printed calendars, such as the oft-copied ‘Shepherd’s Calendar’, first issued in 1493, added to a sense of urgency as more people than ever used the Church’s calendar for business, governing and personal planning.
In 1514 Pope Leo X invited the period’s greatest expert on the calendar, the Dutch astronomer, physician and bishop Paul of Middelburg (c. 1450-1533), to head up a commission on reforming the calendar. A few years earlier, in 1497, Paul had written a strident tract to the pope demanding he reform the calendar. In 1513 he wrote another impassioned tract opening with letters appealing to Leo, the Holy Roman Emperor Maximillian I, the College of Cardinals and the Lateran Council.
As head of Leo’s new commission, Paul started by criticizing past reformers, particularly those who wanted to drop days from the year to correct the calendar’s drift. He proposed fixing the calendar not by dropping days, but by changing the date of the vernal equinox to 10 March--which he wrongly estimated to be the proper date for his time. He suggested that in the future the equinox be allowed to drift through the calendar every 134 years--this (wrong) number coming from a set of astronomic charts considered highly accurate at the time: the Alfonsine Charts, completed in 1272 by astronomers at the Castilian court of King Alfonso X (1221-1284). Paul also proposed a slight rearrangement in the lunar calendar, including dropping a day every 304 years--and the naming of lunar months after the ancient Egyptian months, to avoid using Moslem or Jewish names. The proposals were to be considered in December 1514, with the changes to be made retroactive to 1 January, 1500, when the astrologically minded Paul noted a mean conjunction of the sun and moon had occurred along the Rome meridian at noon on the first day of this important jubilee year. Surely, said Paul, this was a sign from God concerning his desire to reform the calendar.
Leo X ordered letters dispatched in 1514 from the papal curia to all important Christian monarchs asking for opinions on the proposal from their astronomers and other experts. But only a few responded, in part because they were not given much time before the decisive meeting that December.
The British for one did not respond, though four letters from Leo X to Henry VIII survive in the British archives, all apparently unanswered. On 21 July 1514, Leo’s first letter describes the problem and laments that ‘Jews and heretics’ were laughing at the flawed Christian calendar. Leo asked Henry to send his best astronomer or theologian to Rome, or else a written version of their views on the calendar. A year later, on 1 June 1516, the pope’s second letter complains of the poor response to the first missive, which led to the cancellation of the planned December calendar conference. He asks Henry to respond in time for the next session of the council, scheduled for later that year. Two other letters that year repeat the pope’s request, which presumably went out also to other kings who failed to answer. This lack of interest apparently doomed Paul’s effort at reform.
One papal letter that was not ignored prompted a response from a young German-Polish astronomer then living in Frauenburg on the Baltic coast of Poland--listed as a respondent by Paul under the name Nicolaus Copernicus Warmiensis. Known as Mikolaj Kopernik in Poland, we know him by his Latinized pen name of Nicolaus Copernicus (1473-1543).
In his early forties when the papal letter arrived, Copernicus was a canon at Frauenburg’s cathedral in this often cold, stormy coastal town near the Gulf of Danzig in what was once East Prussia. A man with a long nose, wide eyes topped by arching eyebrows and a quiet demeanour--at least this is how he looks in his self-portrait--Copernicus had settled here after years of studying and teaching at universities in Krakow, Bologna and Padua, where he had earned degrees in law and medicine. In 1500 he had travelled to Rome for the jubilee. He also met and worked in these early years with a number of leading scholars, with whom he kept in contact for the rest of his life.
Around 1506, when Copernicus returned to the Frauenburg area, he began the astronomic studies and observations that would occupy the rest of his life. By 1512 he had written a short, unpublished manuscript outlining his early thinking about his planetary theories.* Two years later, in 1514, the pope’s missive arrived, an event alluded to by Copernicus himself in his 1543 dedication for
De revolutionibus
, in which he also tells us his response to the pope’s inquiry:
*This was finally published in 1530.
For not many years ago under Leo X when the Lateran council was considering the question of reforming the Ecclesiastical Calendar, no decision was reached, for the sole reason that the magnitude of the year and the months and the movements of the sun and moon had not yet been measured with sufficient accuracy. From that point on I gave attention to making more exact observations of these things and was encouraged to do so by that most distinguished man, Paul [of Middelburg], Lord Bishop of Fossombrone, who had been present at those deliberations.
After Paul’s commission sputtered out, the matter of the calendar was dropped again for over 60 years during yet another tremendous upheaval in the Church: the rise of Protestantism.
It was born during the final year of the Lateran Council, in 1517, when Martin Luther (1483-1546) tacked a document on the door of the cathedral at Wittenberg in Germany, complaining about the sale of indulgences by the Church. Luther at first did not intend to start a revolution, though he followed his act of defiance by preaching what amounted to a direct challenge against Rome. Insisting that the Bible should be the sole authority in the Church, and that salvation lay solely in faith--the first denying the pope’s authority and the second contradicting core Catholic doctrine--Luther touched a powerful nerve of discontent. In the 1520s he broke off with Rome to head up a movement that swept through Europe, attracting as many as half of all Christians in the West by the mid-century.
This in turn incited a backlash of conservatism in the Catholic Church, and an intense counter-reformative effort by the papacy and loyal Catholic monarchs to stamp out Protestantism. It included a new Inquisition launched by Pope Paul III in 1542 and the founding of the Jesuits in 1540, in part to create religious and theological stalwarts to argue against and fight the spread of Protestantism.
During these years of upheaval Copernicus worked quietly in Frauenburg: writing, taking astronomical observations, fulfilling his duties as a cathedral canon and tending to the occasional patient as a medical doctor of some renown.
Apparently he lived in rooms occupying a three-storey turret set in the cathedral’s thick surrounding walls, built in the fourteenth century as a defence against the pagan-leaning Slavs. Standing high above a small freshwater lagoon just off the Gulf of Danzig, the turret gave the canon an excellent view of the shoreline, the deep-blue Baltic, and the stars. He used relatively simple astronomical instruments--an astrolabe, an armillary sphere,* and various devices to measure the altitudes of celestial objects, including the sun. Copernicus later published some of these observations in
De revolutionibus.
He also jotted them over the years of quiet study in his tower rooms into the flyleaves and margins of books in his library. It was in these rooms that Copernicus worked and reworked the opus that became
De revolutionibus--
which included attempts to properly measure and calculate the length of the year.
*This was a concentric series of metal rings, each representing a planet’s orbit. Arranged in a sphere, they could be used to measure and calculate planetary movements.
Copernicus tried to fulfil his promise to Leo X by making his own fresh calculations based in part on his own sightings, and by using those made by Greek and Arab astronomers over the centuries. Summing up his findings and thoughts in
De revolutioiribus,
he begins a section called ‘On the Magnitude and Difference of the Solar Year’ by first explaining the difference between the two types of ‘years’ measured by astronomers.
First is the seasonal or tropical year, which is the time it takes for the seasons to cycle through and start again. This has been the ‘year’ we have referred to throughout this book and which is the basis for our season-based calendar year. It is determined by measuring the length of time between vernal equinoxes, when the planes of the equator and the sun’s ecliptic intersect in the spring. The other year is the ‘star’ year, also called the sidereal year, which measures the time it takes for the earth to revolve around the sun back to an exact starting point in space. The difference in these two ‘years’, we now know, is about twenty minutes, with the tropical year running faster each year than the sidereal year. Known as the precession of the equinoxes, the phenomenon of a slower tropical year was first discovered by Hipparchus in ancient Alexandria, though it took until Newton for astronomers to understand its cause: gravitational pulls and tugs from the sun and moon, against an earth that is not a perfect sphere--which cause the earth’s axis to wobble slightly.