73: Crisis of Accuracy: Johann Schreck and the 1629 Solar Eclipse

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Johann Schreck to John Faber, Letter dated 1622
“Mr. Galileo de' Galilei could do nothing more appreciated or acceptable to the mission of China than to send his theory of the sun and moon without the tables, since the Chinese cagerly expect of us that we give them a calculation of eclipses more exact than what they have. Tycho has something good, but at times he errs by a quarter of an hour. If what I ask could be had through the intercession of Prince Cesi, he would become with you and Galileo the third benefactor of the mission of China."


In May 1610, as Matteo Ricci lay dying in Beijing, he summoned his successor, Sabatino de Ursis, to his bedside with an urgent warning that would prove prophetic for the next two decades of Jesuit missionary work in China. "The door is still only ajar," Ricci whispered, his voice weakened by years of navigating the treacherous currents of Chinese imperial politics. "One false step, and it will slam shut forever." These words, spoken by the architect of the Jesuit accommodation strategy, captured the fragile balance between opportunity and danger that would shape the mission's future. 

Much of the Jesuit success in China was due to Ricci’s character and temperament, but his death occurred during a time of severe crisis in China that would test his methods to the limit. Which of Ricci’s Jesuit successors would have the skill and strength to navigate these dangerous political waters?

The European scientific revolution and Chinese institutional needs created a unique moment. Weeks before Ricci's death, Galileo revealed his telescopic discoveries that shook European astronomy. Meanwhile, Chinese imperial astronomers faced accuracy issues with their calendar system, resulting in embarrassing eclipse prediction failures that threatened the imperial legitimacy. 

The Jesuits faced a turbulent political landscape marked by swings between acceptance and persecution. The biggest challenge was Shen Que's persecution campaign, which started in 1615. Shen Que (Shan Kay), the minister of rites in Nanking and an orthodox Confucian official, symbolized traditional resistance to foreign ideas. He launched the first organized attack on Christianity in China, using fears of foreign infiltration and religious innovation to target the mission's growing influence. His memorials accused the Jesuits of secret meetings, foreign connections, and revolutionary plots, resulting in an imperial edict in 1617 to expel all missionaries.

The persecution exposed both the vulnerability and resilience of the Jesuit presence. While the expulsion edict forced most missionaries to flee Beijing publicly, fourteen Jesuits stayed hidden throughout China, taking refuge in the homes of loyal Christian converts. This underground survival strategy showed the practical limits of imperial control and the vital importance of the scholarly networks Ricci had built. The flexible enforcement of imperial orders by sympathetic local officials enabled the mission to endure its darkest times while continuing scientific work that would prove vital for its eventual recovery.

The terror worsened during the rule of the eunuch Wei Zhongxian (Way Jhong Shyen) from 1623 to 1627. His removal of reform advocates also stripped away many key protectors of the Jesuits from the government. The execution of over 330 officials highlighted the deadly risks of political opposition. Even dedicated Chinese Christians became silent out of fear, secretly constructing churches and avoiding public support for Western ideas.

The Chongzhen (Chung jen) restoration starting in 1627 opened new doors but also introduced fresh uncertainties. The sixteen-year-old emperor's unfinished reforms allowed corrupt officials to stay in power while giving capable figures like Xu Guangqi a chance to emerge once again. Xu's appointment as senior vice-president of the Board of Rites in 1628 was crucial for the calendar reform effort, but the political base remained weak. The emperor's youth and inexperience, along with increasing external threats from Manchu invasions and internal rebellions, created a situation where scientific expertise could be either a valuable asset or a risky liability, depending on its practical use.

The transmission of advanced European science to China was significantly sped up due to the efforts of  Johann Schreck. He acted as a direct link between Galileo's discoveries and the Far East mission. Born near Sigmaringen in 1576, Schreck studied medicine at the University of Padua from 1603 to 1604 and developed a close friendship with Galileo. This personal connection was historically important because it directly connected Galileo with the Chinese imperial court through a network of scholars and religious groups.

On May 3, 1611, just days after Galileo's admission to the prestigious Accademia dei Lincei on April 25, Schreck became the seventh member of this scientific society dedicated to advancing natural philosophy through empirical study. Prince Federico Cesi's academy provided a platform for intellectual exchange that transcended traditional academic boundaries, where Schreck witnessed Galileo's telescope demonstrations at Villa Malvasia and grasped the revolutionary significance of telescopic astronomy. However, even as he took part in these pioneering scientific discussions, Schreck had already decided to leave his secular academic career for the Jesuit mission to China.

His November 1611 entry into the Jesuit novitiate shocked Galileo and Prince Cesi, who saw it as a loss to the "Company of the Lincei" and a gain to the "Company of Jesus." Kaspar Schoppe's bitter 1615 letter accused Schreck of joining the missionaries out of curiosity and desire to explore exotic things, implying scientific rather than religious motives. Schreck's later writings focus on scientific topics, with few religious references, and his botanical and medical research demonstrates that the mission provided access to Asian knowledge previously unavailable to Europeans.

  Collaborating with Belgian Jesuit Nicolas Trigault, who had returned from China with urgent requests for scientific expertise, Schreck used his extensive European networks to gather over 7,000 scientific works for the planned Beijing library. This great library assembly campaign of 1615-1618 went well beyond simple book collection; it was a deliberate act of knowledge curation aimed at establishing European scientific leadership across multiple fields. The 331 books purchased from the Plantin Moretus bookshop in Antwerp, carefully recorded in surviving documents, included innovative works in astronomy, mathematics, mechanical engineering, medicine, and natural philosophy.

The voyage of the 'Bom Jesus' in 1618 from Lisbon carried 22 missionaries, including top scientist-priests, but an epidemic killed 45 of 636 passengers, including five missionaries. Schreck's medical training proved vital on this perilous journey, as he served as the ship's doctor while battling a fever himself. His survival, along with that of only seven others highlighted the risks and dedication essential for this scientific exchange.

From 1619 to 1621, Schreck's remained imprisoned in Macao due to renewed Chinese persecution of Christians.  This situation forced him to work under harsh conditions. Despite this, he studied Chinese medicine and began botanical research, leading to his lost masterwork, the "Plinius Indicus." His humorous descriptions of struggling with Chinese characters—flying "in and out like doves from a dovecote"—highlight the linguistic challenges faced by Europeans in China. At the same time, his development of technical vocabulary, which remains in modern Chinese, shows his lasting influence.

In 1616, Schreck had received a gift of a telescope from Cardinal Federico Borromeo. The Jesuit brought it with him, and this telescope was probably the first of its kind to reach China, symbolizing a connection between Galileo's discoveries and Chinese scientific progress. 

However, Schreck's persistent eight-year effort to obtain Galileo's specific astronomical data highlights the limits of personal contacts amid institutional conflicts. Starting in 1616 with appeals to Prince Cesi and continuing until 1624 with increasingly urgent requests, Schreck sought to obtain Galileo's eclipse prediction techniques, which were vital for calendar reform and perhaps the survival of the Jesuit order in China. His April 1616 letter expressed frustration over the Holy Office's ban on Galileo and worry about losing important astronomical calculations needed for Chinese calendar work.

The reasoning was compelling. Calendar reform was the "sole title" the Jesuits could rely on to avoid expulsion from the empire. But Galileo's conflicts with Jesuits over sunspots and comets, plus the 1616 Copernican condemnation, made him reluctant to help. His final refusal on May 10, 1624, with "non ho nulla" (I have nothing), marked a key failure that led Schreck to seek other sources.

The alternative was Johannes Kepler. The contrast between Kepler's response and Galileo’s highlights how confessional differences could be overcome through scientific solidarity. When Schreck's 1623 appeal to colleagues finally reached Kepler in November 1627—four years after it was sent—the Protestant astronomer responded promptly and generously, providing detailed explanations and his new Rudolphine Tables. 

Europe's scientific knowledge in China needed to demonstrate not just theory but practical proof of usefulness, which Schreck tested through collaboration with Chinese scholars. Schreck's partnership with scholar Wang Zheng (Wahng Jong) on "The Wonderful Machines of the Far West" represents the height of early Sino-European scientific cooperation. When Zheng arrived in Beijing in 1626 and sought access to European technical works, Schreck possessed some of the most advanced mechanical engineering texts of the Renaissance, including Ubaldi dal Monte's "Mechanicorum Liber" (1577), Simon Stevin's "Fundamentals of Statics" (1586), and the beautifully illustrated machine works of Agostino Ramelli and Jacques Besson. Instead of doing direct translation, which would have taken years, the two scholars created a completely new synthesis that combined European theoretical foundations with Chinese practical concerns.

Schreck explained principles such as gravity, buoyancy, and lever mechanics orally, focusing on fundamental concepts, while Zheng wrote explanations that emphasized simplicity and clarity. This prioritized practical understanding over academic thoroughness, making complex engineering concepts accessible to Chinese artisans and officials. Zheng's copying of European illustrations, despite some technical errors, successfully adapted visual knowledge to Chinese traditions.

The foundation covered mass, equilibrium, and force for all mechanical work. Simple machines focused on levers, balances, and winches, which Chinese artisans could use immediately. The last part detailed 55 complex devices, including mills, pumps, lifting gear, and firefighting tools, tailored for Chinese infrastructure. Crucially, the integration of  measurement and calculation principles supplied the mathematical tools for mechanical innovation.

The introduction of the telescope highlighted another key aspect of Schreck's efforts to disseminate scientific knowledge. Johann Adam Schall von Bell's 1626 treatise provided the first systematic Chinese account of how to build and operate telescopes. Meanwhile, Schreck's 1628 writings provided detailed descriptions of discoveries made using Galileo's telescope, including Venus phases, sunspots, and observations of the Milky Way. The decision to refer to Galileo anonymously as a "celebrated mathematician of the Occident" appears to be a strategic move to present these findings as European achievements rather than individual inventions, likely avoiding controversy associated with Galileo's 1616 censure.

The practical implementation was highly successful. The 1629 imperial order for telescopes showed China's commitment to adopting technology. By 1631, China conducted its first telescopic observations. This progression from theoretical description to practical construction to widespread application illustrates how effective knowledge transfer requires not just transmission but systematic implementation support.

A turning point would occur on June 21, 1629. 

The upcoming solar eclipse on that day would be more than just an astronomical event; it would serve as a carefully planned demonstration of scientific dominance that shifted European understanding from mere curiosity to a matter of national importance. Eclipses were seen as signs of disaster, moments when cosmic order was broken and the emperor's connection with Heaven was called into question. For the young Chongzhen emperor, who faced Manchu invasions, internal rebellions, and court intrigues, astronomical failure was not just a technical mistake but a serious political threat. 

Chinese traditional astronomy, based on Yuan Dynasty methods,  had become increasingly inaccurate over the last 250 years. Meanwhile, the challenging task of aligning the solar year with lunar months required mathematical precision beyond traditional computational limits.

Therefore, Xu Guangqi organized an unprecedented scientific competition. As Deputy Minister of Rites and the empire's most respected scholar, Xu had the authority to host this dramatic showdown between competing knowledge systems. The three schools he brought together represented the full range of astronomical traditions available in early 17th-century China: the traditional Chinese Datong li method, based on calculations that had served the empire for centuries; the Islamic Huihui (Whey Whey) li computational system, representing Arabic astronomical knowledge introduced during the Tang Dynasty; and the European Jesuit method, incorporating the latest Renaissance astronomical techniques.

Schreck supervised the technical preparations for the Jesuits. He crafted new brass armillary spheres and quadrants with precision engraving that outperformed anything at the Beijing Observatory, which still used copies of 14th-century instruments. His trigonometric tables, based on Bartholomäus Pitiscus's advanced mathematical work, offered computational accuracy impossible with traditional Chinese methods. The combination of Tycho Brahe's observational data and Christopher Clavius's mathematical techniques created a predictive system that marked the peak of pre-telescopic astronomy.

The institutional infrastructure supporting this competition reflected the high stakes involved. The creation of an independent calendar reform agency adjacent to the Catholic church in Beijing offered both symbolic and practical benefits. The public demonstration, with officials and scholars present to witness the eclipse, turned what could have been private technical verification into political theater designed to establish scientific credibility before the empire's intellectual elite.

The decisive moment arrived at 11:00 AM on June 21, 1629, during the "hour of the tiger," when the moon started grazing the sun's edge exactly as Schreck predicted. However, modern reconstruction using NASA eclipse calculation software shows a more complex picture than traditional accounts suggest. While European methods excelled at predicting eclipse magnitude and duration, the Chinese system actually demonstrated better accuracy in timing the maximum phase and last contact. The Islamic method performed the worst across all parameters, with errors exceeding thirty minutes. Overall, the European approach proved most accurate, but not decisively better in every aspect.

The political narrative surrounding the eclipse results shows how predetermined conclusions and selective reporting can shape scientific events. Evidence indicates that the Chongzhen emperor had "already made up his mind about the defects of the Chinese method and the merits of the Western method" before the eclipse happened, viewing the event as confirmation rather than a true test. The first observation report focused only on areas where the European method performed better, while the follow-up memorial made "no mention of the bad performance of the Western method" in several parameters.

This interpretation highlights broader political issues around calendar reform. Imperial officials, frustrated by astronomical failures, favored more accurate methods. The claim that the emperor "wisely anticipated" Western accuracy before the eclipse shows the false nature of official stories, as true scientific prediction requires empirical testing, not just wisdom.

The immediate political impact of the eclipse demonstration was transformative for Jesuit influence and Chinese scientific institutions. The imperial edict of September 27, 1629, which mandated comprehensive calendar reform using European methods, marked an unprecedented endorsement of foreign scientific knowledge over traditional Chinese practices. The creation of the European-led Calendrical Bureau (Li-chu), with imperial salaries and official recognition, laid the institutional groundwork for ongoing Western influence in Chinese astronomy.

Schreck's appointment as practical director of the reform efforts, along with fellow Jesuit Nicolò Longobardo, marked the culmination of Matteo Ricci's 1605 vision of using astronomy to gain permanent imperial acceptance.

The institutional integration of European astronomical expertise into the Chinese government represented a major shift from relying on personal relationships to establishing a systematic organization. Jesuits obtained official positions that could potentially last through even the most significant political changes. At the same time, Chinese scholars demonstrated skill in adopting practical scientific methods while rejecting the theological framework Europeans saw as inseparable from their knowledge—a selective adoption pattern that caused lasting tensions in future East-West exchanges.

Schreck's death in 1630 shifted the responsibility for the calendar reform to Johann Adam Schall von Bell and Giacomo Rho, who directly built upon the networks and institutional relationships he had established. The 1629 eclipse demonstrations permanently opened the door that Ricci had warned was “still only ajar.” This established European astronomical influence that lasted until the collapse of the Qing Dynasty in the early 20th century. The eclipse crisis transformed a fragile missionary presence into an essential scientific institution, fulfilling Ricci's vision and surpassing his methods through the systematic application of European knowledge to Chinese imperial needs.

Our next episode will conclude this series on the Jesuit mission to China and the scientific exchange that took place.  We will look at the calendar reform and the conservative Chinese reaction.  All this while the Ming dynasty collapsed and was replaced by the Qing in 1644.

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