In line with what Otared writes about the measurement of distances in the context of Persia and ancient Rome, I am always very surprised to see the precision of the measurements in the evaluation of the circumference of the earth by Eratosthenes of Cyrene. What intrigues me is not really the geometry calculations involved, but the calculation of the distance between Aswan and Alexandria. There is little information on the taking of this measurement: is it Egyptian surveyors (bematists: https://en.wikipedia.org/wiki/Bematist) or the use of an instrument equivalent to a pedometer? see here: https://en.wikipedia.org/wiki/Eratosthenes
On 26 Jan 2022, at 00:17, Hans Hagen via ntg-context <ntg-context@ntg.nl> wrote: […] times (clocks) were definitely different per cityRegarding the issue of the absolute necessity of defining a standard time the book by Peter Galison « Einstein’s Clocks, Poincaré’s Maps » gives some interesting insight. In particular, since after the mid 19th century trains were developed while the time was not standardized, many accidents happened with hundreds of people killed. This led Henri Poincaré, Lorentz and Einstein (among other mathematcians and physicists) to th enotion of relativity… Regarding the measure of the distance, area, volumes and weight indeed each region of the world had its own units because the trade and exchange of products were essentially local. With the progressive extension of the exchanges between regions and countries the need for a standardization appeared more and more. For example the problem of measuring grains is a quite difficult one: if one measures the weight, depending on how much humidity the grains contain, one has different amount of the real stuff. If one measures the volume of the grains, then according how compressed they are, the amount of the grains may be different… (at some point there was a law which stated that when a unit vessel of grains was to be sold, the seller should struck the bottom of the vessel on a table three times and then refill again sthe vessel for it to be full). The measure of the distances on roads in the Persian empire had one unit and one subunit: « parasang » and « mil ». Parasang, which means « big stone » in Persian, was the average distance which a fantassin could walk in a certain amount of time, and was marked by a large piece of stone on the road (this is also reported by Herodotus). Each parasang was divided into three « mil », which means « iron bar » in Persian, and was marked by planting an iron bar on the road side. A parasang is between 5400 and 6000 meters, and thus a « mil » is something about 1800 and 2000 meters. These units were used in many areas outside the Persian empire, and are still used, in particular the parasang, in Iran and Afghanistan (in Iran a parasang is 6 kilometers now). (Personnaly I think the Roman mile has its origin in the Persian « mil »: I think the etymology of the word mile based on the word « mille », a thousand, cannot be correct since it does not correspond to one thousand of any other unit of length used in the Roman empire). Best regards: Otared ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___________________________________________________________________________________
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