Sublunary sphere

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In Aristotelian physics and Greek astronomy, the sublunary sphere is the region of the geocentric cosmos below the Moon, consisting of the four classical elements: earth, water, air, and fire. [1] [2]

Aristotelian physics is a form of natural science described in the works of the Greek philosopher Aristotle (384–322 BCE). In his work Physics, Aristotle intended to establish general principles of change that govern all natural bodies, both living and inanimate, celestial and terrestrial – including all motion, quantitative change, qualitative change, and substantial change.

Cosmos orderly or harmonious system

The cosmos is the universe. Using the word cosmos rather than the word universe implies viewing the universe as a complex and orderly system or entity; the opposite of chaos. The cosmos, and our understanding of the reasons for its existence and significance, are studied in cosmology – a very broad discipline covering any scientific, religious, or philosophical contemplation of the cosmos and its nature, or reasons for existing. Religious and philosophical approaches may include in their concepts of the cosmos various spiritual entities or other matters deemed to exist outside our physical universe.

Moon Earths natural satellite

The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits. The Moon is after Jupiter's satellite Io the second-densest satellite in the Solar System among those whose densities are known.


The sublunary sphere was the realm of changing nature. Beginning with the Moon, up to the limits of the universe, everything (to classical astronomy) was permanent, regular and unchanging – the region of aether where the planets and stars are located. Only in the sublunary sphere did the powers of physics hold sway. [3]

According to ancient and medieval science, aether, also spelled æther or ether and also called quintessence, is the material that fills the region of the universe above the terrestrial sphere. The concept of aether was used in several theories to explain several natural phenomena, such as the traveling of light and gravity. In the late 19th century, physicists postulated that aether permeated all throughout space, providing a medium through which light could travel in a vacuum, but evidence for the presence of such a medium was not found in the Michelson–Morley experiment, and this result has been interpreted as meaning that no such luminiferous aether exists.

Star An astronomical object consisting of a luminous spheroid of plasma held together by its own gravity

A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the estimated 300 sextillion (3×1023) stars in the Universe are invisible to the naked eye from Earth, including all stars outside our galaxy, the Milky Way.

Evolution of concept

Plato and Aristotle helped to formulate the original theory of a sublunary sphere in antiquity [4] - the idea usually going hand in hand with geocentrism and the concept of a spherical Earth.

Plato Classical Greek philosopher

Plato was an Athenian philosopher during the Classical period in Ancient Greece, founder of the Platonist school of thought, and the Academy, the first institution of higher learning in the Western world.

Aristotle philosopher in ancient Greece

Aristotle was a philosopher during the Classical period in Ancient Greece, the founder of the Lyceum and the Peripatetic school of philosophy and Aristotelian tradition. Along with his teacher Plato, he is considered the "Father of Western Philosophy". His writings cover many subjects – including physics, biology, zoology, metaphysics, logic, ethics, aesthetics, poetry, theatre, music, rhetoric, psychology, linguistics, economics, politics and government. Aristotle provided a complex synthesis of the various philosophies existing prior to him, and it was above all from his teachings that the West inherited its intellectual lexicon, as well as problems and methods of inquiry. As a result, his philosophy has exerted a unique influence on almost every form of knowledge in the West and it continues to be a subject of contemporary philosophical discussion.

Spherical Earth idea that the Earth is spherical

The earliest reliably documented mention of the spherical Earth concept dates from around the 6th century BC when it appeared in ancient Greek philosophy, but remained a matter of speculation until the 3rd century BC, when Hellenistic astronomy established the spherical shape of the Earth as a physical given and calculated Earth's circumference. The paradigm was gradually adopted throughout the Old World during Late Antiquity and the Middle Ages. A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan and Juan Sebastián Elcano's expedition's circumnavigation (1519–1522).

Avicenna carried forward into the Middle Ages the Aristotelian idea of generation and corruption being limited to the sublunary sphere. [5] Medieval scholastics like Thomas Aquinas - who charted the division between celestial and sublunary spheres in his work Summa Theologica - also drew on Cicero and Lucan for an awareness of the great frontier between Nature and Sky, sublunary and aetheric spheres. [6] The result for medieval/Renaissance mentalities was a pervasive awareness of the existence, at the Moon, of what C.S. Lewis called 'this "great divide"...from aether to air, from 'heaven' to 'nature', from the realm of gods (or angels) to that of daemons, from the realm of necessity to that of contingence, from the incorruptible to the corruptible"

Avicenna medieval Persian polymath, physician, and philosopher

Ibn Sina, also known as Abu Ali Sina, Pur Sina (پورسینا), and often known in the west as Avicenna was a Persian polymath who is regarded as one of the most significant physicians, astronomers, thinkers and writers of the Islamic Golden Age. He has been described as the father of early modern medicine. Of the 450 works he is known to have written, around 240 have survived, including 150 on philosophy and 40 on medicine.


Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100 to 1700, and a program of employing that method in articulating and defending dogma in an increasingly pluralistic context. It originated as an outgrowth of and a departure from Christian theology within the monastic schools at the earliest European universities. The rise of scholasticism was closely associated with the rise of the 12th and 13th century schools that developed into the earliest modern universities, including those in Italy, France, Spain and England.

Thomas Aquinas Dominican scholastic philosopher of the Roman Catholic Church

Saint Thomas Aquinas was an Italian Dominican friar, Catholic priest, and Doctor of the Church. He is an immensely influential philosopher, theologian, and jurist in the tradition of scholasticism, within which he is also known as the Doctor Angelicus and the Doctor Communis. The name Aquinas identifies his ancestral origins in the county of Aquino in present-day Lazio, Italy.

However, the theories of Copernicus began to challenge the sublunary/aether distinction. In their wake Tycho Brahe's observations of a new star (nova) and of comets in the supposedly unchanging heavens further undermined the Aristotelian view. [7] Thomas Kuhn saw scientists' new ability to see change in the 'incorruptible' heavens as a classic example of the new possibilities opened up by a paradigm shift. [8]

Tycho Brahe Danish astronomer and alchemist

Tycho Brahe was a Danish nobleman, astronomer, and writer known for his accurate and comprehensive astronomical and planetary observations. He was born in the then Danish peninsula of Scania. Well known in his lifetime as an astronomer, astrologer and alchemist, he has been described as "the first competent mind in modern astronomy to feel ardently the passion for exact empirical facts." His observations were some five times more accurate than the best available observations at the time.

Thomas Kuhn American historian, physicist and philosopher

Thomas Samuel Kuhn was an American physicist, historian and philosopher of science whose controversial 1962 book The Structure of Scientific Revolutions was influential in both academic and popular circles, introducing the term paradigm shift, which has since become an English-language idiom.

Literary offshoots

Dante envisaged Mt Purgatory as being so high that it reached above the sublunary sphere, so that “These slopes are free from every natural change”. [9]

Samuel Johnson praised Shakespeare's plays as “exhibiting the real state of sublunary nature, which partakes of good and evil, joy and sorrow, intermingled”. [10]

See also

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Jacques du Chevreul (1595-1649). Jacques du Chevreul was born in Coutances, France and died in Paris, France. Du Chevreul grew up in an educated household and was the son of a magistrate. In 1616, he received a Master of Arts for studying humanities and philosophy at the University of Paris. Du Chevreul continued education at a higher level and received a bachelor of divinity for theology in 1619. He did not start teaching until 1620 where he remained associated with College Harcourt and University of Paris, up until two years before his death when he taught philosophy at the College Royal. Throughout his lifetime Jacques du Chevreul held various teaching and administrative positions including principal and rector. Little is known about his later life. Although he studied subjects such as philosophy, logic, ethics, metaphysics, and physics, he published his two popular books over mathematics. Arithmetica (1622) and Sphaera were both published in Paris, France. Sphaera, du Chevreul’s most popular book was about his view of the world and the universe. He used references from the Bible, Aristotle, and Plato to reject the Copernican model and instead created his own eccentric-epicycle geocentric model of the universe. Du Chevreul believed that the earth was the center of the universe, but that the major planets Venus and Mercury orbited around the sun. He theorized that there were wandering and fixed stars in the heavens and there were a total of thirteen planets in his model. The heavens were in the order of the Moon, the Sun, Mars, Jupiter surrounded by four Medicean stars, Saturn with two satellites, and above all these levels resided God. Du Chevreul's cosmic scheme is a highly original attempt to resist Copernicanism and accommodate Galieleo's telescopic discoveries in an Aristotelian cosmos.


  1. Aristotle, Ethics (1974) p. 357-8
  2. Stephen Toulmin, Night Sky at Rhodes (1963) p. 38 and p. 78
  3. C. C. Gillespie, The Edge of Objectivity (1960) p. 14
  4. Gillespie, p. 13-5
  5. J. J. E. Garcia, Individuation in Scholasticism (1994) p. 41
  6. W. Hooper, C. S. Lewis (1996) p. 529-31
  7. R. Curley, Scientists and Inventors of the Renaissance (2012) p. 6-8
  8. Thomas S. Kuhn, The Structure of Scientific Revolutions (1970) p. 116-7
  9. Dante, Purgatory (1971) p. 235
  10. Samuel Johnson, Selected Writings (Penguin) p. 266

Further reading