Transcript An Introduction to Islamic Astronomy (al-Falak al

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
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Students of Islamic law (Shari’ah)
Students of mathematics, physics,
astronomy, etc.
Mosque imams
Mosque time-keepers (muwaqqits)
Others …
Synopsis
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2.
3.
4.
Geometry and Motion of the Earth
Qiblah
Prayer Times
Moonsighting
1 – The Geometry of the Earth
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Latitude
Longitude
North Pole
South Pole
The Seasons
Motion of the Earth
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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
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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
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The Greenwich Meridien
Lines of longitude as time zones
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360 deg / 24 = 15 deg
The International [Solar] Date Line
(ISDL or IDL): 180 deg E / W
1c – The Poles
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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)
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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
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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
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Shadows sometimes disappear at noon
Outside the Tropics (north and south),
the Sun is never directly overhead at noon
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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
Easts
(Multiple, Two limits)
S
W
Wests
(Multiple, Two limits)
N
Sunrise and Sunset
Season
Autumn
Sunrise
direction
East
Sunset
direction
West
Winter
SE
SW
Spring
East
West
Summer
NE
NW
2- Qiblah formulae !!!
For
Istanbul:
Qiblah Direction: Great Circles
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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
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The correct qiblah direction is always a
“Great Circle” direction
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… 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
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Use The Plough and Polaris to
determine North
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In Somalia, Polaris tells us the qiblah!
Tips for finding the qiblah - 2
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Use the direction of sunrise and sunset
during the seasons
Tips for finding the qiblah - 3
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At noon (zawal), the Sun is always:
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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:
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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.
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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
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Tips for finding the qiblah – 4a
Local Time facing sun gives Qibla
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)
PLACE
May
28
July
16
Afghanistan
13:48
13:57
Bangladesh
15:18
15:27
Bosnia
11:18*
11:27*
Burma
15:18
15:27
Canada, Montreal
15:18*
5:27*
Egypt
11:18
11:27
France
11:18*
11:27*
Germany
11:18*
11:27*
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
11:18
11:27
United Kingdom
10:18*
10:27*
* means that these times are local Daylight Saving Times as observed in those countries.
Tips for finding the qiblah - 5
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Use a compass or qiblah compass
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Magnetic north is near true north
Effect of metal / steel structures, e.g.
inside modern office/apartment blocks
Tips for finding the qiblah - 6
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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)
Zuhr (Afternoon)
Duha (Forenoon)
Asr (Late
afternoon)
Fajr (Dawn)
Tahajjud (Late
night)
Maghrib
(Sunset)
Isha (Night)
Fajr (Dawn)
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False dawn, “like fox’s tail”
True dawn
Angle of Sun beneath horizon:
12-18 deg?
90-minute rule for the UK
Impossible to calculate precisely?
Zuhr (Afternoon)
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Immediately after Zawal (Noon)
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Half-way between sunrise and sunset
‘Asr (late afternoon)
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When sun is lower, cooler, yellower
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One- or two- shadows’ length?
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Easiest way to determine:
half-way between noon and sunset
Maghrib (Sunset)
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When the whole of the sun’s disc
disappears below the horizon
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Calculations of sunset (and sunrise)
have an error of 1-2 minutes either
way because of refraction
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Important for prayer and iftar !
‘Isha (Night)
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When the red or white twilight
disappears
When it gets dark & the stars come out
Angle of Sun beneath horizon:
12-18 deg?
90-minute rule for the UK
Impossible to calculate precisely?
Tips on Prayer Times
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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
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The Earth travels around the Sun once
every 365 days (and 6 hours)
The Moon travels around the Earth once
every 29 ½ days
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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
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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
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Launched 1st Oct 2005 & 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
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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
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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)
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The Shari’ah (Sacred Law) covers all areas
of life
Basic rule: crescent-sighting establishes the
new month
Calculations: controversial; different views
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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)
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Applicability of a valid crescentsighting: two views that can be unified
One view: ikhtilaf al-matali’ (“multiple
horizons”)
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Crescent-sighting applies only “locally”
Nowadays: each state has its own
horizon
Another view: ittihad al-matali’ (“unified
horizons”)
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A single sighting applies for the whole
(Muslim) world
Background - Calculations
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Accurate calculations for the position of the
moon have been around for thousands of years
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However, calculation of the visibility of the new
crescent moon has only become significantly
accurate over the last ~20 years
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E.g. solar and lunar eclipses
Yallop, Ilyas, etc.
Usually, the moon needs to be 15-25 hours old
before the crescent is visible
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Using conjunction (“astronomical birth”) means the
month will start one day too early
Calculating Crescent Visibility
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Simple prediction rules have existed for
millenia (ancient Babylon, Greece, classical
Islam, e.g. al-Bayruni, etc.)
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Modern criteria have been developed by:
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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)
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Moonsighting.com is based on Yallop/Ilyas and
uses five factors only:
1.
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
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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
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With accurate calculations of crescentvisibility, a worldwide lunar calendar is now
possible (Ahmad Shakir, Qaradawi, Kamali,
etc.)
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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)
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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
For Dhul Qa’dah 1426, ILDL
coincides with the Solar dateline
Central
Region
Eastern Region
Links
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www.crescentmoonwatch.org
http://websurf.nao.rl.ac.uk
UK_Islamic_Astronomy yahoogroup
www.moonsighting.com
www.jas.org.jo (Jordanian
Astronomical Society)
www.icoproject.org (Islamic Crescent
Observation Project)