Philosophy Department 00523008 Ma Bole

The Historical Origin of Ptolemaic Astronomy

The emergence of any theory will go through a long development process. What we take for granted today may be unprovable in ancient times. It takes many outstanding people to reach today's level. Astronomy, as a science, is bound to go through this process.

The Basic Contents of Ptolemaic Astronomy

The picture below is a sketch of Ptolemy's theory. Ptolemy introduced the equilibrium point in order to make this geometric model conform to the actual observation results. According to this scheme, the planet moves around an epicyclic circle with L as the center, while L moves around a circle with C as the center, but here C is not the center but slightly deviated. In order to determine the speed of L, he introduced a little E to make EC=CT, to make ∠LEA increase at a uniform speed, and to make L move at a uniform angular velocity instead of a uniform linear velocity. This is Ptolemy's theory, which successfully solves the problem of brightness change of your star, and its calculated value is quite consistent with the actual observation results.

According to this theory, the problems mentioned by Ptolemy in his Motto have been successfully solved. Ptolemy, like other Greek scholars, thought that the mathematical model should be as simple as possible. Ptolemy theory provides a fairly complete evidence that there are some inconvenient laws in nature, and it is also the final answer to the apparent motion of celestial bodies. Throughout the Greek period, the world view did not exceed the motto, and the model of Ptolemy theory became the unchangeable truth that Christians later thought.

Characteristics of Hellenistic Science

Science in the heroic period showed the characteristics of Hellenism, and astronomy also carried the free academic spirit of Greek classical period and the practical knowledge tradition of the East. This is not only because those scholars received Hellenistic education, but also related to the government at that time. Ptolemy's museum is a paradise for those Greek scholars. Ptolemy theory is the product of Hellenism, which is manifested in the following aspects: First, it inherits the spirit of freedom in the Greek period. Ptolemy theory is a set of purely rational geometric models. He used a simple geometric model to simulate the actual celestial motion with high accuracy. And the tools it uses are purely Hellenistic abstract methods, such as this circle and even the wheel. This reflects the rational thinking and speculative tradition of Greece. Secondly, it combines the pragmatic spirit of the East. Ptolemy theory provides a theoretical guarantee for the accuracy of the calendar, which enables a huge empire to be unified in the calendar. At the same time, it overcomes the disadvantages of ancient Greek astronomy, that is, it does not pay attention to actual observation results. Ptolemy theory applies not only the observation data of Egypt and Babylon, but also the observation results of Greek skiers themselves. All the above are the Hellenistic characteristics of Ptolemy's theory, and its Hellenistic characteristics may be reflected in other aspects, which are limited by ability and will not be described or discussed.

Some of my ideas

1. Geocentric theory and Heliocentrism. I don't think there is anything wrong with geocentric theory. Fundamentally, I think it's all a pattern. Ptolemaic system can be said to be basically the same model as modern astronomical results, and its equilibrium point and eccentric circle are another manifestation of modern elliptical trajectory. As for geocentric theory or Heliocentrism, I don't think there is any essential difference, but the origin of the same universe model in the three-dimensional coordinate system of the universe is different. As we know, different coordinate origin equations have different concrete forms, so geocentric theory and Heliocentrism are the correct models, and there is no need to choose one instead of the other. We take Heliocentrism as a simple model.

2. for reading. When I read it, I found that the descriptions of some books were inconsistent. For example, this round or even this round, the discussion on science and technology in history was decided by Apollo, but the reading materials on BBS were not. Only by comparison can we know where there is a problem. Here is the view from BBS, I don't know which one is true. Ask the teacher for advice.

philology

Science and Technology in World History, translated by James E. McClellan, Harold Donne and Wang Mingyang, Shanghai Science and Technology Education Press, 2003.

Ancient and Modern Mathematical Thoughts, translated by Maurice Klein and Zhang Lijing, Shanghai Science and Technology Press, 2002.

Online information

BBS Science General History Edition Related Reading Literature

Articles on the website of Peking University's History of Science and Philosophy of Science and Technology: Comments on Ptolemy (Jiang) and Interpretation of Grand Theory (Ding Xiaoyu)

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On the basic characteristics of Greek science from Ptolemaic astronomy

2009-04- 13 23:00

Look at this article. Are all the students who choose the general history of science? At that time, this article only got 90, please refer carefully ~

Abstract: Ptolemy is a master of western ancient astronomy, and his On Mottoes has long been regarded as the Bible in the field of astronomy. Ptolemaic astronomy not only inherits the characteristics of Greek classical science, but also has obvious Hellenistic color of combining practicality with pure science.

Keywords: Ptolemaic astronomy, Greek science

Astronomy is one of the earliest disciplines in the scientific process, and its development has played an important role in the progress of human society. In the history of astronomy, Ptolemy's influence is so profound that we can't rule it out.

"We know very little about Ptolemy's life. The astronomical observations he reported in Grand Theory ranged from 127 to 14 1, so his birth could not be much later than the beginning of the 2nd century. He wrote several important works after The Great Theory, so his death date is about 165- 170. " [ 1]

Ptolemy's most famous work is Astronomical Masterpieces, with a volume of *** 13. "This book gives a complete mathematical description of the Greek model of the universe, including various motion parameters of the sun, moon and planets. Encyclopedia of Mathematics is the brilliant peak of ancient Greek astronomy. Just like Euclid's Elements of Geometry, it replaced all the early works on this subject. " [2]

Next, this paper will discuss the historical origin and basic content of Ptolemaic astronomy, and the characteristics of Hellenistic science it embodies.

I. Historical origin and basic contents of Ptolemaic astronomy

Ptolemaic astronomy is based on the work of many predecessors, such as Plato, eudoxus, Apollonius, hipparchus and others.

Plato believes that "astronomical research only lies in freely inventing the mathematical model of celestial motion, without examining the actual celestial motion." [3]

He believes that the idea that celestial bodies move in a uniform circle is completely derived from his basic thoughts, which fully embodies the characteristics of pure freedom of Greek science. However, the phenomenon of planet "staying retrograde" has brought great trouble to Plato. "To quote one of his famous words, he instructed astronomers to" save these phenomena "with circles." [4] "

Eudoxus was the first person to put forward this plan. A celestial model proposed by him consists of 27 nested (concentric) celestial spheres, each of which rotates around the earth [5]

This concentric sphere model can better simulate the movement of celestial bodies. Since then, in order to better reflect the laws of celestial bodies, Aristotle has developed eudoxus's celestial spheres from 27 to 55. However, this model is still difficult to explain many problems, such as why the days in the four seasons are different, why the brightness of Venus changes, and why Venus, Mercury and the sun are always close together. In order to solve these problems and make the circular motion more adaptive, Apollonius "developed two powerful mathematical tools, which astronomers can use to build models and simulate the observed celestial motion." These two mathematical tools are the current wheel and the eccentric circle. " [6]

"In hindsight, the introduction of this kind of circle and even wheel made Greek astronomy embark on the road to prosperity. The combination of these two circles, this circle and even wheel, can provide an encouraging first-order approximation for the motion of the five planets. " [7]

Hippocrates and Ptolemy's subsequent work was "the pinnacle of Greek astronomy". [8]

Hipachas combined the Babylonian tradition with the Greek tradition, "using astronomical records and parameters from Babylon to improve the quantitative geometric model of the sun and the moon." [9]

More importantly, he independently discovered the vernal equinox phenomenon. Ptolemy, by summing up and analyzing the previous work, combined with his own thinking, constructed a strict "ptolemaic system" by using the concepts of runner and even wheel, eccentric circle and eccentric coincidence point. This system "is not a qualitative and descriptive system, but a quantitative system that can predict the future position of the planet." [ 10]

People can constantly revise and adjust according to the newly obtained observation data to make it more realistic.

The main point of Ptolemaic astronomy is: "The earth is at the center of the universe, and the planets, the sun, the moon and the stars revolve around the earth from east to west every day. The first orbit closest to the Earth is the Moon, followed by Mercury, Venus, the Sun, Mars, Jupiter and Saturn. The outer layer is the starry sky. The sun, the moon and the stars go directly around the earth. " [ 1 1]

This system can accurately describe the movement of celestial bodies and predict the stars, and has long been regarded as the Bible in the field of astronomy. Even in the Copernican era, Heliocentrism did not completely rule out the theoretical defects of Ptolemy's geocentric theory. "Copernicus's Heliocentrism is not more accurate than Ptolemy's geocentric theory in practical application, and both of them have an error of 1%." [ 12]

These are the historical sources and main contents of Ptolemaic astronomy. When we explore it carefully, it is not difficult to find that it is in the same strain as Greek classical scientific thought, and it embodies obvious Hellenistic color.

Second, the Hellenistic characteristics reflected in Ptolemaic astronomy.

Ptolemaic astronomy was born in the heyday of Hellenism, and its theory naturally showed the new characteristics of Hellenistic science pursuing practicality.

1, Ptolemaic astronomy inherited Greek classical science.

"Hellenistic science is a historical fusion or hybridization between the Greek natural philosophy tradition and the scientific model supported by the state from the Eastern Kingdom." [ 13]

It combines two completely different traditions, focusing on practical oriental science and Greek science, which pursues freedom and does not want to be bound, and forms a brand-new scientific model. Because of this, there are still many characteristics of Greek science in Hellenistic science.

Ptolemy did not completely give up the idea of using circular motion to solve the motion of celestial bodies, but only improved it to some extent to make it more in line with actual observation. He once said in the preface of The Great Theory that "the theory of divine cause of celestial movement or meditation on the material essence of things can only lead to' speculation'. If the purpose is to obtain certainty, mathematics is the only way." "He said in several places in the book that the choice of astronomical model should be based on mathematical simplicity-obviously, he doesn't care about physical feasibility." [ 14]

This passage fully shows that Ptolemaic astronomy is essentially a purely rational science and does not care about its practical significance.

In addition, we can also see the legacy of Greek classical thought from Ptolemy's concept of eccentric consistency. Ptolemy was not bound by Plato's demand for strict uniform circular motion, but put forward a new theory of pursuing truth, which embodied his characteristics as a free and rational ancient Greek scholar. Ptolemy still held a high esteem for the free and unrestrained classical Greek science. Fundamentally speaking, Ptolemaic astronomy is a geometric model based on the concept of "salvation phenomenon" in ancient Greece, which can be described quantitatively by analyzing a large number of data. He didn't think too much about how to realize this model in practice, just to get the simplest mathematical model.

2. Hellenistic features in Ptolemaic astronomy.

As mentioned above, Ptolemy inherited the characteristics of Greek science, but we should also see that there are many characteristics different from Greek science in his research, which are practical and Hellenistic. Historically, Ptolemy really put astronomy on the practical road. "With the help of the supreme theory, mathematical astronomers (and astrologers) can accurately calculate the planetary ephemeris at any time in the future and give the latitude and longitude values of the planetary positions in the table." [ 15]

This undoubtedly plays a very important role in real life, and people can arrange sacrifices and carry out astrology accordingly. When we carefully examine Ptolemy's astronomy class, we will find that there are also non-mathematical considerations in his analysis. "Ptolemy provided physical evidence for the centrality and fixity of the earth-this is not only a mathematical hypothesis, but also an important physical belief." [ 16]

And a pure ancient Greek scholar would not think about the physical meaning of his model. As for Ptolemy's later four books on astrology, it is a practical astronomical work.

In Ptolemy's research, we can also see the obvious Hellenistic color. For example, he attaches great importance to the role of observation data in theoretical research. He first abstracted a geometric model by analyzing a large number of existing data, and then compared the data derived from the model with the actual data. Observation is a practical means, and it is impossible to attach so much importance to observation in Greek times. From this point of view, Ptolemy was actually greatly influenced by oriental pragmatism. In addition, the characteristics of state support for theoretical scientific research in Hellenistic science have also been reflected. In order to better govern the country, the Roman government spared no expense to support the construction of the Alexandria Library, and accumulated a large number of precious books and documents, which played a vital role in promoting scientific development. Ptolemy's observation and research in Alexandria also benefited from the government's attention and support for scientific development.

To sum up, we can find that Ptolemaic astronomy embodies the characteristics of individualism giving way to cosmopolitanism, classical Greek liberal academic spirit and oriental pragmatism in the Hellenistic era.

Third, summary.

As can be seen from the above discussion, Ptolemaic astronomy originated from Greek mathematical astronomy and was developed and established on the basis of many predecessors' work. This theory not only inherits the freedom and rationality of Greek classical science, but also embodies the characteristics of Hellenism in many aspects. In fact, sometimes a wrong theory may be more valuable than a correct one. Although Ptolemaic astronomy seems to be an absurd theory now, its important position in history will not be concealed.

References:

[1] Michael Hosking (Jiang, Guan Zengjian, translated by Niu) (2003). Cambridge illustrates the history of astronomy. Shandong: Shandong Pictorial Publishing House. Page 37

[2] Victor J Katz (translated by Li Wenlin) (2004). General introduction to the history of mathematics. Beijing Higher Education Press. Page 56

[3] Yang Jianye et al (1996). Five Thousand Years of World Science (Second Edition). Wuhan: Wuhan Publishing House. pp: 140。

[4] McClellan III (translated by Wang Mingyang) (2003). Science and technology in world history. Shanghai: Shanghai Science Education Press. Page 77

Wu Xinji, Wen (2005). Fifteen lectures on modern astronomy. Beijing: Peking University Publishing House. pp:6。

[6] McClellan III (translated by Wang Mingyang) (2003). Science and technology in world history. Shanghai: Shanghai Science Education Press. Page 96

[7] Michael Hosking (Jiang, Guan Zengjian, translated by Niu) (2003). Cambridge illustrates the history of astronomy. Shandong: Shandong Pictorial Publishing House. Page 34

[8] Morris Klein (translated by Zhang Lijing, Max Zhang and Jiang Zehan) (2002). Ancient and modern mathematical thoughts (Volume I). Shanghai Shanghai Science and Technology Publishing House. pp: 180。

[9] Michael Hosking (Jiang, Guan Zengjian, translated by Niu) (2003). Cambridge illustrates the history of astronomy. Shandong: Shandong Pictorial Publishing House. Page 35

Chen guang. (1992). History of personality science. Chengdu: Southwest Jiaotong University Press. Page 26

[1 1] Wu Xinji, paper (2005). Fifteen lectures on modern astronomy. Beijing: Peking University Publishing House. pp:7。

Chen guang. (1992). History of personality science. Chengdu: Southwest Jiaotong University Press. Page 28

McClellan III (translated by Wang Mingyang) (2003). Science and technology in world history. Shanghai: Shanghai Science Education Press. Page 90

David Lindbergh (translated by Wang Ming, et al. (200 1). The origin of western science. China Foreign Translation and Publishing Company. pp: 104。

Michael Hosking (Jiang, Guan Zengjian, translated by Niu) (2003). Cambridge illustrates the history of astronomy. Shandong: Shandong Pictorial Publishing House. Page 39

David Lindbergh (translated by Wang Ming, et al. (200 1). The origin of western science. China Foreign Translation and Publishing Company. pp: 104。

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Ptolemy's research results are not his own. "Like Euclid's summary of mathematics in classical Greek times and his famous Elements of Geometry, he systematically summed up the outstanding achievements of Greek astronomy and wrote astronomical masterpieces that have been passed down through the ages.

Astronomical Masterpiece, the Great Theory, is mainly written according to the research results of Hipax, which quotes many astronomical data of Hipax, and of course, the achievements of several major astronomers such as eudoxus, Heraclide, Aristak and Apolloni. Ptolemy "selected Apollo's circle-even wheel theory, Alba's ancient eccentric circle theory, and his original concept of equilibrium point (symmetry point), and finally put forward a complete set of Ptolemy's geocentric astronomical masterpieces."

The main point is: "The earth is at the center of the universe, motionless, and the planets, the moon, the sun and the stars revolve around the earth from east to west every day. The first orbit closest to the earth is the moon, followed by Mercury, Venus, the sun, Mars, Jupiter and Saturn, and the outer layer is the star sky. The sun, the moon and the stars go directly around the earth. " He "seriously considered the problem of the earth's rotation, but unfortunately he immediately denied it."

These are the main contents and historical origins of Ptolemaic astronomy. If combined with the historical background at that time, it is not difficult to find that Ptolemaic astronomy not only inherited the spirit of Greek classical period, but also represented the characteristic science of Hellenistic period.

He still respects the religious theory of ancient Greece and follows the religious statement about God. But at the same time, we can't deny that Ptolemy did a lot of innovative work, which also reflected the new characteristics of science in the Hellenistic period. He is not limited to uniform circular motion, and the antipodal point theory mentioned above has a great influence on classical Greek astronomy. Uniform circular motion, a perfect motion based on religious and aesthetic considerations, no longer exists. "

For those college students who have studied Aristotle's natural philosophy of uniform circular motion of concentric circles, it is difficult enough to accept the eccentric circle and the current circle; It is extremely impossible to accept the' right point'. ""The methods adopted and the knowledge gained by Greek astronomers are completely modern. ...

Interestingly, Copernicus was not satisfied with these practices of Ptolemy and others-he wanted to restore the unified circular nature of the celestial sphere and transfer the center of the universe from the earth to the sun.

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