The Moon Sighting Controversy

by M. A. Malek

In the Islamic calendar, traditionally, the first visibility of the new moon (crescent moon) to an unaided human eye marks the beginning of the month. In particular, sighting is considered essential regarding the start of Ramadan and the two Eids, in order to comply with the rulings of the Shari`ah, which is based on the Prophet's practice in the period when no other scientific means were available. However, the unreliability of the dependence on physical visibility of the moon has led not only to wide variations in the three important dates within the same country, but also to a great disunity among Muslim communities throughout the world.

The problem can be easily solved if the traditional method is abandoned in favor of a purely scientific method. Before outlining this scientific method, I will examine what the Qur'an has to say on this matter. One can then decide whether the scientific approach has any contradictions with what is stated in the Qur'an.

Relevant Qur'anic Guidance

It is He who cleaveth the daybreak (from the dark). He made the night for rest and tranquility, and the sun and the moon for the reckoning (of time). [Q6:96]

It is He who has made the sun the source of light and the moon a reflected light, and measured out the stages for her that you may know the number of years and the count (of time). This is nothing but a part of His constructive design. [Q10:5]

The sun and the moon follow courses (exactly) computed. [Q55:5]

Lo! The number of months with Allah is twelve months by Allah's ordinance in the day that He created the heavens and the earth. [Q9:36]

They ask thee concerning the new moons. Say: They are but signs to mark fixed periods of time in the affairs of men, and for pilgrimage. [Q2:189]

Before discussing the implications of these Qur'anic verses, it is necessary to outline the problems of the visual method, and the ways that the scientific method can overcome these problems.

Problems with the Visual Method

For the moon to be visible with the naked eye, the moon must set after the sun has set. Some people use this condition to define the start of the lunar month, no matter how small the time interval between the two settings. Unfortunately, this method will depend on one's position on the earth, and therefore could be open to doubt regarding the degree of accuracy of the calculation. It also opens the debate on how sunset and moonset should be defined, and if allowance should be made for atmospheric refraction (as is done, for example, in a formalized but not in an actual way in the Astronomical Almanac). If the actual refraction is less or greater than that assumed in the formal computation of the Nautical Almanac Office, sunset may not occur precisely at the tabulated time.

There is another very important factor which has to be taken into account for the lunar crescent to be visible. This is the age of the moon from the instant the conjunction (defined below) starts. This age-criterion has been studied by various people taking random observations, and is usually stated in the form of general rules, such as: "The sightings of the moon younger than 20 hours are rare, and the sightings of the moon older than 24 hours are not uncommon, although its visibility may at times require it to be more than 30 hours old."

Thus the problem of the visual sighting of the crescent moon is caused by several factors; depending on the interval between the conjunction and the next sunset, the actual position of the crescent moon with respect to the horizon, the clarity of the atmosphere, and the visual acuity of the observer. For example, if the conjunction takes place in the very early hours of the morning, it might be possible to sight the crescent moon on the same day, but if it is nearer the time of sunset, then the sighting, most likely, will be on the following day.

There is no way of telling the point of demarcation, which would indicate whether the crescent moon is visible on the day of the conjunction, or on the following day. It is, therefore, no wonder that the visual method, in this day and age, is totally unreliable and must be replaced by something that does not violate the principles outlined by the Qur'an.

The Scientific or the Astronomical Method

The scientific method is based on the physical condition that takes place when the earth, the moon, and the sun are in the same vertical plane, but not necessarily in the same line, and the moon is between the earth and the sun. This condition is known as the "conjunction." In scientific or astronomical terms, the conjunction is defined as the condition when the sun and the moon have the same "right ascension." In effect, this condition is a mark for the start of each of the lunar months, as the instant of its occurrence can be calculated precisely, being independent of any terrestrial locations. In fact, it is so extremely accurate that it would be possible to use the conjunction to construct a lunar calendar extending for hundreds of years.

The Implications of the Scientific Method

First of all, one must accept the fact that the required condition of identifying a lunar month will be met, so long as the scientific method guarantees the presence of the crescent moon, irrespective of whether the crescent moon is visible with the naked eye or not. At conjunction, the moon is not completely shadowed as viewed from the earth. However, the degree of illumination is so low that for us it is completely invisible. The apparent eastward motion of the moon then produces changes, in the shape of an illuminated disk, as a result of the changing geometry of the moon with respect to the sun and the earth. These are called the "phases of the moon," and the Islamic new moon is the instant of the start of the crescent phase. Thus, just after the conjunction, although the crescent moon will not be visible with the naked eye, there is no doubt that it is present in the sky. Hence, scientifically speaking, we can regard the crescent moon as physically present, and the only thing we need to know is the exact time when the crescent moon appears.

Fortunately, the time interval from the conjunction to the crescent phase of the moon is very small, and can be calculated accurately. The maximum time taken by the moon to move away from the sun is 19 minutes, therefore, 19 minutes after the instant of conjunction, the moon can reflect light towards the earth. In other words, scientifically, the crescent phase of the moon starts 19 minutes after the instant of conjunction, although the light may not become visible until about 20 to 30 hours after conjunction. In the U.K, the conjunction times over a number of years can be obtained from the Royal Astronomical Observatory. If we assume that the day changes at 12:00 midnight, then the conjunction can take place anytime between 00:00am to 12:00 midnight on any particular day. This means that the crescent moon can appear anytime between 00:19am of that day to 00:19am of the following day.

Thus, 19 minutes after the instant of conjunction, the Islamic new moon appears. Therefore, Ramadan or any other important event can take place on the following day, i.e the day after the conjunction. It would be easily possible to publish this date well in advance, so that people are not unduly inconvenienced. After all, Allah desires for us ease, not hardship [Q2:185]. Outside the U.K, one needs only to convert the same conjunction time to the appropriate local times, by adding or subtracting the applicable time difference, just like any other international activities. Although the conjunction is independent of any terrestrial location, the international time variations will still apply, simply because of the time gaps that exist between countries. Finally, if as some people suggest, using 12:00 midnight for the change of a day is not acceptable, then one needs to establish an agreed reference time instead of the 12.00 midnight accepted internationally for all other activities.

However, the principle remains the same, i.e to use the conjunction as the start of a lunar month. The Qur'anic guidance advocates the use of both the sun and the moon for the reckoning of time. The use of the exact instant of conjunction is doing just that, as the conjunction starts at the instant when the sun and the moon have the same "right ascension." The second condition that the New Moon is to mark fixed periods of time is also met, as the crescent phase starts 19 minutes after the conjunction. Nowhere does the Qur'an say that the moon has to be observed with the naked eye, rather it is in favor of the astronomical method. There are numerous verses in the Qur'an encouraging us to think, to ponder, to explore, and to gain knowledge:

And He has made subservient to you, from Himself, all that is in the heavens and on earth: In this behold, there are messages indeed for people who think! [Q45:13]

Lo! In the creation of the heavens and the earth, and (in) the difference of the night and day are signs for people of understanding. [Q3:190]

Allah created not this but with truth. He makes the signs manifest for people who have knowledge. [Q10:5]

Posted December 6, 1998. This article was printed in the October-December 1997 issue of "The Message," a United Islamic Association (UIA) publication, London, England.