12

TOSCANELLI’S NEW ASTRONOMY

Relations between China and the West began long before 1434. The Catholic Encyclopedia presents a concise summary:

Some commentators have found China in this passage of Isaias (xlix, 12): “these from the land of Sinim.” Ptolomy divides Eastern Asia into the country of Sinae and Serice…with its chief city Sera. Strabo, Virgil, Horace, Pomponius Mela, Pliny, and Ammianus speak of the Seres, and they are mentioned by Florence among the nations which sent special embassies to Rome at the time of Augustus. The Chinese called the eastern part of the Roman Empire Ta Ts’in (Syria, Egypt, and Asia Minor), Fu-lin during the Middle Ages. The monk Cosmos had a correct idea of the position of China (sixth century). The Byzantine writer, Theophylactis Simocatta (seventh century) gave an account of China under the name Taugas. There is a Chinese record of a Roman Embassy in A.D. 166.1

Tai Peng Wang kindly provided Chinese descriptions of papal envoys.2 The ambassador who reached Florence in 1434 was by no means the first. According to Yu Lizi, Yuan China called the Papal States “the country of Farang” and the Papal States as a whole “Fulin” or “Farang.”3 The official Ming history states that diplomatic exchanges between the Papal States and Ming China began as early as 1371, when Hong Wu, Zhu Di’s father, assigned a foreigner from Fulin or Farang called Nei Kulan (Nicholas?) as the Chinese ambassador to the Papal States to inform the pope of the dynastic change in China. Later on, Hong Wu appointed a delegation led by Pula (Paul?), who brought gifts and tribute to Farang.

After 1371, diplomacy between China and Europe was a two-way street, with the Papal States and China exchanging ambassadors. Yan Congjian in volume 11 of the Shuyu Zhouzi Lu described the visit of the Chinese ambassador to the Papal States in the reign of Zhu Di.

Yan Congjian starts by commenting that Italy’s climate was rather cold, then continues:

Unlike China, the houses here are made of cement but without roof tiles. The people make wine with grapes. Their musical instruments include clarinet, violin, drum and so on. The King [the pope] wears red and yellow shirts. He wraps his head with golden thread woven silk. In March every year the Pope will go to the church to perform his Easter services. As a rule he will be sitting on a red-coloured carrier carried by men to the church. All his prominent ministers [cardinals] dress like the King [the pope] either in green or beige or pink or dark purple and wrap their heads. They ride horses when going out…. Minor offences are usually punished up to two hundred times. Capital offences, however, are punishable with death usually drowning the offenders in the sea. These [Papal] states are peace-loving. As is often the case when a minor dispute or rivalry arose, the disputing states only waged a war of words in the exchange of diplomatic despatches. But if there were a serious conflict erupted, they were prepared to go as far as war. They made gold and silver coinage as their monetary currencies. But unlike the Chinese coinage, which can be stringed as a unit to count, there are no holes in their coinage for such purpose. On the back of the money is the face of the king [the pope] bearing his title and name. The law forbids any monetary coinage made privately. The land of Fulin produces gold, silver, pearls, western cloth, horses, camels, olives, dates and grapes.4

Yan Congjian’s descriptions are reflected in a Pinturicchio fresco of Aeneas Sylvius Piccolomini, the future Pope Pius II.5 Born in 1405 to a distinguished Sienese family, Aeneas was educated at the universities of Siena and Florence. Between 1431 and 1445, he opposed Eugenius IV. In 1445 he suddenly changed sides. He took orders in 1456, became a bishop in 1450 and a cardinal in 1456, and was named pope upon the death of Calixtus III in 1458.

Pinturicchio paints Pius II being carried on a throne into the Basilica of Saint John Lateran, Rome (where Pisanello was also sketching). The pope wears a red-lined cloak, and his hat is wrapped with golden thread. Before him are his cardinals in green, beige, pink, and blue, their heads covered in white tricorn hats. (See colour insert 3.)

A Ming dynasty book, Profiles of Foreign Countries, attests to continued diplomatic exchanges between Ming China and the Catholic Church in Italy.6 This Chinese primary source includes “Lumi” among the foreign nations that paid China an official visit and rendered tribute during Zhu Di’s reign (1403–1424). Lumi is Rome. The name is derived from Lumei, which is what the Song author Zhao Ruqua (1170–1228) called Rome. In his 1225 book Zhufan Zhi (Description of various barbarians), Zhao wrote that “all men are wearing turbans as their headwear. In winter they will be wearing coloured fur or leather coats to keep warm. One of their staple foods is the dish of spaghetti with a sauce of meat. They too have silver and gold currencies used as money. There are forty thousand weaver households in the country living on weaving brocades.”7Clearly, the Chinese were not strangers to the Papal States.

Now for some detective work to see what Pope Eugenius IV, Toscanelli, and his friends Regiomontanus, Alberti, and Nicholas of Cusa learned from Zheng He’s delegate besides obtaining world maps.

After the Chinese ambassador had presented his power of attorney (represented by the brass medallion described in chapter 2) to Eugenius IV, he would have formally presented the Xuan De astronomical calendar, which would have established the precise date of the inauguration of the emperor—“when everything would start anew.”

Zheng He and the fleet had spent two years preparing to leave China and nearly three years reaching Florence. By the time they arrived in 1434 at the court of Eugenius IV, it had been nine years since the emperor’s inauguration. Foreign rulers also had to know the date of the emperor’s birth, which was calculated from conception. In the case of Zhu Zhanji, this would have been 1398. So the calendar had to go back thirty-six years. To certify that the emperor had continued to hold the mandate of heaven during that period, the calendar would also need to show that the prediction of solar and lunar eclipses, comets, positions of planets and stars and untoward lunar conjunctions (the moon with Mercury) had been accurate throughout those thirty-six years—thousands of pieces of astronomical data had to be included.

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One of Pisanello’s sketches showing a Mongol face.

However, the calendar also had to predict the future. This required that it contain astronomical calculations of the accurate positions of sun and moon, tables of the five planets, the positions of stars and comets, dates of solstices and equinoxes, and a method of adapting those dates and times to the latitude of Florence. We know from the Yuan Shi-lu, the official history of Yuan dynasty, that this astronomical data was included in the Shoushi calendar, and one can see a copy of the 1408 calendar in the Pepys Museum in Cambridge, England. Two pages are shown on our 1434 website.

When the Chinese visited Florence in 1434, Toscanelli was in his prime, thirty-seven years old. Since graduating from university twenty years earlier, he had worked with Brunelleschi, a mathematical genius, and other leading intellectuals of the day. In particular, Toscanelli and Brunelleschi had, for the previous thirteen years, been collaborating on the complex spherical trigonometry required to build Florence’s great dome over Santa Maria del Fiore. Toscanelli thus had ample opportunity to observe and accurately map the heavens in detail before the Chinese visit, but neither he nor any other of his circle did so. Toscanelli was a secretive bachelor who lived with his parents until they died, after which he lived with his brother’s family. Although he never cited a particular influence or source for the prodigious mathematical and astronomical skills he displayed after 1434, he did bequeath a considerable collection of books, research papers, astronomical instruments, and world maps to his monastery. All but one of these have disappeared. Aside from that one remaining record—a manuscript housed at the Biblioteca Nazionale Centrale in Florence—we are left primarily with admiring references to him in letters among his friends. But we do know a bit about his actions. Did he behave differently after 1434? If so, how?

Jane Jervis, in “Toscanelli’s Cometary Observations: Some New Evidence”8 examined Toscanelli’s surviving manuscript, a collection of folios. She compared the writing on the folios with that on the letters from Toscanelli to Columbus and Canon Martins and concluded that all but three of the folios were written by Toscanelli. Jervis then compared Toscanelli’s study of two comets—one in 1433, before the Chinese visit, and another in 1456, after the visit. Folios 246 and 248 describe the 1433 comet; folios 246, 252, and 257 describe the 1456 comet.

The first comet pass was on Sunday, October 4, 1433, in the first hour of the night. Toscanelli’s observations consist of a freehand drawing. He did not align the comet’s positions with any stars or planets. No times are listed, nor are right ascensions or declinations of the stars or comets.

This is in stark contrast with Toscanelli’s treatment, twenty-three years later, of the 1456 comet. Folios 246r and v, 252, and 257 contain a wealth of evidence. For the 1456 comet, he uses a Jacob’s staff to give the comet’s altitude (declination) and longitude (right ascension) to within ten minutes of arc.9 Times are now given, as are the declination and right ascensions of the stars (Chinese methods). To achieve this radical improvement in technique, Toscanelli must have had a clock, an accurate measuring device, astronomical tables, and an instrument to show the position of the comet relative to stars and planets.

If true, James Beck’s deduction that Alberti was assisted by Toscanelli in drawing the precise positions of stars, moon, and sun at noon on July 6, 1439 on the dome in the Sacristy of San Lorenzo similarly suggests a great leap in Toscanelli’s scientific capabilities. For many years prior to 1434, Toscanelli had the opportunity to use the dome of Santa Maria del Fiore for astronomical observations. Yet he never did.

By 1475, Toscanelli had adopted a Chinese type of camera obscura, a slit of light and a bronzina (bronze casting), which he inserted in the lantern of the dome of the Florence cathedral. The pinhole camera has several advantages when measuring objects illuminated by the sun. The edges of the circle receive less exposure than the center. Since the focal length of an object’s edges is greater than that of its center, the center is “zoomed in.” Shadows cast by the sun, or vision of the sun itself, thus appear sharper, thinner, and clearer.

By the early Ming dynasty, Zheng He’s astronomers had refined this camera obscura and used it in conjunction with an improved gnomon to enable measurement of the middle of the shadow of the sun within one-hundredth of an inch. Toscanelli used the Chinese method in a most ingenious way, adapting the dome of Santa Maria de Fiore as a solar observatory.

Between May 20 and July 20 the sun at noon shines through the windows of the lantern on the top of the dome. Toscanelli had the lantern windows covered in fabric with a small slit to allow sunlight through at noon. After passing through the slit, the sunlight became a beam. A bronzina was positioned so that the beam landed on it, and in the center of the bronzina was a hole. As the beam struck the bronzina, the hole would channel it down to the marble floor three hundred feet below. On the floor, Toscanelli drew a north-south meridian line, with incisions to note the position of the sun at the summer solstice. Regiomontanus said that using the meridian line, Toscanelli could measure the sun’s altitude (and hence declination) to within two seconds of arc.

In 1754 a Sicilian Jesuit priest, Leonardo Ximénes, experimented with Toscanelli’s instrument. Ximenes compared data from the solstices in Toscanelli’s era to his own measurements of 1756. He found that Toscanelli was able to determine not only the height of the sun at the summer solstice but also the change in height over the years, which resulted from the change in the shape of the earth’s elliptical passage around the sun.

The minute differences in the sun’s altitude from one year to another preoccupied Regiomontanus as well, as he said:

Most astronomers considered the maximum declination of the sun in our days is 24 degrees and 2 minutes but my teacher Peurbach and I have ascertained with instruments that it is 23 degrees and 28 minutes as I have often heard Master Paolo the Florentine [Toscanelli] and Battista Alberti say that by diligent observation they found 23 degrees 30 minutes, the figure I have decided to register in our table.10

What is so important to Toscanelli and Regiomontanus about the precise declination of the sun? When I first joined the Royal Navy in 1953, sailors trooped to the Far East by passenger liner rather than by aircraft. Each day at noon, the ship’s navigator, captain, and officer of the watch would march resplendent in white uniforms on to the open bridge and stand side by side looking at the sun. Shortly before noon they would start taking the altitude of the sun with their sextants. Just before it was at its highest they would cry, “Now! now! now!” Upon the final Now! they would read out the sun’s maximum altitude taken from their sextants. They would then declare the distance traveled from the previous noon. The lucky sweepstakes winner would be announced over the ship’s address system and would be expected to buy drinks all around.

Distance from one day to the next was calculated by the difference in the ship’s latitude. There is a simple formula: Latitude equals 90—sun’s max altitude ± declination. Declination tables of the sun are issued for each day of the year, so with the sun’s altitude, the navigator can determine latitude. It’s that simple.

However, this was not what Regiomontanus, Toscanelli, and Alberti were after. A few miles’ difference (between 23°28' and 23°30') was in itself completely unimportant to Toscanelli. Instead, he, Alberti, and Regiomontanus were interested in the change in the sun’s declination. A copy of that change can be seen in Needham’s graph, by kind permission of Cambridge University Press. It shows the change in the sun’s declination from 2000 B.C. to the present day, determined by Greek and Chinese astronomers for the earlier measurements and by European astronomers for the later ones, ending with Cassini.

From this graph, we can see that Toscanelli’s figure—23°30'—was recorded by the great Islamic astronomer Ulugh Begh also used 23°30' in his massive study completed in Samarkand in 1421—some fifty years before Toscanelli’s measurement. (Regiomontanus’s figure of 23°28' was determined by Cassini two hundred years after Toscanelli, so it would have been inaccurate had Regiomontanus used it.)

This is not some mathematical quibble. If the sun circled the earth, there would be no change in declination. A recognition of the change—the flatter the earth’s trajectory, the smaller the declination—is tantamount to recognition that the earth revolves around the sun in an ellipse.

Their obsession with measuring the change in declination is evidence that Toscanelli, Alberti, and Regiomontanus understood that Aristotle and Ptolomy, who believed the sun revolved in a circle around the earth, were wrong. Consequently, Europeans who followed Toscanelli and Regiomontanus were basing their astronomy on a Chinese, rather than a Greek, foundation. This foundation also enabled Regiomontanus to produce tables to determine latitude in different parts of the world, which he published in 1474. Columbus and Vespucci used them, as described in chapter 21.

The exercises at Santa Maria del Fiore could be duplicated to observe the movement of the moon and produce equations of time of the moon. These, in turn, could be used in combination with the positions of stars to determine longitude (see chapter 4). Regiomontanus produced such tables, and Columbus and Vespucci used them to calculate longitude in the New World. Dias used them to determine the latitude of the Cape of Good Hope.

Each of the instruments Toscanelli used in his observations at Santa Maria del Fiore—camera obscura, gnomon, and clock—was used by Zheng He’s navigators, as were the instruments Toscanelli used to determine the passage of the 1456 comet—Jacob’s staff, clock, and torquetum. All of Toscanelli’s discoveries—declination of the sun, obliquity of the ecliptic, passage of comets, ephemeris tables of the stars and planets—were contained in the 1408 Shoushi astronomical calendar presented to the pope. They were copied and published in Europe by Regiomontanus in 1474.

In his letter to Columbus, Toscanelli said he had received “the most copious and good and true information from distinguished men of great learning who have come here in the Court of Rome [Florence] from the said parts [China].” In his letter to Canon Martins, Toscanelli described his long conversation with the ambassador from China who had visited the pope, and he cited the “many scholars, philosophers, astronomers and other men skilled in the natural sciences” who then governed China.

In my submission, Toscanelli must have obtained his copious new knowledge of astronomy from the “distinguished men of great learning” who had arrived in Florence from China.

Res ipsa loquitur! “The thing speaks for itself.”

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