The Astronomy of Moonsighting: An Islamic Perspective
Usman H Dukku
Biological Sciences Programme
Abubakar Tafawa Balewa University
A paper presented at the
National Conference on Moonsighting
Organized by the
Islamic Studies Section, Department of Education
Ahmadu Bello University, Zaria
From 12th to 16th July 2009
بسم الله الرحمن الرحيم الحمد لله رب العلمين والصلاة والسلام على محمد وعلى آله و صحبه
This paper discusses the application of astronomy to moonsighting. It begins by defining astronomy distinguishing it from astrology, a closely related field often confused with it. It then went further to discuss the accuracy of astronomical calculations and their compatibility with the Sharia injunction of sighting the crescent moon as a means of determining the beginning of lunar months. The paper concludes that astronomical calculations are compatible with moonsighting, within the provisions of the Sharia, and, therefore, recommends that astronomy should complement physical sighting of the crescent in order to enhance the process by checking the errors often associated with moonsighting.
The Astronomy of Moonsighting: An Islamic Perspective
Astronomy is defined as “the scientific study of the universe, especially of the motions, positions, sizes, composition, and behavior of astronomical objects.”1 Closely related to astronomy, and often confused with it, is astrology which is defined as “the study of the positions of the moon, sun, and other planets in the belief that their motions affect human beings.”1
Al-Gazaliy makes a distinction between the two as follows:
“The study of stars (astrology) whose aim is to predict the death or life of someone; and by the appearance of so and so star the death of someone, the perishing of a certain nation or demise of a kingdom is imminent: this is neither certainty nor even an informed guess. This kind (of knowledge) is not sanctioned by the Shari’a. However, the study of stars (astronomy) with which the motions of the planets, the sun and the moon are determined is a natural science and the Shari’a has never refuted it. In fact it serves as a means of reckoning of years, months and times of fasting, pilgrimage and prayers. The rejection of this is a (sign of) failure and ignorance.”2
It can be seen from the above definitions that whereas astronomy is a definitive science based on deductive reasoning, astrology is a conjecture. The subject of this paper is astronomy.
Accuracy of astronomical calculations
Astronomers use accurate calculations to predict astronomical events. The precision of these calculations can easily be confirmed by monitoring a solar or a lunar eclipse – two of the many events predicted by astronomers since ancient times. Has anyone ever witnessed an eclipse occurring at a time other than that predicted by the astronomers? These calculations can be used to confirm past events as well. For example, in the book, Fiqh al-Sirah,3 it is stated that the Prophet (SAWS) set out (from Madinah) for the farewell pilgrimage on 25th Dhu al-Qi'dah 10 A.H. and that the month had 29 days and 1st Dhu al-Hijjah was on a Thursday. Now let us compare this account with astronomical calculations.
According to MoonCalc,4 a computer programme that calculates astronomical events, including crescent visibility, 29th Dhu al-Qi'dah 10 A. H corresponds with Wednesday 26th February 632 A.D. and 1st Dhu al-Hijjah 10 A.H with Thursday 27th February 632 A.D. This also confirms the historical account that the day of Arafat of that year was Friday. The accuracy of these calculations has its origin in the precision with which the heavenly bodies move, as described by the Glorious Qur'an:
"The sun and the moon follow courses exactly computed."5
Ibn Kathir explains the meaning of this verse as follows:
وقوله تعالى الشمس والقمر بحسبان أي يجريان متعاقبين بحساب مقنن لا يختلف ولايضطرب
“They move in their orbit in perfect succession, according to precise calculation that is never delayed nor disturbed.”6
Astronomy of the Moon
Four of the five pillars of Islam, namely, Salah, Zakah, Fasting of the month of Ramadan and Hajj are time bound and the Shariah designated the sun and the moon as objects of timekeeping for performing these duties. This underscores the importance of studying the motions of these objects. The following verses from the Holy Quran and Hadiths of the Holy Prophet (SAWS) describe this role of the moon:
"They ask you concerning the crescent moons. Say: They are but signs to mark fixed periods of time in (the affairs of) men and for Pilgrimage."7
"It is He who made the sun to be a shining glory and the moon to be a light (of beauty), and measured out stages for it, that you might know the number of years and the count (of time)."8
"And the sun runs on its fixed course for a term (appointed). And the Moon, We have measured for it stations (to traverse) till it returns like the old (and withered) lower part of a date-stalk. It is not permitted to the Sun to catch up the Moon, nor can the Night outstrip the Day: Each (just) swims along in (its own) orbit."9
Abu Hurayrah (RA) reported that the Prophet (SAWS) said: "Start fasting upon sighting it (the crescent) and terminate the fast upon sighting it (the crescent) and if it is hidden to you (by clouds), then count the month of Sha'ban to thirty days."10
Abdullah ibn Umar reported that the Messenger of Allah, may Allah bless him and grant him peace, once mentioned Ramadan and said, "Do not begin the fast until you see the new crescent, and do not break the fast (at the end of Ramadan) until you see it. If the new crescent is obscured from you, then work out when it should be."11
Abdullah Ibn Umar (RA) reported that the Prophet (SAWS) said: "We are an uneducated community: We neither write nor calculate. A month is so and so days; meaning sometimes twenty nine and sometimes thirty."12
The moon is the only known natural satellite of Earth. It revolves around Earth, completing one revolution in about 27 days (27 days, 7 hours and 43 minutes). This is called the orbital period or the moon. However, as the moon revolves around the earth, the latter revolves around the sun and at a certain time the three objects lie in the same plane, with the moon in the middle. This moment, termed conjugation (birth of the new moon), marks the end of a lunar month and the beginning of another. The length of a lunar month, also called synodic period, is the period between two successive conjugations and is about 29½ days (29 days, 12 hours and 44 minutes).
The visibility, shape and brightness of the moon, from the earth, depend on the illumination it receives from the sun and this, in turn, depends on the moon’s angular distance from the sun as it moves in its orbit in an easterly direction. The various forms in which the moon appears from the earth, which change daily, are called Moon phases. The most obvious ones are:
New Moon: This phase is completely hidden from Earth because the face of the moon that faces the earth backs the sun and, therefore, is completely dark, since it does not receive any sunlight. It should be noted that the moon does not produce any light; its luminosity is due to the sunlight it reflects.
Waxing Crescent: This phase begins from the first appearance of the moon (which marks the beginning of the lunar month, according to the Shari’a) and ends at the First Quarter Moon.
First Quarter Moon: This occurs about a week from the moment of the New Moon when the moon has travelled a quarter of the distance of its orbit (90 degrees). At this moment the moon looks like a halved disc.
Waxing Gibbous: The appearance of the moon between First Quarter Moon and Full Moon phases.
Full Moon: This occurs about two weeks from the moment of the New Moon when the moon has travelled half the distance of its orbit (180 degrees). At this moment the moon looks like a perfect disc.
Waning Gibbous: The Moon as it appears between the Full Moon and the Last Quarter phases.
Last Quarter Moon: This occurs about three weeks from the last New Moon (and a week to the next New Moon) when the moon has travelled three quarters of the distance of its orbit (270 degrees). At this moment the moon looks like a halved disc.
Waning Crescent: This is the phase from Last Quarter Moon to the disappearance of the moon, hours before the next New Moon.
The phases that are of special importance to our discussion are New Moon, Full Moon, Waning Crescent and Waxing Crescent.
The occurrence of the new moon phase has already been described. What we may need to add here is that the moment of the new moon is the most important reference point in the science of moonsighting: The new (waxing) crescent can only be seen after the New Moon. Caldwell and Laney have this to say on this issue:
“At this time (of the new moon) the moon is always invisible from the earth. When the moon first becomes visible again (always more, usually much more, than half a day after astronomical new moon), observers see a young crescent moon.”13
It is also important to mention that it is at the instant of the New Moon that solar eclipses occur. This makes a solar eclipse an important event in checking the authenticity of a lunar date.
The moment of Full Moon (al badr in Arabic), on the other hand, is midway between two successive conjugations when the three bodies again lie in a straight line, but with the earth in the middle( a lunar eclipse can only occur at this moment). This moment occurs between the 13th and 15th of the lunar month that started with the correct sighting of the moon. The Arabic name for this period (ayyam al bid) is as a result of two phenomena unique to this period, that is, the moon is brightest and there is no total darkness during this period since there is an overlap between daylight and moonlight at dusk and dawn.
Towards the end of the month, that is, after Last Quarter Moon, the moon is described as a waning crescent. It rises in the morning, before sunrise, and it progressively appears thinner and lower until it finally fades away.
As the moon leaves the Sun – Earth line, after conjugation, its face that faces Earth starts getting light from Sun and reflecting it towards Earth. When it reflects sufficient light to be seen from Earth, observers see it as a waxing crescent. Ibn Taymiyya describes these events in the following words:
وَهَذَا الِاجْتِمَاعُ يَكُونُ بَعْدَ الِاسْتِسْرَارِ وَقَبْلَ الِاسْتِهْلَالِ فَإِنَّ الْقَمَرَ يَجْرِي فِي مَنَازِلِهِ الثَّمَانِيَةِ وَالْعِشْرِينَ كَمَا قَدَّرَهُ اللَّهُ مَنَازِلَ ثُمَّ يَقْرُبُ مِنْ الشَّمْسِ فَيَسْتَسِرُّ لَيْلَةً أَوْ لَيْلَتَيْنِ ; لِمُحَاذَاتِهِ لَهَا فَإِذَا خَرَجَ مِنْ تَحْتِهَا جَعَلَ اللَّهُ فِيهِ النُّورَ ثُمَّ يَزْدَادُ النُّورُ كُلَّمَا بَعُدَ عَنْهَا إلَى أَنْ يُقَابِلَهَا لَيْلَةَ الْإِبْدَارِ ثُمَّ يَنْقُصُ كُلَّمَا قَرُبَ مِنْهَا إلَى أَنْ يُجَامِعَهَا14
“This conjugation takes place after the disappearance of the moon and before the new
Crescent. The moon moves in its 28 stations destined for it by Allah; then it approaches the sun and disappears for one or two nights because of its closeness to it (the sun). When the moon leaves Sun’s domain, Allah illuminates it and this illumination increase as the moon moves further away from the sun up to the time of opposition at Full Moon. Thereafter, the illumination diminishes as the moon comes closer to the sun until it conjugates with it.”14
Astronomical Calculations and Crescent Visibility
Whereas astronomical calculations can predict very accurately (without an error) phenomena, that depend on the motions of Sun, Earth and Moon, which are constant and independent of the observer’s location, such as moonrise and set times, the birth of the New Moon, Full Moon and eclipses, they are not sufficient in predicting the visibility of the crescent moon, after New Moon, with that degree of accuracy. This is because non astronomical factors such as weather, land topography and the conditions of the observer also affect crescent visibility. This fact is presented by Ibn Taymiyya in the following words:
وَمِنْ مَعْرِفَةِ الْحِسَابِ الِاسْتِسْرَارُ وَالْإِبْدَارُ الَّذِي هُوَ الِاجْتِمَاعُ وَالِاسْتِقْبَالُ فَالنَّاسُ يُعَبِّرُونَ عَنْ ذَلِكَ بِالْأَمْرِ الظَّاهِرِ مِنْ الِاسْتِسْرَارِ الْهِلَالِيِّ فِي آخِرِ الشَّهْرِ وَظُهُورِهِ فِي أَوَّلِهِ وَكَمَالِ نُورِهِ فِي وَسَطِهِ والحساب يُعَبِّرُونَ بِالْأَمْرِ الْخَفِيِّ مِنْ اجْتِمَاعِ الْقُرْصَيْنِ الَّذِي هُوَ وَقْتُ الِاسْتِسْرَارِ وَمِنْ اسْتِقْبَالِ الشَّمْسِ وَالْقَمَرِ الَّذِي هُوَ وَقْتُ الْإِبْدَارِ فَإِنَّ هَذَا يُضْبَطُ بِالْحِسَابِ . وَأَمَّا الْإِهْلَالُ فَلَا لَهُ عِنْدَهُمْ مِنْ جِهَةِ الْحِسَابِ ضَبْطٌ ; لِأَنَّهُ لَا يُضْبَطُ بِحِسَابٍ يُعْرَفُ كَمَا يُعْرَفُ وَقْتُ الْكُسُوفِ وَالْخُسُوفِ15
"Within the scope of astronomical calculations is the determination of disappearance of the moon and Full Moon, that is conjugation and opposition, respectively. Ordinary people can know these through clear signs such as disappearance of the waning crescent at the end of the month and its appearance at the beginning of the month and complete illumination in the middle of the month. Calculations, on the other hand, detect these using by hidden events such as conjugation of the two discs during the period of disappearance of the moon and from the opposition or the sun and moon which is the moment of Full Moon. Definitely all these events can be determined through calculations. However, the visibility of the crescent cannot be accurately determined by calculations like the time of solar and lunar eclipse.”15
In other words astronomical calculations can tell when and where it is impossible to sight the moon and when and where the moon can be sighted. Computer programmes that simplify these calculations are now available. For example, Accurate Times, a non-technical, easy to use programme, developed by Muhammad Odeh,16 computes, among other things, crescent visibility and prayer times for any given location. In addition it displays the world map with details of crescent visibility for any given month.
Moonsighting and Astronomical calculations
Now, given the accuracy of astronomical calculations and the advancement in technology, which makes it possible to predict when and where the crescent moon can be sighted, should we replace physical sighting of the moon with astronomical calculations?
The view of the majority of jurists is that astronomical calculations should not replace physical sighting of the crescent. However it should be noted that some scholars, such as Mutarrif (among the Tabi’un) and al-Shafi’iy, approve the use of astronomical calculations, in place of physical sighting of the moon, under certain conditions , such as when there is an overcast on the 30th night17. In the same vein, the scholars are unanimous that any claim of moonsighting must be scrutinized and if it contradicts established common and expert knowledge (‘urf) about the moon (astronomy inclusive) it should be rejected. For example, the eminent scholar, a member of the High Judiciary Council of Saudi Arabia, al-Shaykh Abdullah Ibn Sulayman al-Mani’ explains as follows:
ونظراً إلى أن الشهادة بالرؤية يجب أن تكون منفكة عما يكذبها حساً وعقلاً وعرفاً وإلا فيجب ردها فإذا قرر علماء الفلك أن الشمس تغرب قبل ولادة الهلال وجاء من يشهد برؤية الهلال بعد غروب الشمس فيجب رد هذه الشهادة لأنها شهادة غاية ما نقول فيها عند إحساننا الظن بالشاهد بأن الشاهد قد وهم في شهادته وغلط. إذ كيف يُرى الهلال بعد غروب الشمس والحال أن الهلال لم يولد بعد أي أنه لا يزال متقدماً على الشمس إلى جهة الغرب فهو أمامها وهي خلفه من جهة الشرق.18
“For the fact that the testimony of sighting (the moon) should be free from what can nullify it according to practical experience, common sense and common knowledge, if it is not, then it is necessary to reject it. If experts in astronomy confirm that the sun will set before the birth of the New Moon and a witness comes to testify that he has sighted the moon after sunset, it is necessary to reject such a testimony, for it is a testimony about which we can at best say - giving the witness the benefit of doubt – that the witness has erred and strayed in his testimony: for how can the crescent be sighted after sunset while the situation is that the New Moon is not yet born? That is to say the moon is ahead of the sun towards the west - the moon is in the front and the sun behind.” 18
Another eminent scholar, al-Subkiy (683-756 AH), had earlier expressed the same opinion:
"What astronomical calculations can determine is the possibility or otherwise of sighting (the crescent)…..What is meant here is a situation in which an informant informs about his sighting (of the crescent) while it is impossible (according to astronomical calculations) to see it. Information can either be true or false and giving false information may be either deliberate or due to an error; and either of these has limitless causes. Therefore, it is not rational to accept information that is liable to these, or to testify on it, when it is impossible to sight (the crescent), because the law cannot be based on impossibilities. We have not found this issue written, thus we had to analyse it and give a ruling that such a testimony should be rejected. The reason for the (earlier) jurists’ silence on this issue is its rare occurrence (during their time). When it occurred during our time, we got a reason to speak on it. Jurisprudence is a sea no one can traverse and its issues are renewed with the renewal of its events.”2
Still another eminent scholar, Al-Abbadiy, expressed the same opinion:
“If definitive astronomical calculations indicate impossibility of sighting (the crescent), the sighting claim of even a trustworthy person should not be accepted. This is a clear issue. Fasting is not valid under this situation and opposing this is stubbornness and arrogance.”2
This opinion agrees with what happened during the early years of this Ummah when a sighting claim by Anas bn Malik (RA), a companion of the Prophet (SAWS), was rejected because it was found to be an erroneous one. The story goes thus:
“A group of people, among them Hadart Anas b. Malik (RA), were looking for the crescent moon of Ramadan. He was close to 100 (years old). He said: ‘Indeed, I see it; it is there.’ And he kept pointing to (in the sky). However, others did not see any. Iyas looked at Anas (RA) and (found) a hair from his eyebrow bent (over his eye). Iyas rubbed and smoothed his brow. Then he told him:’Abu Hamzah! (Now) show us the moon’s location (in the sky).’ He (Anas RA) kept looking (for it) and then said: ‘I don't see it (now).” 19
Now the answer to our question: Astronomical calculations should compliment actual sighting of the crescent moon rather than replace it.
It may be concluded, from the foregoing, that astronomical science is compatible with the Shari’a injunction of basing the beginning of the lunar months on physical sighting of the crescent moon. It is a useful guide in moonsighting and helps in reducing errors. It is therefore recommended that Muslims all over the world, but in Nigeria in particular, be encouraged to use astronomical knowledge in enhancing physical sighting of the moon. This recommendation is in line with the resolution of the World Fiqh Council during its third conference, held in Amman, Jordan, in 1986.20
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