1434: The Year a Chinese Fleet Sailed to Italy and Ignited the Renaissance. Gavin Menzies
the observer in Beijing and himself; or he can note the time it takes for Aldebaran to come into line with Polaris. If this is, say, six hours (one quarter of twenty-four hours), then his longitude difference from Beijing is 90 degrees (one quarter of 360°).
For the calculation to be accurate, both the observer in Nanjing and the navigator in the Indian Ocean must be looking due north at Polaris. If they wish to use the second method to calculate longitude, both must have precisely the same midnight. They do this as follows: First they use a vertical stick to mea sure the sun’s shadow. When the shadow is shortest, the sun is at its maximum height at midday and is due south. Both observers build a trench running due north-south, a trench that can be flooded to see the reflection of Polaris at night and emptied of water to mea sure the sun’s shadow at midday.
The sun’s shadow when at its shortest can be mea sured on the trench. To get the precise second, the shadow is sharpened by employing a pinhole camera atop a pole called a gnomon (described on the website). By using identical gnomons and a standardized pinhole camera, the observers in Nanjing and the Indian Ocean can each determine the same due south/north and the same instant when the sun is at its highest—that is, midday. Our experiments described on the 1434 website have shown that they can calculate this to within two seconds. They can now use a standardized clock to calculate midnight, twelve hours after midday. The 1434 website explains how this Chinese clock worked and how, in Zheng’s era, refinements were built to compensate for different temperatures and air pressures, which would otherwise have affected the number of drips coming out of the clock. Thus time was accurate to within two seconds.
Using the water clock, the observer in Nanjing and the observer in the Indian Ocean establish the same midnight. After sunset the trench is flooded and two poles are placed on either side of the trench; a line is suspended horizontally between the poles. Another line is hung vertically so the observer can see the reflection of the vertical string in the water of the trench in line with Polaris. At the instant of midnight, the navigator in the Indian Ocean looks at the star in line with Polaris reflected in the water, which is in line with the string. (In our example, on day 141 this star is Betelgeuse.) His tables for day 141 say that in Nanjing the star is Aldebaran. From that, he can determine his longitude. According to Robert Cribbs, the method is accurate to within two seconds, which amounts to a maximum error of three degrees in longitude, negligible for mapping the world.
This method requires the navigator to be on land. However, Professor Cribbs has also developed a method of determining longitude at sea by using the equation of time of the moon and the angular distance between the moon and a selected star. To deploy this method (see 1434 website) some calculus is required to establish the future position of the moon for the 1,461-day cycle. By 1280, Guo Shoujing had established a system very similar to calculus. The results appeared in his tables and calendar, which were adopted by the Ming in 1384. Consequently, they were available to Zheng He’s fleets, as were tables of declination of the sun.
Thanks to Tai Peng Wang, who brought the matter to my attention, and to the work of Xi Feilong, Yang Xi, and Tang Xiren, who have recently discovered the star maps of Zheng He’s voyages, we know which stars Zheng He’s fleet actually used to determine latitude and longitude on their passage to India. They sailed with the monsoon winds, starting across the Indian Ocean from the northwest tip of Sumatra at Pulau Rondo, now called Banda Atjeh, on October 10, 1432, determining latitude and longitude as follows: “Gauging the vertical positions of the given stars above the horizon in the east, west, north and south, they reached Sri Lanka.” Using Vega, Sagittarius, Gemini, and Poseidon, they arrived at Calicut (11° N, 76° E) on December 10. See the TPW paper “Zheng He’s delegation to the Papal Court at Florence” on the 1434 website.
Finally, how accurate were Zheng He’s navigators? Two answers produce the same result: their mea surement of declination at 22°2330'' (correct to within two miles) and the accuracy of the eye, which can be judged to within a quarter of a degree—the full moon appears large but its diameter is under half a degree (thirty miles).
It is my submission that Zheng He’s navigators were able to calculate latitude to within half a degree, or thirty miles, and longitude to within two seconds, or three degrees. When the fleets arrived in Venice and Florence, their methods of calculating latitude and longitude were transferred to Europeans. In due course, Columbus and Vespucci used them to reach the New World.
Notes Chapter 4
Extensive notes on www.gavinmenzies.net.
On January 19, 1431, the fleets left Nanjing, China. They in-variably sailed in January because of the free power provided by the monsoons, which to this day determine sailing patterns from China across the Indian Ocean to India and Africa.1
Monsoons are caused by the difference in temperature between the massive Himalayan plateau and the sea. In summer the Asian landmass becomes hotter than the ocean, sucking winds and water vapor off the sea. In April the southwest monsoon is heralded by westerly winds in the Indian Ocean. By May the southwest monsoon hits Indochina to reach its peak and constancy in July, by which time winds reach thirty knots in the South China Sea. By now India is flooded with monsoon rain. During September the temperature drops, and by November, when the Himalayas have become bitterly cold, air is drawn off the mountains by the warmer seas.
The northeast monsoon starts in late December, after which the wind gradually abates until April, when the cycle begins again. Ships sailing between China, India, and Africa took advantage of these monsoons to sail before the wind, returning on the next monsoon to their respective countries. They awaited the change of monsoon in some sheltered harbor. For example, in Southeast Asia, by the time Indian ships had arrived in the Malacca Strait with the southwest monsoon winds, Chinese junks had not yet departed their home ports. By the time the Chinese arrived, the Indian ships were gone. Hence the need for harbors around the Indian Ocean where goods could be stored from one monsoon season to the next. The Chinese and Arabs built entrepôt ports in Southeast Asia and around the Indian Ocean where goods were warehoused en route to their final destinations.
Monsoons were so predictable—and important—that they were incorporated into Arab calendars, which illustrated the highly synchronized system of regular shipping between Egypt, East Africa, India, and the Gulf. For example, one such calendar describes day 68 (March 16): “End of sailing of Indian ships from India to Aden: no-one ventures after this day.” (See research of Tai Peng Wang in notes).
Zheng He’s fleets took advantage of this Islamic navigational calendar, joining the regular schedule of shipping. As the historian Paul Lunde points out in “The Navigator Ahmad Ibn Majid,” on day 100 (April 15) the last fleet from India was scheduled to arrive in Aden. The departure from Egypt of the first ships of the convoy, owned by the Karimi merchants, was timed so the convoy’s arrival coincided with the Indians’. Four months later, on August 14 (day 220), the last ships from Egypt arrived in Aden. Six days later, ships from Sri Lanka and Coramandel set out on their voyage home. The last departure from Aden, powered by the monsoon, was on day 250 (September 13).
In Zheng He’s era, ocean trade was dominated by the Arabs and Chinese. The Chinese made goods that the rest of the world craved—principally, porcelain and silk. Chinese junks carried these valuable cargoes to Malacca, India, and Cairo. Malacca was virtually a Chinese colony. In Calicut, on the Malabar Coast of India, Chinese and Arab traders met in equal numbers.
Relations between the Chinese and Arabs had been friendly for centuries. In Cairo the Chinese were an established minority. Likewise, there was a substantial Arab quarter in the Chinese port of Quanzhou. Many Arab navigators and interpreters joined Zheng He’s fleets.
In every respect—numbers, ship construction, cargo capacity, range, defense, communications, supplies,