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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. 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.Lindberg, ''Beginnings of Western Science'', p. 251. When scholars applied Pto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johannes Kepler
Johannes Kepler (; ; 27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best known for his laws of planetary motion, and his books '' Astronomia nova'', '' Harmonice Mundi'', and '' Epitome Astronomiae Copernicanae''. These works also provided one of the foundations for Newton's theory of universal gravitation. Kepler was a mathematics teacher at a seminary school in Graz, where he became an associate of Prince Hans Ulrich von Eggenberg. Later he became an assistant to the astronomer Tycho Brahe in Prague, and eventually the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He also taught mathematics in Linz, and was an adviser to General Wallenstein. Additionally, he did fundamental work in the field of optics, invented an improved version of the refracting (or Keplerian) tele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Callippus
Callippus (; grc, Κάλλιππος; c. 370 BC – c. 300 BC) was a Greek astronomer and mathematician. Biography Callippus was born at Cyzicus, and studied under Eudoxus of Cnidus at the Academy of Plato. He also worked with Aristotle at the Lyceum, which means that he was active in Athens prior to Aristotle's death in 322 BC. He observed the movements of the planets and attempted to use Eudoxus' scheme of connected spheres to account for their movements. However, he found that 27 spheres was insufficient to account for the planetary movements, and so he added seven more for a total of 34. According to the description in Aristotle's ''Metaphysics'' (XII.8), he added two spheres for the Sun, two for the Moon, and one each for Mercury, Venus, and Mars. Callippus made careful measurements of the lengths of the seasons, finding them (starting with the spring equinox) to be 94 days, 92 days, 89 days, and 90 days. This variation in the seasons implies a variation in the speed of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concentric Spheres
The cosmological model of concentric (or homocentric) spheres, developed by Eudoxus, Callippus, and Aristotle, employed celestial spheres all centered on the Earth. In this respect, it differed from the epicyclic and eccentric models with multiple centers, which were used by Ptolemy and other mathematical astronomers until the time of Copernicus. Origins of the concept of concentric spheres Eudoxus of Cnidus was the first astronomer to develop the concept of concentric spheres. He was originally a student at Plato's academy and is believed to have been influenced by the cosmological speculations of Plato and Pythagoras."Eudoxus of Cnidus." Complete Dictionary of Scientific Biography. Vol. 4. Detroit: Charles Scribner's Sons, 2008. 465–467. Gale Virtual Reference Library. Web. 2 June 2014. He came up with the idea of homocentric spheres in order to explain the perceived inconsistent motions of the planets and to develop a uniform model for accurately calculating the movement of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timaeus (dialogue)
''Timaeus'' (; grc-gre, Τίμαιος, Timaios, ) is one of Plato's dialogues, mostly in the form of long monologues given by Critias and Timaeus, written 360 BC. The work puts forward reasoning on the possible nature of the physical world and human beings and is followed by the dialogue '' Critias''. Participants in the dialogue include Socrates, Timaeus, Hermocrates, and Critias. Some scholars believe that it is not the Critias of the Thirty Tyrants who appears in this dialogue, but his grandfather, who is also named Critias. It has been suggested from some traditions ( Diogenes Laertius (VIII 85) from Hermippus of Smyrna (3rd century BC) and Timon of Phlius ( 320 – 235 BC)) that ''Timaeus'' was influenced by a book about Pythagoras, written by Philolaus, although this assertion is generally considered false. Introduction The dialogue takes place the day after Socrates described his ideal state. In Plato's works, such a discussion occurs in the '' Republic''. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parmenides
Parmenides of Elea (; grc-gre, Παρμενίδης ὁ Ἐλεάτης; ) was a pre-Socratic Greek philosopher from Elea in Magna Graecia. Parmenides was born in the Greek colony Greek colonization was an organised Colonies in antiquity, colonial expansion by the Archaic Greece, Archaic Greeks into the Mediterranean Sea and Black Sea in the period of the 8th–6th centuries BC. This colonization differed from the Iron Ag ... of Elea, from a wealthy and illustrious family. His dates are uncertain; according to Doxography, doxographer Diogenes Laërtius, he flourished just before 500 BC, which would put his year of birth near 540 BC, but in the dialogue ''Parmenides (dialogue), Parmenides'' Plato has him visiting Athens at the age of 65, when Socrates was a young man, c. 450 BC, which, if true, suggests a year of birth of c. 515 BC. He is thought to have been in his prime (or "floruit") around 475 BC. The single known work by Parmenides is a poem whose original title is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenophanes
Xenophanes of Colophon (; grc, Ξενοφάνης ὁ Κολοφώνιος ; c. 570 – c. 478 BC) was a Greek philosopher, theologian, poet, and critic of Homer from Ionia who travelled throughout the Greek-speaking world in early Classical Antiquity. As a poet, Xenophanes was known for his critical style, writing poems that are considered among the first satires. He also composed elegiac couplets that criticised his society's traditional values of wealth, excesses, and athletic victories. He also criticised Homer and the other poets in his works for representing the gods as foolish or morally weak. His poems have not survived intact; only fragments of some of his work survives in quotations by later philosophers and literary critics. Xenophanes is seen as one of the most important pre-Socratic philosophers. A highly original thinker, Xenophanes sought explanations for physical phenomena such as clouds or rainbows without references to divine or mythological explanations, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pythagoras
Pythagoras of Samos ( grc, Πυθαγόρας ὁ Σάμιος, Pythagóras ho Sámios, Pythagoras the Samian, or simply ; in Ionian Greek; ) was an ancient Ionian Greek philosopher and the eponymous founder of Pythagoreanism. His political and religious teachings were well known in Magna Graecia and influenced the philosophies of Plato, Aristotle, and, through them, the West in general. Knowledge of his life is clouded by legend, but he appears to have been the son of Mnesarchus, a gem-engraver on the island of Samos. Modern scholars disagree regarding Pythagoras's education and influences, but they do agree that, around 530 BC, he travelled to Croton in southern Italy, where he founded a school in which initiates were sworn to secrecy and lived a communal, ascetic lifestyle. This lifestyle entailed a number of dietary prohibitions, traditionally said to have included vegetarianism, although modern scholars doubt that he ever advocated complete vegetarianism. The teachin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anaximenes Of Miletus
Anaximenes of Miletus (; grc-gre, Ἀναξιμένης ὁ Μιλήσιος, translit=Anaximenēs ho Milēsios; ) was an Ancient Greek, Ionian Pre-Socratic philosopher from Miletus in Asia Minor (modern-day Turkey), active in the latter half of the 6th century BC. The details of his life are obscure because none of his work has been preserved. Anaximenes' ideas are only known today because of comments about him made by later writers, such as Aristotle. As the last of the three philosophers of the Milesian School, considered the first philosophers of the Western world, Anaximenes is best known and identified as a younger friend or student of Anaximander, who was himself taught by the first philosopher Thales. Each developed a distinct cosmology without completely rejecting their predecessors views. Each were material monists who sought to discover the ''arche;'' the one, underlying physical yet divine basis of everything. Thales proposed all was made of water; Anaximander pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sphere Of Fire
Sphere of fire is the name given in Ptolemaic astronomy to the sphere intervening between, and separating, the Earth and the Moon. Traditional concept Building on Empedocles's vision of the world as a four-level cake of stacked fundamental elements - earth, water, air and fire - with fire at the top, Aristotle saw the sublunary world as surmounted by the sphere of fire. Aristotle's conception became prevalent in the Hellenic world, and was given a distance scale by Ptolemy: “taking the radius of the spherical surface of the Earth and the water as the unit, the radius of the spherical sphere which surrounds the air and fire is 33, the radius of the lunar sphere is 64....”. The Middle Ages broadly inherited the concept of the four elements of earth, water, air and fire arranged in concentric spheres about the earth as centre: as the purest of the four elements, fire - and the sphere of fire - stood highest in the ascending sequence of the '' scala naturae'', and closest to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anaximander
Anaximander (; grc-gre, Ἀναξίμανδρος ''Anaximandros''; ) was a pre-Socratic Greek philosopher who lived in Miletus,"Anaximander" in '' Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 1, p. 403. a city of Ionia (in modern-day Turkey). He belonged to the Milesian school and learned the teachings of his master Thales. He succeeded Thales and became the second master of that school where he counted Anaximenes and, arguably, Pythagoras amongst his pupils. Little of his life and work is known today. According to available historical documents, he is the first philosopher known to have written down his studies, although only one fragment of his work remains. Fragmentary testimonies found in documents after his death provide a portrait of the man. Anaximander was an early proponent of science and tried to observe and explain different aspects of the universe, with a particular interest in its origins, claiming that nature is ruled by laws, just like h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancient Greece
Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of culturally and linguistically related city-states and other territories. Most of these regions were officially unified only once, for 13 years, under Alexander the Great's empire from 336 to 323 BC (though this excludes a number of Greek city-states free from Alexander's jurisdiction in the western Mediterranean, around the Black Sea, Cyprus, and Cyrenaica). In Western history, the era of classical antiquity was immediately followed by the Early Middle Ages and the Byzantine period. Roughly three centuries after the Late Bronze Age collapse of Mycenaean Greece, Greek urban poleis began to form in the 8th century BC, ushering in the Archaic period and the colonization of the Mediterranean Basin. This was followed by the age of Classica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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