Planetary Mechanism and its Conceptual Manifestation

Abstract: The Western concept of planeta was introduced to East Asia during the late Ming period. Although European cosmology had been transitioning from geocentrism to heliocentrism since the Renaissance, the verbatim translated Chinese term you xing遊星 (wandering star) employed in Huan You Quan寰有詮 (Interpretations of Beings of the Universe) and its associated theoretical descriptions still epitomized numerous basic assumptions of geocentric systems. As the paradigm shift in cosmology was accomplished, the meaning of this astronomical term and its translation underwent significant changes. Technological progress and the advent of the concept of gravitation eventually opened up a broad and deep vision of an infinite universe for humankind through a comprehensive spatial revolution. Thus, once the origins of the term xing xing行星 (revolving star) are inspected in methods of translation history or conceptual history, the contemporary notions of planet immediately reveal obvious defects which can no longer be ignored. Life and technology on spherical celestial bodies are irrelevant to the precise definition of "planetary"; rather, essentially it must be solely defined as fundamental and singular gravitational dependency within a system of point masses. This is the ultimate situation that humankind cannot alter or escape in the final analysis. Following the speculative paths of Carl Schmitt and Liu Cixin, maintaining a sober understanding of "planetary" helps humankind abandon its fixation on the imagery of Terra and resolutely project its entire historical existence into the void.

Introduction

In March 2024, the International Union of Geological Sciences (IUGS) confirmed that one of its committees had rejected the proposal to end the Holocene and start the Anthropocene. There is something prudent about this resolution at this point in time: although human activity has overtaken climate change as the most important geological agent on the surface of this planet, the plan to inscribe the proper name of "human" (ἄνθρωπος) in stratigraphic taxonomy by means of self-reference seems to be too bold. At the same time, the discussion of the planetary or planetarity, promoted by Berggruen Institute, is in full swing, offering us a vision of a future where humankind, natural beings, and technological objects will inhabit a finite planet in an interdependent symbiosis.

Reassessing the conceptual framework of terrestrial ecology from a position of reflecting on anthropocentrism has considerable academic and practical benefits. But wait, is it irrelevant which human language we are thinking in at the moment when we are trying to unleash the theoretical potential of "planetarity"? Did the modern Chinese word xing xing行星 and the English word "planet" come into being at the same time in history and go through the same evolutionary process? Is there really a logical and transparent congruence between the two? Do people from both sides understand the words used by each other well enough to reveal the full meaning of the concept? Will an unreflective correspondence theory of vocabulary helpdevelopthe cutting-edge notion of "planetarity" in order to gain a foothold in the face of the day by daydecaying traditional philosophy of humanism?

In this paper, the author takes the position that it is only by diving into translation history that we can detect the inevitable and unbridgeable gap between any words or between any concept and the real object it refers to,thus showing how the conceptual mechanism, as an ever-changing historical motive, unfolds and manifests itself on the actual level. Passing through the many vernacular and academic terms ready-to-hand yet unnoticed in the epistemological space, each etymological enquiry initiated from a conceptual-historical perspective contains in itself profound philosophical questionsfar beyond our imagination.

The Introduction of the Western Concept of Planeta into the Chinese-Speaking World: Stella Errans and You Xing

Jede Übersetzung in die je eigene Gegenwart impliziert eine Begriffsgeschichte.

Each translation into its own present implies a conceptual history.

——Reinhart Koselleck

On a certain day in the fifth to sixth year (1625-1626) of the Tianqi period of the Ming Dynasty (1368-1644), in Hangzhou Prefecture, the fifty-five-year-old Li Zhizao travelled in a sedan chair to visit a friend. As soon as he settled in, he lifted the curtains to let in sunlight and fresh air, then reached into his sleeve for a manuscript: the first draft of Huan You Quan寰有詮(Interpretations of Beings of the Universe), which he had already finished editing and translating. Leaning close to the page to read – a necessity given his cataracts and near-blindness – he searched for a passage that had been on his mind for some time. His eyes, though veiled by clouded lenses, shone with intensity as he scrutinized the words. The sedan chair swayed slightly as it travelled, and after a few moments, Li Zhizao turned his head to look out of the window at the blur of the passing landscape, pondering and lost in thought.

Nam quibusdam visum est, unam tantum esse sphaeram, in qua stellae fixae eundem situm perpetuo servantes insiderent; planetae vero alii aliis altiores ab una parte ad aliam instar piscium transmearent: quasi esset haec sphaera ceu praealtum mare, ubi alii pisces in imo natant, alii in medio, in summo alii.

LIBER II. CAPVT V. QVAESTIO I. ARTICVLVS I.

“Decem esse sphaeras mobiles.”

或謂天惟一重，列宿同居於此，各恒守其相距之所；七政亦居此天，但或遠如木星土星，或近如月與金星，其動不恒，如魚之遊。(Someone says that the heaven is but a single sphere, where all the stars reside together, each permanently maintaining its own distance. The Seven Governances also dwell in this heaven, some of them as distant as Jupiter and Saturn, and others as near as the Moon and Venus. Their movements are not constant, much like the swimming of fish.)

卷之四“渾圜篇第五（隨論四）”之“論天有幾重（二支）”

(Book IV, Chapter V, Total Sphericity: On the Number of Heavens)

Porro licet stellae fixae nullum motum subeant, praeter eos quibus earum sphaera vertitur; tamen inferiorum septem orbium planetae aliter se habent: circumaguntur enim alio sibi proprio ac peculiari motu, ob quem errones dicuntur: non quasi per omnes coeli partes passim ac sine lege discurrant, sed quia ultra motus suae principalis sphaerae alium sibi vindicant. Moveri autem hunc in modum planetas, bifariam ostenditur. Primum, quia experimento compertum est, eundem planetam nunc magis, nunc minus a terra distare: quod certe fieri non posset, nisi proprio circumactu nunc sublimiorem, nunc humiliorem sedem teneret. Atque haec causa fuit, cur Astrologi planetarum motum ponerent in circulis excentricis: quorum una pars magis a terra abiungitur, diciturque Aux; altera versus terram maxime accedit, & oppositum Augis appellatur.

LIBER II. CAPVT VIII. QVAESTIO I. ARTICVLVS II.

“Sidera errantia, praeter motus suae sphaerae principalis, alium sibi proprium habere; non tamen per se in gyrum agi.”

不遊星但繇天動，無自動者。七政則不然，各有本動，因有本動，故曰遊星。蓋所以謂之遊星者，非其任遊普天、漫無規序也，惟於渾天運動之外別有本動耳。何以證之？曰：七政之距地，時高時下，各有不同。若其本天運動之外更無他動，何以致此乎？原本天之運動恒一不爽，設使七政但因天動而動，則其距地遠近亦宜恒一。今既不然，則其遠遠近近，必皆各自有一本動也。然是本動非各政本體之動。測天者謂七政各有小輪，小輪之中心與渾天之中心各又不同，七政各居小輪邊際，隨輪上下，或就或離於地。(The non-wandering stars are only driven by the motions of the heavens; none of them moves by itself. The Seven Governances, however, do not move in such a manner; each has its proper motion, and because of the proper motion, they are called wandering stars. The term "wandering star" does not imply that they roam aimlessly across the vast sky, randomly without rule, but rather that they have their own distinct motion beyond the motions of the celestial spheres. How can this be proven? It is said that the distances of the Seven Governances from the Earth vary at different times. If there were no other motion beyond the motion of one's own celestial sphere, how could this variation occur? The motion of a celestial sphere is constant and accurate. If the Seven Governances move solely because of the motions of the heavens, then their distances from the Earth should also remain constant. Since this is not the case, their varying distances must be due to their proper motions. However, this proper motion is not the motion of each celestial body itself. Those who measure the heavens say that each of the Seven Governances moves in small orbits, with the center of each small orbit differing from the center of the celestial spheres. The Seven Governances reside at the edges of these small orbits, moving up and down with them, sometimes approaching and sometimes receding from the Earth.)

卷之五“星運篇第八（隨論三）”

(Book V, Chapter VIII, Motions of Stars)

According to Li Zhizao's own accounts, since his seclusion in the third year of the Tianqi period (1623), he resumed his studies in Western Learning following the guidance of the Jesuit Francisco Furtado on the basis of the work of their predecessors. Comparisons by later scholars show that they began with a Renaissance textbook on natural philosophy, Commentarii Collegii Conimbricensis, Societatis Jesu, in quatuor libros De Coelo, Aristotelis Stagiritae (1593), to collaborate in the compilation of Huan You Quan (1628). As a part of the translation project of Aristotle's philosophy in late Ming and early Qing, this Chinese treatisetranslated from Latin is a follow-up to the foundational works of Michele Ruggieri's Tianzhu Shilu天主實錄(The True Record of the Lord of Heaven, 1584), Matteo Ricci's Kunyu Wanguo Quantu坤輿萬國全圖(The Complete Map of the Myriad Countries on the Earth, 1602) and Qiankun Tiyi乾坤體義(Structure and Meaning of Heaven and Earth, 1608), and Manuel Dias Jr.'s Tian Wen Lüe天問畧(Epitome of Questions on the Heavens, 1615), which forms a systematic introduction to Western astronomy and cosmology. Nowadays, the Coimbra commentary on De Coelo and Huan You Quan can be regarded as invaluable archives in the transition period of human cosmology. Based on the geocentric system of Ptolemy's Almagest, both of them argued for a cosmic model of the ten-fold hard celestial spheres, which are the Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, Firmament, Crystalline Heaven and the Primum Mobile in descending order of proximity, with the stars orbiting with their respective solid celestial spheres,“heavens being like wooden planks, and the moon, the sun and the stars being like the knots on the wooden planks” (天如木版然，日月星如版上之節然).

From the cited passages and related sections, it can be seen that Li Zhizao uses the two-character term you xing遊星 (wandering star) to translate the Latin terms planeta, stella errans, and sidus errans, while the three-character term bu you xing不遊星 (non-wandering star) is used to translate expressions like stella/sidus inerrans, stella fixa, and sidus fixum. The Latin term planeta is directly borrowed from the Ancient Greek πλάνης/πλανήτης, which has omitted the generic determination ἀστήρ (star), retaining only the specific difference. Therefore, the Latin language itself needs to use the combination stella errans (wandering star) to clarify this borrowed term. The key points of this concept are twofold. First, from the geocentric perspective, you xing refers to the seven celestial bodies (including the Sun and Moon) that exhibit noticeable positional changes relative to the stars in the celestial background, while bu you xing –or chang ding bu dong zhi xing常定不動之星 (fixed stars)– refers to celestial bodies that make up the deep space background and do not exhibit noticeable relative positional changes. Second, the Coimbra commentary on De Coelo points out that the seven celestial bodies have peculiar motions besides the motions of their respective solid celestial spheres. Although these motionsare not completely without regularity (passim ac sine lege), they are somewhat complex and difficult to decipher compared withthe motions of their own celestial spheres, which is why the seven celestial bodies are referred to as errones (wanderers or rovers). The verb erro also carries the meaning of “to err” or “to make a mistake.”

To more accurately explain the orbits of the seven celestial bodies, Ptolemy did not adopt Aristotle's concentric system but instead made improvements based on Hipparchus's celestial sphere model. Theoretically, the introduction of the eccentric system and the model of the equant (ben tian da lun本天大輪, the great wheel) and the epicycle (xiao lun小輪, the small wheel) effectively addressed the issues of perigee and apogee for the seven celestial bodies, as well as the puzzling stationary phenomena(you liu zhi xing有留之星, planetae stationarii) and retrograde motion that occasionally appeared in the apparent motion of the five planets, excluding the Sun and Moon. Li Zhizao's use of you xing to translate planeta stems from the indispensability of the present active participle errans in the phrase stella errans: you (wandering) essentially characterizes these types of celestial bodies.

However, the description of such astronomical phenomena neither yielded an accurate principle of their motion nor provided a rational explanation for their true causes. At that time, Newtonian mechanics was far from being established, and both the Coimbra commentary on De Coelo and Huan You Quan remained within the framework of the Aristotelian four causes and four elements, modified through a creationist perspective. They explained free fall by attributing it to the tendency of the earth element to return to its natural place (i.e.huanyu zhi xin寰宇之心, center of the cosmos), and regarded the attractive force of magnets (electromagnetic force) and the tidal force of the Moon (gravitational force) as han cang zhi li含藏之力(occult forces). Even though both works adopted Jean Buridan's theory of impetus to explain forced motion in terms of impulse or impressed force, they still maintained that changes in the force acting on an object would immediately cause changes in its velocity (rather than acceleration). When explaining the motion of the celestial spheres, they had to resort to the ad hoc, unfalsifiable hypothesis of lingzhe/tianshen yun tian靈者/天神運天(intelligences/angels moving the heavens), which has nothing to do with natural science.

From You Xing to Xing Xing: The Exchange of Motion and Stillness Between the Sun and the Earth

יָסַד-אֶרֶץ עַל-מְכוֹנֶיהָ בַּל-תִּמּוֹט עוֹלָם וָעֶד

He has established the Earth on its foundations,

that it should not be moved for ever and ever.

——Tehillim 104:5

Although the Jesuits in China, through translation, hoped to introduce the authoritative cosmology of European textbooks to the Chinese intellectual elite, they also sought to incorporate recent astronomical observation records in their works, which greatly impressed Chinese literatiwho were open-mindedtowardsWestern learning. However, hindsight reveals that the conceptual systems in the Coimbra commentary on De Coelo and Huan You Quan lagged behind the most advanced astronomical theories in the West at that time, which were now going on the defensive as the paradigm shift in cosmology had already been launched.

In 1543, after Copernicus's hypothesis about celestial motions had been circulating in academic communities for a long time, he finally agreed to publish his lifetime research, On the Revolutions of the Celestial Spheres (De revolutionibus orbium coelestium), marking theemergence of the modern heliocentric theory. Since Aristarchus, the Sun was once againpositioned in the middle of the celestial model, while the Earth was removed from the eternally motionless center of the cosmos and relegated to one of the moving celestial bodies. Before this, with a multitude of distorted concepts of nature, the combination of ancient Hebrew creationism and ancient Greek geocentrism had dominated humankind's understanding of the universe for nearly two millennium. In the following two hundred years, the heliocentric theory was improved by Kepler's laws and Newtonian mechanics, successfully passing numerous observational tests, therebyestablishing its prominent status in modern human thought.

In 1792, Motoki Yoshinaga/Ryoei 本木良永, an interpreter of Dutch and scholar of Rangaku in Nagasaki, wrote Taiyō Kyūri Ryōkai Setsu太陽窮理了解説 (A Detailed Explanation of Solar Theory) and Seijutsu Hongen Taiyō Kyūri Ryōkai Shinsei Tenchi Nikyū Yōhō Ki星術本原太陽窮理了解新制天地二球用法記 (The Fundamentals of Astronomy: Notes on a Detailed Explanation of Solar Theory and the Usage of New Celestial and Terrestrial Globes), introducing heliocentric theory to Japan. Motoki used the ancient astronomical term kōsei恒星 (fixed star) to translate the Dutch "vaste Starren".Then he transliterated "Planeeten" as puranēten甫剌捏夜天 (プラネーテン) while traditional term "Dwaalster" was transliterated as dowārusuteru読瓦而数得耳 (ドワールステル), and both were combined to yield the interpretive term madoihoshi / madohihoshi惑星 (マドイホシ/マドヒホシ, kun'yomi), which means the courses and degrees of the movements of these celetial bodies confuse the astronomers. Even though the simplicity, explanatory power, and computational accuracy of the heliocentric system had relatively improved, the term madoihoshi still, in its literal sense, retained the traditional geocentric definition. Due to this translation's subsequent success in the competition with yūsei遊星 and kōsei/gyōsei行星, Japanese remains the only language in the East Asian sinoscript culture that uses wakusei惑星 (わくせい, on'yomi) to refer to the planets.

Returning to the Chinese context, the use of the term xing xing行星in modern Chinese appeared as early as the beginning of the 19th century. In 1815, London missionary Robert Morrison and his assistant William Milne founded the first modern newspaper aimed at a Chinese audience, titled "Cha Shisu Meiyue Tongji Zhuan察世俗每月統記傳" (The Monthly Record of Current Events) in Malacca. The entire volume for the year of Jia Qing Bing Zi(嘉慶丙子年全卷，1816) introduced the heliocentric theory using Chinese illustrations and mentioned seven xing xing (referring to the Earth, the five visible planets, and Uranus). At this point, the literal meaning of "planet" had significantly diminished, leading to a focus on the orbital description in the heliocentric system with the translation xing xing (revolving star). This term was subsequently included in the English-Chinese dictionary (1847-48) compiled by Walter Henry Medhurst and gradually became a standard term in modern Chinese. The transition from the wandering nature of you to the constant regularity of xing concretely reflects the fundamental shift from geocentrism to heliocentrism, thereby shaping contemporary views of the universe.

Spatial Revolution: The Emergence of the Concept of "Gravity" or "Gravitation"

Gravitas materiam ita constituit, ut materia sit objectiva gravitas.

Gravity constitutes matter in such a way that matter is objective gravity.

——Georg Wilhelm Friedrich Hegel

While Copernicus may have still believed in solid celestial spheres and a closed universe, the paradigm shift initiated by the heliocentric theory, since Bruno, directed astronomical research and ultimately resulted in numerous theoretical outcomes that earlier thinkers had not foreseen. What exactly happened during this shift in the history of ideas? As geocentrism was step by step replaced with heliocentrism, we can observe at least seven distinct theoretical transitions and transformations, all traceable in Huan You Quan: (1) from natural teleology to natural mechanics; (2) from the theory of impetus to Newtonian mechanics; (3) from the theory of aether (the divide between unchangeable matter above the moon and changeable matter below) to a view of cosmic material homogeneity; (4) from the solid celestial spheres to celestial bodies which orbit in the void; (5) from the equant-epicycle model to the ellipse-foci model; (6) from the hypothesis of the Primum Mobile to the theory of Earth's rotation; (7) from a closed world to an infinite universe. Among these superseding theories, which one insight definitively emerged as the cornerstone for all others and constituted the concept of planet? Clearly, it was Newton's law of universal gravitation. This law elucidated the motion of massive celestial bodies at a macroscopic level, reinforcing the foundational principles of the heliocentric model and offering theoretical coherence to the new understanding of the cosmos. In contrast, the geocentric system had to maintain itself by positing both that the earth is the heaviest body and that celestial bodies are neither light nor heavy, a distinction clearly reflected in the discussions within Huan You Quan.

According to Aristotle's teleological explanation, the four elements or the four simple bodies (fire, air, water, and earth) in the sublunar world are arranged by weight from top to bottom: the fire sphere is at the top of the sublunar realm, the air and water spheres are positioned between the fire and earth, while Terra, formed from the condensation of earth, resides at the center of the cosmos, “itself settled below all falling bodies, and that is why it is called absolutely heavy”(自安於諸降體之下，是謂至重). In the absence of external forces, each of the four elements moves in a straight line toward its natural place. The destination of each mixed body before its dissolution is determined by the proportion of its constituent elements. And the fact that mixed bodies contain a certain amount of earthgives them weight, "since if there is any thing heavy, it is because of the heaviness of earth". (蓋凡具重體者皆以土之重爲重故也) ." When a heavy object enters free fall,its speed of motion increases as it approaches the center of the earth (凡具重體者，繇其自然之動而動，其行愈遠，其動愈疾).

In contrast, the celestial bodies in the supralunar world do not exhibit generation and corruption; they revolve around the earth in a never-ending, uniform, circular motion. Aristotle deduced that the celestial realm must be composed of the fifth essence (πέμπτη οὐσία, quinta essentia, meaning "aether"). Although celestial bodies are also a combination of matter and form, they do not possess weight, for "celestial bodies are neither light nor heavy, which will never be destroyed" (天體非輕非重，爲永不壞). We know that the Earth's volume is negligible compared to the vastness of the universe, and data from Huan You Quan shows that fixed stars ranging from first to sixth magnitude, as well as Saturn, Jupiter, and the Sun, are all significantly larger than the Earth. Even Mars is slightly larger than the Earth. Despite this, the 1,022 fixed stars and the seven celestial bodies are said to revolve around the tiny Earth at an incredibly high speed. This presents a fundamental issue.

It is thus evident that the geocentric theory, based on everyday experience and theological assumptions, unfolds in the following circular argument: celestial bodies revolve around the Earth, therefore they are composed of a special matter that is weightless; because celestial bodies are made of a weightless special matter, they can revolve around the Earth without obstruction. The heliocentric theory must operate on two fronts to reconstruct this argument: celestial bodies in the universe also undergo generation and corruption, and they are composed of matterwhichis similar with that in the sublunar world and possesses weight; thus, when the densities are on the same order of magnitude, the tiny bodies must revolve around the enormous ones. And it is precisely because celestial bodies operate in this way that they must possess weight.

The changes in the generation and corruption of celestial bodies were highlighted by the explosion of Tycho's supernova (SN 1572), referred to in Huan You Quan as "a peculiar star appeared" (有異星見). Perhaps considering the potential implications of various astronomical observations, Huan You Quan uniquely reverses the theoretical position of the Coimbra commentary on De Coelo, modifying its assertion to state that bodies in the supralunar and sublunar realms have different forms, but their matter belongs to the same category.

Originally, within the conceptual framework of the geocentric system, "weight" or "heaviness" was defined as the potential or tendency of objects containing the element of earth to descend to the center of the cosmos. At this time, "βάρος/pondus" and "βαρύτης/gravitas,"were largely treated as synonyms despite their subtle differences. However, as Renaissance scholars one after another broke free from the constraints of Aristotelian natural philosophy, gravitas began to be used more frequently to refer to a type of force. Newton, in his Philosophiæ Naturalis Principia Mathematica, explicitly assigned a new meaning to gravitas, defining it as a form of centripetal force (vis centripeta), namely "force of gravity" (vis gravitatis). Planets are perpetually influenced by gravity, which pulls them away from their straight-line motion. This force causes their paths to bend, allowing them to follow circular orbits through the void at designated speeds. From phenomena such as planets and tides, it can be inferred that all objects are heavy (gravia sunt) relative to each other and are governed by gravity (gravitant); gravity is an interaction force generated by the self-aggregation of all matter, proportional to the quantity of material (quantitas materiae) or mass (massa), and it follows the inverse square law of distance. This is the principle of universal gravitation (gravitas universalis).

Until the early seventeenth century, the idea of planets floating in the vacuum was still difficult for scholastic scholars to accept. "Nature abhors the vacuum" (natura vacuum abhorret); in Huan You Quan, "xu kong虛空 (vacuum)" is rejected as a kind of non-being by the common nature of the cosmos, and the notion that celestial bodies traverse the thin regions of the sky alone was criticized as an erroneous doctrine. Ancient atomists viewed the vacuum as an empty background for the motion and collision of particles, but "vacuum" (κενόν) in Aristotle's Physics is not a realist concept; rather, it is a negative concept based on theoretical inference. According to him, a vacuum should be understood as a space of extension lacking existing entities. Such a vacuum is not a prerequisite for motion, as in positionalmovements (displacements) and particularly in the rotation of a continuum, successive objects can simultaneously occupy space for one another (IV. 7, 214a30), which is a statement clearly seeing the solid celestial spheres as its ideal template. Moreover, the existence of a vacuum would render motion impossible. On one hand, a vacuum cannot be the cause of natural motion. Since there are no differences within a vacuum, objects would not have a tendency to move toward any specific location, particularly as the Earth remains stationary at the center of an isotropic universe. (IV. 8, 214b30). On the other hand, it would lead to all forced motion becoming infinite and instantaneous, as the speed of an object's motion is inversely proportional to the density of the medium it traverses and directly proportional to its weight. Furthermore,once the medium is absent, the vacuum has no proportionality relative to fullness, causing objects to traverse the vacuum at speeds exceeding all proportions (IV. 8, 215b20), causing all objects to move at the same speed (IV. 8, 216a20). As previously mentioned, Aristotle postulates that objects must be constantly propelled to maintain motion, and their speed must depend on the magnitude of the force applied; thus, the existence of a vacuum inevitably leads to paradoxes. The discussions about celestial bodies, projectiles, vacuum, and the unmoved mover/first mover merely reiterate the same prejudice: from the very beginning, Aristotle had already logically and unconditionally presupposed the priority of stillness (ἠρεμία)/immobility (ἀκινησία) over motion (κίνησις). In doing so, he made it impossible to view stillness and uniform straight-line motion as equivalent, as Galileo and Newton did with inertial frames of reference. From plenism to Newton's first law, natural philosophy has traversed a long and winding road.

Regardless of Newton's theistic beliefs, his detailed descriptions of the principle of efficient causes, Kepler's laws, Newton's laws of motion, and the law of universal gravitation succinctly capture the key aspects of the two-body problem. They offer a mathematical solution that replaces the ambiguous qualitative explanations found in teleological systems.Once the quantitative relationships between the forces acting on objects, their masses, and the distances between them are established, it becomes evident that xing xing (revolving stars), including Earth, orbit the Sun, rather than the other way around: you xing (wandering stars), including the Sun and other celestial bodies, orbiting Earth. (Newton emphasized that Kepler's second law applies to the Earth-Moon system, but it applies to the primary planets only when they belong to a heliocentric system.) Consequently, the notion that "宗动天一日一周以带动其下诸天运转" is also refuted. Stars do not orbit either the Earth or the Sun, and the imagined boundaries of the cosmos do not exist. Later developments in measuring distance of celestial bodies and the discovery of cosmic expansion further opened up an infinitely vast perspective.

In the terminological choices and naming decisions for theoretical entities like planeta and gravitas, we observe the persistence of old concepts. As the paradigms shift, more precise definitions modify the conceptual scope of the same terms, gradually eliminating inadequate habitual understandings. However, this time the situation may be different: modern English-Chinese dictionaries have translated the physical meanings of "gravity" and "gravitation" into terms such as zhong xing重性, wu xiang yin zhe物相引者, wu fu xiang zhe物附向者, huxiang qianyin互相牽引, di xin li地心力, xi li吸力, xi li 翕力, she li攝力, and zhong li重力, eventually establishing yin li引力 in Chinese. In modern times, people commonly view gravity as a mutual attraction based on mass, particularly when celestial bodies are in a state of weightlessness/apesanteur in the universe. However, with the illustrations of spacetime curvature from general relativity, the concept of zhong重(gravitas) has once again taken center stage in our understanding of gravity.

Final Situation: Gravitational Dependence and its Conceptual Necessity

Using this model, supercomputers calculated thatthe Sun had already evolved away from the main sequence on the Hertzsprung-Russell diagram...
Five billion years of majestic life were now a fleeting dream. The Sun had died.
——Liu Cixin

The inquiry into the history of the concept "planet" serves a singular purpose—to raise the following question: Have we, even today, truly grasped the ontological significance of the heliocentric theory? If planetarity is intended to define the nature of planets, then it must refer to a quality that, once absent, renders the term "planet" inapplicable. Therefore, "life" and "technology" are clearly inessential components of the concept of "planet": the vast majority of planets do not possess the conditions for the existence of either, yet we persist in defining planetarity through concepts related to those.

Pierre Teilhard de Chardin understands planetarity as the formation of the "sphere of nous" (noosphère). Gayatri Chakravorty Spivak juxtaposes planetarity with globalization from a postcolonial perspective. Yuk Hui (許煜) argues that planetarization is a total mobilization of matter and energy, with technological science reshaping life as a planetary phenomenon, while planetary thinking aims to alter and overcome planetarization and create diversity across biological, mental, and technological dimensions. Scholars Jonathan S. Blake and Nils Gilman from the Berggruen Institute advocate for transcending the perspectives of nation-states and humankind to describe the earth's condition as a complex biochemical network engaged in feedback loops of interdependence among carbon elements, microorganisms, and multiple species. Theirgoalis the reconstruction ofthe Earth's political ecology for shared prosperity.Tobias Rees argues that the new reality perspective of earth transformation theory suggests that celestial phenomena are revealed to humanity through sensors and satellite technology. In contrast, planetarity is shaped by established technologies, creating a body of knowledge referred to as the planetary system. This prompts us to examine the ontological foundations of modernity.

All theseattempts at conceptualization are undoubtedly necessary, but they simultaneously reveal their own inadequacy. Defining "the planetary" and "planetarity" with terms like "celestiality" and "biologicality" ultimately amounts to continuing to affirm aform of "globality," "earthliness," and "habitability." A non-historical understanding based on the concept of xing qiu星球 (sphericalcelestial body) claims to acknowledge and endorse heliocentrism. But in fact itperceivesthe Earth as an abstract sphere suspended in space, completely oblivious to its mass, density, crust composition, magnetic field, axial tilt, orbital eccentricity, and the G2V-type main sequence star that serves as the barycenter (βαρύ + κέντρον) of the solar system and the source of ultimate significance.Upon this conceptual foundation, regardless of the emphasis on expressions like tian ren he yi (天人合一, the unity of heaven and humankind), wanwu gongsheng (万物共生, the symbiosis of all things), yinyuan zhengti (因缘整体, interdependent wholeness), "difference" and "diversity," correlationism—appearing as life-centrism—functions merely as a modern variant of idealism or subjectivism. It ultimately reinforces an anthropocentric ontotheology. We can thus turn Carl Schmitt's famous proposition on its head: all essential concepts of anthropocentrism are theologized natural concepts. As noted in Huan You Quan, "寰中庶物，咸有相關之義，如一身百體，皆相聯合而成." However, the interconnections among all things at the level of efficient cause do not imply that relationality occupies a foundational position at the ontological level. We have not made much progress compared to four hundred years ago. Some basic truth about planetarity seems to have fallen into oblivion, as if it were unknown to the‘cutting-edge’ thought of the present.

A planet is neither a globe (globus) nor the Earth (orbis terrarum). It is a dynamic evolution mechanism of a spatial system that transcends mere technical understanding of a single celestial body. The crucial point in the concept of xing xing行星 lies in the characterxing行 (moving or revolving) rather than in xing星 (star or celestial body). This clearly implies a categorical priority of motion over stillness. The appropriate essential definition of planetarity can only be the fundamental and singular gravitational dependency within a specific point-mass system. "Fundamental" means that the fate of a planet ultimately depends on the mass center of its system (such as a star, binary star, black hole, etc.), while "singular" indicates that the planet has not deviated from its orbit due to perturbations from other celestial bodies of comparable mass.

This allows us to reassess the definition of a planet in the solar system as established by the International Astronomical Union (IAU) in 2006:

(a) A planetorbits the Sun (xing行, continuous motion guaranteed by single gravitational dependency);

(b) A planetpossesses sufficient mass for its self-gravity to overcome rigid forces, achieving a hydrostatic equilibrium state (xing星, taking on a nearly spherical shape due to isotropic gravitational fields);

(c) A planet has already cleared its orbital neighbourhood of other bodies except for its own satellites (it exerts dominant gravitational influence and spatial occupation [Raumnahme]).

The concept of gravitational influence is central to the definition of planetarity. Once the existence of gravity is acknowledged, exoplanets and satellites, comets, and stars can all be encompassed by the ontological notion of “planet”: the Moon is a planet of Earth, the Earth is a planet of the Sun, and the Sun is a planet moving around the center of the Milky Way. Within what is referred to as a stellar system, stars in the main sequence provide a stable environment for planets through their mass-gravity, ensuring that planets neither exceed the Roche limit and break apart nor reach escape velocity and drift away. Moreover, the heat generated from thermonuclear reactions, constrained by their own gravity, is a near-infinite dissipation and serves as a source of energy for life on the surfaces of planetsin their circumstellar habitable zone. In other words, in any language that may emerge in the past or future, the concept of “the Sun” will always possess an ontologicalnecessity that “the Moon” lacks (even though it may initially be considered as ayou xing). Conscious life thus situated within this system must define its understanding of time (year) and space (astronomical unit, light-year, parsec) through planetary motion, stellar distribution, and the speed of light.

This planetary predicament is precisely at the core of Liu Cixin's science fiction writing. The unsolvable three-body problem leads to a stark division between the Stable Era and the Chaotic Era in the three-body world, with its civilizations acting as absolute others that covet and invade the Earth-Sun system. In The Three-Body Problem, the number 3 is pivotal, while in The Wandering Earth, it is marked as 0: the former represents the continual demise of planetary civilizations under triple gravitational dependency, while the latter signifies the collapse of dependency caused by a sudden change in the singular gravitational source.In reality, if we merely understand Earth as a planeta in the sense of stella errans or you xing, wakusei, then the term "wandering" does not add any new attributes to "Earth." The reason Earth must "wander" is that it was once a stable xing xing but now must take action in response to its precarious planetary situation. Liu Cixin's Euclidean-style sociological deductions about the survival laws in the "Dark Forest" also stem from an intuitive grasp of planetarity.

In the foreseeable future, planetarity will reimain the necessary condition and ultimate parameters of existence for humankind and all forms of life. As long as a civilization lacks the ability to meaningfullymanipulate extremely large masses, regardless of whether it expands into the cosmos or faces extinction due to missteps, it will not alter the facticity (Faktizität) of this fundamental condition that arises after objects within the universe acquire mass (via the Higgs mechanism).From a perspective completely unrelated to creationism, we can even say: "All things were made through it, and without it, nothing was made that has been made." This is far more real than any so-called philosophical concept. The modalities in which bizarre, grotesqueand illusory subjects existare at least partially predetermined a priori in their rapid rotation.

From this perspective, the entire history of human astronomy can be seen as a history of "blue-eyed islanders" engaging in self-reflective reasoning, as well as a restoration of the conceptual necessity of non-anthropocentrism. Initially, we could only observe the movements of celestial bodies without feeling our own motion. However, we ultimately deduced our position in the universe through the movements of other celestial bodies, thereby gaining a rough understanding of our current range of activities and the limits of our lifespan.

Newton's mechanics executes strict deductions to derive Kepler's laws, thereby proving the soundness of the heliocentric model. Conversely, the persistence of the geocentric model implies ignorance of Newton's second law and the law of universal gravitation. In other words, a biological species that refuses to acknowledge the heliocentric model for any reason would undoubtedly fail the "3C civilization level test" before the imminent visit of the carbon-based federation fleet from the Milky Way, as described in The Village Teacher. Consequently, in case of emergency (nötigenfalls), the star upon which they rely for survival should be ruthlessly destroyed by a "singularity bomb," even if figures like Aristotle, Confucius, and Jesus have emerged within that civilization. (As for why the Sun, rather than the Earth, should be destroyed, is a question that ought to becontemplated in light of the principles of planetarity.)

In the context of planetarity, it is essential to be pragmatic at all times, avoiding the pursuit of subjectivized, moralized, or ethicized justification for self-aggrandizement. Contrary to the hasty and superficial conclusions of Enlightenment thinkers, the establishment of the heliocentric model did not demonstrate the supreme authority of human reason in the world; rather, it opened a window toward the unfathomable universe. It represents the minimum threshold of interstellar cognition, the first half-step taken to relinquish all dignity when confronting the entirety of the cosmos. Only by setting aside the conceited dignity rooted in human exceptionalism can we hope for genuine interspecies coexistence and the continuity of civilization, thus determining the future trajectory of world history.

Expansion of Order: Decision Towards the Vacuum

Was ist unser Element? ... Für uns sind diese Elemente nämlich einfache und anschauliche Namen. Es sind Gesamtkennzeichnungen, die auf verschiedene große Möglichkeiten menschlicher Existenz hinweisen.

What is our element? ... For us, these elements are precisely simple and illustrative names.

They are overall designations,which point to different grand possibilities of human existence.

——Carl Schmitt

The unfolding of world history in the planetary sense is not only related to the cosmological revolution but closely intertwined with the evolution of legal foundations, dynamic technologies, and means of warfare. Schmitt's incisive historical analysis gains new significance from a planetary perspective. According to his theoretical observations, the driving force of human history arises from the fierce confrontation between land powers and sea powers, stemming from the mortal struggle between Behemoth (בְּהֵמוֹת) and Leviathan (לִוְיָתָן). The opening of Land und Meer (Land and Sea) states that the human is a terrestrial being (Landwesen), a groundling or land-dweller (Landtreter). Since the basic order of law (νόμος) is rooted in the possession, distribution, and utilization of land, we unthinkingly refer to this "terraqueous globe" as "Earth" (Erdball, Erdkugel) rather than "sea globe" (Seeball). In the era of land power, land warfare meant the occupation of territory, establishing public security orders, and creating a binary relationship of protection and obedience. Naval warfare originally existed merely as an extension of land warfare onto the sea; the invention of cannons and warships transformed naval battles from hand-to-hand combat aboard ships to a means of blockading and besieging enemy economic trade, aiming for total destructive outcomes. With the expansion of the British Empire, the mode of existence in world history decisively shifted from solid land to the ocean, as the two elements, earth and water, became the fundamental laws of the Earth. The means of vehicle propulsion evolved from oars (water) and sails (air) to steam engines (fire-water-air) and internal combustion engines (fire-air). The expansion into airspace again highlighted the dynamics of air and fire independent of water. Air combat, as a self-contained mode of interaction, prevented any combatants from establishing connections, eliminating the two-dimensional plane that allowed for interaction between land and sea powers. Supersonic/subsonic flight, ground bombing, and the struggle for air superiority in three-dimensional space transformed traditional lootings (Beutekrieg) into wars purely of annihilation (Vernichtungskrieg).

Extending this line of reasoning further, what changes occur in this spatial order when we transcend the boundaries of Earth and turn our gaze toward the cosmos? It is precisely during this process of reasoning that we find a convergence of concerns between Liu Cixin and Schmitt (with Alfred Thayer Mahan's theory of sea power serving as a common reference for both). Liu Cixin astutely observes that we have consistently tended to understand cosmic navigation more through the lens of the ocean (water element) rather than the sky (air element):

Chang Weisi nodded. “In fact, the navy’s not all that far removed from space. Don’t they call them ‘space ships’ rather than ‘space (air)planes’? [Don’t they call them ‘space fleet’ rather than ‘space (air)crafts’?] That’s because space and the ocean have long been linked together in the popular mind.”

The Three-Body Problem II: The Dark Forest

In summary, the theory of the four elements still governs our understanding of cosmic space. However, the logistical differences revealed by varying speeds of movement and supply methods in modern technological systems have forced us to reimagine the legitimacy of this atavistic system.

Space stations, symbolizing the earth element, function as large-scale hubs for modular assembly and operations in near-Earth orbit. They facilitate human presence, long-term habitation, and space research.The launch vehicle represented by the fire element is a fuel-based transitory jet propulsion system capable of transporting an object to first cosmic velocity, enabling it to overcome the earth's gravity and enter the region from near-Earth orbit to geosynchronous orbit. From there, it is jettisoned stage by stage as it runs out of fuel, where it is typically irrecoverable The air element represents space airplanes, which share similar functions and range of motion with launch vehicles but face significant technical challenges in terms of reuse and recovery. Once space ships or starships accelerate to second cosmic velocity, they can escape Earth’s gravity and embark on interstellar journeys; but even though it is already the fastest of all spacecraft, and even if it could surpass the current state of the art and cruise at close to the speed of light, it would still be too slow for the endless reaches of space. We thus intuitively still grasp it in terms of the oceanic low-speed voyages of the age of geographic discovery, as opposed to the high speeds of short, close-range flights in mid-air. This is why science fiction often likens the journey to "the sea of stars" (hoshi no taikai星の大海), reflecting the long journey through the universe. With sufficient energy, humankind sheds its terrestrial ties and glides into the cosmic deep (praealtum mare) like aquatic creatures.

Both The Three-Body Problem and The Wandering Earth meticulously depict accelerated/decelerated motion measured against the speed of light, while The Village Teacher explores space jumps powered by vast stellar energy. Over billions of years of evolutionary time, interstellar interactions are bound to face absolute disparities between species and civilizations. It’s likely that there exists an exponential technological gap between two civilizations: one with interstellar navigation capabilities and one without. The technology of the side with interstellar navigation capabilities would be so highly developed that the unattainable high-speed movement of the other side must seem slow to it. This suggests that interstellar warfare may resemble a form of looting, employing the unique right of capture (jus praedae) to seize planets and even stars as spoils."If various weapons appear inherently unequal, then the concept of interactive warfare envisioned on an equal plane collapses." As seen in The Three-Body Problem, this leads to a deeply discriminatory notion of warfare—where one side views the other as mere "insects." We must not passively wait for interstellar/intersidereal enemies (hostes) to reshape our spatial consciousness, akin to Indigenous Americans awaiting European "discovery." Instead, our priority should be to anticipate future objects and the expansion of the spatial order through cosmological speculation and the planning (Entwurf) inherently found in science fiction.

Any researcher who has intuitively grasped the true scale of the solar system is likely to be struck by the same realization: the solar system is so vast that the Sun itself can only be seen as a luminous point mass, while countless dimmer point masses are nearly impossible to observe. Without Kepler's laws, the motion of all non-luminous celestial bodies would be incomprehensible; it is only by appealing to gravitational dependency that we can define the relationships of subordination between planets across vast distances. In the vast expanse of exoplanetary space, which is billions of times larger than our solar system, neither planets nor stars can be seen as isolated islands in an ocean, making it challenging to conceptualize the image of Earth. This reality highlights both the rationality of understanding cosmic space through the water element and the fundamental heterogeneity that sets cosmic space apart from terrestrial environments.

Today, the actual scale of the universe and the realistic possibilities of interstellar warfare have reduced celestial bodies to zero-dimensional points. This situation urgently demands that humans shift their frame of existence from Earth to the vacuum between the stars, much like the historical transition from land to sea.

The lack of western metaphysical reasoning in Chinese thought has never allowed for a rigorous understanding of the sublunar world and the universe itself, as reflected in vernacular terms like tiankong天空 (sky) and kongqi空氣 (air). Accordingly, concepts such as taixu太虛 (the great vacuum) and taikong太空 (space),derived from ancient ideas about the night sky, merely express degrees of qi氣 (air) and kong空 (emptiness). Thus, kongjian空間(space, spatium inane) cannot be understood as an absolute "nothingness." The concept of vacuum in modern astrophysics similarly encompasses a range of very high vacuum regions, from interplanetary and interstellar spaces to intergalactic spaces, where various molecules, neutral atoms, ions, and cosmic rays are dispersed, with hydrogen and helium being the most abundant. Zhenkong真空 (vacuum; lit. true emptiness) in the modifier-head structure is not the opposite of xukong/kongxu虛空/空虛 (void/emptiness; the character xu虛 means “fake” in certain circumstances) in the coordination structure, but rather, the former is a quantifiable expression of the latter, and the latter serves as a symbolic reference to the former. Entering into an unbounded void does not signify a transformation from one element among the four to another but rather a shift from elements to non-elements in an existentialist sense. We must further inquire: what it means for a species to choose the vacuum, a non-element, as its entire historical mode of existence? The planetary mechanisms operating in the vacuum suggest that humankind is destined to be unanchored. Yet, within this absolute otherness of non-elemental space, there are unexplored cosmic resources, as well as new means of energy acquisition, modes of existence, and foundations of rights.

The fear of the vacuum (horror vacui) reveals that humankind remains constrained by a terrestrial perspective. But we have no choice. "We must fly out! ... Don't ask why, just exert the utmost effort to fly outward, as far as possible!" Liu Cixin's intuitive understanding of planetarity demonstrates a leap from "what is" to "what ought to be". With the help of future writings of varying degrees of authenticity, such as The Three-Body Problem, The Wandering Earth, and Taking Care of God, he passionately calls for us to overcome our fear of rootlessness, urginghumankind to bravelyto turn toward the universe. Humankind is not a bounded entity. When it adapts to the disorientation of existence brought on by freedom from inherent elements and their movements, its form and definition shift according to the substantial differences of the space it inhabits. The Nomos of the Earth that prioritize humanity will inevitably crumble. As human beings throw their historic existence into the infinite vacuum, a new measure of law and justice must be born.