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Eratosthenes of Cyrene (/ ɛr ə ˈ t ɒ s θ ə n iː z /; Ancient Greek: Ἐρατοσθένης [eratostʰénɛːs]; c. 276 BC – c. 195/194 BC) was an Ancient Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist.
1883 reconstruction of Eratosthenes' map [9] Eratosthenes (276–194 BCE) drew an improved world map, incorporating information from the campaigns of Alexander the Great and his successors. Asia became wider, reflecting the new understanding of the actual size of the continent. Eratosthenes was also the first geographer to incorporate parallels ...
He was a devoted geographer who set out to reform and perfect the map of the world. Eratosthenes argued that accurate mapping, even if in two dimensions only, depends upon the establishment of accurate linear measurements. He was the first to calculate the Earth's circumference (within 0.5 percent accuracy). [28]
Furthermore, the fact that Eratosthenes's measure corresponds precisely to 252,000 stadia might be intentional, since it is a number that can be divided by all natural numbers from 1 to 10: some historians believe that Eratosthenes changed from the 250,000 value written by Cleomedes to this new value to simplify calculations; [27] other ...
Posidonius calculated the Earth's circumference by reference to the position of the star Canopus.As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria he saw it ascend as far as 7 + 1 ⁄ 2 degrees above the horizon (the meridian arc between the latitude of the two locales is actually 5 degrees 14 minutes).
The angle between the sunbeam and a gnomon (vertical pole) at Alexandria allowed Eratosthenes to estimate Earth's circumference. Under the assumption that the Sun is very far away, the ancient Greek geographer Eratosthenes performed an experiment using the differences in the observed angle of the Sun from two different locations to calculate ...
Eratosthenes (c. 276 – c. 194/195 BC), a Greek mathematician who calculated the circumference of the Earth and also the distance from the Earth to the Sun. Hipparchus (c. 190 – c. 120 BC), a Greek mathematician who measured the radii of the Sun and the Moon as well as their distances from the Earth. On the Sizes and Distances
Around 200 BCE Eratosthenes determines that the radius of the Earth is roughly 6,400 km. [43] Circa 150 BCE Hipparchus uses parallax to determine that the distance to the Moon is roughly 380,000 km. [44] The work of Hipparchus about the Earth-Moon system was so accurate that he could forecast solar and lunar eclipses for the next six centuries.