Stack Exchange
log in

Alexandre Eremenko

 Discussion on question by Mikhail Kat…

Imported from a comment discussion on hsm.stackexchange.com/qu...
Alexandre Eremenko
Mar 6, 2024 09:51
In your first sentence you confuse "non-euclidean geometry" with hyperbolic one. Non-eucidean geometry includes also the geometry of the "elliptic plane" (2-dimensional projective plane) which is essentially spherical geometry. Spherical geometry was invented by ancient Greeks, and developed by Islamic scholars. There is no hint of hyperbolic geometry anywhere before 19th century.
 

 Discussion on answer by Alexandre Ere…

Imported from a comment discussion on hsm.stackexchange.com/qu...
Alexandre Eremenko
Mar 28, 2023 12:32
@JimmyJames: Ptolemy cites Hipparchus opinion that his and Archimedes observations of individual equinoxes had error at most 1/4 of a day. Modern data more or less confirm this.
Alexandre Eremenko
Mar 28, 2023 12:32
@JimmyJames:The timing is performed using ordinary sundial (gnomon). To catch the moment of an equinox, a special instrument was made which consists of a bronze disk carefully placed (in Alexandria) parallel to the celestial equator. The solstice is the moment when both sides of the disk are "equally illuminated", using Ptolemy's expression. If you are interested in the subject, you can read Ptolemy and commentaries which I refer to in my ans.
Alexandre Eremenko
Mar 28, 2023 12:32
@JimmyJames: I inserted the explanation how the year length was derived to my answer.
Alexandre Eremenko
Mar 28, 2023 12:32
@JimmyJames: Ptolemy gives the length of the year as 365;14,48 days (this is a sexagesimal fraction). Or 365+1/4-1/300. This is more precise than the year of 365 1/4 on which Julian calendar is based.
Alexandre Eremenko
Mar 28, 2023 12:32
@Jagerber: Ptolemy did all his math correctly:-) So whatever disagreement with modern data exists, it is due to the fundamental experimental constants: the length of the year, the lengths of the seasons and inclination of ecliptic. These are reasonably good for that time (and for all practical purposes), but of course his observational data are not as precise as we have now.
Alexandre Eremenko
Mar 28, 2023 12:32
@Toby Bartels: I am not sure that Ptolemy was aware of tides. They are never mentioned in the Almagest (I checked the index). I have not checked his Geography. Anyway, whatever observations of the tides could be made in antiquity, they would not help with equation of time, which is much more precise.
Alexandre Eremenko
Mar 28, 2023 12:32
@Jagerber: Ptolemy gives a table of equation of time and its derivation. They are sufficiently accurate, for his values of inclination of ecliptic, length of the year and lengths of seasons. If you want to compare the numbers, just look in Ptolemy; his book is available in a good English translations with detailed comments.
Alexandre Eremenko
Mar 28, 2023 12:32
I added astronomical definition of a season to my answer.
 

 Discussion on question by მამუკა ჯიბლ…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
May 25, 2022 13:33
@მამუკაჯიბლაძე @მამუკა ჯიბლაძე: To my understanding the pretext of the 2008 attack on Georgia was the alleged shelling of N Osetia by Georgian troops. And one of the initial goals of the war was overthrow of Saakashvili government. If this is correct, then there is a complete analogy: the initial "cause" of the 2022 offeisive was the alleged Ukrainian attack on DNR, and one of the initial goals was overthrow of Zelenski government.
Alexandre Eremenko
May 24, 2022 21:56
@მამუკა ჯიბლაძე: On my opinion, this is an interesting discussion but this site does not encourage long discussions in comments. I will be glad to continue on e-mail, if you wish.
Alexandre Eremenko
May 24, 2022 21:56
@მამუკა ჯიბლაძე you wrote: "never discussed possibility of granting Ukraine control over Donetsk/Luhansk". It did for all those 8 years. The plan was to incorporate them in Ukraine, and to give them control over Ukraine's policies. This is what Minsk agreement was about, from the Russian perspective.
Alexandre Eremenko
May 24, 2022 21:56
მამუკა ჯიბლაძე So you think that in 2008 war there was no goal of destroying Georgia as the independent state. OK, you probably know better. But otherwise the pretext is very similar. The current war goals seem to change, but the constant component is that they want to keep DNR/LNR intact.
Alexandre Eremenko
May 24, 2022 21:56
As a Georgian, why don't you mention the Russian war against Georgia in 2008? It was very similar, though on a smaller scale.
 

 Discussion on question by Vorac: Wher…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Apr 8, 2022 10:50
Bulgarians settled in the area where they are now centuries before they "met Christiandpom". And what "Turkish features" could they have at that time?
Alexandre Eremenko
Apr 8, 2022 10:50
For example, this article en.wikipedia.org/wiki/Bulgarians#Ethnogenesis explains the modern views on the origin of Bulgarians.
Alexandre Eremenko
Apr 8, 2022 10:50
A quick search in Wikipedia shows that your home history lessons and books are just lying.
 

 Discussion on answer by John Strachan…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Apr 1, 2022 21:44
Notice that 12 of these wars are Russian invasions.
 

 Discussion on question by hm2020: "In…

Imported from a comment discussion on mathoverflow.net/questio...
Alexandre Eremenko
Feb 21, 2021 20:00
The "holomorphic Peano curve" is not smooth. There are no smooth Peano curves.
 

 Discussion on question by com.prehens…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Apr 26, 2020 14:06
A geometric method to produce a straightedge is described in the book by M. Berger, Geometry revealed (Springer 2010) on p. 116. Greek mathematics had no tools to justify this method, but it is possible that they knew it empirically.
 

 Discussion on question by Noldorin: W…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Feb 14, 2020 17:25
@Gangus: I am sot sure that Murat really fought (did himself any shooting) in Russia. He was a commander after all. So perhaps Charles XII/Peter I are the last examples who really waved their swords:-)
Alexandre Eremenko
Feb 14, 2020 17:25
@Gangnus: I do not think Bernadot fought after he became a king. Same applies to other Napoleon marshals, like Murat (King of Naple).
Alexandre Eremenko
Feb 14, 2020 17:25
Napoleon I (if you count him as a king) was engaged in combat, using guns, for example, though this was before he became an emperor.
 

 Discussion on answer by Tomas By: Who…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Feb 14, 2020 16:30
@Thomas By: I am sure Peter was personally involved in combat. In naval battles, for example.
Alexandre Eremenko
Feb 14, 2020 16:30
Peter never had a rank of supreme commander. His official rank was "bombardier-captain" (artillerist). But he really participated in naval battles.
Alexandre Eremenko
Feb 14, 2020 16:30
Charles not only "killed at least one Ottoman soldier", he was killed in action himself.
Alexandre Eremenko
Feb 14, 2020 16:30
To Charles XII one can certainly add Peter I of Russia. He did take part in actual fighting, both on land and sea. Same as Charles.
 

 Discussion on question by Vitor C Goe…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Jan 17, 2020 13:16
Naturally, German racist theories assumed Germans superior. Chinese racist theories supposed that Chinese are superior.
 

 Discussion on question by Mark: Did t…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Aug 6, 2019 19:22
Your question has an implicit assumption that US DID have plans to defeat Germany. This is not clear at all. US was not in war in 1940.
 

 Discussion on answer by T.E.D.: Which…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
May 21, 2019 23:45
Kartvelian language family (spoken mostly Caucasus) is missing in this excellent answer.
 

 Discussion on question by d-b: Where …

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Apr 18, 2019 23:58
Which bank payed 2% interest all the time since Caesar was assassinated?
 

 Discussion on question by Math Wizard…

Imported from a comment discussion on hsm.stackexchange.com/qu...
Alexandre Eremenko
Apr 17, 2019 00:42
Typing "Arabic numerals" on Wikipedia shows you the story of their invention, in India by the way.
 

 Discussion on question by PeaceLoveDo…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Mar 6, 2019 03:26
The usual evidence generally permitted at the trials. Eyewitness accounts, for example. Some of the Soviet accusations were actually dismissed on the trials: they could not prove them.
 

 Discussion on question by Pavel: Has …

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Jan 8, 2019 12:45
How far is "near"?
 

 Discussion on question by Tomislav Os…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Nov 30, 2018 00:44
Of course not. Why should anyone agree with such a weird statement?
 

 Discussion on question by DrZ214: Did…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Jun 15, 2018 23:53
Some people considered transition to a Latin-based alphabet during the period of Westernization, before and after the revolution. But it did not gain large support.
 

 Discussion on answer by JMS: What was…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
May 29, 2018 14:49
@axsvl77: Who cares about Newton's religious views? How do they affect his science? Do you care about modern scientists religious views?
Alexandre Eremenko
May 29, 2018 14:49
Religion dominance of science until 1900?? On your opinion, science of Galileo and Newton was dominated by religion?
 

 Discussion on question by HannesH: Is…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Apr 3, 2018 08:15
Same reasons as to call the Russian emperor "Tsar", and German submarine "U-boat".
 

 Discussion on answer by axsvl77: How …

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Jul 11, 2017 13:26
@axsvl77: No, it is not the same thing. It would be the same thing if these technologies were developed by the Aztecs.
Alexandre Eremenko
Jul 11, 2017 13:26
@axsvl77: and the sources you give about bows is from the modern people who try to construct "these bows", without citing any historical source. Is there ANY evidence that their reconstruction is correct? What do we really know about Mongolian bows of that time?
Alexandre Eremenko
Jul 11, 2017 13:26
@axsvl77: your point about bows will be convincing if you will show that the composite bows of Hunns (or Parthians, or even ancient Greeks of the Troyan war time) were somehow inferior. Speaking of the siege technology, their main adversary was China. And they borrowed this technology from China, and employed Chinese technicians to operate it, as their own (Mongolian) sources certify.
Alexandre Eremenko
Jul 11, 2017 13:26
Technology?? You must be kidding. All their technology was either thousands years old or taken from China.
 

 Discussion on question by user24000: …

Imported from a comment discussion on history.stackexchange.co...
Alex
Oct 12, 2016 12:16
"Anywhere" is not a noun.
 

 Discussion on answer by Anixx: Why ha…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Aug 25, 2016 16:41
"Russia never planned an aggressive war"???
 

 Discussion on answer by Luboš Motl: W…

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Jan 26, 2016 17:30
@Lubos Motl: you want me to believe that the Roman sculpture of the 2nd century Nubian girl is shown there for political correctness?
Alexandre Eremenko
Jan 26, 2016 17:30
@Lubos Motl: you wrote: "Nubians are of pure all white race". Would you care to look in Wikipedia at some pictures of them? Modern and ancient.
Alexandre Eremenko
Jan 26, 2016 17:30
What about "Nubians"? If "aethyops" means a race, were Nubians also "aethyops"? Or some third race?
 

 Discussion between Alex and ahmed

Imported from a comment discussion on history.stackexchange.co...
Alexandre Eremenko
Jan 26, 2016 02:01
Most Jews spoke Yiddish in daily life, and there was a rich literature. But choice of Hebrew for Israel practically killed it.
Alexandre Eremenko
Jan 26, 2016 01:59
I also recommend "Welsh language" in Wikipedia. Hebrew is of course a unique exception. It helps that it always was a "sacred language" so educated Jews always learned it. But European Jews spoke Yiddish, a completely different, Germanic language, and after the extermination of the Jewish communities in East Europe, the language is nearly extinct. Israel had an alternative to make Yiddish of Hebrew the official language.