Abstract
Drawing on the rich and detailed records of astronomical activities in early imperial China, Cullen describes what Chinese people, 2000 years ago, thought about the heavens. He examines the practices of astronomical observation, instrumentation, and calculation from the late third century BCE to the fall of Han, covering nearly four and a half centuries. This book introduces the kind of astronomy that was based on careful and detailed records of past observations of the movements of the sun, moon, and planets and also describes the calculations aimed at predicting their motions in the future, what is usually called “mathematical astronomy” in Western traditions.
The book offers a narrative story, summarizing research by the author and many other scholars. It should be useful and interesting both to historians of science and general historians of China who want to know about the astronomy of this period. Cullen explicitly indicates that he wants the volume to be accessible to non-specialists. Readers seeking access to the principal sources mentioned in this book can refer to Cullen’s The Foundations of Celestial Reckoning: Three Ancient Chinese Astronomical Systems, published in 2017 by Routledge.
Heavenly Numbers has eight chapters which focus on different topics. Chapters one and two explain the importance of the calendar in the Chinese imperial state and how the calendar was used as a means of social control over imperial subjects. The contents and underlying structures of calendrical calculation are also outlined in the first part of this book. Chapters three and four tell the story of an emperor’s search for personal immortality and its outcome, viz., the first great astronomical reform in Chinese history in 104 BCE. This episode had wide-ranging consequences that included the humiliation of the leading astronomical office and creation of an expert group charged with a programme of testing observationally the merits claimed by the contending sides. Cullen provides full details of the structure and theory underlying the first complete extant astronomical calculation system, dating from around 10 CE, which was based on the astronomical reform of 104 BCE.
In Chapter five, Cullen explains the cosmic models gai tian (canopy model) and hun tian (sphere-heavens model). He also introduces the measurements and instruments used for shaping these models. Cullen’s 1996 book, Astronomy and Mathematics in Ancient China: The Zhou Bi Suan Jing presented the document zhou bi following the doctrine of the gai tian cosmography. In Heavenly Numbers, Cullen again reviews the debates between these two cosmos models and the process by which the hun tian replaced the gai tian.
In Chapters six and seven, Cullen moves to the restoration and re-creation of an astronomical system in the Eastern Han (25–220 CE) and the debates on it from various sides. A long series of archival documents enables readers to see how experts argued for their point of view. The debates occurred through the preparation of written documents, but also sometimes in public confrontations in the presence of large numbers of government officials.
In Chapter eight, Cullen recounts the work of Liu Hong, the most important person discussed at length in this book. Liu Hong is the first Chinese astronomer who constructed a theory of the moon, the first inequality lunar motion in longitude and the lunar motion in latitude, which was sufficiently detailed and accurate to enable the prediction of solar eclipses. Based on his earlier and recent researches, Cullen tries to prove that Liu Hong probably successfully predicted eclipses in 178 CE or later, which is the end of the Xiping period. Evidence shows that it was not long after the time of Liu Hong that astronomers in China began the practice of predicting and announcing the occurrence of solar eclipses in advance.
The book ends with a brief epilogue that introduces the persistence of remnants of the ancient Chinese astronomical tradition from the end of the Han period to the present.
In the pre-modern world, Chinese mathematical astronomy is probably the most fully documented example of a quantitative and predictive observational science. However, there are few works available in English to explain the details of this astronomy in early imperial China. This book seeks to fill this yawning gap.