Moon sighting between Science and Religion

Moon Sighting
Between Science and Religion
Dr. Hussein Mhanna

Constant Controversy
• Causes?
• Scientific or religious?
• Can we find a unifying solution?
• Or is it natural to have this
controversy?

The Moon’s motion
• Fastest cosmic object
in our sky:
crosses 13 degrees daily
(compared to 1 degree
by the Sun daily)
• The Moon takes 27.3
days to orbit Earth,
but the lunar phase
cycle (from new
Moon to new Moon)
is 29.5 days.

Conditions for Crescent Visibility
• Birth of New Moon
• Illumination of the moon
• Duration after sunset
• Elevation above the horizon

1. New Moon Birth
• At the end of a lunar month the Moon passes
between the Earth and the Sun;
• This moment is called "New Moon Birth" or
conjunction.
• At this moment the sunlight falling on the moon
cannot come to the earth. In other words new
moon is "No Moon".
• No one can see this "New Moon" even by most
powerful telescopes.
• The conjunction can occur at any time between
24 hours.

2. Illumination of the moon
• In order for the bright (illuminated) side
of the moon to be visible to an observer
on earth, the angular distance between
the moon and the sun needs to reach a
certain value.
• This distance is called:
Moon’s elongation

Moon’s Elongation
• Is the apparent distance between the moon
and the sun in the horizon.
• From the birth of the new moon forward, this
distance increases until it reaches a degree
where the bright side of the moon becomes
visible as a crescent.
• Elongation is measured in degrees.
• Each degree = 2 hours of the moon’s age.

Elongation required for Visibility
• No consensus between scientists
• In ancient times, scientists considered 12
degrees as the minimum requirement
• Later scientists moved it to 10 degrees
• Recent scientists moved it down to 8
degrees, with a possible visibility at 7
degrees.

3. Duration after sunset
• The time difference between sunset and
moonset.
• How long the moon stays above the
horizon after sunset.
• So if the sun set at 6:00 p.m. and the
moon set at 6:30 p.m., the moon’s
duration after sunset is 30 minutes.

Duration required for Visibility
• A certain time must pass after sunset for the
crescent to be visible.
• The horizon is too bright right after sunset
that it overcomes the faint light of the small
crescent, which makes it very difficult to spot.
• The longer the crescent stays above the
horizon after sunset, the greater the
possibility for visibility.
• No consensus on the required duration.

4. Elevation of the Moon
• It’s the height of the moon above the
horizon.
• The higher the moon, the further it is from
the bright horizon, the greater the
possibility for visibility.
• It is measured in degrees.
• No consensus on the required degree.
• Opinions vary between 4, 5 and 6.

06:31:13ً‫مساء‬ ‫غروبًالشمس‬
06:38:27ً‫مساء‬ ‫غروبًالقمر‬
0‫س‬07‫د‬14‫ث‬ ‫المكث‬
°8.785 ‫االستطاله‬
°0.611 ‫االرتفاع‬
°8.649ً‫يسار‬
‫الشمس‬
ً‫بعدًالقمرًأفقيا‬
0.44% ‫االضاءة‬
16ً‫س‬49ً‫د‬19‫ث‬ ‫عمرًالقمر‬
‫مستحيلة‬ ‫شبه‬
(‫عمليا‬ ‫مستحيلة‬)
‫إمكانيةًالرؤية‬
‫اإلستهالل‬ ‫جدول‬
‫القطي‬ ‫منطقة‬ ‫يف‬‫ف‬

06:30:40‫مساء‬ ‫غروبًالشمس‬
07:15:35‫مساء‬ ‫غروبًالقمر‬
0‫س‬44‫د‬55‫ث‬ ‫المكث‬
°18.545 ‫االستطالة‬
°8.731 ‫االرتفاع‬
°15.884ً‫يسار‬
‫الشمس‬
ً‫بعدًالقمرًأفقيا‬
2.60% ‫اإلضاءة‬
40‫س‬48‫د‬46‫ث‬ ‫عمرًالقمر‬
‫ممكنة‬ ‫إمكانيةًالرؤية‬
‫اإلستهالل‬ ‫جدول‬
‫القطي‬ ‫منطقة‬ ‫يف‬‫ف‬

• Ignoring local conditions for the moment and
visualizing the problem from outside the
Earth's atmosphere, the size and brightness
of the lunar crescent depend on only one
astronomical quantity: the elongation of the
Moon from the Sun, which is the apparent
angular distance between their centers. For
this reason, the elongation has also been
called the arc of light.
• If the value of the elongation at any instant is
known, the width of the crescent can be
computed.

Additional Factors
• The elongation as a function of the Moon's
age depends on several factors:
• The Moon's elongation at New Moon
• The speed of the Moon in its orbit
• The distance of the Moon
• The observer's location

Test your knowledge
True or False:
• Distance between the moon and Earth is
constant?
• Speed of the moon is constant?
• Orbit of the moon is circular?

The Moon's elongation at New Moon
• The elongation of the Moon at New Moon is
not necessarily 0. The Moon's center may pass
directly in front of the Sun at New Moon
(when a solar eclipse will occur) or it may be
as much as five degrees to the north or south
of the Sun. That is, the Moon can start the
month with an elongation ranging from zero
to 5 degrees.

The speed of the Moon in its orbit
• The Moon's orbit is elliptical, and its speed is
greatest when it is near perigee (closest to the
Earth), least near apogee (furthest from the
Earth).
• If perigee occurs near New Moon, the Moon
will appear to be moving away from the Sun in
the sky at a greater than average rate.

The distance of the Moon
• Because of its elliptical orbit, the distance of
the Moon varies. Even if the Moon moved
with a constant speed, its angular motion as
viewed from the Earth would be greater when
the Moon is near perigee. Similarly, a nearby
automobile appears to be moving quicker
than a more distant one, even if they are
actually moving at the same speed.

• The combined effect of these factors gives
geocentric elongation of the Moon from the
Sun at an age of one day can vary between
about 10 and 15 degrees.
• This large range of possible elongations in the
one-day-old Moon is critical.

• The prediction of the first sighting of the early
crescent Moon is an interesting problem
because it simultaneously involves a number
of highly non-linear effects.
• Stated in less technical language, many things
are changing very rapidly.

Effects to be considered
• The geometry of the Sun, Moon, and natural
horizon
• The width and surface brightness of the
crescent
• The absorption of moonlight and the
scattering of sunlight in the Earth's
atmosphere
• The physiology of human vision.

A logical question
• With all the scientific
advancements that we have, why
can’t we find a solution?

An unexpected answer!
• Despite all the technology we have,
modern science hasn’t been able to put
accurate criteria for moon sighting.
• The motion of the Moon differs from
that of the Sun.
• This peculiarity limits our ability to
apply accurate early predictions

• Although the date and time of each New
Moon can be computed exactly, the visibility
of the lunar crescent as a function of the
Moon's "age"—the time counted from New
Moon—depends upon many factors and
cannot be predicted with certainty.
Source: The Astronomical Applications
Department of the U.S. Naval Observatory
http://aa.usno.navy.mil/faq/docs/crescent.php

Visibility Maps
• Visibility maps are made according to criteria
developed by scientists.
• Oldest known criteria were developed by the
Babylonians.
• Many criteria were developed after that.
• Most used criteria nowadays is Yallop's.

How accurate are these maps?
• Several examples in recent history showed
that visibility maps are not accurate enough.
• There were years when visibility was not
possible according to the maps, yet the
crescent was sighted.
• And years where maps predicted easy visibility
yet no crescent was sighted despite perfect
conditions.
• Most recent example: Eid Al-Fetr 1435

As you can see from this map for Shawwal 1435 AH, the crescent
of eid Al-Fetr was supposed to be “visible with the naked eye
under perfect conditions” in south America, however there were
no confirmed sightings of the crescent that night.

Conclusion
• Visibility maps, and astrological
calculations cannot be used as a sole
basis for determining the beginning of
lunar months.
• They can only be used as a guide for
moon-sighting.

Big Moon (must be 2nd day moon?)
• In order for a crescent to be visible, the moon
has to at least about 16 hours old.
• Imagine 2 situations:
Situation 1 Situation 2
Age of the moon at Sunset 16 hours 15 hours
Crescent Visible Yes No
Age on the next day 16+24 = 40 15+24 = 39

Result
• It’s clear that a crescent 40 hours old and
another 39 hours old will look almost the
same size to the naked eye.
• Yet the 1st crescent is a 2nd day moon.
• Whereas the 2nd one is still the 1st day of the
month.

Quran
•{‫ر‬ْ‫ه‬َ‫ش‬َ‫ن‬‫ا‬َ‫ض‬َ‫م‬َ‫ر‬َ‫ي‬ِ‫ذ‬َّ‫ل‬‫ا‬َ‫ل‬ِ‫ز‬‫ن‬‫أ‬ِ‫يه‬ِ‫ف‬‫ق‬ْ‫ل‬‫ا‬‫آن‬ْ‫ر‬‫ى‬ً‫د‬‫ه‬ِ‫َّاس‬‫ن‬‫ل‬ِ‫ل‬ِ‫ي‬َ‫ب‬َ‫و‬‫ات‬َ‫ن‬َ‫ن‬ِ‫م‬
‫ى‬َ‫د‬ْ‫ْل‬‫ا‬ِ‫ان‬َ‫ق‬ْ‫ر‬‫ف‬ْ‫ل‬‫ا‬َ‫و‬‫ن‬َ‫م‬َ‫ف‬ََ‫د‬ِ‫ه‬َ‫ش‬َُ‫م‬ُ‫ك‬‫ن‬ِ‫م‬‫ا‬ََ‫ر‬ْ‫ه‬َّ‫لش‬َُ‫ه‬ْ‫م‬ُ‫ص‬َ‫ي‬ْ‫ل‬َ‫ف‬‫ن‬َ‫م‬َ‫و‬َ‫ن‬‫ا‬َ‫ك‬‫ا‬ً‫يض‬ِ‫ر‬َ‫م‬
ْ‫َو‬‫أ‬‫ى‬َ‫ل‬َ‫ع‬‫ر‬َ‫ف‬َ‫س‬‫َّة‬‫د‬ِ‫ع‬َ‫ف‬ْ‫ن‬ِ‫م‬‫ام‬َّ‫ي‬َ‫أ‬َ‫خ‬‫أ‬َ‫ر‬‫يد‬ِ‫ر‬‫ي‬‫الل‬‫م‬‫ك‬ِ‫ب‬ْ‫س‬‫ي‬ْ‫ل‬‫ا‬َ‫ر‬َ‫ل‬َ‫و‬‫يد‬ِ‫ر‬‫ي‬‫م‬‫ك‬ِ‫ب‬
َ‫ر‬ْ‫س‬‫ع‬ْ‫ل‬‫ا‬ْ‫ا‬‫و‬‫ل‬ِ‫م‬ْ‫ك‬‫ت‬ِ‫ل‬َ‫و‬َ‫ة‬َّ‫د‬ِ‫ع‬ْ‫ل‬‫ا‬َ‫ك‬‫ت‬ِ‫ل‬َ‫و‬ْ‫ا‬‫و‬ ِ‫ّب‬َ‫الل‬‫ى‬َ‫ل‬َ‫ع‬‫ا‬َ‫م‬ْ‫م‬‫اك‬َ‫د‬َ‫ه‬َ‫و‬ْ‫م‬‫ك‬َّ‫ل‬َ‫ع‬َ‫ل‬
َ‫ن‬‫و‬‫ر‬‫ك‬ْ‫ش‬َ‫ت‬}(185)‫سورة‬‫البقرة‬
• The month of Ramadhan [is that] in which was revealed the
Qur'an, a guidance for the people and clear proofs of
guidance and criterion. So whoever sights [the new moon of]
the month, let him fast it; and whoever is ill or on a journey -
then an equal number of other days. Allah intends for you
ease and does not intend for you hardship and [wants] for you
to complete the period and to glorify Allah for that [to] which
He has guided you; and perhaps you will be grateful.

2 key words in the verse
1. ََ‫د‬ِ‫ه‬َ‫ش‬ which means: sights
2. ََ‫ر‬ْ‫ه‬َّ‫الش‬ which means: month
The 1st word “sights” clearly denotes “eyes” not
“calculations”.
The 2nd word as translated to “month”, doesn’t
make sense in the context of the verse, how can
some one see a “month”… so what does it mean?!
• Why didn’t Allah just use the word “moon”, or
“crescent”?! Instead he used a word that is
usually translated as “month”.

Why the Quran used: “Month”
• The Arabic word used “ََ‫ر‬ْ‫ه‬َّ‫”الش‬ has a common origin
as the word “ََ‫ر‬َ‫ه‬َ‫ش‬” which means “to make well-
known/famous/renowned”.
• So it seems now that Allah wanted the month of
Ramadhan to start with a crescent that is well-
known/famous/renowned.
• In other words, a crescent that can easily be seen
by everyone, not just those with extraordinary
eyes, or with complicated equipment. The
following hadith makes it more clear…

Hadith
‫قال‬‫اإلمام‬‫جعفر‬‫الصادق‬(‫ع‬):
‫إن‬‫شهر‬‫رمضان‬‫يضة‬‫ر‬‫ف‬‫من‬‫ائض‬‫ر‬‫ف‬‫هللا‬‫فال‬‫تؤدوا‬‫بالتظين‬!
‫وليس‬‫رؤية‬‫اهلالل‬‫ان‬‫يقوم‬‫عدة‬‫فيقول‬‫واحد‬‫قد‬‫أيته‬‫ر‬‫ويقول‬‫اآلخرون‬‫مل‬‫ن‬‫ره‬‫إذا‬‫رآه‬‫واحد‬
‫رآه‬‫مئة‬‫وإذا‬‫رآه‬‫مئة‬‫رآه‬‫ألف‬
Imam As-Sadeq said: The month of Ramadhan is a
religious obligation/duty from Allah, so do NOT perform
(fasting) based on assumptions! And moonsighting is not
when one person comes and says “I saw it” whereas
others say “We didn’t”. If one sees it, a hundred should
be able to see it as well, and if a hundred can see it, a
thousand should be able to see it.

Another hadith
َ‫قالَاإلمامَحممدَالباقر‬(‫ع‬:)‫أيتموه‬‫ر‬َ‫أيتمَاهلاللَفصومواَوإذا‬‫ر‬َ‫إذا‬َ‫فافطروا‬
َ‫أيَوالَبالتظينَولكن‬‫ر‬‫وليسَهوَبال‬‫بالرؤية‬
Imam Al-Baqer also spoke about this issue:
“If you saw the crescent moon (at the beginning
of Ramadhan) then start fasting, and if you saw
it (at the end of the month), then break your
fast (observe eid), and it is not by personal
opinion nor by assumption, but by sighting!

Question to ponder on
• Is this science of astrological calculations new?
• Weren’t the ancient Chinese astrologists
experts in this science thousands of years
before Islam?!
• Didn’t the Prophet and Imams know about it?
• Did they use it?
• If not, why?

• It’s clear that the Prophet (PBUH) depended only on eye-
sighting of the crescent.
• It’s known now that the visibility of the new crescent starts
in the western parts of the world (North America in winter,
and South America in summer), and that’s why people in
the west very often see the crescent a day or two before it
becomes visible to the people in the east.
• So if there were Muslims in the time of the Prophet living in
the Americas, they would have started the lunar month at
least one day before the Prophet and the Muslims of the
Medina, since they could see the crescent earlier.
• So if the rule is that month must start based not on sighting
but on knowledge that the crescent can be sighted
anywhere in the world (calculations), shouldn’t the Prophet
have made these calculations? Or even easier than that,
wasn’t he able to get the “news” of moon sighting in the
west from Allah through the angel Gebrail?!

‫بخي‬ ‫وأنتم‬ ‫عام‬ ‫كل‬‫ر‬

Sources
• www.kitabati.net/subject.php?id=22
• www.qanaa.net/?id=36
• http://www.sh-omair.com/
• Wikipedia
• www.crescentwatch.org
• www.islamicmoon.com
• www.moonsighting.com/faq_ms.html
• http://aa.usno.navy.mil/faq/docs/crescent.php
• www.staff.science.uu.nl/~gent0113/islam/islam_lunvis.htm
• www.shiaonlinelibrary.com
• www.Quran.com
• http://www.sistani.org/arabic/qa/0483/

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