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  • astronomy - How did Eratosthenes determine that Alexandria and Syene . . .
    How did Eratosthenes determine that Alexandria and Syene were on the same meridian? Ask Question Asked 6 years, 4 months ago Modified 1 year, 4 months ago
  • Is it known where Eratosthenes first heard of the well of Syene?
    Eratosthenes had heard from travelers about a well in Syene (now Aswan, Egypt) with an interesting property: at noon on the summer solstice, which occurs about June 21 every year, the sun illuminated the entire bottom of this well, without casting any shadows, indicating that the sun was directly overhead
  • reference request - How did Eratosthenes know the distance between . . .
    The main sources are Cleomedes and Strabo, and neither of them is reliable, so basically we do not know what Eratosthenes actually did And not just for the distance, see How did Eratosthenes determine that Alexandria and Syene were on the same meridian?
  • astronomy - Why does Eratosthenes method for calculating the . . .
    Why does Eratosthenes method for calculating the circumference of the Earth requires the city of Alexandria and Syene to be in the same meridian?
  • How did Eratosthenes knew the exact time of the day?
    At Syene the longitude of the North South showed no shadow on the solstice, since the tilt of the earth is 23 5° and Syene's latitude is 24° An assistant in Alexandria could have made the same measurement when the East West shadow was 0, and came up with 7 2° North South There was no need to make simultaneous time measurements
  • Circular reasoning in Eratostheness measurement of the Earths . . .
    I remember that I read, some time ago, that Erathostenes calculated the circumfernce of the Earth using the distance between Syene and Alexandria, calculated in turn by others starting from the circumference of the Earth
  • Why did Columbus think the Earth was much smaller than it is?
    Cleomedes assumes that the distance between Syene and Alexandria was 5,000 stadia (a figure that was checked yearly by professional bematists, mensores regii) 6 He assumes the simplified (but false) hypothesis that Syene was precisely on the Tropic of Cancer, saying that at local noon on the summer solstice the Sun was directly overhead
  • How did Eratosthenes know the Sun was very far away?
    Eratosthenes calculated the radius of the Earth from the difference of the lengths of shadows between Aswan and Alexandria were different (see also here) But this could also happen if the Earth w
  • cosmology - History of Science and Mathematics Stack Exchange
    On the other hand, Alexandria is located 800 800 km (= 5000 = 5000 stadia) northwards from Syene In this configuration, Anaxagoras has measured an angle of 7, 2° 7, 2 ° between the vertical in Alexandria and the direction of the sunrays shining in Alexandria
  • Where does the word ``sine (as in $\\sin x$) come from?
    The Greeks never measured curves They got hung up on st line and compass Unlike Indians who were more practical who used straight edge and string and eliminated all unrequired niceties Indians also developed equations for differences to calculate quantities such as pi by finite differences rather than limits of infinite series





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