reference request - How did Eratosthenes know the distance …
网页2020年3月28日 · So the actual latitude difference between Alexandria and Syene is closer to about 789,950 meters, or about 5,009.1946 stadia, than to 4,927.07 stadia. So maybe Eratosthenes made a lucky guesstimate, as Frigo suggests, that was rather close to the accurate distance by chance.
Is it known where Eratosthenes first heard of the "well of Syene"?
网页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. Eratosthenes then measured the angle ...
How did Eratosthenes knew the exact time of the day?
网页2017年7月13日 · 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.
astronomy - Why does Eratosthenes method for calculating the ...
网页2022年12月18日 · $\begingroup$ That sounds like a really good reason that I didn't consider, since they didn't have precise clock back then, it makes sense.
Why did Columbus think the Earth was much smaller than it is?
网页2022年1月10日 · 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. He ...
How did Eratosthenes know the Sun was very far away?
网页2022年8月21日 · This is a long answer, explaining more or less step to step why the data available to Eratosthenes indicted that the Sun should be a vast distance from the Earth, thus makings its diverging rays almost parallel when they struck the Earth.
Did the ancient Greeks have zero in their number system?
网页2017年5月26日 · Conveniently, 7.2 degrees is 1/50th of a full circle ( 50 x 7.2° = 360° ). Eratosthenes understood that if he could determine the distance between Alexandria and Syene, he would merely have to multiply that distance by 50 to find the circumference of Earth! $\endgroup$ –
middle ages - History of Science and Mathematics Stack Exchange
网页2021年7月7日 · Ptolemy believed that the equatorial regions of the Earth were too hot to be inhabited, so he counted only “habitable” climata. The first one, as you pointed out, is the parallel of Meroe, where the longest day (June solstice) lasts 13 hours. Then for Syene, the longest day would last 13½ hours, and so on, until the clima of the ...
cosmology - History of Science and Mathematics Stack Exchange
网页2024年2月25日 · Syene is a city located (nearly) on the Cancer tropic, which means that on June $21$ at noon, the Sun is at the zenith of, say, an object. More specifically, the object has no shadow. On the other hand, Alexandria is located $800$ km ($=5000$ stadia) northwards from Syene.
discoveries - When was the issue of time zones at different …
网页His calculation of the circumference of the earth was based on the assumption that Alexandria and Aswan (Syene) have the same longitude. The different angle of the shadow in the two localities does not therefore have any bearing on the question of time differences between places with different longitudes. $\endgroup$ –