Talk:Eratosthenes

If you want to mention the various names of the Ptolemy III, please do so on his page, not here.

Okay

I also removed He also assumed these two cities were on the same meridian. His method for computing the Earth's size does not depend on the two cities being on the same meridian. It always works as long as you know the distance of the two cities. The information on the Astronomy online page is incorrect. AxelBoldt

I am not so shure about this. It seems quite accurate. But we shall check this out again. First I have to freshen my memories about all those old measures: stadia, Egyptian ell, Arabic ell, and so forth ... --XJamRastafire 22:54 Sep 19, 2002 (UTC)

---

The measurement of the inclination of the ecliptic with an angle error 7'.

The above confuses me Lir 16:08 Nov 3, 2002 (UTC)

I'll check this soon as possible. You can also put this statement temporarly out from Eratosthenes article. It is hard to see the exact values from these ancient scientists. Also I have Eartosthenes' value for Earth circumference to be 39,690 km, and you put in the article 42,000 km. What is correct? Hard to tell, also. --XJam 16:18 Nov 3, 2002 (UTC)

I find it really hard to tell when somebody responds if they respond on their own page. I dont understand what an angle error 7' means.

We know that the inclination of the ecliptic is 23° 26' 27.77" so his error was 23° 26'+7'=33' or 23° 26'-7'=19'. This statement is okay for me. Please let me know, what you do not understand still. I have to check what was his actual error. +7' or -7'.

I would guess that issue regarding Eartosthenes' value has to do with the conversion from 250,000 stades to kilometers.

Also take a look at astronomy and astrophysics I think it should mainly be a disambiguation page. Other's seem to think otherwise. Before I edited it they had large amounts of text which I moved to positional astronomy, history of astronomy, radio astronomy etc. but they want to move it all back-I think thats a bad idea. Lir 16:26 Nov 3, 2002 (UTC)

This is a good idea for shure. I don't know why should be everything on that page.

from activemind.com conversion is: 1 stade = 607 ft or 185 meters (mile = 5280 feet so 1 stade = .11 mile) which would give Eartosthene's value to be 46,000 km Lir 16:27 Nov 3, 2002 (UTC)

Aristotle refers to the calculation of "mathematicians" who had investigated the subject (without naming them) that the earth was 400,000 stades in circumference. This distinction may belong to Eudoxus of Cnidus (ca. 370 B.C.) who also estimated its measurement at 400,000 stades. A calculation of 300,000 stades is credited to Dicæarchus (died 296 B.C.), a student of Aristotle

Thus 5,000 stades x 50 equals 250,000 stades, the circumference of the earth. But as a mathematical ploy, in order to achieve a number divisible by 60 or 360, so as to correlate stades with his subdivisions or degrees, he emended this to 252,000 stades [ a stade, stadion, stadia ), originally the distance covered by a plough before turning, was 600 feet of whatever standard was used]. A conversion to modern units of measure finds Eratosthenes' calculation to be somewhere between 45,007 km (27,967 miles) to 39,690 km (24,663 miles), as compared to actual equatorial circumference of 40,075 km (24,902 miles). Lir 16:30 Nov 3, 2002 (UTC)

Yes I know this. There were three stades in usage at that time as I know. The smallest was 157 m, the largest was 211 m. Many times we take medium value of 172 m. We can also find another value of 184.2 m. We also believe that Eratosthenes' value was 15 % too big. (You wrote 5 %). --XJamRastafire 16:47 Nov 3, 2002 (UTC)

How was the length was actually measured. The Nile

itself (along which the passage must have been made) makes a couple of quite significat curves north of Thebes, for instance. How were these compensated for? Also, how were the measurement done? If it was paced -- that would add a significant uncertainty.

Another thing: Would you not think a scholar like E. used a well founded value of the stadion? I'm sure the different stadion in different cities was a problem known at the time? As an Egyptian scholar, perhaps E. used the 3 / 5 Egyptian royal cubit definition of the Greek foot, by which we get 188.3 m with an uncertainty of maybe 1 % based on the variation of the cubit standards.

-- Egil 08:32 Feb 14, 2003 (UTC)

I had translated this page into chinese ,i think it is okay.But now i have a question:there is a sentense Aswan is in fact slightly north of the tropic

so where is assumption?Is it possible the actor forgot to write the sentense "assuming aswan local on the tropic of the cancer"--heryu 11:13, 8 Dec 2004 (UTC)