Talk:Eratosthenes

(re)sources

You may want to check this passage from The Story of Geographical Discovery How the World Became Known by Joseph Jacobs, at []=112130 gutenberg. --MATIA 22:21, 30 August 2005 (UTC)

Two passages from John Lord:

• []=42620 http://www.gutenberg.org/catalog/world/fulltext-context?fulltext=eratosthenes&fk_files[]=42620
• []=11535 http://www.gutenberg.org/catalog/world/fulltext-context?fulltext=eratosthenes&fk_files[]=11535

By William Stevenson, A General History and Collection of Voyages and Travels - Volume 18

• []=99196 http://www.gutenberg.org/catalog/world/fulltext-context?fulltext=eratosthenes&fk_files[]=99196

Williams, Edward Huntington, Williams, Henry Smith, History of Science, a — Volume 1

• []=38860 http://www.gutenberg.org/catalog/world/fulltext-context?fulltext=eratosthenes&fk_files[]=38860

Apollonius Rhodius,

• []=36838 http://www.gutenberg.org/catalog/world/fulltext-context?fulltext=eratosthenes&fk_files[]=36838

--MATIA 22:56, 30 August 2005 (UTC)

beta

ERATOSTHENES, "THE SURVEYOR OF THE WORLD" from Williams' A History of Science gutenberg 1hci10.txt

An altogether remarkable man was this native of Cyrene, who came to Alexandria from Athens to be the chief librarian of Ptolemy Euergetes. He was not merely an astronomer and a geographer, but a poet and grammarian as well. His contemporaries jestingly called him Beta the Second, because he was said through the universality of his attainments to be "a second Plato" in philosophy, "a second Thales" in astronomy, and so on throughout the list. He was also called the "surveyor of the world," in recognition of his services to geography. Hipparchus said of him, perhaps half jestingly, that he had studied astronomy as a geographer and geography as an astronomer. It is not quite clear whether the epigram was meant as compliment or as criticism...

Kerr's General History and Collection of Voyages and Travels gutenberg 13606-8

Ptolemy Euergetes was particularly attentive to the interests of the library at Alexandria. The first librarian appointed by Ptolemy the successor of Alexander, was Zenodotus; on his death, Ptolemy Euergetes invited from Athens Eratosthenes, a citizen of Cyrene, and entrusted to him the care of the library: it has been supposed that he was the second of that name, or of an inferior rank in learning and science, because he is sometimes called Beta; but by this appellation nothing else was meant, but that he was the second librarian of the royal library at Alexandria. He died at the age of 81, A.C. 194. He has been called a second Plato, the cosmographer and the geometer of the world: he is rather an astronomer and mathematician than a geographer, though geography is indebted to him for some improvements in its details, and more especially for helping to raise it to the accuracy and dignity of a science. By means of instruments, which Ptolemy erected in the museum at Alexandria, he ascertained the obliquity of the ecliptic to be 23° 51' 20". He is, however, principally celebrated as the first astronomer who measured a degree of a great circle, and thus approximated towards the real diameter of the earth. --MATIA 21:42, 5 September 2005 (UTC)

i've got a question how did eratosthenes get the name bata??? Aasin (talk) 18:10, 25 March 2008 (UTC)

Measurement of the Earth

How did Erathothenes know that the Sun was very far away, in comparison to the size of the Earth? If you don't know that the Sun is far away, the observations can also be explained by a flat Earth and the Sun being close to the Earth (or a combination of the two). --Bubba73 (talk) 05:03, 4 October 2005 (UTC)

The moon is far away, by parallax. This rquires simultaneous observation at distant points; but simultaneity can be obtained by waiting for a lunat eclipse. The Sun is even further away (at half-moon, the triangle EMS has a right angle at M; the angle at E can be measured directly; the ratio of the two distances is the cosine of that angle.) --Septentrionalis 05:16, 4 October 2005 (UTC)

I assume that this was known at the time. Is that right? --Bubba73 (talk) 00:05, 23 October 2005 (UTC)

If I recall correctly, but I don't have a source in front of me; any history of Greek astronomy should do. --Septentrionalis 22:32, 23 October 2005 (UTC)

Sorry to say this, but mathematically, Eratosthenes did not really proof that the earth was not flat, but like a ball. Because in his "evidence" he assumed that the rays, which come from the sun, are parallel. If I were a solicitor of the ancient Greek world view, I could say that the rays needn ´t be parallel. The sun can also be round (as a solicitor of the ancient Greek view of the world, I would only have to defend the thesis that the earth is flat). So the sun rays can also be anti-parallel. But then the earth can be flat and it is no contradiction, if the stick of Eratosthenes cast a cloud in Syene, but not in Alexandria during the same time.

If you put 2 pens on a desk and an electric light bulb exactly over 1 pen, then this pen will surely not cast a cloud, but the other pen, which is not directly over the light bulb, does.

So Eratosthenes did not give an evidence. If one argued that then the sun would then be too close to the earth (because the distance sun earth can be measured with the sentence of Pythagoras) and therefor the earth would be burnt, one could say (as a solicitor of the ancient Greek view of the world) that nobody knows how hot the sun is and via the Gods, like Zeus the hot rays of the sun are cooled :-).

However, Eratosthenes did not give any mathematical evidences of the earth of being round and no evidences of the length of the equator. —The preceding unsigned comment was added by 134.95.141.49 (talk) 14:58, 25 April 2007 (UTC).

My understanding is that a spherical Earth was the accepted opinion among Greek scientists. Eratosthenes was therefore not concerned with proving that the Earth was not flat, he was merely attempting to measure it. 193.203.156.239

The Greeks knew. By looking at their ports and out to sea one can easy notice that the earth is not flat (by the way ships disapear). --Firebird 01:14, 16 October 2007 (UTC)

I think the part about the sun appearing as disk, as opposed to a point, is rather irrelevant. A disk is fine, as you can simply measure based on the center of it. So just saying that the sun is not infinitely far away is sufficient.--Robbrown 05:04, 2 August 2007 (UTC)

Furthermore, it's not particularly difficult to measure the angular size of the sun's disk (about 1/2 degree), so that can be accounted for in any angular measure of the shadow. Never assume these people were stupid.

Fred Hoyle, a recently deceased and well-respected astronomer, points out that the distances in ancient Egypt were fairly well known. Runners were used to carry messages between cities and they had, over time, developed the knowledge of the distances to a fair level of accuracy - about 1%. The Itinerary stadia is suitable for runners' distances and since it gives an error for the size of the Earth (IIRC) of about 4%, Hoyle argues, reasonably IMNSHO, that Eratosthenes "got-it-right".

I think the section should be changed to be more neutral, with a proper discussion of the interpretation of his work. It currently reeks of POV. Michael Daly 21:23, 13 September 2007 (UTC)

Time to remove the disputed tag?

Due to the finding of the arbitration commity (see Wikipedia:Requests_for_arbitration/Rktect#Remedies) there should be an opportunity to reach sufficient consensus so that the disputed tag can be removed. Anyone disagrees? --Egil 17:09, 22 October 2005 (UTC)

What is or was disputed? --Bubba73 (talk) 00:06, 23 October 2005 (UTC)

Afaik only contributions from Rktect, see Wikipedia:Requests_for_arbitration/Rktect/Evidence. I just want to make sure there is nothing else. -- Egil 00:35, 23 October 2005 (UTC)

Things appear to be adequate. Lose the tag already. --Mashford 19:58, 20 November 2005 (UTC)

cleanup and disputed

Well, someone had to do it... :) So I started. I think I've merged most new content, left some out. For instance:

"There are two theories concerning Plato's machine..."

because that's not related to Eratosthenes life at all (it's about doubling the cube which rktect was pushing) and because the latter part it's taken verbatim from another website (which is mentioned, but still it's copyvio). I could use some help to put in shape the earth's measurement section. I also removed the part taken verbatim from the math biographies page at the Erastothenes contributions section (for the same reasons outlined above) I finally took out the Strabo thing since I couldn't really understand its relevance (maybe on the entry of Strabo if there is one wold be more appropiated). --( drini's _vandalproof page ☎ ) 17:03, 30 November 2005 (UTC)

Date of librarianship

When did Eratosthenes become the Library's head Librarian? This article says 236 BC, but I looked over at Britannica, and it says 255 BC- a pretty important difference. --maru (talk) Contribs 02:24, 6 January 2006 (UTC)

Lots of dates in antiquity are disputed or uncertain -- it'd take a bit of research to find out exactly what the possible range of dates is, which I don't have time to do just at the minute, but I can well believe it's uncertain to +/- 20 years or even more. In addition, ancient Greek dates are normally in the form "236/235 BCE" because the year ran from midsummer to midsummer. Petrouchka 11:10, 22 February 2006 (UTC)

Shape of Earth

Did Eratosthenes necessarily assume a spherical earth to make his math work? I always assume he did from my understanding. I assume also that Plato had a spherical earth in his philosophy because of the ideal of the sphere as perfect. Mike Logghe

Seems so likely that it's barely worth doubting, I'd suspect. AFAIK it's only in the last century or three that it's been known that the earth isn't spherical. Petrouchka 11:13, 22 February 2006 (UTC)

(1) Add a link to the famous map? (2) The map has a mystery

(I offer apologies in advance if i'm not adding my comment properly.)

(1) The article describes one of Erato's important contributions as, "A map of the entire known world". Such described map seems to be the map displayed at <http://en.wikipedia.org/wiki/Image:Iran.jpg#filelinks>; such displayed map is also shown at <http://en.wikipedia.org/wiki/Persia> and is there attributed to Erato. I don't know how to cite that link in the Erato article, so maybe someone else will do it. Thanks.

(2) The displayed map has words in English, such as "Northern Ocean". So Erato did not write such words on the map that is attributed to him. (Erato probably wrote Greek, I gather from the article.) So perhaps the English words were added centuries after Erato drew the map?? Bo99 23:11, 1 March 2006 (UTC)

A drawing would help

I think, a drawing would help to understand the method of Eratosthenes. Who can make and insert it? --84.136.239.196 01:23, 1 May 2007 (UTC)

"He also made what he thought was a map of the Earth."

The above text appears in the first paragraph - it implies that Eratosthenes was somehow wrong, and that he hadn't actually created a map of the Earth. I think it needs better wording - just because it wasn't particularly accurate, doesn't make it any less a map of the Earth. David 10:34, 23 May 2007 (UTC)

Fleet of Circumnavigation

The report should at least be mentioned of a fleet equipped by Eratosthenes in 232 BC to circumnavigate the Earth heading East through the Indian Ocean and reaching the Isthmus of Panama. The crew was Cyrenaican (Libyan), captain Rata and navigator Maui. Inscriptions around the Pacific and Maori Legends tell of events. The controversial name of Barry Fell, who grew up with Maori children, is attached to this. This reference is in Italian: http://www.liutprand.it/Eratost.htm hgwb 19:17, 9 June 2007 (UTC)

One question about measurement of the Earth

One thing I've wondered is, how was Eratosthenes able to determine the exact time to make the measurement places 800 km from each other? I can think of a few ways it could be done, but all would have a high degree of error given what would be available at the time, I'm wondering if there is any evidence showing how he did it himself. -- Suso 03:28, 12 June 2007 (UTC)

If you measure at noon, the shadow of a vertical stick is going to be shortest. So, just trace the tip of the shadow in sand or on a paper. An added advantage is that you don't have to line up one spot exactly north of the other - the error is not that important if you know exactly how far apart they are going straight up north. (measuring the funny shadow line can be done later, in the afternoon or the next day. retostamm 13:57, 20 Aug 2007 (PST).

5000

In the text, in an article by Rawlins, "5000" appears twice. In the original, it appears once. —Preceding unsigned comment added by 86.141.242.167 (talk) 13:09, 22 December 2007 (UTC) This depends on the computer used.

Sieve of Eratosthenes

Should the Sieve of Eratosthenes be in this article somewhere?