Aristarchus of Samos
|Born||c. 310 BC|
|Died||c. 230 BC (age c. 80)|
Aristarchus of Samos ( // ; Greek : Ἀρίσταρχος ὁ Σάμιος, Aristarkhos ho Samios; c. 310 – c. 230 BC) was an ancient Greek astronomer and mathematician who presented the first known heliocentric model that placed the Sun at the center of the known universe, with the Earth revolving around the Sun once a year and rotating about its axis once a day. He was influenced by Philolaus of Croton, but Aristarchus identified the "central fire" with the Sun, and he put the other planets in their correct order of distance around the Sun. Like Anaxagoras before him, he suspected that the stars were just other bodies like the Sun, albeit farther away from Earth. His astronomical ideas were often rejected in favor of the geocentric theories of Aristotle and Ptolemy. Nicolaus Copernicus knew about the possibility that Aristarchus had a 'moving Earth' theory (though it is unlikely that he was aware that it was a heliocentric theory). Aristarchus also estimated the sizes of the Sun and Moon as compared to Earth's size, and the distances to the Sun and Moon. He is considered as one of the greatest astronomers of antiquity, along with Hipparchus, and one of the greatest thinkers in human history.
The original text has been lost, but a reference in Archimedes' book The Sand Reckoner (Archimedis Syracusani Arenarius & Dimensio Circuli) describes a work in which Aristarchus advanced the heliocentric model as an alternative hypothesis to geocentrism:
You are now aware ['you' being King Gelon] that the "universe" is the name given by most astronomers to the sphere the centre of which is the centre of the earth, while its radius is equal to the straight line between the centre of the sun and the centre of the earth. This is the common account (τὰ γραφόμενα) as you have heard from astronomers. But Aristarchus has brought out a book consisting of certain hypotheses, wherein it appears, as a consequence of the assumptions made, that the universe is many times greater than the "universe" just mentioned. His hypotheses are that the fixed stars and the sun remain unmoved, that the earth revolves about the sun on the circumference of a circle, the sun lying in the middle of the orbit, and that the sphere of the fixed stars, situated about the same centre as the sun, is so great that the circle in which he supposes the earth to revolve bears such a proportion to the distance of the fixed stars as the centre of the sphere bears to its surface.
Aristarchus suspected the stars were other sunsthat are very far away, and that in consequence there was no observable parallax, that is, a movement of the stars relative to each other as the Earth moves around the Sun. Since stellar parallax is only detectable with telescopes, his accurate speculation was unprovable at the time.
It is a common misconception that the heliocentric view was held as sacrilegious by the contemporaries of Aristarchus.Lucio Russo traces this to Gilles Ménage's printing of a passage from Plutarch's On the Apparent Face in the Orb of the Moon, in which Aristarchus jokes with Cleanthes, who is head of the Stoics, a sun worshipper, and opposed to heliocentrism. In the manuscript of Plutarch's text, Aristarchus says Cleanthes should be charged with impiety. Ménage's version, published shortly after the trials of Galileo and Giordano Bruno, transposes an accusative and nominative so that it is Aristarchus who is purported to be impious. The resulting misconception of an isolated and persecuted Aristarchus is still transmitted today.
According to Plutarch, while Aristarchus postulated heliocentrism only as a hypothesis, Seleucus of Seleucia, a Hellenistic astronomer who lived a century after Aristarchus, maintained it as a definite opinion and gave a demonstration of it,but no full record has been found. In his Naturalis Historia , Pliny the Elder later wondered whether errors in the predictions about the heavens could be attributed to a displacement of the Earth from its central position. Pliny and Seneca referred to the retrograde motion of some planets as an apparent (and not real) phenomenon, which is an implication of heliocentrism rather than geocentrism. Still, no stellar parallax was observed, and Plato, Aristotle, and Ptolemy preferred the geocentric model, which was held as true throughout the Middle Ages.
The heliocentric theory was revived by Copernicus,after which Johannes Kepler described planetary motions with greater accuracy with his three laws. Isaac Newton later gave a theoretical explanation based on laws of gravitational attraction and dynamics.
After realizing that the Sun was much larger than the Earth and the other planets, Aristarchus concluded that planets revolved around the Sun. But this brilliant insight, it turned out, "was too much for the philosophers of the time to swallow and astronomy had to wait 2000 years more to find the right path."
The only known surviving work usually attributed to Aristarchus, On the Sizes and Distances of the Sun and Moon , is based on a geocentric world view. It has historically been read as stating that the angle subtended by the Sun's diameter is two degrees, but Archimedes states in The Sand Reckoner that Aristarchus had a value of half a degree, which is much closer to the actual average value of 32' or 0.53 degrees. The discrepancy may come from a misinterpretation of what unit of measure was meant by a certain Greek term in the text of Aristarchus.
Aristarchus claimed that at half moon (first or last quarter moon), the angle between the Sun and Moon was 87°.He might have proposed 87° as a lower bound, since gauging the lunar terminator's deviation from linearity to one degree of accuracy is beyond the unaided human ocular limit (with that limit being about three arcminutes of accuracy). Aristarchus is known to have also studied light and vision.
Using correct geometry, but the insufficiently accurate 87° datum, Aristarchus concluded that the Sun was between 18 and 20 times farther away than the Moon. 50', and the Sun's distance is actually about 400 times that of the Moon.) The implicit false solar parallax of slightly under three degrees was used by astronomers up to and including Tycho Brahe, c. AD 1600. Aristarchus pointed out that the Moon and Sun have nearly equal apparent angular sizes, and therefore their diameters must be in proportion to their distances from Earth; thus, the diameter of the Sun was calculated to be between 18 and 20 times the diameter of the Moon.(The true value of this angle is close to 89°
The lunar crater Aristarchus is named after him.
Copernicus himself admitted that the theory was attributed to Aristarchus, though this does not seem to be generally known. ... Here, however, there is no question of the Earth revolving around the sun, and there is no mention of Aristarchus.But it is a curious fact that Copernicus did mention the theory of Aristarchus in a passage which he later suppressed:The Philolaus-Aristarchus passage is then given in untranslated Latin, without further comment. This is then followed by.quoting in full Archimedes's passage about Aristarchus's helicentric theory from 'The Sand Reckoner' (using its alternative title Arenarius)', seemingly without mentioning that The Sand Reckoner was not in print until a year after Copernicus's death (unless this is mentioned in a passage not currently shown by Google Books.).
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects show a larger parallax than farther objects when observed from different positions, so parallax can be used to determine distances.
In astronomy, the geocentric model is a superseded description of the Universe with Earth at the center. Under the geocentric model, the Sun, Moon, stars, and planets all orbit Earth. The geocentric model was the predominant description of the cosmos in many ancient civilizations, such as those of Aristotle in Classical Greece and Ptolemy in Roman Egypt.
The League of Corinth, also referred to as the Hellenic League, was a confederation of Greek states created by Philip II in 338–337 BC. The League was created in order to unify Greece military forces under Macedonian leadership (hegemony) in their combined conquest of Persia.
Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Universe. Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center. The notion that the Earth revolves around the Sun had been proposed as early as the 3rd century BC by Aristarchus of Samos, but at least in medieval Europe, Aristarchus' heliocentrism attracted little attention—possibly because of the loss of scientific works of the Hellenistic period.
The Sand Reckoner is a work by Archimedes, an Ancient Greek mathematician of the 3rd century BC, in which he set out to determine an upper bound for the number of grains of sand that fit into the universe. In order to do this, he had to estimate the size of the universe according to the contemporary model, and invent a way to talk about extremely large numbers. The work, also known in Latin as Archimedis Syracusani Arenarius & Dimensio Circuli, which is about eight pages long in translation, is addressed to the Syracusan king Gelo II, and is probably the most accessible work of Archimedes; in some sense, it is the first research-expository paper.
Nicolaus Copernicus was a Renaissance polymath, active as a mathematician, astronomer, and Catholic canon, who formulated a model of the universe that placed the Sun rather than Earth at its center. In all likelihood, Copernicus developed his model independently of Aristarchus of Samos, an ancient Greek astronomer who had formulated such a model some eighteen centuries earlier.
The fixed stars compose the background of astronomical objects that appear not to move relative to each other in the night sky compared to the foreground of Solar System objects that do. Generally, the fixed stars are taken to include all stars other than the Sun. Nebulae and other deep-sky objects may also be counted among the fixed stars.
Acharnae or Acharnai was a deme of ancient Athens. It was part of the phyle Oineis.
Earth orbits the Sun at an average distance of 149.60 million km, and one complete orbit takes 365.256 days, during which time Earth has traveled 940 million km. Ignoring the influence of other solar system bodies, Earth's orbit is an ellipse with the Earth-Sun barycenter as one focus and a current eccentricity of 0.0167; since this value is close to zero, the center of the orbit is close, relative to the size of the orbit, to the center of the Sun.
Seleucus of Seleucia was a Hellenistic astronomer and philosopher. Coming from Seleucia on the Tigris, Mesopotamia, the capital of the Seleucid Empire, or, alternatively, Seleukia on the Erythraean Sea, he is best known as a proponent of heliocentrism and for his theory of the origin of tides.
The Copernican Revolution was the paradigm shift from the Ptolemaic model of the heavens, which described the cosmos as having Earth stationary at the center of the universe, to the heliocentric model with the Sun at the center of the Solar System. This revolution consisted of two phases; the first being extremely mathematical in nature and the second phase starting in 1610 with the publication of a pamphlet by Galileo. Beginning with the publication of Nicolaus Copernicus’s De revolutionibus orbium coelestium, contributions to the “revolution” continued until finally ending with Isaac Newton’s work over a century later.
On the Sizes and Distances is widely accepted as the only extant work written by Aristarchus of Samos, an ancient Greek astronomer who lived circa 310–230 BCE. This work calculates the sizes of the Sun and Moon, as well as their distances from the Earth in terms of Earth's radius.
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Greek astronomy is astronomy written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras. It is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the language of scholarship throughout the Hellenistic world following the conquests of Alexander. This phase of Greek astronomy is also known as Hellenistic astronomy, while the pre-Hellenistic phase is known as Classical Greek astronomy. During the Hellenistic and Roman periods, much of the Greek and non-Greek astronomers working in the Greek tradition studied at the Musaeum and the Library of Alexandria in Ptolemaic Egypt.
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. This model positioned the Sun at the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths, modified by epicycles, and at uniform speeds. The Copernican model displaced the geocentric model of Ptolemy that had prevailed for centuries, which had placed Earth at the center of the Universe. Copernican heliocentrism is often regarded as the launching point to modern astronomy and the Scientific Revolution.
Abrotonum Abrotonon, pronounced Avrotonon, is an ancient Greek name of Thracian origin, as well as the name of a plant.
The Epistula ad Carpianum or Letter of Eusebius is the title traditionally given to a letter from Eusebius of Caesarea to a Christian named Carpianus.
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.
The Iron Age Greek migrations were effected by a population of émigrés from amidst the displacements and reconstruction that occurred in Greece proper from the middle of the 11th century to end of the 9th century BCE. These movements resulted in the settlement of the Aegean islands, Cyprus, Crete and the western coast of Asia Minor and the founding of new cities which afterwards became centers of the Greek civilization. The migrations were effected in consecutive waves by tribal groupings known as the Aeolic, Ionian, Doric and Achaean (Arcadian) migrations. These movements differed from the Greek colonisation of the Archaic period in that they were more ad hoc affairs instead of the result of a planned process of colonisation on the part of the mother city, and they are less well-documented historically, often with a mythologized or semi-legendary leader such as Hercules or Orestes being recorded as the leader of the colonists.
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