Aristarchus eratosthenes and archimedes biography
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Early Astronomy in the University of Michigan Collections
The use of spheres to explain the motion of stars and planets was indeed the key for the development of a more scientific astronomy. The Greeks developed a model of the cosmos as a sphere and introduced the concept of celestial sphere. This is fully developed in the Hellenistic period with Euclid’s Phenomena (ca. 320 BCE), which discusses both the celestial sphere and all the main circles drawn on its surface (celestial equator, tropics, circumpolar circles, ecliptic).
In the Hellenistic period a series of astronomical texts were composed that dealt with the concept of the celestial sphere and spherical astronomy to tackle some astronomical problems (e.g., the risings and setting times of constellations), such as Autolycus’ On the Moving Sphere and On Risings and Settings (ca. 320 BCE). The observations by Aristyllus and Timocharis carried out at Alexandria in ca. 290 BCE, which have reached us through Ptolemy, are the oldest observations we have in Greek astronomy.
Aristarchus of Samos (ca. 310-230 BCE) is one of the most prominent astronomers of the Hellenistic period. Although Greek astronomy remained fundamentally geocentric (due also to the influence of Aristotelian physics), in his Sand Reckoner Archi
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Eratosthenes
Greek mathematician, geographer, poet (c. 276 – c. 195/194 BC)
This article is about the Greek scholar of the third century BC. For other uses, see Eratosthenes (disambiguation).
Eratosthenes of Cyrene (; Ancient Greek: Ἐρατοσθένης[eratostʰénɛːs]; c. 276 BC – c. 195/194 BC) was an Ancient Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandria. His work is comparable to what is now known as the study of geography, and he introduced some of the terminology still used today, even coining the terms geography and geographer.[1]
He is best known for being the first person known to calculate the Earth's circumference, which he did by using the extensive survey results he could access in his role at the Library. His calculation was remarkably accurate (his error margin turned out to be less than 1%).[2][3] He was the first to calculate Earth's axial tilt, which similarly proved to have remarkable accuracy.[4][5] He created the first global projection of the world, incorporating parallels and meridians based on the available geographic knowledge of his era.[4]
Eratosthene
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Quick Info
Samos, Greece
Greece
Biography
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