Astronomy and timekeeping
Family: Knowledge: science, medicine, astronomy and the rest · 73 entries
Entries on this theme
Event
Umar adopts the Hijra as the starting point of the calendar
between 634 and 644 CE · 13 AHUmar gathered the Companions to fix a settled date for administering the young state. Ali said the calendar should begin from the year the Prophet emigrated and left the land of polytheism, and Umar adopted it.A comet appears, 905
between 1499 and 1500 CE · 905 AHIn 905 a tailed star rose from the east of Najd — its rising from Aries, its tail over Yemen and its course toward Syria.
Person
al-Khwarizmi
780 CE · 164 AHMuhammad ibn Musa al-Khwarizmi, numbered by al-Mas'udi among Islam's astronomers.Yahya al-Khayyat al-Falaki Abu Ali Yahya ibn Ghalib
Baghdadi astronomer and astrologer of the third century AH, a pupil of Masha'allah; died 250 AH (864 CE), though biographers differ on the date.al-Balkhi Abu Ma'shar Ja'far ibn Muhammad
Astrologer and astronomer Abu Ma'shar Ja'far ibn Muhammad al-Balkhi, leading figure of his time in his field, of Balkh in Khurasan; died 272 AH (886 CE).Abu al-Wafa' al-Buzjani, Muhammad ibn Muhammad
940 CE · 328 AHOne of the leading Muslim scholars of mathematics and astronomy, born in Buzjan in Khurasan.Kushyar ibn Labban al-Jili
969 CE · 360 AHAn astronomer and mathematician, named after Gilan in northern Iran.Al-Biruni, Muhammad ibn Ahmad
973 CE · 362 AHBorn in Kath, the old city of Khwarazm. One of the leading astronomers, mathematicians, geographers and historians of his age.Ibn Mu'adh al-Jayyani, Muhammad
989 CE · 379 AHA mathematician and astronomer from an Andalusian family, named after Jaen.al-Khujandi Abu Mahmud Hamid ibn al-Khidr
Mathematician and astronomer of the fourth century AH, a resident of Rayy near Tehran; died 391 AH (1000 CE).Umar Khayyam
1048 CE · 439 AHA mathematician, astronomer, philosopher and poet. Little is known of his life.Al-Badi' al-Astarlabi
A native of Baghdad and one of the leading astronomers and astrolabists of his time.al-Jaghmini Mahmud ibn Muhammad
1154 CE · 549 AHAmong the scientific pioneers of Anatolia within Islamic civilisation, named after the village of Jaghmin; died 618 AH (1220 CE).al-Tiflisi Jamal al-Din Abu al-Fadl Habash ibn Ibrahim
Physician, astrologer, lexicographer and man of letters from Tiflis, who served the Seljuks in medicine and astronomy and wrote mostly in Persian; died 629 AH (1231 CE).Ibn al-Banna al-Marrakushi, Ahmad ibn Muhammad
1256 CE · 654 AHA scholar of Marrakesh in mathematics, arithmetic and astronomy, who wrote on the arithmetical sciences.Al-Abhari, Athir al-Din al-Mufaddal ibn Umar
One of the best-known scholars of Islamic thought in logic, astronomy and mathematics. The nisba al-Abhari refers to the town of Abhar; his birthplace is not firmly established.Shihab al-Din Ibn al-Majdi
c. 1366 CE · 767 AHIbn al-Majdi (b. Cairo 767) — jurist, calculator and astronomer who 'surpassed and uniquely held his age' in geometry and the science of timekeeping alongside fiqh, inheritance-arithmetic and Arabic; author of the famed Sharh al-Abqariyya on fara'id among many works; died Friday night 21 Dhu al-Qa'da 850.al-Khalili Abu Imran Musa ibn Muhammad
Astronomer who grew up in Damascus and wrote a treatise on astronomy; died 1402 CE.al-Tizini Muhammad ibn Muhammad
1424 CE · 828 AHHanafi astronomer and mathematician of Aleppo, named after the town of Tizin near Aleppo; born 828 AH (1424 CE), died 911 AH (1505 CE).Molla Muhyi al-Din al-Tukshari
A master of Arabic, the legal and rational sciences and riyada; pupil of Fath Allah al-Shirwani, Husam al-Tuqati and Yusuf Bali b. Muhammad al-Fanari; Friday preacher alternately at Hagia Sophia and Mehmed II's mosque — and when 'the time of judgement' drew near he completed his tafsir recital at Hagia Sophia, told the people he had asked God to spare him only until the khatm of the Qur'an, prayed the amen with them, went home, sickened and died in 901.Tantawi Jawhari
1870 CE · 1287 AHAn Egyptian Islamic scholar with contributions to Qur'anic commentary and the natural sciences.Abd al-Rahman al-Fasi
Draft card for Abd al-Rahman al-Fasi, the seventeenth-century astronomer, musician and historian of Fez, d. 1685; the biographical entry is not yet checked on the page.Abu Ali al-Khayyat
Draft card for Abu Ali Yahya ibn Ghalib al-Khayyat, the ninth-century astrologer author of Kitab al-Mawalid, d. 844; the biographical entry is not yet checked on the page.Ahmad ibn al-Ha'im
Draft card for Ahmad ibn Muhammad ibn al-Ha'im, the fifteenth-century Egyptian jurist and mathematician, d. 1412; the biographical entry is not yet checked on the page.al-Bitruji Abu Ishaq Nur al-Din
Among the great Arab astronomers, of Andalusi origin from Bidrush near Cordoba, active in the sixth century AH.al-Nayrizi
Draft card for Abu al-Abbas al-Fadl ibn Hatim al-Nayrizi, the tenth-century astronomer and mathematician who commented on Euclid and wrote a zij, d. 922; the history-of-science entry is not yet checked on the page.Hassan al-Jabarti
Draft card for Hassan ibn Ibrahim al-Jabarti, the eighteenth-century mathematician, theologian and father of the historian Abd al-Rahman; the biographical entry is not yet checked on the page.Ibn al-Ha'im al-Ishbili
Draft card for Ahmad ibn Muhammad Ibn al-Ha'im al-Ishbili, the thirteenth-century astronomer and mathematician author of al-Zij al-Kamil; the biographical entry is not yet checked on the page.Maslama al-Majriti
Draft card for Maslama ibn Ahmad al-Majriti of Cordoba, the tenth-century mathematician, astronomer and alchemist to whom Ghayat al-Hakim is ascribed, d. 1007; Ibn al-Nadim's Fihrist entry is not yet checked on the page.Muhyi al-Din al-Maghribi
Draft card for Muhyi al-Din al-Maghribi, the Andalusi-born astronomer of the Maragha observatory who composed new zijes and critiqued parts of Ptolemaic astronomy, d. 1280; the biographical entry is not yet checked on the page.Najm al-Din al-Katibi al-Qazwini
Draft card for Najm al-Din Ali ibn Umar al-Katibi al-Qazwini, the thirteenth-century logician and astronomer author of Hikmat al-Ayn and al-Risala al-Shamsiyya, d. 1277; the biographical entry is not yet checked on the page.Naubakht
Draft card for Naubakht, the Persian astrologer who cast the horoscope for Baghdad's founding under al-Mansur, d. 777; the biographical entry is not yet checked on the page.Sa'id al-Andalusi
Draft card for Sa'id ibn Ahmad al-Andalusi, qadi of Toledo, astronomer and historian of science author of Tabaqat al-Umam, d. 1070; the biographical entry is not yet checked on the page.Shams al-Din al-Khalili
Draft card for Shams al-Din Abu Abd Allah al-Khalili, the fourteenth-century Damascus astronomer and muwaqqit who produced the famous qibla and prayer-time tables, d. 1380; the biographical entry is not yet checked on the page.Sharaf al-Din al-Tusi
Draft card for Sharaf al-Din al-Muzaffar al-Tusi, the twelfth-century mathematician and astronomer who taught at the Maragha observatory and wrote on geometry and algebra, d. 1213; the history-of-science entry is not yet checked on the page.al-Ashraf Umar ibn al-Muzaffar, al-Ghassani
A Yemeni ruler of the Rasulid line who wrote on the astrolabe, veterinary medicine and simple drugs, drawing on Ibn al-Baytar and al-Zahrawi.Yusuf Sarvestani
Draft card for Yusuf Sarvestani, the thirteenth-century writer, astronomer and calligrapher, d. 1281; the biographical entry is not yet checked on the page.Zayn al-Din al-Amidi
Draft card for Zayn al-Din Ali al-Amidi, the fourteenth-century Diyarbakir merchant and instrument-maker of water- and astronomical clocks, d. 1314; the biographical entry is not yet checked on the page.
Building
Concept
Qibla-finding by stars, winds, mountains and rivers
Al-Umari devotes the fourth gate of Masalik al-Absar to the qibla and its proofs: determination by stars, then winds, then mountains, then rivers — the field methods by which the lands' people fixed the Kaaba's bearing before precision astronomy.Sizes of the heavenly bodies
al-Farghani estimates the apparent and true sizes of the Sun, Moon, planets and fixed stars relative to the Earth, and ranks the bodies from the Sun down to Mercury. Many of the printed figures are garbled in the OCR and are flagged.Distances of the heavenly bodies from the Earth
al-Farghani gives the distances of the Moon, Sun and the five planets, and of the sphere of the fixed stars, in Earth radii and in miles, taking the Earth's diameter as 6500 miles. The figures are internally consistent with that radius; the least Moon distance is doubtful (OCR).The seven climates
Seven climates in each quarter of the earth — settlement reaching 24 degrees beyond the equator, the southern quarter desolate with heat, the rest drowned — and the fourth climate, Iraq, holding the fairest share where the sun's ray falls purest.The second motion (the planets' own motion along the zodiac)
The second motion is the proper motion of the sun and planets along the zodiac from west to east, about poles outside those of the first motion, and opposite to it in direction.The first motion (diurnal rotation of the heavens)
The first motion is the daily turning of the whole heavens from east to west, carrying sun, moon, planets and stars in one revolution each day and night, about two fixed poles, one north and one south.The solstices
The two solstices are the points of greatest distance from the equinoctial circle, north and south: the summer solstice at the beginning of Cancer, and the winter solstice at the beginning of Capricorn. The day is longest at the summer solstice and shortest at the winter solstice.The equinoxes
The equinoxes are the two points where the zodiac cuts the equinoctial circle: the vernal equinox at the beginning of Aries and the autumnal equinox at the beginning of Libra. On those days night and day are equal everywhere on the earth.The fixed stars
The stars whose positions relative to one another do not change. They share one motion from east to west with the sphere of stars, and al-Farghani adds a slow motion of one degree per hundred years around the poles of the zodiac, completed in 36,000 years. He counts 1,022 stars in six magnitudes, fifteen of them in the first.The Arabic lunar year
The Arabic lunar year has twelve months, alternately thirty and twenty-nine days: six full and six hollow. Its absolute count is 354 days, with eleven days added every thirty years, so the year that takes the fraction has seven full months and five hollow.The compared calendars: Syriac, Roman, Coptic and Persian
al-Farghani gives the months of the Syriac, Roman, Coptic and Persian calendars. The Syriac and Roman years have 365 1/4 days with a day added every four years; the Persian year has 365 days with five days inserted between Aban and Adhar; the Coptic year has twelve months of thirty days and five extra days at the end.The Jalali calendar
The Jalali (Malikshahi) solar calendar, reformed under the Seljuq sultan Malik-Shah with a group of astronomers including Omar Khayyam. It is described in Golius's note on the Persian months, not in the author's own text.The eras used in the calendars
al-Farghani lists five eras in order: Nabonassar, Philip, Alexander, the Hijra and Yazdegerd, with the intervals between them in years and days. The first is called Bukhtansar in the Arabic and Nabonassar in the Latin.The equator
The equator is the circle on the earth parallel to the equinoctial circle, dividing the earth into northern and southern halves; it is the first limit of the inhabited quarter, where day and night are always equal.The horizon circle
The horizon circle divides the visible sky from the hidden sky, its pole at the zenith; al-Farghani notes that it bisects only the equinoctial circle among the parallels, and cuts every other parallel unequally.Solar and lunar eclipses
A solar eclipse is the moon coming between the sun and the earth at conjunction; a lunar eclipse is the moon entering the earth's shadow at opposition. al-Farghani treats them in chapters 28 to 30: parallax changes what is seen, and the least interval between eclipses of either kind is six lunar months.Equal hours
Hours of constant length, made by dividing the day and night together into twenty-four parts, so each hour is fifteen degrees of the sphere's turn. The astronomers, al-Farghani reports, count the day and night from midday to midday.The zodiac (ecliptic)
The zodiac is the great circle traced by the sun's own motion from west to east; it is divided into twelve equal signs of thirty degrees each, from Aries to Pisces, and it cuts the equinoctial circle at the two equinoxes.Epicycle
A small orb carried on the eccentric deferent, in which the body moves. The centre of the epicycle moves round the deferent circle, and the epicycle explains the stations and retrogression of the planets. al-Farghani gives the epicycle radii in units where the deferent radius is sixty, with the figures printed for Saturn, Jupiter, Mars, Venus, Mercury and the Moon.Eccentric orb
An orb whose centre is off the earth's centre, so that a body's distance from the earth varies between apogee and perigee. al-Farghani gives the sun one eccentric orb whose centre lies two and a half parts off the earth's centre, when the orb's radius is sixty parts.The motions of the moon
al-Farghani builds the moon's apparent motion along the zodiac from five circular motions: the body on its epicycle, the centre of the epicycle on the eccentric, the centre of the eccentric on a small circle, the inclined circle carrying the nodes, and the motion of the whole sphere equal to that of the fixed stars.Rising out of the sun's rays (heliacal rising)
The reappearance of a star or planet after it has been hidden in the sun's rays: it rises in the east before dawn once it clears the sun (called al-mashriq bil-ghadawat), and sets in the west after dusk (al-maghrib bil-'ashaya). The period of concealment depends on the distance from the sun, the speed and the latitude.Parallax
The difference between where a body appears from the earth's surface and where it lies as seen from the earth's centre. al-Farghani gives its largest value for the moon as about one degree four minutes in longitude, and says it is not perceptible for the planets above the sun.The earth's sphericity
The astronomers' earth in al-Mas'udi's report: a sphere hung at heaven's centre like a yolk in the egg, a point against the sky's circle, drawing heavy bodies as the magnet draws iron, split by the equator — its circumference 9,000 farsakhs at 25 farsakhs the degree, ninety degrees from equator to each pole.The sphericity of the heavens
al-Farghani holds that the heavens are spherical and turn with all their stars as a sphere turns, about two fixed poles, north and south. His proof is that the stars rise, climb, pass the meridian and set in the same order, and that the stars near the north pole circle it in parallel paths.The moon's night-litany
The Arabs' question-and-answer litany on the moon each night of the month — first night 'a suckling kid, its folk milked into a pail', two 'tales of two false tribes', eight 'a loaf split by brothers', thirteen 'a dazzling moon', fifteen 'the full, the days spent' — through the month's wane.The lunar mansions
The twenty-eight stars or star groups that the moon passes in its monthly course, listed by Arabic name from al-Sharatayn at the head of Aries to al-Hut (Pisces). al-Farghani gives them as chapter 20 of his treatise.The obliquity of the ecliptic
The obliquity of the ecliptic is the greatest distance between the zodiac and the equinoctial circle. Ptolemy's value, as al-Farghani gives it, is 23 degrees 51 minutes; the value from the measurement made under al-Ma'mun is 23 degrees 35 minutes.Measuring the earth
Estimating the earth's circumference by measuring one degree of a north-south meridian in cubits. al-Farghani gives the degree as 56 2/3 miles, using the mile of 4,000 black cubits, the measurement made in the days of al-Ma'mun with a number of scholars present. That gives a circumference of 20,400 miles and a diameter of about 6,500 miles.Retrograde motion of the planets
al-Farghani explains that the five planets appear to move backward along the zodiac when they are in the inner part of their epicycle, because their motion on the epicycle toward the west outweighs the motion of the epicycle's centre eastward; the retrogression is greatest at perigee.The planets' reign and the world's cycles
The astronomers' doctrine of world-cycles: Virgo now reigns 7,000 years — this world's age — Jupiter assisting; when the governing planet completes its full course the world ends, the cycle returns to the first, persons and forms recur with their matter, and so forever — Aries' reign 12,000 years, Taurus' 11,000.Seasonal (temporal) hours
Hours whose length follows the length of the day and night: the arc of day is divided into twelve, and the arc of night likewise, so day-hours lengthen in summer and shorten in winter. al-Farghani sets them against the equal hours.
Work
al-Zij al-Sabi (The Sabian Zij)
An astronomical handbook by al-Battani on computing star positions and the zodiac. It opens with the reckoning of the sphere and of chords, then treats the obliquity of the ecliptic, the risings of the zodiac in each city, latitude found by observation, shadows and altitudes, the meridian, and the distances of the stars and planets.Elements of Astronomy (Jawami' 'ilm al-nujum)
al-Farghani's treatise on astronomy, printed by Golius as the Elementa astronomica. Its thirty chapters run from the calendar and the shape of the heavens through the planetary motions, the lunar mansions, the risings from the sun's rays and the eclipses. This record covers the front matter and chapters 8 to 30 printed in the Arabic text.
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