Talk:Ibn Yunus

message: Ibn Yunus surname was Al-Sadafi, a very well known yemeni arab tribe from Hadramaut in Yemen, that had immagrated during the Islamic expansion mostly to Egypt and Al-Andalus. The historian Ibn Khaldun says :
"بنو الصدف - بفتح الصاد وكسر الدال المهملتين حي من حضرموت وحضرموت يأتي نسبه عند ذكره في حرف الحاء المهملة حضر منهم جماعة فتح مصر مع عمرو بن العاص واختلطوا بها‏."
Translated: Banu al-sadaf - ...are a district of Hadramaut...some of them attended the opening of Egypt(Islamic conquest of egypt) with A'mr ibn al-A's, then they stayed there.
Jidan 10:56, 5 December 2006 (UTC)
thread_title:  Background info on Ibn Yunus Family 

message: :Where the article says under Pendulum
:"Recent encyclopaedias[13] and popular accounts[14] continue to repeat the claim that the tenth century astronomer Ibn Yunus used a pendulum for time measurement, despite the fact that it has been known for nearly a hundred years that this is based on nothing more than an error made in 1684 by the Savilian Professor of Astronomy at Oxford and Arabist Edward Bernard.[15]"
:Because our view of both sun and moon cuts 0.5 degree, of which there are 360 increments in the 180 degrees horizon to horizon, and the rotation of our planet on its axis cuts 1 degree every 4 minutes, our astronomical observations provide a clock (360deg/(24×60)min = 0.25 deg/min) with which we can make observations of the time to the nearest hour by noting their positions with the naked eye, and finer observations by setting a pendulum to a length of a meter whereupon it will make 90 swings while the sun or moon pass through 3 degrees in 12 minutes and 450 swings in an hour. At their zenith either sun or moon have cut 90 degrees or six hours; at 45 degrees they have cut 3 hours, at 15 degrees 1 hour. As a rule of thumb if you hold your hand up at arms length with your fingers spread it cuts 30 degrees and your five fingers allow a further division to 6 degrees or 24 minutes. Close your hand to a fist and it cuts 22.5 degrees. Results may vary somewhat but you can use that surveyer's technique to locate which decan the sun or moon are in and if you wish check your results by using a plumb bob to establish a meridian through which the sun and moon may enter and pass to get noon or midnight to an accuracy of 1 minute when they have passed half way through.
:The Egyptians began using star clocks for time measurements in the pyramid age. and either a plumb bob or the straight edge of a reflecting pool aligned with the meridian in the Rameside period (see discussion pp 72-75) If a plumb bob their instrument was the Mekhert (mhrt) and Bey used in surveying possibly with the addition of a grid of threads to locate both the decan star and its height above the horizon. pp 98-106 there is discussion of the "creation of a system of equations for hour lengths" because the sidereal day is 3 minutes 51 seconds shorter than the solar day. Page 127 begins the discussion of the use of the plumb bob or Mekhert (mhrt) in shadow clocks during the daytime from the beginning of the New Kingdom.142.0.102.12 (talk) 05:34, 15 April 2015 (UTC)
thread_title:  Article 

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thread_title:  External links modified 

message: I will bet that those who mentioned a pendulum were not that off as the Oxford scholar would want us to believe.
Read Crichton E.M. Miller's fascinating book "The Golden Thread of Time" (2000) and you will begin to connect the dots. Stjohn1970 (talk) 03:15, 27 December 2022 (UTC)
thread_title:  pendulum or plumb bob