Talk:Eratosthenes

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Eratosthenes' measure of Earth circumference[edit]

Original image

New image

In these changes, @PostaDiDonna: replaced the illustration File:Eratosthenes_measure_of_Earth_circumference.svg with File:Eratostene--Calcolo_Raggio_Terrestre.jpg.

Though I agree with the new caption noting that Syene and Alexandria are not on the same meridian, I believe that the original image is more accurate as the angle is to scale and being an SVG, it can be easily translated.

May I get a second opinion on this?

Thanks,
cmɢʟee⎆τaʟκ 22:26, 26 August 2021 (UTC)[reply]

Done I've updated it as there has been no objection. cmɢʟee⎆τaʟκ 22:43, 19 April 2022 (UTC)[reply]

Better late than never, they say… Well, I have looked at @PostaDiDonna:’s changes on this page as well as on Earth's circumference#Eratosthenes and frankly, this user’s edits look biased to me. Basically the only reference they quote is Lucio Russo’s book The Forgotten Revolution, and they even went so far as to remove most if not all other references when they disagreed with that book.

While it is a very good and informative book, I hardly see how it makes it worth removing other references, such as Ian Ridpath’s book The Illustrated Encyclopedia of the Universe; Albert van Helden’s book Measuring the Universe: Cosmic Dimensions from Aristarchus to Halley; or an article by Raymond Mercier in The History of Cartography.

I consider the removal of these references a loss for the Wikipedia community—not everyone will, like I did, delve deep into the history of the pages to find other references than Russo’s book.

I have left a long message on their user page (although they seem to have stopped visiting Wikipedia in September 2020) asking for their rationale for replacing all those references by a single reference.

Meanwhile, I will try my best to modify the pages Earth's circumference#Eratosthenes and Eratosthenes to mention the above sources once again, giving them a more neutral point of view.

CielProfond (talk) 03:35, 9 April 2023 (UTC)[reply]

Come to think of it, I suspect PostaDiDonna to be Dennis Rawlins or someone close to him, as one of his articles is also extensively referenced.

CielProfond (talk) 03:59, 9 April 2023 (UTC)[reply]

Wrong value for the estimation of Earth's circumference?[edit]

The article currently states [Eratosthenes] estimated that the meridian has a length of 252,000 stadia (39,060-40,320 km), with an error on the real value between −2.4% and +0.8% (assuming a value for the stadion between 155 and 160 metres) but I am fairly certain the upper limit here is incorrect (as stated in this source which claims it is 29,000 miles or around 46,000km). However, I am hesitant to change the article due to a source being referenced for the values currently used. I would refer to the source itself but I am unable to access the source (as it is a book). SailorFox (talk) 09:03, 28 November 2021 (UTC)[reply]

@SailorFox: (I moved this new talk page section to the bottom.) This question is mentioned in the last sentence of Stadion_(unit)#Calculations, and the source there ([1]) seems to support the notion that the margin of error on this calculation has a lot more uncertainty than just 2 or 3%. Danstronger (talk) 14:51, 28 November 2021 (UTC)[reply]

The estimation of one stade equal to 155-160 meter is misleading. It should be changed to 185 meter. The cited source (Donald Engels (1985). The Length of Eratosthenes' Stade. American Journal of Philology 106 (3): 298–311. doi:10.2307/295030) clearly states that one stade was 185 meter and not 155-160 meter, which gives an estimate of 46,000km to earth's diameter. The estimation of one stade being equal to 185 meter is the one accepted by most scholars (see, e.g., page 20 in Ptolemaais, Klaudios, J. Lennart Berggren, and Alexander Jones. Ptolemy's Geography: an annotated translation of the theoretical chapters. Princeton University Press, 2000.)

Geometric shapes[edit]

Hy I want to put some information about geometry 103.150.209.69 (talk) 17:34, 1 June 2022 (UTC)[reply]

Fantasy portrait[edit]

So we get another one of these fabricated portraits of the 17th/18th century, without explanation and without sourcing (even in the commons file). Good work! 2A02:AA1:1020:A09C:59CD:2C68:3B5E:177A (talk) 16:58, 25 July 2022 (UTC)[reply]

Yup, because they're public domain! What would you prefer? Furius (talk) 19:22, 25 July 2022 (UTC)[reply]

A note that it's a fantasy portrait (and not based on, say, a contemporary sculpture) would be a good start. Then add source info. 2A02:AA1:1020:A09C:59CD:2C68:3B5E:177A (talk) 09:41, 26 July 2022 (UTC)[reply]

Ok, I've chased this down and it turns out that it is based on an ancient object. No idea whether Lippert had any good reason for thinking sad object depicted Eratosthenes. Probably not. Furius (talk) 20:37, 26 July 2022 (UTC)[reply]

Measurement made at Local Apparent Noon (LAN)[edit]

This section:

The simplified method works by considering two cities along the same meridian and measuring both the distance between them and the difference in angles of the shadows cast by the sun on a vertical rod (a gnomon) in each city at noon on the summer solstice.

I don't think there is any requirement for the two cities to be at the same meridian if each measurement is taken at Local Apparent Noon (LAN). At LAN in Syene at summer solstice there would be no shadow and at Alexandria On the same day LAN could be determined as the time the shadow of a gnomon was at it shortest.CaptCarlsen (talk) 16:31, 17 February 2024 (UTC)[reply]

. Daianaz12 (talk) 14:32, 23 April 2024 (UTC)[reply]