5.2 Zone of Uncertainty (ZOU) in Calculations
Looking at the Visibility curves shown earlier in this paper, we find that the models can give 3 answers. Either the model can tell for sure that Hilal would not be visible in our area. Or they could tell for sure that the Hilal would be visible. Or in about 25% of the cases, when the Western part of our Matla is in the “Zone of Uncertainty”, the Calculations can NOT give a definite answer. This uncertainty is due to variations of atmospheric optics etc.
Dr. Mohammad Ilyas of Malaysia, the founder of modern day Hilal visibility models, in his book "A Modern Guide to Astronomical Calculations of Islamic Calendar, Times and Qibla" (Page 69), cautions readers on the limitations of science (and scientists) by pointing out that: "there are numerous ill informed astronomers assuming the role of experts who on occasions have made claims about astronomical calculability of the visibility far beyond the limit permitted by the then status of our standing of the underlying physical phenomenon...the ability ‘to land man on the lunar surface’ has been wrongly assumed to be a valid defence of the astronomical calculability. This reflects the lack of understanding of the physical aspects of a New Moon’s first visibility as distinct from locating the body accurately".
5.3 Use Calculations to Negate False sighting, but NOT to completely Replace Sighting
Thus if the calculations say with Certainty that Hilaal can not be visible, then we should Reject / Negate the False sighting and reduce errors. But when we happen to be in the Zone of Uncertainty, then we should use actual sighting only. We should keep on refining [visibility] calculations models using worldwide data, and atmospheric optics research, as being done at www.icoproject.org so that they become more and more accurate and the move to replace sighting completely with calculations could become as natural as using calculations for Salaah times. Until that stage comes, we still need to use sighting. According to the 4 dominant Madhabs (Ref. Kitaab al-Fiqh alal Madhahibil Ar’b’ah), and according to Imam Nawawi (Ref. Sharhul Muslim) and Sheikh Ibn Taimiyah (Ref. Majmu' Fatawa) etc., Calculations can NOT replace sighting. I feel that we may use [visibility] calculations for affirmation too, but ONLY outside the Zone of Uncertainty. Past Islamic Scholars like Imam Taqi al-Din al-Subki (d.1355 GC) said in one of his rulings on the subject: “Calculation provides certain and confirmed information, while testimony based on sighting provides only probable information. What is probable cannot counterbalance what is certain, let alone be preferred to it.
Evidence is accepted only if what is testified for is possible physically, logically and legally. If we assume that calculation indicates with certainty the impossibility of sighting, then a testimony of sighting must be rejected because it testifies to what is impossible. Islamic law does not make impossible requirements.” (Source: Arab News, 05 November 2002). Also, Sheikh Ibn Taimiya has written on how long it takes for the Hilal to appear after the “old moon” (seen at Fajr) disappears. Ibn Taimiya has also given a Fatwa that if the Altitude of the Hilal at Sunset is less than a certain degree, it is impossible to see and if it is more than another limit, we can see it easily, if there are no physical obstacles. However in between these limits there are differences, and we can not be certain one way or another. But of course none of these support calculations to completely replace sighting. Besides Zone of Uncertainty in Calculations makes it necessary that we continue using Hilal sighting in with Calculations in a complementary fashion.
Sheikh AlOthaimeen RH of Saudi Arabia has given a nice Fatwa about Solar Eclipse and Islamic dates [Arabic]
I repeat for emphasis from this Fatwa of Sheikh AlOthaimeen RH: "As for the belief in the power of the Almighty Allah, there is no doubt that the Almighty Allah is Capable to do anything. And He is also capable to combine the two moons, and to separate them and to dim them or to make them shining in their light at any time. … But the rules that the Almighty Allah laid down concerning the sun and the moon of this world are fixed, and do not change, except in case of a miracle for a Prophet or in the honor of a Wali."
This fatwa is also published in: Al-Daawah Magazine, Issue No. 1725, Dated: 6 Shawwal 1420, Saudi Arabia.