Presentation on theme: "An Introduction to Islamic Astronomy (al-Falak al-Shar’i)"— Presentation transcript:
1An Introduction to Islamic Astronomy (al-Falak al-Shar’i) With the Name of Allah, All-Merciful, Most MercifulAn Introduction to Islamic Astronomy (al-Falak al-Shar’i)Usama HasanIslamic Circles, Muslim World League,Saturday 25th Sha’ban 1428 / 8th September 2007
2Who will benefit, in sha’ Allah Students of Islamic law (Shari’ah)Students of mathematics, physics, astronomy, etc.Mosque imamsMosque time-keepers (muwaqqits)Others …
3Synopsis Geometry and Motion of the Earth Qiblah Prayer Times Moonsighting
41 – The Geometry of the Earth LatitudeLongitudeNorth PoleSouth PoleThe Seasons
5Motion of the EarthThe Earth spins on its axis once in 24 hours (from west to east): one day and nightThe axis of the Earth’s spin is inclined at 23.5 deg to the direction of its motion around the Sun
61a - Latitude The Equator The Tropic of Cancer (23.5 deg N) The Tropic of Capricorn (23.5 deg S)Local latitude is given by the altitude of the North Star (northern hemisphere only)
71b - Longitude The Greenwich Meridien Lines of longitude as time zones 360 deg / 24 = 15 degThe International [Solar] Date Line (ISDL or IDL): 180 deg E / W
81c – The Poles At the North Pole, all directions are South At the South Pole, all directions are NorthThe North Star (Pole Star, Polaris, al-najm al-shimali, najm al-qutb) is directly above the North PoleThe Earth’s axis points to the North Star
91d – The Seasons: Earth’s Annual Motion around the Sun
11The Seasons (cont’d)At the Spring & Autumn equinoxes, the Sun is directly above the EquatorAt the Winter Solstice, the Sun is directly above the Tropic of CapricornAt the Summer Solstice, the Sun is directly above the Tropic of Cancer(For northern hemisphere: vice-versa for the southern hemisphere)
12The Seasons – Implications for Shadow Lengths Between the Tropics (i.e. in Tropical and Equatorial regions of the earth), there are times during the year when the Sun is directly overhead at noonShadows sometimes disappear at noonOutside the Tropics (north and south), the Sun is never directly overhead at noonShadows never disappear at noon
13Annual Motion of the Sun, Moon, Planets & Stars “Lord of the Two Easts, Lord of the Two Wests!So which of the favours of your Lord will you deny?”(al-Rahman 55:17-18)“Lord of the East(s) and West(s) …”(Muzzammil 73:9, Ma’arij 70:40)
14Annual Motion of the Sun, Moon, Planets & Stars (Q. 55:17) SUMMER SOLSTICEEQUINOXESWINTER SOLSTICENENSWEasts (Multiple, Two limits)Wests(Multiple, Two limits)
15Sunrise and Sunset Season Sunrise direction Sunset direction Autumn EastWestWinterSESWSpringSummerNENW
17Qiblah Direction: Great Circles A “Great Circle” is a circumference of the Earth that has the centre of the Earth at its centreAll lines of longitude are Great CirclesNo line of latitude is a Great Circle, except for the Equator, which is a GCThere are many inclined Great Circles
19Comparison of Great Circle Route and Loxodrome on the Mercator Projection. The loxodrome is a line of constant heading, and the great circle, although appearing longer than the loxodrome, is actually the shortest route between New York and London.
20Qiblah directionThe correct qiblah direction is always a “Great Circle” direction… unless you believe that the Earth is flatE.g. from the USA, is the qiblah SE or NE ?
21Tips for finding the qiblah - 1 Use The Plough and Polaris to determine NorthIn Somalia, Polaris tells us the qiblah!
22Tips for finding the qiblah - 2 Use the direction of sunrise and sunset during the seasons
23Tips for finding the qiblah - 3 At noon (zawal), the Sun is always:Due South if you are north of the Tropic of CancerDue North if you are south of the Tropic of CapricornBetween the Tropics, it will be overhead, N or S
24Tips for finding the qiblah – 4 (Khalid Shaukat): When the Sun is overhead at the Ka’bah: It is not advisable to determine the Qibla specially for a Masjid using an ordinary compass. The following method which uses the sun is more reliable and accurate. It has been observed for centuries and reported in many books by Muslims around the world that two times a year the sun comes overhead above Ka'bah. This is observational fact for centuries, and is used to set the correct Qibla direction in places far from Makkah by Muslims for last so many centuries.Those two dates and times are:May 28 at 12:18pm Local Civil Time at MakkahJuly 16 at 12:27pm Local Civil Time at Makkah
25Tips for finding the qiblah – 4a Local Time facing sun gives QiblaPLACEMay 28July 16Afghanistan13:48 13:57Bangladesh15:18 15:27Bosnia11:18*11:27*Burma15:18Canada, Montreal15:18*5:27*Egypt11:1811:27FranceGermanyIndia14:4814:57Indonesia,Jakarta16:1816:27Iran13:48*13:57*Malaysia17:18 17:27Pakistan14:18 14:27Palestine12:18*12:27*South AfricaUnited Kingdom10:18*10:27*This method applies at local Makkah noon between and around these two dates also, because Makkah is only two degrees from the Tropic of Cancer, i.e.the method applies throughout May, June and July with good accuracy (UH)* means that these times are local Daylight Saving Times as observed in those countries.
26Tips for finding the qiblah - 5 Use a compass or qiblah compassMagnetic north is near true northEffect of metal / steel structures, e.g. inside modern office/apartment blocks
27Tips for finding the qiblah - 6 If all else fails …Most satellite dishes in UK point SE !Hadith, “What is between the East and the West is the qiblah,” based on the ayah, “To Allah belongs the East and the West: wherever you turn, there is the Face of God.”
28Daily Prayer Times (Solar) “Establish the Prayer from the Decline of the Sun until the Darkness of the Night, and the Dawn Recitation …” (Qur’an, 17:78)
29Fajr (Dawn) False dawn, “like fox’s tail” True dawn Angle of Sun beneath horizon: deg?90-minute rule for the UKImpossible to calculate precisely?
30Zuhr (Afternoon) Immediately after Zawal (Noon) Half-way between sunrise and sunset
31‘Asr (late afternoon) When sun is lower, cooler, yellower One- or two- shadows’ length?Easiest way to determine: half-way between noon and sunset
32Maghrib (Sunset)When the whole of the sun’s disc disappears below the horizonCalculations of sunset (and sunrise) have an error of 1-2 minutes either way because of refractionImportant for prayer and iftar !
33‘Isha (Night) When the red or white twilight disappears When it gets dark & the stars come outAngle of Sun beneath horizon: deg?90-minute rule for the UKImpossible to calculate precisely?
34Tips on Prayer Times Try not to use a watch or prayer timetable! But if you must …Problem of Fajr / Isha time in the Summer …
36The Moon - Basic FactsThe Earth travels around the Sun once every 365 days (and 6 hours)The Moon travels around the Earth once every 29 ½ daysA lunar year of 12 lunar months has 355 daysPhases of the moon result from parts of the Moon reflecting the Sun’s light towards the EarthA lunar month has either 29 or 30 days (hadith)
38Looking for the New Crescent Only visible after sunsetMust wait for the sun’s glare to die downExperience shows that the best time to see the crescent is about 20 minutes after sunset (when the sun is 5° below horizon)Perfect timing if the Sunnah is followed (Salat al-Maghrib should be fairly short)Look at the western horizon, near where the sun set
39The MOONWATCH ProjectLaunched 1st Oct & will run for several years (www.crescentmoonwatch.org)A mass-experiment for the UK publicPart of Einstein Year (2005 is 100 years since the publication of Relativity theory)Everyone is encouraged to look for the new crescent every month and report their observations via the above websiteWill help improve HM Nautical Almanac Office’s crescent-visibility calculations, in sha’ Allah
40Moonsighting - History The Islamic calendar is a purely lunar oneIslam abolished the Pre-Islamic Arabian method of intercalationUntil relatively recently, the start of each lunar month was determined purely by observation of the new crescent moonIf cloudy, use a simple alternating 29/30 day ruleCommunication constraints meant there was no controversy across the vast Muslim lands
41Moonsighting – Islamic Law (1) The Shari’ah (Sacred Law) covers all areas of lifeBasic rule: crescent-sighting establishes the new monthCalculations: controversial; different viewsCannot be used to determine new monthCan be used to reject false crescent-sightingsCan be used to determine new month
42Moonsighting – Islamic Law (2) Applicability of a valid crescent-sighting: two views that can be unifiedOne view: ikhtilaf al-matali’ (“multiple horizons”)Crescent-sighting applies only “locally”Nowadays: each state has its own horizonAnother view: ittihad al-matali’ (“unified horizons”)A single sighting applies for the whole (Muslim) world
43Background - Calculations Accurate calculations for the position of the moon have been around for thousands of yearsE.g. solar and lunar eclipsesHowever, calculation of the visibility of the new crescent moon has only become significantly accurate over the last ~20 yearsYallop, Ilyas, etc.Usually, the moon needs to be hours old before the crescent is visibleUsing conjunction (“astronomical birth”) means the month will start one day too early
44Calculating Crescent Visibility Simple prediction rules have existed for millenia (ancient Babylon, Greece, classical Islam, e.g. al-Bayruni, etc.)Modern criteria have been developed by:Bernard Yallop (ex-director of the Royal Observatory Greenwich)Mohammad Ilyas (Malaysia)Schaefer (kept the details secret)Odeh (Jordanian Astronomical Society)
45Calculating Crescent Visibility (2) Moonsighting.com is based on Yallop/Ilyas and uses five factors only:The angle between Sun and MoonThe (angular) height of the Moon above the horizonEarth-Moon distanceEarth-Sun distanceA measure of pollution in the atmosphereMoonsighting.com’s predictions have proved accurate every month since 1994!
49Towards a Unified Lunar Calendar With accurate calculations of crescent-visibility, a worldwide lunar calendar is now possible (Ahmad Shakir, Qaradawi, Kamali, etc.)There are 3 major possibilities:Use the visibility curve as an ILDLFix everything wrt one place, e.g. MeccaCompromise: the Unified Hejra Calendar (divide the world into three time zones)
50Proposal 1: Crescent-Visibility curve as ILDL (International Lunar Date-Line) 30 Shawwal 14261 Dhul Qa’dah 1426
51Proposal 2: Fix everything wrt one place, e.g. Makkah 30 Shawwal 1426Makkah1 Dhul Qa’dah 1426
52Proposal 3: the Unified Hejra Calendar (www.icoproject.org) Western RegionCentral RegionEastern Region
53Proposal 3: the Unified Hejra Calendar (www.icoproject.org) Western RegionCentral RegionEastern RegionFor Dhul Qa’dah 1426, ILDL coincides with the Solar dateline