Dynamics of the celestial spheres
Encyclopedia
Ancient, medieval and Renaissance
astronomers and philosophers developed many different theories about the dynamics of the celestial spheres
. They explained the motions of the various nested spheres in terms of the materials of which they were made, external movers such as celestial intelligences, and internal movers such as motive souls or impressed forces. Most of these models were qualitative, although a few of them incorporated quantitative analyses that related speed, motive force and resistance.
, the celestial regions were made “mostly out of fire” on account of its mobility. Later Platonists, such as Plotinus
, maintained that although fire moves naturally upward in a straight line toward its natural place at the periphery of the universe, when it arrived there, it would either rest or move naturally in a circle. An account which was compatible with Aristotle
's meteorology
of a fiery region in the upper air, drug along underneath the circular motion of the lunar sphere. However, the spheres themselves were made entirely of a special fifth element, that took its name, Aether (Αἰθήρ)
, from the personification in mythology: the bright, untainted upper atmosphere in which the gods dwell, as distinct from the dense lower atmosphere, Aer (Ἀήρ). Unlike the four terrestrial elements, earth
, water
, air
and fire
, that give rise to the generation and corruption of natural substances by their mutual transformations; aether was unchanging, moving always with a uniform circular motion
that was uniquely suited to the celestial spheres, which were eternal. Earth and water had a natural heaviness (gravitas), which they expressed by moving downward toward the center of the universe. Fire and air had a buoyant lightness (levitas), such that they moved upward, away from the center. Aether, being neither heavy nor light, moved naturally around the center.
, created according to mathematical principles, which governed the daily motion of the heavens (the motion of the Same) and the opposed motions of the planets along the zodiac
(the motion of the Different). As a teleological cause, Aristotle proposed eternal unmoved mover
s, gods whom the spheres desired to mimic, as best they could, by uniform circular motion. Aristotle determined that an individual unmoved mover would be required to insure each individual motion in the heavens. While stipulating that the number of spheres, and thus gods, is subject to revision by astronomers, he estimated the total was 47 or 55, depending on which of the two contemporary models one took into consideration. In On the Heavens
, Aristotle was content with the view of eternal circular motion as moving itself, in the manner of Plato's world-soul, which lent support to three principles of celestial motion: an internal soul, an external unmoved mover, and the celestial material (aether).
(c.90–168) rejected the Aristotelian concept of an external prime mover, maintaining instead that the planets have souls and move themselves with a voluntary motion. Each planet sends out motive emissions that direct its own motion and the motions of the epicycle and deferent that make up its system, just as a bird sends out emissions to its nerves that direct the motions of its feet and wings.
John Philoponus
(490–570) considered that the heavens were made of fire, not of aether, yet maintained that circular motion is one of the two natural motions of fire. In a theological work, On the Creation of the World (De opificio mundi), he denied that the heavens are moved by either a soul or by angels, proposing that "it is not impossible that God, who created all these things, imparted a motive force to the moon, the sun, and other stars — just as the inclination to heavy and light bodies, and the movements due to the internal soul to all living beings — in order that the angels do not move them by force." This is interpreted as an application of the concept of impetus
to the motion of the celestial spheres. In his earlier commentary on Aristotle's Physics, Philoponus compared the innate power or nature that accounts for the rotation of the heavens to the innate power or nature that accounts for the fall of rocks.
(c.872–c.950) and Avicenna
(c.980–1037), following Plotinus, maintained that Aristotle's movers, called intelligences, came into being through a series of emanations
beginning with God. A first intelligence emanated from God, and from the first intelligence emanated a sphere, its soul, and a second intelligence. The process continued down through the celestial spheres until the sphere of the moon, its soul, and a final intelligence. They considered that each sphere was moved continually by its soul, seeking to emulate the perfection of its intelligence. Avicenna maintained that besides an intelligence and its soul, each sphere was also moved by a natural inclination (mayl).
A Spanish Muslim interpreter of Aristotle, al-Bitruji (d. c.1024), proposed a radical transformation of astronomy that did away with epicycles and eccentrics, in which the celestial spheres were driven by a single unmoved mover at the periphery of the universe. The spheres thus moved with a "natural nonviolent motion." but was a The mover's power diminished with increasing distance from the periphery so that the lower spheres lagged behind in their daily motion around the Earth; this power reached even as far as the sphere of water, producing the tides.
More influential for later Christian thinkers were the teachings of Averroes
(1126–1198), who agreed with Avicenna that the intelligences and souls combine to move the spheres but rejected his concept of emanation. Considering how the soul acts, he maintained that the soul moves its sphere without effort, for the celestial material has no tendency to a contrary motion.
Later in the century, a commentator on the Islamic theologian
Adud al-Din al-Iji (1281–1355), under the influence of the Ash'ari
doctrine of occasionalism
, which maintained that all physical effects were caused directly by God's will rather than by natural causes, rejected non-religious science and astronomy, and maintained that the celestial spheres were "imaginary things" and "more tenuous than a spider's web".
, Plato's picture of the heavens was dominant among European philosophers, which led Christian thinkers to question the role and nature of the world-soul. With the recovery of Aristotle
's works in the twelfth and thirteenth centuries, Aristotle's views supplanted the earlier Platonism
, and a new set of questions regarding the relationships of the unmoved movers to the spheres and to God emerged.
In the early phases of the Western recovery of Aristotle
, Robert Grosseteste
(c.1175–1253), influenced by medieval Platonism and by the astronomy of al-Bitruji, rejected the idea that the heavens are moved by either souls or intelligences. Adam Marsh
's (c.1200–1259) treatise On the Ebb and Flow of the Sea, which was formerly attributed to Grosseteste, maintained al-Bitruji's opinion that the celestial spheres and the seas are moved by a peripheral mover whose motion weakens with distance.
Thomas Aquinas
(c.1225–1274), following Avicenna, interpreted Aristotle to mean that there were two immaterial substances responsible for the motion of each celestial sphere, a soul that was an integral part of its sphere, and an intelligence that was separate from its sphere. The soul shares the motion of its sphere and, through its love and desire for the unmoved separate intelligence, causes the sphere to move. Avicenna, al-Ghazali
, Moses Maimonides, and most Christian scholastic philosophers
identified Aristotle's intelligences with the angels of revelation, thereby associating an angel with each of the spheres. Moreover, Aquinas rejected the idea that celestial bodies are moved by an internal nature, similar to the heaviness and lightness that moves terrestrial bodies. Attributing souls to the spheres was theologically controversial, as that could make them animals. After the Condemnations of 1277, most philosophers came to reject the idea that the celestial spheres had souls.
In two slightly different discussions, John Buridan (c.1295–1358) suggested that when God created the celestial spheres, he began to move them, impressing in them a circular impetus that would be neither corrupted nor diminished, since there was neither an inclination to other movements nor any resistance in the celestial region. He noted that this would allow God to rest on the seventh day, but he left the matter to be resolved by the theologians.
Nicole Oresme (c.1323-1382) explained the motion of the spheres in traditional terms of the action of intelligences, coupled with a consideration in terms of a power and resistance impressed in the spheres when God created the heavens. In discussing the relation of the moving power of the intelligence, the resistance of the sphere, and the circular velocity
, he said "this ratio ought not to be called a ratio of force to resistance except by analogy, because an intelligence moves by will alone ... and the heavens do not resist it."
According to Grant, except for Oresme, scholastic thinkers did not consider the force-resistance model to be properly applicable to the motion of celestial bodies, although some, such as Bartholomew Amicus, thought analogically in terms of force and resistance. By the end of the Middle Ages it was the common opinion among philosophers that the celestial bodies were moved by external intelligences, or angels, and not by some kind of an internal mover.
(1473–1543) transformed Ptolemaic astronomy and Aristotelian cosmology by moving the Earth from the center of the universe, he retained both the traditional model of the celestial spheres and the medieval Aristotelian views of the causes of its motion. Copernicus follows Aristotle to maintain that circular motion is natural to the form of a sphere. However, he also appears to have accepted the traditional philosophical belief that the spheres are moved by an external mover.
Although Johannes Kepler
's (1571–1630) cosmology eliminated the celestial spheres, he held that the planets were moved both by an external motive power, which he located in the Sun, and a motive soul associated with each planet. In an early manuscript discussing the motion of Mars, Kepler considered the Sun to cause the circular motion of the planet. He then attributed the inward and outward motion of the planet, which transforms its overall motion from circular to oval, to a moving soul in the planet since the motion is "not a natural motion, but more of an animate one". In various writings, Kepler often attributed a kind of intelligence to the inborn motive faculties associated with the stars.
In the aftermath of Copernicanism the planets came to be seen as bodies moving freely through a very subtle aethereal medium. Although many scholastics continued to maintain that intelligences were the celestial movers, they now associated the intelligences with the planets themselves, rather than with the celestial spheres.
Renaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...
astronomers and philosophers developed many different theories about the dynamics of the celestial spheres
Celestial spheres
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus and others...
. They explained the motions of the various nested spheres in terms of the materials of which they were made, external movers such as celestial intelligences, and internal movers such as motive souls or impressed forces. Most of these models were qualitative, although a few of them incorporated quantitative analyses that related speed, motive force and resistance.
The celestial material and its natural motions
In considering the physics of the celestial spheres, scholars followed two different views about the material composition of the celestial spheres. For PlatoPlato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...
, the celestial regions were made “mostly out of fire” on account of its mobility. Later Platonists, such as Plotinus
Plotinus
Plotinus was a major philosopher of the ancient world. In his system of theory there are the three principles: the One, the Intellect, and the Soul. His teacher was Ammonius Saccas and he is of the Platonic tradition...
, maintained that although fire moves naturally upward in a straight line toward its natural place at the periphery of the universe, when it arrived there, it would either rest or move naturally in a circle. An account which was compatible with Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
's meteorology
Meteorology (Aristotle)
Meteorology is a treatise by Aristotle which contains his theories about the earth sciences. These include early accounts of water evaporation, weather phenomena, and earthquakes....
of a fiery region in the upper air, drug along underneath the circular motion of the lunar sphere. However, the spheres themselves were made entirely of a special fifth element, that took its name, Aether (Αἰθήρ)
Aether (mythology)
Aether , in Greek mythology, is one of the Protogenoi, the first-born elementals. He is the personification of the upper sky, space, and heaven, and is the elemental god of the "Bright, Glowing, Upper Air." He is the pure upper air that the gods breathe, as opposed to the normal air that mortals...
, from the personification in mythology: the bright, untainted upper atmosphere in which the gods dwell, as distinct from the dense lower atmosphere, Aer (Ἀήρ). Unlike the four terrestrial elements, earth
Earth (classical element)
Earth, home and origin of humanity, has often been worshipped in its own right with its own unique spiritual tradition.-European tradition:Earth is one of the four classical elements in ancient Greek philosophy and science. It was commonly associated with qualities of heaviness, matter and the...
, water
Water (classical element)
Water is one of the elements in ancient Greek philosophy, in the Asian Indian system Panchamahabhuta, and in the Chinese cosmological and physiological system Wu Xing...
, air
Air (classical element)
Air is often seen as a universal power or pure substance. Its supposed fundamental importance to life can be seen in words such as aspire, inspire, perspire and spirit, all derived from the Latin spirare.-Greek and Roman tradition:...
and fire
Fire (classical element)
Fire has been an important part of all cultures and religions from pre-history to modern day and was vital to the development of civilization. It has been regarded in many different contexts throughout history, but especially as a metaphysical constant of the world.-Greek and Roman tradition:Fire...
, that give rise to the generation and corruption of natural substances by their mutual transformations; aether was unchanging, moving always with a uniform circular motion
Uniform circular motion
In physics, uniform circular motion describes the motion of a body traversing a circular path at constant speed. The distance of the body from the axis of rotation remains constant at all times. Though the body's speed is constant, its velocity is not constant: velocity, a vector quantity, depends...
that was uniquely suited to the celestial spheres, which were eternal. Earth and water had a natural heaviness (gravitas), which they expressed by moving downward toward the center of the universe. Fire and air had a buoyant lightness (levitas), such that they moved upward, away from the center. Aether, being neither heavy nor light, moved naturally around the center.
The causes of celestial motion
As early as Plato, philosophers considered the heavens to be moved by immaterial agents. Plato believed the cause to be a world-soulAnima Mundi
Anima mundī is Latin meaning "the soul of the world" which can refer to:*Anima mundi, the soul of the world*Anima Mundi , a 1991 documentary film directed by Godfrey Reggio*Anima Mundi , a Brazilian video and film festival...
, created according to mathematical principles, which governed the daily motion of the heavens (the motion of the Same) and the opposed motions of the planets along the zodiac
Zodiac
In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...
(the motion of the Different). As a teleological cause, Aristotle proposed eternal unmoved mover
Unmoved mover
The unmoved mover is a philosophical concept described by Aristotle as a primary cause or "mover" of all the motion in the universe. As is implicit in the name, the "unmoved mover" is not moved by any prior action...
s, gods whom the spheres desired to mimic, as best they could, by uniform circular motion. Aristotle determined that an individual unmoved mover would be required to insure each individual motion in the heavens. While stipulating that the number of spheres, and thus gods, is subject to revision by astronomers, he estimated the total was 47 or 55, depending on which of the two contemporary models one took into consideration. In On the Heavens
On the Heavens
On the Heavens is Aristotle's chief cosmological treatise: it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world...
, Aristotle was content with the view of eternal circular motion as moving itself, in the manner of Plato's world-soul, which lent support to three principles of celestial motion: an internal soul, an external unmoved mover, and the celestial material (aether).
Later Greek interpreters
In his Planetary Hypotheses, PtolemyPtolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
(c.90–168) rejected the Aristotelian concept of an external prime mover, maintaining instead that the planets have souls and move themselves with a voluntary motion. Each planet sends out motive emissions that direct its own motion and the motions of the epicycle and deferent that make up its system, just as a bird sends out emissions to its nerves that direct the motions of its feet and wings.
John Philoponus
John Philoponus
John Philoponus , also known as John the Grammarian or John of Alexandria, was a Christian and Aristotelian commentator and the author of a considerable number of philosophical treatises and theological works...
(490–570) considered that the heavens were made of fire, not of aether, yet maintained that circular motion is one of the two natural motions of fire. In a theological work, On the Creation of the World (De opificio mundi), he denied that the heavens are moved by either a soul or by angels, proposing that "it is not impossible that God, who created all these things, imparted a motive force to the moon, the sun, and other stars — just as the inclination to heavy and light bodies, and the movements due to the internal soul to all living beings — in order that the angels do not move them by force." This is interpreted as an application of the concept of impetus
Impetus
Impetus may refer to:* Impetus , a re-release of the EP Passive Restraints* Impetus , a concept very similar to momentum* Jean Buridan#Impetus Theory, middle-ages treatment on impetus and its originator Jean Buridan...
to the motion of the celestial spheres. In his earlier commentary on Aristotle's Physics, Philoponus compared the innate power or nature that accounts for the rotation of the heavens to the innate power or nature that accounts for the fall of rocks.
Islamic interpreters
The Persian philosophers, al-FarabiAl-Farabi
' known in the West as Alpharabius , was a scientist and philosopher of the Islamic world...
(c.872–c.950) and Avicenna
Avicenna
Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...
(c.980–1037), following Plotinus, maintained that Aristotle's movers, called intelligences, came into being through a series of emanations
Emanationism
Emanationism is an idea in the cosmology or cosmogony of certain religious or philosophical systems. Emanation, from the Latin emanare meaning "to flow from" or "to pour forth or out of", is the mode by which all things are derived from the First Reality, or Principle...
beginning with God. A first intelligence emanated from God, and from the first intelligence emanated a sphere, its soul, and a second intelligence. The process continued down through the celestial spheres until the sphere of the moon, its soul, and a final intelligence. They considered that each sphere was moved continually by its soul, seeking to emulate the perfection of its intelligence. Avicenna maintained that besides an intelligence and its soul, each sphere was also moved by a natural inclination (mayl).
A Spanish Muslim interpreter of Aristotle, al-Bitruji (d. c.1024), proposed a radical transformation of astronomy that did away with epicycles and eccentrics, in which the celestial spheres were driven by a single unmoved mover at the periphery of the universe. The spheres thus moved with a "natural nonviolent motion." but was a The mover's power diminished with increasing distance from the periphery so that the lower spheres lagged behind in their daily motion around the Earth; this power reached even as far as the sphere of water, producing the tides.
More influential for later Christian thinkers were the teachings of Averroes
Averroes
' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...
(1126–1198), who agreed with Avicenna that the intelligences and souls combine to move the spheres but rejected his concept of emanation. Considering how the soul acts, he maintained that the soul moves its sphere without effort, for the celestial material has no tendency to a contrary motion.
Later in the century, a commentator on the Islamic theologian
Islamic theology
Islamic theology is a branch of Islamic studies regarding the beliefs associated with the Islamic faith. Any religious belief system, or creed, can be considered an example of aqidah. However, this term has taken a significant technical usage in Islamic history and theology, denoting those...
Adud al-Din al-Iji (1281–1355), under the influence of the Ash'ari
Ash'ari
The Ashʿari theology is a school of early Muslim speculative theology founded by the theologian Abu al-Hasan al-Ash'ari...
doctrine of occasionalism
Occasionalism
Occasionalism is a philosophical theory about causation which says that created substances cannot be efficient causes of events. Instead, all events are taken to be caused directly by God...
, which maintained that all physical effects were caused directly by God's will rather than by natural causes, rejected non-religious science and astronomy, and maintained that the celestial spheres were "imaginary things" and "more tenuous than a spider's web".
Medieval Western Europe
In the Early Middle AgesEarly Middle Ages
The Early Middle Ages was the period of European history lasting from the 5th century to approximately 1000. The Early Middle Ages followed the decline of the Western Roman Empire and preceded the High Middle Ages...
, Plato's picture of the heavens was dominant among European philosophers, which led Christian thinkers to question the role and nature of the world-soul. With the recovery of Aristotle
Recovery of Aristotle
The "Recovery of Aristotle" refers to the copying or re-translating of most of Aristotle's other books , from Greek or Arabic text into Latin, during the Middle Ages, of the Latin West...
's works in the twelfth and thirteenth centuries, Aristotle's views supplanted the earlier Platonism
Renaissance of the 12th century
The Renaissance of the 12th century was a period of many changes at the outset of the High Middle Ages. It included social, political and economic transformations, and an intellectual revitalization of Western Europe with strong philosophical and scientific roots...
, and a new set of questions regarding the relationships of the unmoved movers to the spheres and to God emerged.
In the early phases of the Western recovery of Aristotle
Recovery of Aristotle
The "Recovery of Aristotle" refers to the copying or re-translating of most of Aristotle's other books , from Greek or Arabic text into Latin, during the Middle Ages, of the Latin West...
, Robert Grosseteste
Robert Grosseteste
Robert Grosseteste or Grossetete was an English statesman, scholastic philosopher, theologian and Bishop of Lincoln. He was born of humble parents at Stradbroke in Suffolk. A.C...
(c.1175–1253), influenced by medieval Platonism and by the astronomy of al-Bitruji, rejected the idea that the heavens are moved by either souls or intelligences. Adam Marsh
Adam Marsh
Adam Marsh was an English Franciscan, scholar and theologian.-Biography:He was born about 1200 in the diocese of Bath, and educated at Oxford under the famous Grosseteste....
's (c.1200–1259) treatise On the Ebb and Flow of the Sea, which was formerly attributed to Grosseteste, maintained al-Bitruji's opinion that the celestial spheres and the seas are moved by a peripheral mover whose motion weakens with distance.
Thomas Aquinas
Thomas Aquinas
Thomas Aquinas, O.P. , also Thomas of Aquin or Aquino, was an Italian Dominican priest of the Catholic Church, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus, Doctor Communis, or Doctor Universalis...
(c.1225–1274), following Avicenna, interpreted Aristotle to mean that there were two immaterial substances responsible for the motion of each celestial sphere, a soul that was an integral part of its sphere, and an intelligence that was separate from its sphere. The soul shares the motion of its sphere and, through its love and desire for the unmoved separate intelligence, causes the sphere to move. Avicenna, al-Ghazali
Al-Ghazali
Abu Hāmed Mohammad ibn Mohammad al-Ghazzālī , known as Algazel to the western medieval world, born and died in Tus, in the Khorasan province of Persia was a Persian Muslim theologian, jurist, philosopher, and mystic....
, Moses Maimonides, and most Christian scholastic philosophers
Scholasticism
Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100–1500, and a program of employing that method in articulating and defending orthodoxy in an increasingly pluralistic context...
identified Aristotle's intelligences with the angels of revelation, thereby associating an angel with each of the spheres. Moreover, Aquinas rejected the idea that celestial bodies are moved by an internal nature, similar to the heaviness and lightness that moves terrestrial bodies. Attributing souls to the spheres was theologically controversial, as that could make them animals. After the Condemnations of 1277, most philosophers came to reject the idea that the celestial spheres had souls.
In two slightly different discussions, John Buridan (c.1295–1358) suggested that when God created the celestial spheres, he began to move them, impressing in them a circular impetus that would be neither corrupted nor diminished, since there was neither an inclination to other movements nor any resistance in the celestial region. He noted that this would allow God to rest on the seventh day, but he left the matter to be resolved by the theologians.
Nicole Oresme (c.1323-1382) explained the motion of the spheres in traditional terms of the action of intelligences, coupled with a consideration in terms of a power and resistance impressed in the spheres when God created the heavens. In discussing the relation of the moving power of the intelligence, the resistance of the sphere, and the circular velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
, he said "this ratio ought not to be called a ratio of force to resistance except by analogy, because an intelligence moves by will alone ... and the heavens do not resist it."
According to Grant, except for Oresme, scholastic thinkers did not consider the force-resistance model to be properly applicable to the motion of celestial bodies, although some, such as Bartholomew Amicus, thought analogically in terms of force and resistance. By the end of the Middle Ages it was the common opinion among philosophers that the celestial bodies were moved by external intelligences, or angels, and not by some kind of an internal mover.
The movers and Copernicanism
Although Nicolaus CopernicusNicolaus Copernicus
Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....
(1473–1543) transformed Ptolemaic astronomy and Aristotelian cosmology by moving the Earth from the center of the universe, he retained both the traditional model of the celestial spheres and the medieval Aristotelian views of the causes of its motion. Copernicus follows Aristotle to maintain that circular motion is natural to the form of a sphere. However, he also appears to have accepted the traditional philosophical belief that the spheres are moved by an external mover.
Although Johannes Kepler
Johannes Kepler
Johannes Kepler was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his eponymous laws of planetary motion, codified by later astronomers, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican...
's (1571–1630) cosmology eliminated the celestial spheres, he held that the planets were moved both by an external motive power, which he located in the Sun, and a motive soul associated with each planet. In an early manuscript discussing the motion of Mars, Kepler considered the Sun to cause the circular motion of the planet. He then attributed the inward and outward motion of the planet, which transforms its overall motion from circular to oval, to a moving soul in the planet since the motion is "not a natural motion, but more of an animate one". In various writings, Kepler often attributed a kind of intelligence to the inborn motive faculties associated with the stars.
In the aftermath of Copernicanism the planets came to be seen as bodies moving freely through a very subtle aethereal medium. Although many scholastics continued to maintain that intelligences were the celestial movers, they now associated the intelligences with the planets themselves, rather than with the celestial spheres.
Primary sources
- Aristotle, MetaphysicsMetaphysics (Aristotle)Metaphysics is one of the principal works of Aristotle and the first major work of the branch of philosophy with the same name. The principal subject is "being qua being", or being understood as being. It examines what can be asserted about anything that exists just because of its existence and...
- Aristotle, On the heavensOn the HeavensOn the Heavens is Aristotle's chief cosmological treatise: it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world...
- Plato, TimaeusTimaeus (dialogue)Timaeus is one of Plato's dialogues, mostly in the form of a long monologue given by the title character, written circa 360 BC. The work puts forward speculation on the nature of the physical world and human beings. It is followed by the dialogue Critias.Speakers of the dialogue are Socrates,...