# An Introduction to Islamic Astronomy (al-Falak al-Shar’i)

## Presentation on theme: "An Introduction to Islamic Astronomy (al-Falak al-Shar’i)"— Presentation transcript:

An Introduction to Islamic Astronomy (al-Falak al-Shar’i)
With the Name of Allah, All-Merciful, Most Merciful An Introduction to Islamic Astronomy (al-Falak al-Shar’i) Usama Hasan Islamic Circles, Muslim World League, Saturday 25th Sha’ban 1428 / 8th September 2007

Who will benefit, in sha’ Allah
Students of Islamic law (Shari’ah) Students of mathematics, physics, astronomy, etc. Mosque imams Mosque time-keepers (muwaqqits) Others …

Synopsis Geometry and Motion of the Earth Qiblah Prayer Times
Moonsighting

1 – The Geometry of the Earth
Latitude Longitude North Pole South Pole The Seasons

Motion of the Earth The Earth spins on its axis once in 24 hours (from west to east): one day and night The axis of the Earth’s spin is inclined at 23.5 deg to the direction of its motion around the Sun

1a - 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)

1b - Longitude The Greenwich Meridien Lines of longitude as time zones
360 deg / 24 = 15 deg The International [Solar] Date Line (ISDL or IDL): 180 deg E / W

1c – The Poles At the North Pole, all directions are South
At the South Pole, all directions are North The North Star (Pole Star, Polaris, al-najm al-shimali, najm al-qutb) is directly above the North Pole The Earth’s axis points to the North Star

1d – The Seasons: Earth’s Annual Motion around the Sun

The Seasons (cont’d) At the Spring & Autumn equinoxes, the Sun is directly above the Equator At the Winter Solstice, the Sun is directly above the Tropic of Capricorn At the Summer Solstice, the Sun is directly above the Tropic of Cancer (For northern hemisphere: vice-versa for the southern hemisphere)

The 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 noon Shadows sometimes disappear at noon Outside the Tropics (north and south), the Sun is never directly overhead at noon Shadows never disappear at noon

Annual 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)

Annual Motion of the Sun, Moon, Planets & Stars (Q. 55:17)
SUMMER SOLSTICE EQUINOXES WINTER SOLSTICE N E N S W Easts (Multiple, Two limits) Wests (Multiple, Two limits)

Sunrise and Sunset Season Sunrise direction Sunset direction Autumn
East West Winter SE SW Spring Summer NE NW

2- Qiblah formulae !!! For Istanbul:

Qiblah Direction: Great Circles
A “Great Circle” is a circumference of the Earth that has the centre of the Earth at its centre All lines of longitude are Great Circles No line of latitude is a Great Circle, except for the Equator, which is a GC There are many inclined Great Circles

Examples of Great Circles

Comparison 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.

Qiblah direction The correct qiblah direction is always a “Great Circle” direction … unless you believe that the Earth is flat E.g. from the USA, is the qiblah SE or NE ?

Tips for finding the qiblah - 1
Use The Plough and Polaris to determine North In Somalia, Polaris tells us the qiblah!

Tips for finding the qiblah - 2
Use the direction of sunrise and sunset during the seasons

Tips for finding the qiblah - 3
At noon (zawal), the Sun is always: Due South if you are north of the Tropic of Cancer Due North if you are south of the Tropic of Capricorn Between the Tropics, it will be overhead, N or S

Tips 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 Makkah July 16 at 12:27pm Local Civil Time at Makkah

Tips for finding the qiblah – 4a
Local Time facing sun gives Qibla PLACE May 28 July 16 Afghanistan 13:48   13:57 Bangladesh 15:18   15:27 Bosnia 11:18* 11:27* Burma 15:18 Canada, Montreal 15:18* 5:27* Egypt 11:18 11:27 France Germany India 14:48 14:57 Indonesia,Jakarta 16:18 16:27 Iran 13:48* 13:57* Malaysia 17:18  17:27 Pakistan 14:18  14:27 Palestine 12:18* 12:27* South Africa United Kingdom 10:18* 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.

Tips for finding the qiblah - 5
Use a compass or qiblah compass Magnetic north is near true north Effect of metal / steel structures, e.g. inside modern office/apartment blocks

Tips 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.”

Daily 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)

Fajr (Dawn) False dawn, “like fox’s tail” True dawn
Angle of Sun beneath horizon: deg? 90-minute rule for the UK Impossible to calculate precisely?

Zuhr (Afternoon) Immediately after Zawal (Noon)
Half-way between sunrise and sunset

‘Asr (late afternoon) When sun is lower, cooler, yellower
One- or two- shadows’ length? Easiest way to determine: half-way between noon and sunset

Maghrib (Sunset) When the whole of the sun’s disc disappears below the horizon Calculations of sunset (and sunrise) have an error of 1-2 minutes either way because of refraction Important for prayer and iftar !

‘Isha (Night) When the red or white twilight disappears
When it gets dark & the stars come out Angle of Sun beneath horizon: deg? 90-minute rule for the UK Impossible to calculate precisely?

Tips on Prayer Times Try not to use a watch or prayer timetable!
But if you must … Problem of Fajr / Isha time in the Summer …

4 - Moonsighting

The Moon - Basic Facts The Earth travels around the Sun once every 365 days (and 6 hours) The Moon travels around the Earth once every 29 ½ days A lunar year of 12 lunar months has 355 days Phases of the moon result from parts of the Moon reflecting the Sun’s light towards the Earth A lunar month has either 29 or 30 days (hadith)

Phases of the Moon

Looking for the New Crescent
Only visible after sunset Must wait for the sun’s glare to die down Experience 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

The MOONWATCH Project Launched 1st Oct & will run for several years (www.crescentmoonwatch.org) A mass-experiment for the UK public Part 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 website Will help improve HM Nautical Almanac Office’s crescent-visibility calculations, in sha’ Allah

Moonsighting - History
The Islamic calendar is a purely lunar one Islam abolished the Pre-Islamic Arabian method of intercalation Until relatively recently, the start of each lunar month was determined purely by observation of the new crescent moon If cloudy, use a simple alternating 29/30 day rule Communication constraints meant there was no controversy across the vast Muslim lands

Moonsighting – Islamic Law (1)
The Shari’ah (Sacred Law) covers all areas of life Basic rule: crescent-sighting establishes the new month Calculations: controversial; different views Cannot be used to determine new month Can be used to reject false crescent-sightings Can be used to determine new month

Moonsighting – Islamic Law (2)
Applicability of a valid crescent-sighting: two views that can be unified One view: ikhtilaf al-matali’ (“multiple horizons”) Crescent-sighting applies only “locally” Nowadays: each state has its own horizon Another view: ittihad al-matali’ (“unified horizons”) A single sighting applies for the whole (Muslim) world

Background - Calculations
Accurate calculations for the position of the moon have been around for thousands of years E.g. solar and lunar eclipses However, calculation of the visibility of the new crescent moon has only become significantly accurate over the last ~20 years Yallop, Ilyas, etc. Usually, the moon needs to be hours old before the crescent is visible Using conjunction (“astronomical birth”) means the month will start one day too early

Calculating 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)

Calculating Crescent Visibility (2)
Moonsighting.com is based on Yallop/Ilyas and uses five factors only: The angle between Sun and Moon The (angular) height of the Moon above the horizon Earth-Moon distance Earth-Sun distance A measure of pollution in the atmosphere Moonsighting.com’s predictions have proved accurate every month since 1994!

Crescent Visibility Curve – Tues 11 Sept 2007

Crescent Visibility Curve – Wed 12 Sept 2007 (eve of Ramadan 1428)

Crescent Visibility Curve – Thurs 13 Sept 2007

Towards 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 ILDL Fix everything wrt one place, e.g. Mecca Compromise: the Unified Hejra Calendar (divide the world into three time zones)

Proposal 1: Crescent-Visibility curve as ILDL (International Lunar Date-Line)
30 Shawwal 1426 1 Dhul Qa’dah 1426

Proposal 2: Fix everything wrt one place, e.g. Makkah
30 Shawwal 1426 Makkah 1 Dhul Qa’dah 1426

Proposal 3: the Unified Hejra Calendar (www.icoproject.org)
Western Region Central Region Eastern Region

Proposal 3: the Unified Hejra Calendar (www.icoproject.org)
Western Region Central Region Eastern Region For Dhul Qa’dah 1426, ILDL coincides with the Solar dateline