Talk:Earth's circumference

Number of feet equals number of days?!

According to: Nicholas Mann (1 February 2005). Sedona, Sacred Earth: A Guide to the Red Rock County. Light Technology Publishing. p. 98. ISBN 978-1-62233-652-4.

• “The geometer John Michell realized that if 360 divided the earth's equatorial circumference of 24,902.95 miles, the resulting measure of 365,243 feet is directly equivalent to the 365.243 days of the year.”

I can’t find this fact anywhere else. Has anyone seen this before?

Onceinawhile (talk) 20:26, 2 December 2018 (UTC)

Hadn’t heard of it. Cute coincidence, but no significance. Strebe (talk) 02:42, 3 December 2018 (UTC)

The article reports the equitorial circumference as 24,901.461 miles, though. I suspect 24,902.95 is simply a fabrication by someone who did the math in the opposite direction. -- Beland (talk) 19:13, 12 January 2019 (UTC)

Best of both?

Hi @Strebe: I am conscious that we were on opposite sides of the AFD, but that you have a great deal of knowledge and value to bring to this subject. Now that we have reached a consensus (which of course could still change in future) is there anything you would recommend changing in this article or the Earth radius article to assuage your concerns? Onceinawhile (talk) 18:34, 16 December 2018 (UTC)

Thanks, @Onceinawhile:. If I came to Wikipedia looking for information about earth's radius or circumference, I would have no idea why these two articles are separate. We have drawn a historical distinction between the two, which I get: When the earth was considered to be a sphere, people thought in terms of circumference, but when the earth’s oblateness was recognized, modern geodesy developed the many notions of “radius” we now recognize. However, these notions are not distinct in most people’s minds. At the very least, the two articles need a “For … see …” template at the top of each to at least try to direct people to the article most likely to meet their needs (—good luck making that distinction in a short phrase). People are also going to view the use of possessive in the title here versus not in the Earth radius article to be arbitrary and inconsistent. Strebe (talk) 18:10, 29 December 2018 (UTC)

Requested move 6 January 2019

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this section.

The result of the move request was: no consensus to move any of the pages to the proposed titles via this move request; in most cases, it does not appear that requesting the moves individually would result in consensus, either. Dekimasuよ! 23:45, 13 January 2019 (UTC)

---

• Earth's circumference → Circumference of Earth
• Earth's crustal evolution → Crustal evolution of Earth
• Earth's energy budget → Energy budget of Earth
• Earth's internal heat budget → Internal heat budget of Earth
• Figure of the Earth → Figure of Earth
• Earth's orbit → Orbit of Earth
• Earth radius → Radius of Earth
• Earth's rotation → Rotation of Earth
• Earth's shadow → Shadow of Earth

– These titles are more encyclopedic because they do not include an apostrophe for possession. If I asked you which title is more encyclopedic, would you say History of Earth or Earth's history? Most people would probably agree that the first one is more encyclopedic. Mstrojny (talk) 22:49, 6 January 2019 (UTC)

• Oppose. While the current names might not be what I would have picked, the current names are correct, so the hassle of changing the names isn't worth it. Jc3s5h (talk) 23:24, 6 January 2019 (UTC)

I do not agree. The articles of the orbits of Venus and Mars are called Orbit of Venus and Orbit of Mars. I would at least move Earth's orbit to Orbit of Earth. --Mstrojny (talk) 23:40, 6 January 2019 (UTC)

• Part oppose re Earth's energy budget, that's the phrase used in the title of NASA's main outreach page. Granted, its not an encyclopedia but so what? Re the others, in my opinion both the good faith proposal and the only response so far (from Jc3s5h) are variants of WP:IJUSTLIKEIT and mean little. Instead, we should emphasize the most common and familiar expression on a case by case basis. Specific page editors are the best qualified to know what that is, and I have no opinion about these others. NewsAndEventsGuy (talk) 23:58, 6 January 2019 (UTC)
• Part oppose for same reasons as NewsAndEventsGuy. Some of these titles are terms of art, specifically at least Figure of the Earth and Earth radius. Strebe (talk) 06:10, 7 January 2019 (UTC)
• Comment Should it be Circumference of the Earth instead? Lugnuts ^{Fire Walk with Me} 11:25, 7 January 2019 (UTC)
• Different - Earth religion is about nature worship, not religion on Earth in general, so that shouldn't move. For the others, I agree that the possessives are awkward and the prepositional phrases are more natural search terms, but I would prefer to use "the" before "Earth", as in "Radius of the Earth". Sure, the possessive forms are also used, so there should be redirects from things like "Earth radius" (which is not enough of a term of art that it means anything different than "radius of the Earth", and Wikipedia is written for a general audience). -- Beland (talk) 18:17, 7 January 2019 (UTC)
• Comment Different sources have different rules about using the word the before Earth. Also, a lot of sources say not to capitalize Earth when it is preceded by the. MOS:CELESTIALBODIES says not to capitalize earth when it is not used in an astronomical context. Here are some other sources I looked at: Earth (capitalization), When to Capitalize “Earth” , Should You Capitalize the Word "Earth"? Hope this helps. --Mstrojny (talk) 20:39, 7 January 2019 (UTC)
• Procedural oppose. These article titles, while appearing similar, are too different to be considered under the same proposal and should be broken up into different nominations. Rreagan007 ([[User talk:|talk]]) 21:47, 7 January 2019 (UTC)

@Rreagan007: I'd be happy to break this down into different nominations. Just tell me which articles should be at different nominations and I'd be happy to do that. --Mstrojny (talk) 22:09, 7 January 2019 (UTC)

@Rreagan007: I would agree. I arrived here looking at the topic of Earth religion, and Religion on Earth has no where near the same, appropriate meaning. There are many diverse religions/faiths that have existed long before neopagan was a term, and neopagan itself is limiting. The group of referenced titles would be more suitably addressed as individual discussions. --nikerbop (talk) 18:30, 8 January 2019 (UTC)

• Oppose all, per above discussion. Earth religion is the proper name for the neopagan term. The present word arrangements on the rest seem the easiest to search for, although Earth's shadow is a page I want to check out (Cat Stevens missed a good song title). Randy Kryn (talk) 00:34, 8 January 2019 (UTC) .... The Dwarves dived deep and they awoke, the balrog of...which I spoke, it's a silly song but it's no joke, the balrog is a nasty bloke, Oh I'm being followed by an Earth Shadow.... Earth shadow Earth shadow... NewsAndEventsGuy (talk) 01:33, 8 January 2019 (UTC)
• Comment I have removed Earth religion from this request because the title I suggested has nothing to do with the topic. --Mstrojny (talk) 20:40, 8 January 2019 (UTC)
• Oppose all The proposed titles are more confusing and harder to search for._{ZXCVBNM (TALK)} 11:16, 11 January 2019 (UTC)
• @Jc3s5h, NewsAndEventsGuy, Strebe, Lugnuts, Beland, Rreagan007, Nikerbop, Randy Kryn, and Zxcvbnm: Question If consensus is against moving these pages, would you be fine if I move Orbit of Venus and Orbit of Mars to Venus's orbit and Mars's orbit respectively? Mstrojny (talk) 15:44, 12 January 2019 (UTC)
  • There is no need to make the titles consistent, but do create redirects from Venus's orbit and Mars's orbit. [[User:|Jc3s5h]] (talk) 15:50, 12 January 2019 (UTC)
    • @Jc3s5h: One of the principles on deciding an article title is consistency per WP:CRITERIA. Is there a valid reason why the titles should not be consistent with one another? Mstrojny (talk) 18:38, 12 January 2019 (UTC)
  • For those article I don't care either way is great. I'm glad you're interested in working on them, thanksNewsAndEventsGuy (talk) 16:01, 12 January 2019 (UTC)
  • I prefer "Orbit of" for all articles, so I wouldn't move anything to the possessive. But redirects are a good idea. -- Beland (talk) 18:53, 12 January 2019 (UTC)

---

The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

What is the most common search phrase used by the users? That should dictate the answer to the question earth's or of the earth. — Preceding unsigned comment added by 98.202.180.17 (talk) 15:27, 7 January 2019 (UTC)

Inconsistency?

The opening sentence says the polar value is 40,007.86 km. But the end of the third paragraph says it's 39,941 kilometres. Have I missed something obvious? — Preceding unsigned comment added by Barti Ddu (talk • contribs) 09:39, 11 February 2019 (UTC)

I agree. I have removed the figures at the end of the third paragraph, which lacked a citation to a reliable source. Jc3s5h (talk) 10:59, 11 February 2019 (UTC)

Stadia

I have seen this statement about stadia. The logic is quite bad. It says that the distance between Alexandria to Syene was 5000 stadia. This was a public record, something that was not calculated by Eratosthenes himself. The article says that the precision depends on his choice of stadia. That was not his choice. The distance is already measured using a specific unit and it was already as accurate as it was accurate. That is to say that the relative error of the circumference is about the same as the error of the distance between two places and this has nothing to do with Eratosthenes himself or his choice of the said unit. We can say "if we take that the unit was..." but not Eratosthenes. — Preceding unsigned comment added by 84.78.250.6 (talk) 09:05, 2 October 2019 (UTC)

The text doesn’t say that Eratosthenes chose, so I don’t get what you’re ranting about. Strebe (talk) 09:21, 2 October 2019 (UTC)

This sentence:

"Depending on whether he used the "Olympic stade" (176.4 m) or the Italian stade (184.8 m),"

He did not use anything that was not set already. We can say "Depending on whether the "Olympic stade" (176.4 m) or the Italian stade (184.8 m) was used,". The way it is in the text now, it implies that he could choose either just we do not know which one. No. The unit was set already. This subtle error exists in other places, not just Wikipedia. I would read the text through and clear this out so it is more obvious that the unit was set already. — Preceding unsigned comment added by 84.78.250.6 (talk) 10:07, 2 October 2019 (UTC)

That does not begin to get to the heart of the matter. Regardless of which it actually was, we do not know the length of it, so why does it matter if someone might misinterpret the text to mean that Eratosthenes made a decision about units? (I disagree that people would misinterpret that anyway...) The precision implied in the text body is blatantly fictitious, despite the citations. Better citations are needed and the history section needs to be completely rewritten with the understanding that our own knowledge of the units used has huge uncertainties. The breathless claims of accuracy are rubbish. Strebe (talk) 18:16, 2 October 2019 (UTC)

Islamic Golden Age

Under the 'History of calculation' section, the first two subsections are 'Eratosthenes' and 'Posidonius'. Both are Greek and great contributors to this field. The third subsection is simply called 'further developments', despite focusing on two scholars from the Islamic Golden Age. I propose the name of this section be changed to 'Islamic Golden Age'. It would be more inclusive and more accurate. Ledvelvet21 (talk) 15:53, 4 June 2020 (UTC)

What is your proposal for the final paragraph of that section? Strebe (talk) 17:31, 4 June 2020 (UTC)

I would propose a fourth subsection entitled 'Christopher Columbus'. Columbus' voyage(s) took place in a different timeframe, historical period, and location as compared to the other two scientists mentioned in this section. Al-Ma'mun and Al-Biruni were scientists who are tied together through a similar timeframe (800/1000), historical period (Islamic Golden Age), and relative geography (Iran/Iraq). The aforementioned Columbus voyage took place in the late 1400's, during the 'Age of Exploration' (alternatively, 'Age of Colonization'), and in Europe/the Americas. Alternative title proposals accepted Ledvelvet21 (talk) 23:15, 4 June 2020 (UTC)

I think Columbus’s inclusion, if warranted at all, is a different matter. I have updated the article; feel free to improve. Strebe (talk) 01:21, 5 June 2020 (UTC)

Article should start with the exact values

This article used to provide the exact values for the circumference around the poles and the equator in the first paragraph, but was changed in January 2020 to approximate values matching the original definitions of the kilometre and nautical mile (which have since changed). I tried to fix it as much as I could, but I think it would be a good idea to change it back so the first paragraph provides the correct information. —Cousteau (talk) 11:35, 29 June 2020 (UTC)

Only things that are counted can have exact values (and even then, only if the counting was done perfectly). Measured quantities such as the circumference of the Earth are never exact. Jc3s5h (talk) 13:23, 29 June 2020 (UTC)

Dip ≠ magnetic dip

In the section Islamic Golden Age, "dip angle" is used to mean the angle between a horizontal plane and a line toward the horizon. But the link put on it takes you to an article talking only about magnetic dip, which means the angle between the earth’s magnetic field lines and the horizontal plane.

• So the problem I see is that the link leads to an unrelated article.

Wiktionary (EN) has two entries: "dip of the horizon" and "dip of the needle", corresponding to the two meanings.

There doesn’t seem to be a Wikipedia article on "horizon dip" or "dip (geology)": both redirect to other articles, of which the latter might be a good candidate for the link: Strike and dip. There does seem to be a clear difference between "dip (geology)" and "horizon dip", but that is a bit beyond me.

"Horizon dip" redirects to Horizon, but there the term "dip" is only used embedded in the text, i.e. not defined or described in itself. That article does have an interesting external link under "Further Reading", so a second solution to the matter would be to change the link on "dip angle" in the current article to that: https://aty.sdsu.edu/explain/atmos_refr/dip.html

• In a related matter, the disambiguation list Dip#Geometry_and_science could be updated, as it (still?) contains dip (geology) and horizon dip, two article references that are now only redirects. --Geke (talk) 15:24, 5 August 2020 (UTC)

Thanks for noticing. Please fix as per your recommendation. Strebe (talk) 23:03, 5 August 2020 (UTC)

Polar “circumference” is a solecism

Ellipses have perimeters, not circumferences. The defunct citation of no particular reliabililty does say “circumference”, a usage that has polluted the few other Web pages that mention “polar circumference”. It’s not a term that appears in scientific literature. If this article is going to talk about the polar perimeter, it should state that it’s elliptical and give a reference to a more complete explanation (Meridional arc). Strebe (talk) 03:01, 17 September 2020 (UTC)

@Strebe: both Ellipse#Circumference and Circumference#Ellipse beg to disagree. fgnievinski (talk) 04:45, 27 April 2021 (UTC)

Circumference#Ellipse starts out “Circumference is used by some authors” in reference to ellipses, implying that the rest do not. I never see that usage in geophysical literature. The equatorial circumference is calculable from the equatorial radius, but the polar “circumference” is not calculable from the polar radius. Seems like that could easily confuse people. Strebe (talk) 06:23, 28 April 2021 (UTC)

Rename to "History of Earth's circumference measurement"

To better reflect the current scope, as per section titles. fgnievinski (talk) 20:06, 22 April 2021 (UTC)

Please see WP:RM. There is a process of consensus-building to go through BEFORE such a move. Onceinawhile (talk) 06:40, 24 April 2021 (UTC)

Requested move 27 April 2021

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review after discussing it on the closer's talk page. No further edits should be made to this discussion.

The result of the move request was: No consensus to move (non-admin closure) (t · c) buidhe 21:40, 6 May 2021 (UTC)

---

Earth's circumference → History of Earth's circumference measurement or History of Earth's circumference determination – To better reflect the current scope, as per section titles. fgnievinski (talk) 04:42, 27 April 2021 (UTC)

• Oppose. The article should describe the current value, as well as providing historical information. It is unfortunate that the article merely gives two values with no discussion of the meaning of the given values, or a comparison of alternate values. That is an area for improvement. But the title ought to describe what the article should be, not what it is in it's current sub-standard condition. Jc3s5h (talk) 18:06, 27 April 2021 (UTC)

• @Jc3s5h: that is already covered at length in Earth's radius, modulo 2π. fgnievinski (talk) 18:31, 27 April 2021 (UTC)
  • Earth's radius does not address Earth's circumference. Depending on which definition is used, the circumference is not necessarily 2π times the radius. Jc3s5h (talk) 19:32, 27 April 2021 (UTC)
    • there are only two Earth circumferences: equatorial, C_a=2π*a, with a for equatorial radius; and polar, C_b=4*a*E(e), where the polar radius b enters via the eccentricity, e=(1-b²/a²)^0.5. so both circumferences are defined directly based on the two radii. mathematically, the present article is 100% redundant with Earth's radius. it's only the historical aspects that would seem to be unique. and barely so, given the wide overlap with history of geodesy and history of meridian arc measurement. fgnievinski (talk) 20:27, 27 April 2021 (UTC)
      • I'm not a big fan of discussing closely related ideas in separate articles. Maybe some mergers are appropriate. Current Earth's radius seems overly technical and inaccessible. Perhaps the most technical aspects should be trimmed and it should be extended to also cover Earth's radius. Jc3s5h (talk) 20:35, 27 April 2021 (UTC)
        • @Jc3s5h: You mean, to extend Earth's radius to also cover Earth's circumference? I'd be all in favor of that. In fact, I've just created Earth_radius#Derived_geometrical_quantities -- would that suffice? fgnievinski (talk) 01:57, 28 April 2021 (UTC)
          • Yes, that's what I meant. The section you added seems barely sufficient. It might be nice to add some actual values, rather than making the reader do it. Jc3s5h (talk) 21:04, 28 April 2021 (UTC)
            • Done. fgnievinski (talk) 21:38, 28 April 2021 (UTC)
  • @Fgnievinski: If this article is moved, what do you propose to do with Earth's circumference? If it were simply to continue to be a redirect to this article there doesn't seem to be much point to a move. Would you redirect it to Earth's radius or do you have something else in mind? Station1 (talk) 22:49, 27 April 2021 (UTC)
    • @Station1: I propose to redirect it to Earth_radius#Derived_geometrical_quantities. And perhaps rephrase the renaming as "History of Earth's size measurement"? fgnievinski (talk) 01:57, 28 April 2021 (UTC)

• Oppose. The article already states where to go for technical details in its “For” section at the top. The proposed name is ungainly. I can imagine people searching on “Earth's circumference”, which ought to bring them to this article, but I can’t imagine people thinking to type “History of Earth's circumference measurement”. As noted, a redirect would take care of this, but relying on a redirect for most of the traffic suggests to me that the redirect is the right title. I think most people want few simple facts such as this article already provides. Strebe (talk) 06:46, 28 April 2021 (UTC)

• @Strebe: I thought you'd be pleased with the proposed narrowing of scope for the present article. After all, you've nominated it for deletion, arguing that "The article has no substantive content that does or could differ from Earth radius."? fgnievinski (talk) 19:24, 28 April 2021 (UTC)

• @Fgnievinski: I opposed the creation of the page. If it’s going to stay, I oppose renaming it. I’m fine with deleting it as long as no material is lost. Strebe (talk) 03:07, 29 April 2021 (UTC)

• The only material that could be lost, meaning that it's not duplicated elsewhere, would seem to be just the first two paragraphs of section Earth's circumference#Historical use in the definition of units of measurement. And, even so, there's some level of original synthesis there, because the original definitions use the quarter meridian instead of Earth's circumference, for example:

Once it has been chosen as base, will either the whole meridian or a sensible part of it be taken as a unit? The wholeness [circumference]? Out of question! The half, that stretches from one pole to the other, may not be easily conceived by our mind because of the part which is located "below", in the other hemisphere. This is not the case of the quarter of the meridian that, on the contrary, can be easily imagined: it stretches from one pole to the equator. In the future it will be said: France opened the divider and pointed it on one pole and the equator, a sentence that will be greatly successful. There is another reason, that is really scientific and supports the meridian: its quarter is the arc intersected by the right angle. That's right: however, why should it be considered as a further advantage? Simply because the right angle is considered as the natural angle, the angle of the vertical and the gravity. It is the unit-angle, the degree is nothing but its subdivision. (Denis Guedj, Le Mètre du monde, Le Seuil, 2000.)

So, this whole article could easily be merged into Meridian arc#History. fgnievinski (talk) 04:19, 29 April 2021 (UTC)

Comment: I've just created quarter meridian, upon which the historical definition of the metre was based. fgnievinski (talk) 19:24, 28 April 2021 (UTC)

Comment: I've created Meridian_arc#The_nautical_mile, moving a subsection from Latitude. It seems a good target for merging from Earth's circumference#Historical use in the definition of units of measurement fgnievinski (talk) 01:25, 1 May 2021 (UTC)

Comment: The real topic is Figure of the Earth. But that article would be very long if it included everything about the topic, including the history of its measurement. A sensible solution is to split the history by level of detail (sphere, ellipsoid, geoid) and by technical sophistication (measuring an arc of meridian, using satellites, ...). But what we have are articles on equivalent values (radius, circumference, arc of meridian, history of the metre, ...) each of which covers some of the history, allowing inconsistencies to appear when they are edited. There is also an article on grade measurement which is shorter than the corresponding German article de:Gradmessung. JonH (talk) 08:19, 1 May 2021 (UTC)

That's an excellent pointer, thank you! Yes, Geodesy is much richer in the German literature, Wikipedia included. But I've detected a mistranslation: "Gradmessung" should not be "Grade measurement" but "Arc measurement"; this is attested by Torge (2008) Geodesy (Geodäsie), which gives, e.g.:

• "Fig. 1.2: Gradmessung des Eratosthenes." [1]
• "Fig. 1.2: Arc measurement of Eratosthenes." [2]

I've renamed that article according to the sources above: arc measurement. By the way: it exists is several other Wikipedia languages, so it seems an excellent target for merging the entirety of Earth's circumference, which only exists in the English Wikipedia. fgnievinski (talk) 06:18, 2 May 2021 (UTC)

I've created redirects for each of the arc measurements buried in Paris meridian, many of which would probably deserve a separate article; these and more are listed in Arc measurement#See also. fgnievinski (talk) 06:31, 3 May 2021 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Definition of nautical mile

The section Earth's_circumference#Historical_use_in_the_definition_of_units_of_measurement says that "Gunter used Snell's circumference [24,024 statute miles] to define a nautical mile as 6,080 feet". But 24024 × 5280 / 21600 = 5872.533, so it is hard to see how Gunter found the exact definition that would be used some 300 years later. In 2018, I made a similar comment at Talk:Nautical_mile#Gunter's_definition and other editors agreed and changed that article in 2019. But it seems that in the meantime the "information" had been copied into this article. JonH (talk) 01:32, 2 May 2021 (UTC)

The English statute mile was not standardized until after Gunter’s proposal. The relevant act was passed in 1593 asWeights_and_Measures_Acts_(UK)#35_Elizabeth_c._6. I’m not sure that this accounts for the discrepancy, but it seems relevant. The source in this article is as confusing as this article’s text, which is unfortunate. We need a better source. Strebe (talk) 01:50, 2 May 2021 (UTC)

The best source I know for the history of the nautical mile is A. B. Moody, The Nautical Mile PDF, International Hydrographic Review, XXVII (1), 1950, pp 77-85. It does not mention Gunter, so perhaps he only played a minor role. "Edmund Gunter (1581–1626)" by C. H. Cotter (Journal of Navigation, Volume 34, Issue 3, September 1981, pp. 363-367), says "he concluded that a one-degree arc of a meridian is equivalent to 352000 feet. This gave 5866 feet per minute of arc, a figure considerably in excess of the generally accepted value of 5000 feet. ... He drew the attention of English mariners to the need to improve their navigational practice by adopting a more accurate measure for the nautical mile. ... Gunter suggested the division of a degree-arc of the Earth's surface into a hundred parts or 'centesmes'." So it seems that he did not invent the nautical mile, nor define it as 6080 feet. I hope someone, with more time than me, can use the Moody history to improve this article and/or the Nautical mile article. (Thanks to Fgnievinski for taking up my suggestion in the section above.) JonH (talk) 13:15, 2 May 2021 (UTC)

Eratosthenes' measure of Earth circumference

Original image

New image

In this change, @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 22:29, 26 August 2021 (UTC)

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

Unit to measure earth.

Best unit to measure the circumference of earth is fit or yards or miles or inches? 2409:4042:4CC3:8F49:0:0:5F4B:E80B (talk) 09:39, 20 November 2021 (UTC)

Opening section

Accuracy is the proximity of measurement results to the true value; precision is the degree to which repeated (or reproducible) measurements under unchanged conditions show the same results.

The opening section says "The physical length of each unit of measure has remained close to what it was determined to be at the time, but the precision of measuring the circumference has improved since then."

Surely this should be "The physical length of each unit of measure has remained close to what it was determined to be at the time, but the accuracy of measuring the circumference has improved since then."

See Accuracy and precision. --SGBailey (talk) 18:24, 9 June 2022 (UTC)

Yes, I think "accuracy" is a better word to use. Jc3s5h (talk) 20:13, 9 June 2022 (UTC)

Years (or estimates) for Eratosthenes and Posidonius

It would be good if someone knowledgeable could add the years (or approximations thereof) in which Eratosthenes and Posidonius made their estimates. The other historical measurements have date anchors of one ilk or another. Cellmaker (talk) 23:58, 30 March 2023 (UTC)

I agree, also, seeing as Eratosthenes died a few decades before Posidonius was born (and thus made his calculations before Posidonius made his), should the subsections on the two not be switched around to have Eratosthenes first? Phslhs (talk) 16:07, 14 March 2024 (UTC)

First illustration typo. It should say about circumference is about 25,000 miles, not 35,000.

See more detailed second illustration. CharlesHBennett (talk) 13:59, 5 August 2024 (UTC)

I've removed that illustration. It's meant to show Eratosthenes' estimate, but no matter how you measure that, 35,000 miles is wrong (compare the original at noaa.gov, which says 25,000 miles). The later illustration showing 40,000 km is largely duplicative anyway, so we can do with just that one. Station1 (talk) 19:10, 5 August 2024 (UTC)