Aristarchus of Samos

Aristarchus of Samos (/ˌærəˈstɑːrkəs/; 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 it. 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.[2] Like Anaxagoras before him, he suspected that the stars were just other bodies like the Sun, albeit further away from Earth. His astronomical ideas were often rejected in favor of the geocentric theories of Aristotle and Ptolemy. Nicolaus Copernicus attributed the heliocentric theory to Aristarchus.[3]

Aristarchus of Samos
Aristarchos von Samos (Denkmal).jpeg
Statue of Aristarchus of Samos at the Aristotle University of Thessaloniki
Bornc. 310 BC
Diedc. 230 BC (age c. 80)
  • Scholar
  • Mathematician
  • Astronomer


The original text has been lost, but a reference in Archimedes' book The Sand Reckoner (Archimedis Syracusani Arenarius & Dimensio Circuli) describes a work by Aristarchus in which he 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 (τά 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.[4]

Aristarchus suspected the stars were other suns[5] that 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.[6] 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.[6] In the manuscript of Plutarch's text, Aristarchus says Cleanthes should be charged with impiety.[6] 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.[6] The resulting misconception of an isolated and persecuted Aristarchus is still transmitted today.[6][7]

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[8] 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.[9] Pliny[10] and Seneca[11] 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,[12] 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.

Distance to the Sun (lunar dichotomy)

Aristarchus working
Aristarchus's 3rd-century BC calculations on the relative sizes of (from left) the Sun, Earth and Moon, from a 10th-century AD Greek copy

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 ½ 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.[13]

Aristarchus claimed that at half moon (first or last quarter moon), the angle between the Sun and Moon was 87°.[14] 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 degrees of accuracy). Aristarchus is known to have also studied light and vision.[15]

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.[16] (The true value of this angle is close to 89° 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.[17]

See also


  1. ^ "Aristarchus of Samos: Mathematician and astronomer". World History. 8 September 2015. Archived from the original on 7 May 2018. Retrieved 29 November 2018.
  2. ^ Draper, John William (2007) [1874]. "History of the Conflict Between Religion and Science". In Joshi, S. T. (ed.). The Agnostic Reader. Prometheus. pp. 172–173. ISBN 978-1-59102-533-7.
  3. ^ George Kish (1978). A Source Book in Geography. Harvard University Press. p. 51. ISBN 978-0-674-82270-2.
  4. ^ Heath, Thomas (1913), p. 302. The italics and parenthetical comments are as they appear in Heath's original.
  5. ^ Louis Strous. "Who discovered that the Sun was a star?". Retrieved 2014-07-13.
  6. ^ a b c d e Russo, Lucio (2013-12-01). The Forgotten Revolution: How Science Was Born in 300 BC and Why it Had to Be Reborn. Translated by Levy, Silvio. Springer Science & Business Media. p. 82, fn.106. ISBN 9783642189043. Retrieved 13 June 2017.; Russo, Lucio; Medaglia, Silvio M. (1996). "Sulla presunta accusa di empietà ad Aristarco di Samo". Quaderni Urbinati di Cultura Classica (in Italian). Fabrizio Serra Editore. New Series, Vol. 53 (2): 113–121. JSTOR 20547344.
  7. ^ Plutarch. "De facie quae in orbe lunae apparet, Section 6". Perseus Digital Library. Tufts University. Retrieved 13 June 2017.
  8. ^ Plutarch, Platonicae quaestiones, VIII, i
  9. ^ Neugebauer, O. (1975). A History of Ancient Mathematical Astronomy. Studies in the History of Mathematics and Physical Sciences. 1. Springer-Verlag. pp. 697–698.
  10. ^ Naturalis historia, II, 70
  11. ^ Naturales quaestiones, VII, xxv, 6–7
  12. ^ Joseph A. Angelo (14 May 2014). Encyclopedia of Space and Astronomy. Infobase Publishing. p. 153. ISBN 978-1-4381-1018-9.
  13. ^
  14. ^ Greek Mathematical Works, Loeb Classical Library, Harvard University, 1939–1941, edited by Ivor Thomas, volume 2 (1941), pages 6–7
  15. ^ Heath, 1913, pp. 299–300; Thomas, 1942, pp. 2–3.
  16. ^ A video on reconstruction of Aristarchus' method, in Turkish without subtitles.
  17. ^ Kragh, Helge (2007). Conceptions of cosmos: from myths to the accelerating universe: a history of cosmology. Oxford University Press. p. 26. ISBN 0-19-920916-2.


Further reading

External links

280 BC

Year 280 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Laevinus and Coruncanius (or, less frequently, year 474 Ab urbe condita). The denomination 280 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.

Aristarchos 2.3 m Telescope

The New Greek Telescope project of the National Observatory of Athens (NOA) was funded by the European Commission and the General Secretariat for Research and Technology of the Hellenic Ministry of Development. The telescope had its first light test in 2005, and became the largest telescope in Greece when it became fully operational at the Chelmos Observatory site in 2007. The telescope has a Ritchey-Chrétien configuration with a primary mirror with a diameter of 2.3 m. The mount is of the altazimuth kind. The telescope is operated by the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS) of the NOA.

Observations with the Aristarchos telescope have provided a measurement of the distance to the planetary nebula KjPn8.

Aristarchus's inequality

Aristarchus's inequality (after the Greek astronomer and mathematician Aristarchus of Samos; c. 310 – c. 230 BCE) is a law of trigonometry which states that if α and β are acute angles (i.e. between 0 and a right angle) and β < α then

Ptolemy used the first of these inequalities while constructing his table of chords.

Aristarchus (crater)

Aristarchus, named after the Greek astronomer Aristarchus of Samos, is a prominent lunar impact crater that lies in the northwest part of the Moon's near side. It is considered the brightest of the large formations on the lunar surface, with an albedo nearly double that of most lunar features. The feature is bright enough to be visible to the naked eye, and displays unusually bright features when viewed through a large telescope. It is also readily identified when most of the lunar surface is illuminated by earthshine. The crater is deeper than the Grand Canyon.The crater is located at the southeastern edge of the Aristarchus plateau, an elevated area that contains a number of volcanic features, such as sinuous rilles. This area is also noted for the large number of reported transient lunar phenomena, as well as recent emissions of radon gas as measured by the Lunar Prospector spacecraft.

Diodorus of Alexandria

Diodorus of Alexandria or Diodorus Alexandrinus was a gnomonicist, astronomer and a pupil of Posidonius.

Federico Commandino

Federico Commandino (1509 – 5 September 1575) was an Italian humanist and mathematician.

Born in Urbino, he studied at Padua and at Ferrara, where he received his doctorate in medicine. He was most famous for his central role as translator of works of ancient mathematicians. In this, his sources were primarily written in Greek and secondarily in Arabic, while his translations were primarily in Latin and secondarily in Italian. He was responsible for the publication of many treatises of Archimedes. He also translated the works of Aristarchus of Samos (On the sizes and distances of the Sun and the Moon), Pappus of Alexandria (Mathematical collection), Hero of Alexandria (Pneumatics), Ptolemy of Alexandria (Planisphere and Analemma), Apollonius of Perga (Conics) and Euclid of Alexandria (Elements). Among his pupils was Guidobaldo del Monte and Bernardino Baldi. Commandino maintained a correspondence with the astronomer Francesco Maurolico. The proposition known as Commandino's theorem first appears in his work on centers of gravity.


Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System. 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 the medieval world, Aristarchus's heliocentrism attracted little attention—possibly because of the loss of scientific works of the Hellenistic Era.It was not until the 16th century that a mathematical model of a heliocentric system was presented, by the Renaissance mathematician, astronomer, and Catholic cleric Nicolaus Copernicus, leading to the Copernican Revolution. In the following century, Johannes Kepler introduced elliptical orbits, and Galileo Galilei presented supporting observations made using a telescope.

With the observations of William Herschel, Friedrich Bessel, and other astronomers, it was realized that the Sun, while near the barycenter of the Solar System, was not at any center of the universe.

History of sundials

A sundial is a device that indicates time by using a light spot or shadow cast by the position of the Sun on a reference scale. As the Earth turns on its polar axis, the sun appears to cross the sky from east to west, rising at sun-rise from beneath the horizon to a zenith at mid-day and falling again behind the horizon at sunset. Both the azimuth (direction) and the altitude (height) can be used to create time measuring devices. Sundials have been invented independently in every major culture and become more accurate and sophisticated as the culture developed.

List of Greek mathematicians

In historical times, Greek civilization has played one of the major roles in the history and development of mathematics. To this day, a number of Greek mathematicians are considered for their innovations and influence on mathematics.

List of discoveries

This article presents a list of discoveries and includes famous observations. Discovery observations form acts of detecting and learning something. Discovery observations are acts in which something is found and given a productive insight. The observation assimilates the knowledge of a phenomenon or the recording of data using instruments.

Nicolaus Copernicus

Nicolaus Copernicus (; Polish: Mikołaj Kopernik; German: Nikolaus Kopernikus; Niklas Koppernigk; 19 February 1473 – 24 May 1543) was a Renaissance-era mathematician and astronomer who formulated a model of the universe that placed the Sun rather than the Earth at the center of the universe, in all likelihood independently of Aristarchus of Samos, who had formulated such a model some eighteen centuries earlier.The publication of Copernicus' model in his book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), just before his death in 1543, was a major event in the history of science, triggering the Copernican Revolution and making a pioneering contribution to the Scientific Revolution.Copernicus was born and died in Royal Prussia, a region that had been part of the Kingdom of Poland since 1466. A polyglot and polymath, he obtained a doctorate in canon law and was also a mathematician, astronomer, physician, classics scholar, translator, governor, diplomat, and economist. In 1517 he derived a quantity theory of money—a key concept in economics—and in 1519 he formulated an economic principle that later came to be called Gresham's law.

On the Sizes and Distances (Aristarchus)

On the Sizes and Distances (of the Sun and Moon) (Περὶ μεγεθῶν καὶ ἀποστημάτων [ἡλίου καὶ σελήνης], Peri megethon kai apostematon) 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.

The book was presumably preserved by students of Pappus of Alexandria's course in mathematics, although there is no evidence of this. The editio princeps was published by John Wallis in 1688, using several medieval manuscripts compiled by Sir Henry Savile. The earliest Latin translation was made by Giorgio Valla in 1488. There is also a 1572 Latin translation and commentary by Frederico Commandino.


Samos (; Greek: Σάμος, Greek pronunciation: [ˈsamos]) is a Greek island in the eastern Aegean Sea, south of Chios, north of Patmos and the Dodecanese, and off the coast of Asia Minor, from which it is separated by the 1.6-kilometre (1.0 mi)-wide Mycale Strait. It is also a separate regional unit of the North Aegean region, and the only municipality of the regional unit.

In ancient times Samos was an especially rich and powerful city-state, particularly known for its vineyards and wine production. It is home to Pythagoreion and the Heraion of Samos, a UNESCO World Heritage Site that includes the Eupalinian aqueduct, a marvel of ancient engineering. Samos is the birthplace of the Greek philosopher and mathematician Pythagoras, after whom the Pythagorean theorem is named, the philosopher Epicurus, and the astronomer Aristarchus of Samos, the first known individual to propose that the Earth revolves around the sun. Samian wine was well known in antiquity, and is still produced on the island.

The island was governed by the semi-autonomous Principality of Samos under Ottoman suzerainty from 1835 until it joined Greece in 1912.

Sosigenes of Alexandria

Sosigenes of Alexandria (Greek: Σωσιγένης ὁ Ἀλεξανδρεύς) was a Greek astronomer from Ptolemaic Egypt who, according to Roman historian Pliny the Elder, was consulted by Julius Caesar for the design of the Julian calendar.Little is known about him apart from Pliny's Natural History. Sosigenes appears in Book 18, 210-212:

"... There were three main schools, the Chaldaean, the Egyptian, and the Greek; and to these a fourth was added in our country by Caesar during his dictatorship, who with the assistance of the learned astronomer Sosigenes (Sosigene perito scientiae eius adhibito) brought the separate years back into conformity with the course of the sun."In Book 2, chapter 6, Sosigenes is credited with work on the orbit of Mercury:

"The star next to Venus is Mercury, by some called Apollo; it has a similar orbit, but is by no means similar in magnitude or power. It travels in a lower circle, with a revolution nine days quicker, shining sometimes before sunrise and sometimes after sunset, but according to Cidenas and Sosigenes never more than 22 degrees away from the sun."Some sources state that the Julian calendar was designed by Aristarchus of Samos, although it is not clear where this conclusion originates. Ptolemy III Euergetes, Aristarchus' contemporary, did indeed decree a reform of the Egyptian calendar in 238 BC, but it was never implemented. The reform, however, would have added an extra day (leap day) to the 365-day Egyptian calendar every four years, a feature shared by the Julian calendar.

Sosigenes was portrayed by Hume Cronyn in the 1963 movie Cleopatra. This portrayal is heavily fictionalized: he serves as Cleopatra's tutor/adviser and later her envoy to Rome. He is ultimately murdered in the Forum by Octavian, commencing his war against Egypt. None of these events are present in historical record, and were invented for the film.

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.

Thomas Little Heath

Sir Thomas Little Heath (; 5 October 1861 – 16 March 1940) was a British civil servant, mathematician, classical scholar, historian of ancient Greek mathematics, translator, and mountaineer. He was educated at Clifton College. Heath translated works of Euclid of Alexandria, Apollonius of Perga, Aristarchus of Samos, and Archimedes of Syracuse into English.

Timeline of discovery of Solar System planets and their moons

The timeline of discovery of Solar System planets and their natural satellites charts the progress of the discovery of new bodies over history. Each object is listed in chronological order of its discovery (multiple dates occur when the moments of imaging, observation, and publication differ), identified through its various designations (including temporary and permanent schemes), and the discoverer(s) listed.

Historically the naming of moons did not always match the times of their discovery. Traditionally, the discoverer enjoys the privilege of naming the new object; however, some neglected to do so (E. E. Barnard stated he would "defer any suggestions as to a name" [for Amalthea] "until a later paper" but never got around to picking one from the numerous suggestions he received) or actively declined (S. B. Nicholson stated "Many have asked what the new satellites" [Lysithea and Carme] "are to be named. They will be known only by the numbers X and XI, written in Roman numerals, and usually prefixed by the letter J to identify them with Jupiter."). The issue arose nearly as soon as planetary satellites were discovered: Galileo referred to the four main satellites of Jupiter using numbers while the names suggested by his rival Simon Marius gradually gained universal acceptance. The International Astronomical Union (IAU) eventually started officially approving names in the late 1970s.


Timocharis of Alexandria (Greek: Τιμόχαρις or Τιμοχάρης, gen. Τιμοχάρους; c. 320–260 BC) was a Greek astronomer and philosopher. Likely born in Alexandria, he was a contemporary of Euclid.


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