Aristarchus of Samos

[[File:Aristarchos logo big.png|right|thumb|165pxpx|Now pay attention, kids. This will blow your minds!]]{{sciencenav}}
'''Aristarchus'''<ref group=note>The Latinized version "Aristarchus" is more commonly used among English speakers than the original Greek name "Aristarchos".</ref> {{lived|ca. 310 BCE|ca. 230 BCE}} was a third century [[BCE]] [[Greece|Greek]] [[philosopher]]. He first proposed that the [[planet]]s of the [[Solar system]] orbit the [[Sun]].

Aristarchus tried to measure the sizes of the [[Moon]] and the Sun using geometric calculations.  Though his measuring instruments were unable to provide accurate results (he determined the angle between the Sun and a half-Moon to be 87 degrees; the actual angle is ~89.833 degrees), he still figured out that the sun is very much larger and further from Earth than the moon, and hypothesized that the smaller [[Earth]] orbits the larger Sun. Aristarchus is our only ancient reference to [[heliocentrism]], which we know about because of a vague reference in Archimedes. He says: "Aristarchus of Samos brought out a book consisting of some hypotheses, ... ''His hypotheses are that the fixed stars and the sun remain unmoved, that the earth revolves about the sun in the circumference of a circle, the sun lying in the middle of the orbit''<ref>https://physics.weber.edu/carroll/Archimedes/sand.htm</ref>. That book is lost, and how he came to those hypotheses remains unknown.

==Reactions==
Aristarchus's hypothesis is the first known challenge to the [[Geocentrism|dominant geocentric model]], though it ultimately failed to convince many. One of Aristarchus' opponents was the Stoic philosopher Cleanthes, who regarded the Sun as a divine entity<ref>Cicero, De Natura Deorum, ii. 15.</ref>. At some point, Aristarchus claimed that Cleanthes should be indicted for impiety, though there is a common myth that it was Aristarchus being accused by Cleanthes (which arises from a 17th-century translation of Plutarch, where the translator reversed the subject and object of the sentence; older Latin manuscripts have Aristarchus stating that Cleanthes ought to be indicted).<ref> Lucio Russo, Silvio M. Medaglia, Sulla presunta accusa di empietà ad Aristarco di Samo, in "Quaderni urbinati di cultura classica", n.s. 53 (82) (1996), pp. 113–121</ref><ref>Russo, Lucio. The forgotten revolution: how science was born in 300 BC and why it had to be reborn. Springer Science & Business Media, 2013.</ref>

Aristarchus had a small following including {{wpl|Seleucus of Seleucia|Seleucus of Babylon}} but the theory of Aristarchus remained unpopular.  Instead, [[Aristotle|Aristotelian]] and later Hipparchan/[[Ptolemy|Ptolemaic]] geocentric ideas dominated [[science]] until the second half of the 17th century.  

In 1514, nearly two millennia later, [[Nicolaus Copernicus|Copernicus]] took up heliocentrism, originally citing Aristarchus.<ref>[http://www.britannica.com/EBchecked/topic/34377/Aristarchus-of-Samos Aristarchus of Samos]</ref> The discoveries of [[Galileo]] firmly discredited the Ptolemaic system, [[Kepler]] later developed the heliocentric model that accurately describes our solar system, while [[Newton]] put it on a physically justified basis at the end of the 17th century.

Today some recognize Aristarchus as a pioneer in [[astronomy]] though later heliocentrists are much better known.  Greece named an astronomical telescope after Aristarchus.<ref>[http://helmos.astro.noa.gr/ Aristarchos Telescope]</ref>, and one of the most prominent {{wpl|Aristarchus (crater)|craters}} in the [[Moon]] was named after him.

==External links==
*{{see-wp|Aristarchus of Samos}}
*[http://www-history.mcs.st-and.ac.uk/Mathematicians/Aristarchus.html Aristarchus of Samos], ''The MacTutor History of Mathematics archive'', School of Mathematics and Statistics, University of St Andrews, Scotland
*[http://www.astro.cornell.edu/academics/courses/astro2201/aristarchus.htm Aristarchus of Samos], Astronomy 2201 course, Cornell University
==Notes==
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==References==
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[[Category:Astronomy]]
[[Category:Greece]]
[[Category:History of science]]
[[Category:Philosophers]]
[[Category:Scientists]]

Categories: Astronomy, Greece, History of science, Philosophers, Scientists