History of the center of the Universe

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https://en.wikipedia.org/wiki/History_of_the_center_of_the_Universe 

 

Figure of the heavenly bodies — An illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568 (Bibliothèque Nationale, Paris), depicting Earth as the centre of the Universe.

 

The center of the Universe is a concept that lacks a coherent definition in modern astronomy; according to standard cosmological theories on the shape of the universe, it has no center.

Historically, different people have suggested various locations as the center of the Universe. Many mythological cosmologies included an axis mundi, the central axis of a flat Earth that connects the Earth, heavens, and other realms together. In the 4th century BCE Greece, philosophers developed the geocentric model, based on astronomical observation; this model proposed that the center of the Universe lies at the center of a spherical, stationary Earth, around which the Sun, Moon, planets, and stars rotate. With the development of the heliocentric model by Nicolaus Copernicus in the 16th century, the Sun was believed to be the center of the Universe, with the planets (including Earth) and stars orbiting it.

In the early-20th century, the discovery of other galaxies and the development of the Big Bang theory led to the development of cosmological models of a homogeneous, isotropic Universe, which lacks a central point and is expanding at all points.

Outside astronomy

In religion or mythology, the axis mundi (also cosmic axis, world axis, world pillar, columna cerului, center of the world) is a point described as the center of the world, the connection between it and Heaven, or both. 

Mount Hermon in Lebanon was regarded in some cultures as the axis mundi.

Mount Hermon was regarded as the axis mundi in Canaanite tradition, from where the sons of God are introduced descending in 1 Enoch (1En6:6). The ancient Greeks regarded several sites as places of earth's omphalos (navel) stone, notably the oracle at Delphi, while still maintaining a belief in a cosmic world tree and in Mount Olympus as the abode of the gods. Judaism has the Temple Mount and Mount Sinai, Christianity has the Mount of Olives and Calvary, Islam has Mecca, said to be the place on earth that was created first, and the Temple Mount (Dome of the Rock). In Shinto, the Ise Shrine is the omphalos. In addition to the Kun Lun Mountains, where it is believed the peach tree of immortality is located, the Chinese folk religion recognizes four other specific mountains as pillars of the world. 

A 1581 map depicting Jerusalem as the center of the world.

Sacred places constitute world centers (omphalos) with the altar or place of prayer as the axis. Altars, incense sticks, candles and torches form the axis by sending a column of smoke, and prayer, toward heaven. The architecture of sacred places often reflects this role. "Every temple or palace--and by extension, every sacred city or royal residence--is a Sacred Mountain, thus becoming a Centre." The stupa of Hinduism, and later Buddhism, reflects Mount Meru. Cathedrals are laid out in the form of a cross, with the vertical bar representing the union of Earth and heaven as the horizontal bars represent union of people to one another, with the altar at the intersection. Pagoda structures in Asian temples take the form of a stairway linking Earth and heaven. A steeple in a church or a minaret in a mosque also serve as connections of Earth and heaven. Structures such as the maypole, derived from the Saxons' Irminsul, and the totem pole among indigenous peoples of the Americas also represent world axes. The calumet, or sacred pipe, represents a column of smoke (the soul) rising form a world center. A mandala creates a world center within the boundaries of its two-dimensional space analogous to that created in three-dimensional space by a shrine.

In medieval times some Christians thought of Jerusalem as the center of the world (Latin: umbilicus mundi, Greek: Omphalos), and was so represented in the so-called T and O maps. Byzantine hymns speak of the Cross being "planted in the center of the earth."

Center of a flat Earth

The Flammarion engraving (1888) depicts a traveller who arrives at the edge of a Flat Earth and sticks his head through the firmament.

 

The Flat Earth model is a belief that the Earth's shape is a plane or disk covered by a firmament containing heavenly bodies. Most pre-scientific cultures have had conceptions of a Flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period (early centuries AD) and China until the 17th century. It was also typically held in the aboriginal cultures of the Americas, and a flat Earth domed by the firmament in the shape of an inverted bowl is common in pre-scientific societies.

"Center" is well-defined in a Flat Earth model. A flat Earth would have a definite geographic center. There would also be a unique point at the exact center of a spherical firmament (or a firmament that was a half-sphere).

Earth as the center of the Universe

The Flat Earth model gave way to an understanding of a Spherical Earth. Aristotle (384–322 BCE) provided observational arguments supporting the idea of a spherical Earth, namely that different stars are visible in different locations, travelers going south see southern constellations rise higher above the horizon, and the shadow of Earth on the Moon during a lunar eclipse is round, and spheres cast circular shadows while discs generally do not.

This understanding was accompanied by models of the Universe that depicted the Sun, Moon, stars, and naked eye planets circling the spherical Earth, including the noteworthy models of Aristotle (see Aristotelian physics) and Ptolemy. This geocentric model was the dominant model from the 4th century BCE until the 17th century CE.

Sun as center of the Universe

The heliocentric model from Nicolaus Copernicus' De revolutionibus orbium coelestium

Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a relatively stationary Sun at the center of our Solar System. The word comes from the Greek (ἥλιος helios "sun" and κέντρον kentron "center").

The notion that the Earth revolves around the Sun had been proposed as early as the 3rd century BCE by Aristarchus of Samos, but had received no support from most other ancient astronomers.

Nicolaus Copernicus' major theory of a heliocentric model was published in De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), in 1543, the year of his death, though he had formulated the theory several decades earlier. Copernicus' ideas were not immediately accepted, but they did begin a paradigm shift away from the Ptolemaic geocentric model to a heliocentric model. The Copernican revolution, as this paradigm shift would come to be called, would last until Isaac Newton’s work over a century later.

Johannes Kepler published his first two laws about planetary motion in 1609, having found them by analyzing the astronomical observations of Tycho Brahe. Kepler's third law was published in 1619. The first law was "The orbit of every planet is an ellipse with the Sun at one of the two foci."

On 7 January 1610 Galileo used his telescope, with optics superior to what had been available before. He described "three fixed stars, totally invisible by their smallness", all close to Jupiter, and lying on a straight line through it. Observations on subsequent nights showed that the positions of these "stars" relative to Jupiter were changing in a way that would have been inexplicable if they had really been fixed stars. On 10 January Galileo noted that one of them had disappeared, an observation which he attributed to its being hidden behind Jupiter. Within a few days he concluded that they were orbiting Jupiter: Galileo stated that he had reached this conclusion on 11 January. He had discovered three of Jupiter's four largest satellites (moons). He discovered the fourth on 13 January.

His observations of the satellites of Jupiter created a revolution in astronomy: a planet with smaller planets orbiting it did not conform to the principles of Aristotelian Cosmology, which held that all heavenly bodies should circle the Earth. Many astronomers and philosophers initially refused to believe that Galileo could have discovered such a thing;  by showing that, like Earth, other planets could also have moons of their own that followed prescribed paths, and hence that orbital mechanics didn't apply only to the Earth, planets, and Sun, what Galileo had essentially done was to show that other planets might be "like Earth".

Newton made clear his heliocentric view of the Solar System – developed in a somewhat modern way, because already in the mid-1680s he recognised the "deviation of the Sun" from the centre of gravity of the solar system. For Newton, it was not precisely the centre of the Sun or any other body that could be considered at rest, but rather "the common centre of gravity of the Earth, the Sun and all the Planets is to be esteem'd the Centre of the World", and this centre of gravity "either is at rest or moves uniformly forward in a right line" (Newton adopted the "at rest" alternative in view of common consent that the centre, wherever it was, was at rest).

Milky Way's galactic center as center of the Universe

Before the 1920s, it was generally believed that there were no galaxies other than our own (see for example The Great Debate). Thus, to astronomers of previous centuries, there was no distinction between a hypothetical center of the galaxy and a hypothetical center of the universe.

Great Andromeda Nebula by Isaac Roberts (1899)

In 1750 Thomas Wright, in his work An original theory or new hypothesis of the Universe, correctly speculated that the Milky Way might be a body of a huge number of stars held together by gravitational forces rotating about a Galactic Center, akin to the Solar System but on a much larger scale. The resulting disk of stars can be seen as a band on the sky from our perspective inside the disk. In a treatise in 1755, Immanuel Kant elaborated on Wright's idea about the structure of the Milky Way. 

The 19th century astronomer Johann Heinrich von Mädler proposed the Central Sun Hypothesis, according to which the stars of the universe revolved around a point in the Pleiades.

The nonexistence of a center of the Universe

In 1917, Heber Doust Curtis observed a nova within what then was called the "Andromeda Nebula". Searching the photographic record, 11 more novae were discovered. Curtis noticed that novas in Andromeda were drastically fainter than novas in the Milky Way. Based on this, Curtis was able to estimate that Andromeda was 500,000 light-years away. As a result, Curtis became a proponent of the so-called "island Universes" hypothesis, which held that objects previously believed to be spiral nebulae within the Milky Way were actually independent galaxies.

In 1920, the Great Debate between Harlow Shapley and Curtis took place, concerning the nature of the Milky Way, spiral nebulae, and the dimensions of the Universe. To support his claim that the Great Andromeda Nebula (M31) was an external galaxy, Curtis also noted the appearance of dark lanes resembling the dust clouds in our own galaxy, as well as the significant Doppler shift. In 1922 Ernst Öpik presented an elegant and simple astrophysical method to estimate the distance of M31. His result put the Andromeda Nebula far outside our galaxy at a distance of about 450,000 parsec, which is about 1,500,000 ly. Edwin Hubble settled the debate about whether other galaxies exist in 1925 when he identified extragalactic Cepheid variable stars for the first time on astronomical photos of M31. These were made using the 2.5 metre (100 in) Hooker telescope, and they enabled the distance of Great Andromeda Nebula to be determined. His measurement demonstrated conclusively that this feature was not a cluster of stars and gas within our galaxy, but an entirely separate galaxy located a significant distance from our own. This proved the existence of other galaxies.

Expanding Universe

Hubble also demonstrated that the redshift of other galaxies is approximately proportional to their distance from the Earth (Hubble's law). This raised the appearance of our galaxy being in the center of an expanding Universe, however, Hubble rejected the findings philosophically:

...if we see the nebulae all receding from our position in space, then every other observer, no matter where he may be located, will see the nebulae all receding from his position. However, the assumption is adopted. There must be no favoured location in the Universe, no centre, no boundary; all must see the Universe alike. And, in order to ensure this situation, the cosmologist, postulates spatial isotropy and spatial homogeneity, which is his way of stating that the Universe must be pretty much alike everywhere and in all directions."

The redshift observations of Hubble, in which galaxies appear to be moving away from us at a rate proportional to their distance from us, are now understood to be a result of the metric expansion of space. This is the increase of the distance between two distant parts of the Universe with time, and is an intrinsic expansion whereby the scale of space itself changes. As Hubble theorized, all observers anywhere in the Universe will observe a similar effect.

Copernican and cosmological principles

The Copernican principle, named after Nicolaus Copernicus, states that the Earth is not in a central, specially favored position. Hermann Bondi named the principle after Copernicus in the mid-20th century, although the principle itself dates back to the 16th-17th century paradigm shift away from the geocentric Ptolemaic system. 

The cosmological principle is an extension of the Copernican principle which states that the Universe is homogeneous (the same observational evidence is available to observers at different locations in the Universe) and isotropic (the same observational evidence is available by looking in any direction in the Universe). A homogeneous, isotropic Universe does not have a center.

Celestial spheres

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Celestial_spheres 

Geocentric celestial spheres; Peter Apian's Cosmographia (Antwerp, 1539)

The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others. In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element (quintessence), like jewels set in orbs. Since it was believed that the fixed stars did not change their positions relative to one another, it was argued that they must be on the surface of a single starry sphere.

In modern thought, the orbits of the planets are viewed as the paths of those planets through mostly empty space. Ancient and medieval thinkers, however, considered the celestial orbs to be thick spheres of rarefied matter nested one within the other, each one in complete contact with the sphere above it and the sphere below. When scholars applied Ptolemy's epicycles, they presumed that each planetary sphere was exactly thick enough to accommodate them. By combining this nested sphere model with astronomical observations, scholars calculated what became generally accepted values at the time for the distances to the Sun (about 4 million miles), to the other planets, and to the edge of the universe (about 73 million miles). The nested sphere model's distances to the Sun and planets differ significantly from modern measurements of the distances, and the size of the universe is now known to be inconceivably large and continuously expanding.

Albert Van Helden has suggested that from about 1250 until the 17th century, virtually all educated Europeans were familiar with the Ptolemaic model of "nesting spheres and the cosmic dimensions derived from it". Even following the adoption of Copernicus's heliocentric model of the universe, new versions of the celestial sphere model were introduced, with the planetary spheres following this sequence from the central Sun: Mercury, Venus, Earth-Moon, Mars, Jupiter and Saturn.

Mainstream belief in the theory of celestial spheres did not survive the Scientific Revolution. In the early 1600s, Kepler continued to discuss celestial spheres, although he did not consider that the planets were carried by the spheres but held that they moved in elliptical paths described by Kepler's laws of planetary motion. In the late 1600s, Greek and medieval theories concerning the motion of terrestrial and celestial objects were replaced by Newton's law of universal gravitation and Newtonian mechanics, which explain how Kepler's laws arise from the gravitational attraction between bodies.

History

Early ideas of spheres and circles

In Greek antiquity the ideas of celestial spheres and rings first appeared in the cosmology of Anaximander in the early 6th century BC. In his cosmology both the Sun and Moon are circular open vents in tubular rings of fire enclosed in tubes of condensed air; these rings constitute the rims of rotating chariot-like wheels pivoting on the Earth at their centre. The fixed stars are also open vents in such wheel rims, but there are so many such wheels for the stars that their contiguous rims all together form a continuous spherical shell encompassing the Earth. All these wheel rims had originally been formed out of an original sphere of fire wholly encompassing the Earth, which had disintegrated into many individual rings. Hence, in Anaximanders's cosmogony, in the beginning was the sphere, out of which celestial rings were formed, from some of which the stellar sphere was in turn composed. As viewed from the Earth, the ring of the Sun was highest, that of the Moon was lower, and the sphere of the stars was lowest.

Following Anaximander, his pupil Anaximenes (c. 585–528/4) held that the stars, Sun, Moon, and planets are all made of fire. But whilst the stars are fastened on a revolving crystal sphere like nails or studs, the Sun, Moon, and planets, and also the Earth, all just ride on air like leaves because of their breadth. And whilst the fixed stars are carried around in a complete circle by the stellar sphere, the Sun, Moon and planets do not revolve under the Earth between setting and rising again like the stars do, but rather on setting they go laterally around the Earth like a cap turning halfway around the head until they rise again. And unlike Anaximander, he relegated the fixed stars to the region most distant from the Earth. The most enduring feature of Anaximenes' cosmos was its conception of the stars being fixed on a crystal sphere as in a rigid frame, which became a fundamental principle of cosmology down to Copernicus and Kepler.

After Anaximenes, Pythagoras, Xenophanes and Parmenides all held that the universe was spherical. And much later in the fourth century BC Plato's Timaeus proposed that the body of the cosmos was made in the most perfect and uniform shape, that of a sphere containing the fixed stars. But it posited that the planets were spherical bodies set in rotating bands or rings rather than wheel rims as in Anaximander's cosmology.

Emergence of the planetary spheres

Instead of bands, Plato's student Eudoxus developed a planetary model using concentric spheres for all the planets, with three spheres each for his models of the Moon and the Sun and four each for the models of the other five planets, thus making 26 spheres in all. Callippus modified this system, using five spheres for his models of the Sun, Moon, Mercury, Venus, and Mars and retaining four spheres for the models of Jupiter and Saturn, thus making 33 spheres in all. Each planet is attached to the innermost of its own particular set of spheres. Although the models of Eudoxus and Callippus qualitatively describe the major features of the motion of the planets, they fail to account exactly for these motions and therefore cannot provide quantitative predictions. Although historians of Greek science have traditionally considered these models to be merely geometrical representations, recent studies have proposed that they were also intended to be physically real or have withheld judgment, noting the limited evidence to resolve the question.

In his Metaphysics, Aristotle developed a physical cosmology of spheres, based on the mathematical models of Eudoxus. In Aristotle's fully developed celestial model, the spherical Earth is at the centre of the universe and the planets are moved by either 47 or 55 interconnected spheres that form a unified planetary system, whereas in the models of Eudoxus and Callippus each planet's individual set of spheres were not connected to those of the next planet. Aristotle says the exact number of spheres, and hence the number of movers, is to be determined by astronomical investigation, but he added additional spheres to those proposed by Eudoxus and Callippus, to counteract the motion of the outer spheres. Aristotle considers that these spheres are made of an unchanging fifth element, the aether. Each of these concentric spheres is moved by its own god—an unchanging divine unmoved mover, and who moves its sphere simply by virtue of being loved by it.

Ptolemaic model of the spheres for Venus, Mars, Jupiter, and Saturn with epicycle, eccentric deferent and equant point. Georg von Peuerbach, Theoricae novae planetarum, 1474.

In his Almagest, the astronomer Ptolemy (fl. ca. 150 AD) developed geometrical predictive models of the motions of the stars and planets and extended them to a unified physical model of the cosmos in his Planetary hypotheses. By using eccentrics and epicycles, his geometrical model achieved greater mathematical detail and predictive accuracy than had been exhibited by earlier concentric spherical models of the cosmos. In Ptolemy's physical model, each planet is contained in two or more spheres, but in Book 2 of his Planetary Hypotheses Ptolemy depicted thick circular slices rather than spheres as in its Book 1. One sphere/slice is the deferent, with a centre offset somewhat from the Earth; the other sphere/slice is an epicycle embedded in the deferent, with the planet embedded in the epicyclical sphere/slice. Ptolemy's model of nesting spheres provided the general dimensions of the cosmos, the greatest distance of Saturn being 19,865 times the radius of the Earth and the distance of the fixed stars being at least 20,000 Earth radii.

The planetary spheres were arranged outwards from the spherical, stationary Earth at the centre of the universe in this order: the spheres of the Moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn. In more detailed models the seven planetary spheres contained other secondary spheres within them. The planetary spheres were followed by the stellar sphere containing the fixed stars; other scholars added a ninth sphere to account for the precession of the equinoxes, a tenth to account for the supposed trepidation of the equinoxes, and even an eleventh to account for the changing obliquity of the ecliptic. In antiquity the order of the lower planets was not universally agreed. Plato and his followers ordered them Moon, Sun, Mercury, Venus, and then followed the standard model for the upper spheres. Others disagreed about the relative place of the spheres of Mercury and Venus: Ptolemy placed both of them beneath the Sun with Venus above Mercury, but noted others placed them both above the Sun; some medieval thinkers, such as al-Bitruji, placed the sphere of Venus above the Sun and that of Mercury below it.

Middle Ages

Astronomical discussions

The Earth within seven celestial spheres, from Bede, De natura rerum, late 11th century

 

A series of astronomers, beginning with the Muslim astronomer al-Farghānī, used the Ptolemaic model of nesting spheres to compute distances to the stars and planetary spheres. Al-Farghānī's distance to the stars was 20,110 Earth radii which, on the assumption that the radius of the Earth was 3,250 miles, came to 65,357,500 miles. An introduction to Ptolemy's Almagest, the Tashil al-Majisti, believed to be written by Thābit ibn Qurra, presented minor variations of Ptolemy's distances to the celestial spheres. In his Zij, Al-Battānī presented independent calculations of the distances to the planets on the model of nesting spheres, which he thought was due to scholars writing after Ptolemy. His calculations yielded a distance of 19,000 Earth radii to the stars.

Around the turn of the millennium, the Arabic astronomer and polymath Ibn al-Haytham (Alhacen) presented a development of Ptolemy's geocentric epicyclic models in terms of nested spheres. Despite the similarity of this concept to that of Ptolemy's Planetary Hypotheses, al-Haytham's presentation differs in sufficient detail that it has been argued that it reflects an independent development of the concept. In chapters 15–16 of his Book of Optics, Ibn al-Haytham also said that the celestial spheres do not consist of solid matter.

Near the end of the twelfth century, the Spanish Muslim astronomer al-Bitrūjī (Alpetragius) sought to explain the complex motions of the planets without Ptolemy's epicycles and eccentrics, using an Aristotelian framework of purely concentric spheres that moved with differing speeds from east to west. This model was much less accurate as a predictive astronomical model, but it was discussed by later European astronomers and philosophers.

In the thirteenth century the astronomer, al-'Urḍi, proposed a radical change to Ptolemy's system of nesting spheres. In his Kitāb al-Hayáh, he recalculated the distance of the planets using parameters which he redetermined. Taking the distance of the Sun as 1,266 Earth radii, he was forced to place the sphere of Venus above the sphere of the Sun; as a further refinement, he added the planet's diameters to the thickness of their spheres. As a consequence, his version of the nesting spheres model had the sphere of the stars at a distance of 140,177 Earth radii.

About the same time, scholars in European universities began to address the implications of the rediscovered philosophy of Aristotle and astronomy of Ptolemy. Both astronomical scholars and popular writers considered the implications of the nested sphere model for the dimensions of the universe. Campanus of Novara's introductory astronomical text, the Theorica planetarum, used the model of nesting spheres to compute the distances of the various planets from the Earth, which he gave as 22,612 Earth radii or 73,387,747 100/660 miles. In his Opus Majus, Roger Bacon cited Al-Farghānī's distance to the stars of 20,110 Earth radii, or 65,357,700 miles, from which he computed the circumference of the universe to be 410,818,517 3/7 miles. Clear evidence that this model was thought to represent physical reality is the accounts found in Bacon's Opus Majus of the time needed to walk to the Moon and in the popular Middle English South English Legendary, that it would take 8,000 years to reach the highest starry heaven. General understanding of the dimensions of the universe derived from the nested sphere model reached wider audiences through the presentations in Hebrew by Moses Maimonides, in French by Gossuin of Metz, and in Italian by Dante Alighieri.

Philosophical and theological discussions

Philosophers were less concerned with such mathematical calculations than with the nature of the celestial spheres, their relation to revealed accounts of created nature, and the causes of their motion.

Adi Setia describes the debate among Islamic scholars in the twelfth century, based on the commentary of Fakhr al-Din al-Razi about whether the celestial spheres are real, concrete physical bodies or "merely the abstract circles in the heavens traced out… by the various stars and planets." Setia points out that most of the learned, and the astronomers, said they were solid spheres "on which the stars turn… and this view is closer to the apparent sense of the Qur'anic verses regarding the celestial orbits." However, al-Razi mentions that some, such as the Islamic scholar Dahhak, considered them to be abstract. Al-Razi himself, was undecided, he said: "In truth, there is no way to ascertain the characteristics of the heavens except by authority [of divine revelation or prophetic traditions]." Setia concludes: "Thus it seems that for al-Razi (and for others before and after him), astronomical models, whatever their utility or lack thereof for ordering the heavens, are not founded on sound rational proofs, and so no intellectual commitment can be made to them insofar as description and explanation of celestial realities are concerned."

Christian and Muslim philosophers modified Ptolemy's system to include an unmoved outermost region, the empyrean heaven, which came to be identified as the dwelling place of God and all the elect. Medieval Christians identified the sphere of stars with the Biblical firmament and sometimes posited an invisible layer of water above the firmament, to accord with Genesis. An outer sphere, inhabited by angels, appeared in some accounts.

Edward Grant, a historian of science, has provided evidence that medieval scholastic philosophers generally considered the celestial spheres to be solid in the sense of three-dimensional or continuous, but most did not consider them solid in the sense of hard. The consensus was that the celestial spheres were made of some kind of continuous fluid.

Later in the century, the mutakallim Adud al-Din al-Iji (1281–1355) rejected the principle of uniform and circular motion, following the Ash'ari doctrine of atomism, which maintained that all physical effects were caused directly by God's will rather than by natural causes. He maintained that the celestial spheres were "imaginary things" and "more tenuous than a spider's web". His views were challenged by al-Jurjani (1339–1413), who maintained that even if the celestial spheres "do not have an external reality, yet they are things that are correctly imagined and correspond to what [exists] in actuality".

Medieval astronomers and philosophers developed diverse theories about the causes of the celestial spheres' motions. They attempted to explain the spheres' motions in terms of the materials of which they were thought to be 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 incorporated quantitative analyses that related speed, motive force and resistance. By the end of the Middle Ages, the common opinion in Europe was that celestial bodies were moved by external intelligences, identified with the angels of revelation. The outermost moving sphere, which moved with the daily motion affecting all subordinate spheres, was moved by an unmoved mover, the Prime Mover, who was identified with God. Each of the lower spheres was moved by a subordinate spiritual mover (a replacement for Aristotle's multiple divine movers), called an intelligence.

Renaissance

Thomas Digges' 1576 Copernican heliocentric model of the celestial orbs

Early in the sixteenth century Nicolaus Copernicus drastically reformed the model of astronomy by displacing the Earth from its central place in favour of the Sun, yet he called his great work De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres). Although Copernicus does not treat the physical nature of the spheres in detail, his few allusions make it clear that, like many of his predecessors, he accepted non-solid celestial spheres. Copernicus rejected the ninth and tenth spheres, placed the orb of the Moon around the Earth, and moved the Sun from its orb to the center of the universe. The planetary orbs circled the center of the universe in the following order: Mercury, Venus, the great orb containing the Earth and the orb of the Moon, then the orbs of Mars, Jupiter, and Saturn. Finally he retained the eighth sphere of the stars, which he held to be stationary.

The English almanac maker, Thomas Digges, delineated the spheres of the new cosmological system in his Perfit Description of the Caelestiall Orbes … (1576). Here he arranged the "orbes" in the new Copernican order, expanding one sphere to carry "the globe of mortalitye", the Earth, the four classical elements, and the Moon, and expanding the sphere of stars infinitely to encompass all the stars and also to serve as "the court of the Great God, the habitacle of the elect, and of the coelestiall angelles."

Johannes Kepler's diagram of the celestial spheres, and of the spaces between them, following the opinion of Copernicus (Mysterium Cosmographicum, 2nd ed., 1621)

 

In the sixteenth century, a number of philosophers, theologians, and astronomers—among them Francesco Patrizi, Andrea Cisalpino, Peter Ramus, Robert Bellarmine, Giordano Bruno, Jerónimo Muñoz, Michael Neander, Jean Pena, and Christoph Rothmann—abandoned the concept of celestial spheres. Rothmann argued from observations of the comet of 1585 that the lack of observed parallax indicated that the comet was beyond Saturn, while the absence of observed refraction indicated the celestial region was of the same material as air, hence there were no planetary spheres.

Tycho Brahe's investigations of a series of comets from 1577 to 1585, aided by Rothmann's discussion of the comet of 1585 and Michael Maestlin's tabulated distances of the comet of 1577, which passed through the planetary orbs, led Tycho to conclude that "the structure of the heavens was very fluid and simple." Tycho opposed his view to that of "very many modern philosophers" who divided the heavens into "various orbs made of hard and impervious matter." Edward Grant found relatively few believers in hard celestial spheres before Copernicus and concluded that the idea first became common sometime between the publication of Copernicus's De revolutionibus in 1542 and Tycho Brahe's publication of his cometary research in 1588.

In his early Mysterium Cosmographicum, Johannes Kepler considered the distances of the planets and the consequent gaps required between the planetary spheres implied by the Copernican system, which had been noted by his former teacher, Michael Maestlin. Kepler's Platonic cosmology filled the large gaps with the five Platonic polyhedra, which accounted for the spheres' measured astronomical distance. In Kepler's mature celestial physics, the spheres were regarded as the purely geometric spatial regions containing each planetary orbit rather than as the rotating physical orbs of the earlier Aristotelian celestial physics. The eccentricity of each planet's orbit thereby defined the radii of the inner and outer limits of its celestial sphere and thus its thickness. In Kepler's celestial mechanics, the cause of planetary motion became the rotating Sun, itself rotated by its own motive soul. However, an immobile stellar sphere was a lasting remnant of physical celestial spheres in Kepler's cosmology.

Literary and visual expressions

"Because the medieval universe is finite, it has a shape, the perfect spherical shape, containing within itself an ordered variety....
"The spheres ... present us with an object in which the mind can rest, overwhelming in its greatness but satisfying in its harmony."

C. S. Lewis, The Discarded Image, p. 99
 

Dante and Beatrice gaze upon the highest Heaven; from Gustave Doré's illustrations to the Divine Comedy, Paradiso Canto 28, lines 16–39

In Cicero's Dream of Scipio, the elder Scipio Africanus describes an ascent through the celestial spheres, compared to which the Earth and the Roman Empire dwindle into insignificance. A commentary on the Dream of Scipio by the Roman writer Macrobius, which included a discussion of the various schools of thought on the order of the spheres, did much to spread the idea of the celestial spheres through the Early Middle Ages.

Nicole Oresme, Le livre du Ciel et du Monde, Paris, BnF, Manuscrits, Fr. 565, f. 69, (1377)

 

Some late medieval figures noted that the celestial spheres' physical order was inverse to their order on the spiritual plane, where God was at the center and the Earth at the periphery. Near the beginning of the fourteenth century Dante, in the Paradiso of his Divine Comedy, described God as a light at the center of the cosmos. Here the poet ascends beyond physical existence to the Empyrean Heaven, where he comes face to face with God himself and is granted understanding of both divine and human nature. Later in the century, the illuminator of Nicole Oresme's Le livre du Ciel et du Monde, a translation of and commentary on Aristotle's De caelo produced for Oresme's patron, King Charles V, employed the same motif. He drew the spheres in the conventional order, with the Moon closest to the Earth and the stars highest, but the spheres were concave upwards, centered on God, rather than concave downwards, centered on the Earth. Below this figure Oresme quotes the Psalms that "The heavens declare the Glory of God and the firmament showeth his handiwork."

The late-16th-century Portuguese epic The Lusiads vividly portrays the celestial spheres as a "great machine of the universe" constructed by God. The explorer Vasco da Gama is shown the celestial spheres in the form of a mechanical model. Contrary to Cicero's representation, da Gama's tour of the spheres begins with the Empyrean, then descends inward toward Earth, culminating in a survey of the domains and divisions of earthly kingdoms, thus magnifying the importance of human deeds in the divine plan.

Astral plane

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Astral_plane 

The astral spheres were thought to be planes of angelic existence intermediate between earth and heaven.

The astral plane, also called the astral realm or the astral world, is a plane of existence postulated by classical (particularly neo-Platonic, where it originated), medieval, oriental, and esoteric philosophies and mystery religions. It is the world of the celestial spheres, crossed by the soul in its astral body on the way to being born and after death, and is generally believed to be populated by angels, spirits or other immaterial beings. In the late 19th and early 20th century the term was popularised by Theosophy and neo-Rosicrucianism.

Another view holds that the astral plane or world, rather than being some kind of boundary area crossed by the soul, is the entirety of spirit existence or spirit worlds to which those who die on Earth go, and where they live out their non-physical lives. It is understood that all consciousness resides in the astral plane. Some writers conflate this realm with heaven or paradise or union with God itself, and others do not. P. Yogananda wrote in Autobiography of a Yogi, "The astral universe . . . is hundreds of times larger than the material universe . . .[with] many astral planets, teeming with astral beings." (p.416) When Alice Bailey writes of seeing "Masters . . . upon the inner spiritual planes [who]. . . work with Christ and the planetary hierarchy," she refers to a vision she had of the unseen astral realm that these and countless other beings inhabit. Christ being in that realm, it is hard to construe it as a non-heaven.

The Barzakh, olam mithal or intermediate world in Islam is a related concept. In Judaism, it is known as the "World of Yetzirah", according to Lurianic Kabbalah.

History

Dante's heavens and hells symbolised the astral spheres and their associated virtues and vices.

 

Plato and Aristotle taught that the stars were composed of a type of matter different from the four earthly elements - a fifth, ethereal element or quintessence. In the "astral mysticism" of the classical world the human psyche was composed of the same material, thus accounting for the influence of the stars upon human affairs. In his commentaries on Plato's Timaeus, Proclus wrote;

Man is a little world (mikros cosmos). For, just like the Whole, he possesses both mind and reason, both a divine and a mortal body. He is also divided up according to the universe. It is for this reason, you know, that some are accustomed to say that his consciousness corresponds with the nature of the fixed stars, his reason in its contemplative aspect with Saturn and in its social aspect with Jupiter, (and) as to his irrational part, the passionate nature with Mars, the eloquent with Mercury, the appetitive with Venus, the sensitive with the Sun and the vegetative with the Moon.

Such doctrines were commonplace in mystery-schools and Hermetic and gnostic sects throughout the Roman Empire and influenced the early Christian church. Paul's Second Epistle to the Corinthians contains a reference to the astral plane or astral projection: "I know a man in Christ who fourteen years ago was caught up to the third heaven. Whether it was in the body or out of the body I do not know—God knows."

Among Muslims the "astral" world-view was soon rendered orthodox by Quranic references to the Prophet's ascent through the seven heavens. Scholars took up the Greek Neoplatonist accounts as well as similar material in Hindu and Zoroastrian texts. The expositions of Ibn Sina (Avicenna), the Brotherhood of Purity and others, when translated into Latin in the Norman era, were to have a profound effect upon European mediaeval alchemy and astrology. By the 14th century Dante was describing his own imaginary journey through the astral spheres of Paradise.

Throughout the Renaissance, philosophers, Paracelsians, Rosicrucians and alchemists continued to discuss the nature of the astral world intermediate between earth and the divine. Once the telescope established that no spiritual heaven was visible around the solar system, the idea was superseded in mainstream science.

The Astral Plane and Astral Experience

Planes of existence Gross and subtle bodies
Theosophy

Full list

Rosicrucian

The 7 Worlds & the 7 Cosmic Planes The Seven-fold constitution of Man The Ten-fold constitution of Man

Thelema

Body of light | Thelemic mysticism

Hermeticism

Hermeticism | Cosmogony

Surat Shabda Yoga

Cosmology

Jainism

Jain cosmology

Sufism

Sufi cosmology

Hinduism

Talas/Lokas - Tattvas, Kosas, Upadhis

Buddhism

Buddhist cosmology

Gnosticism

Seven earths

Kabbalah

Atziluth > Beri'ah > Yetzirah > Assiah Sephirot

Fourth Way

Ray of Creation The Laws Three Centers and Five Centers

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According to occult teachings the astral plane can be visited consciously through astral projection, meditation and mantra, near death experience, lucid dreaming, or other means. Individuals that are trained in the use of the astral vehicle can separate their consciousness in the astral vehicle from the physical body at will. The first stage in development, according to Ramacharaka, is "mastery of the physical body and its care and attention", which pertains not only to the physical body but also to its double in the astral. In addition, one must spend time tuning the "instinctive mind". The first three subdivisions of the instinctive mind are passions, desires, and lusts. The second stage is the intellect, otherwise known as the sharpening of the mind. Someone operating largely out of the instinctive mind would "have only a glimmering of intellect", therefore those who are centered in the intellect would only have an inkling of the spiritual. Once both stages are completed the spiritual mind can be awakened. 

In early theosophical literature the term "astral" may refer to the aether. Later theosophical authors such as Annie Besant and C. W. Leadbeater make the astral finer than the etheric plane but "denser" than the mental plane. In order to create a unified view of seven bodies and remove earlier Sanskrit terms, an etheric plane was introduced and the term "astral body" was used to replace the former kamarupa - sometimes termed the body of emotion, illusion or desire. Some of those propounding such claims explain their belief that letting go of desires is spiritual progress by noting that, the more one lets go of earthly 'desire' feelings, the less tied down to the physical world, a world of illusion, and the more connected to the astral, where all is visible and known.

According to Max Heindel's Rosicrucian writings, desire-stuff may be described as a type of force-matter, in incessant motion, responsive to the slightest feeling. The desire world is also said to be the abode of the dead for some time subsequent to death. It is also the home of the archangels. In the higher regions of the desire world thoughts take a definite form and color perceptible to all, all is light and there is but one long day. 

In his book Autobiography of a Yogi, Paramhansa Yogananda provides details about the astral planes learned from his guru.

 Yogananda claims that nearly all individuals enter the astral planes after death. There they work out the seeds of past karma through astral incarnations, or (if their karma requires) they return to earthly incarnations for further refinement. Once an individual has attained the meditative state of nirvikalpa samadhi in an earthy or astral incarnation, the soul may progress upward to the "illumined astral planet" of Hiranyaloka.

After this transitional stage, the soul may then move upward to the more subtle causal spheres where many more incarnations allow them to further refine before final unification.

In popular culture

• The astral plane was mentioned in Episodes 4 and 5 of Season 1 in Netflix's series The Chilling Adventures of Sabrina the Teenage Witch.
• The FX television show, American Horror Story, Season 3 (also known as Coven) and Season 8 (also known as Apocalypse) mention and perform the act of Descensum as a way of traveling to the astral plane.
• The song, "Astral Plane", was featured on the album The Order of Time by Valerie June
• In the FX television show Legion, it is a spiritual plane where Charles Xavier destroys the Shadow King, leading up to the hibernation of Charles' son known as Legion, who finds himself fighting for his humanity in this same realm.
• The song, “Dream Weaver”, by Gary Wright, also mentions “Fly me high through the starry skies / maybe to an astral plane”
• The tabletop role-playing game, Shadowrun, refers to the Astral Plane, also known as Astral Space.
• The song "Astral Plane" appears on the self titled album by The Modern Lovers.
• The song "Over The Mountain" by Ozzy Osbourne mentions "Where did I wander, where do you think I wandered to / I've seen life's magic, astral plane I travel through".
• The Marvel Comics Astral Plane, frequently mentioned in stories featuring both Dr. Strange and the X-men.
• The Astral Plane was featured in the 2016 Marvel Studios Movie Dr. Strange.
• The Astral Plane is the final level of NetHack, where one has to sacrifice the Amulet of Yendor on the correct altar to ascend to the status of Demigod.
• The Astral Plane appears in the tabletop role-playing game Dungeons & Dragons.