Why is it that every year Muslims on opposite sides of Earth can't agree when Ramadan starts?

In a Nutshell: The issue of moonsighting illustrates the purpose of the central acts of Islam that make up its five pillars. Each of these upholds not some personal faith of individuals, but the very polity to which these individuals belong. The detailed rules of the prayers, fasting, hajj and zakat provide guidance and clarity on how a community is to be formed, which importantly requires an Imam or Caliph - something the prophet (saw) showed how to establish during his mission in Mecca visible in Medina. If the community finds itself in discord and disarray, its members can only blame themselves for not having established the Caliphate as they were instructed. Ramadan is regularly marred by moonsighting debates with otherwise ordinary words acquiring greater rhetorical and ideological force: "Local!" "Global!" "Sighting!" "Calculations" "Saudi" "Morocco" "Pakistan". Each term is backed by arguments, evidences, documents and video clips. Is there a way out of this impasse? I believe there is if we read our political context, history and classical scholarship with care. Evidences The main evidences used on this issue comprise the following: Abu Hurayrah narrates Allah's Messenger (saw) said, صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ غُمِّيَ عَلَيْكُمْ فَأَكْمِلُوا الْعَدَدَ "Observe fast on sighting it (the moon) and break (fast) on sighting it (the new moon). If the sky is cloudy for you, then complete the number (of thirty)." (Sahih Muslim, 2379) Abu Hurayrah narrates Allah's Messenger (saw) said: صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ غُمِّيَ عَلَيْكُمُ الشَّهْرُ فَعُدُّوا ثَلاَثِينَ "Observe fast on sighting it (the new moon) and break it on sighting it. But if (due to clouds) position of the month is concealed from you, you should then count thirty (days)." (Sahih Muslim, 2380) Abdullah ibn Umar narrates Allah's Messenger (saw) once mentioned Ramadan and said: لَا تَصُومُوا حَتَّى تَرَوْا الْهِلاَلَ وَلَا تُفْطِرُوا حَتَّى تَرَوْهُ فَإِنْ غَمًّ عَلَيكُمْ فَاُقْدِرُوا لَهُ "Do not begin the fast until you see the moon, and do not break the fast (at the end of Ramadan) until you see it. If the new moon is concealed from you, then calculate it (when it should be.)" (Al-Muwatta, 18.1.1) Abdullah ibn Abbas narrates Allah's Messenger (saw) once mentioned Ramadan and said: لا تَصُومُوا حَتَّى تَرَوُا الْهِلالَ، فَإِنْ غُمَّ عَلَيْكُمْ فَأَكْمِلُوا الْعِدَّةَ ثَلاثِينَ "Do not start the fast or break it until you see the new moon. If the new moon is obscured from you, then complete a full thirty days." (Al-Muwatta, 18.1.3) Abdullah ibn Abbas narrates a Bedouin came to the Prophet (saw) and said, جَاءَ أَعْرَابِيٌّ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ إِنِّي رَأَيْتُ الْهِلاَلَ - قَالَ الْحَسَنُ فِي حَدِيثِهِ يَعْنِي رَمَضَانَ - فَقَالَ ‏"‏ أَتَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ ‏"‏ ‏.‏ قَالَ نَعَمْ ‏.‏ قَالَ ‏"‏ أَتَشْهَدُ أَنَّ مُحَمَّدًا رَسُولُ اللَّهِ ‏"‏ ‏.‏ قَالَ نَعَمْ ‏.‏ قَالَ ‏"‏ يَا بِلاَلُ أَذِّنْ فِي النَّاسِ فَلْيَصُومُوا غَدًا  "I have sighted the moon." (Al-Hasan added in his version: "means that of Ramadan.") He (the Prophet) asked, "Do you testify that there is no god but Allah?" He replied, "Yes." He again asked, "Do you testify that Muhammad is the Apostle of Allah?" He replied, "Yes." And he testified that he sighted the moon. He said, "Bilal, announce to the people they must fast tomorrow." (Abu Dawud, 2333) Abu Umayr ibn Anas reported on the authority of some of his paternal uncles who were companions of the Prophet (saw) that some men came riding to the Prophet (saw) and testified that they had sighted the new moon on the previous day. He, therefore, commanded the people to break the fast and to their place of prayer in the morning. (Abu Dawud, 1153) Ibn Abbas reported the Muslims did not begin fasting since they did not see the moon. Then a man came from outside of Medinah and told the Prophet that he saw the moon. The Prophet asked him if he was a Muslim to which the man answered in the affirmative. The Prophet then said, "Allahu Akbar, one is enough for all Muslims." The Prophet fasted and asked the people to stop eating and start fasting (Al-Mabsut 3-52). We saw from the above narration, the issue is very simple: it times of unambiguity, the moon must be sighted by trustworthy Muslims and in times of ambiguity, the month of Sha'ban should be completed thirty days. As simple as this. Juristic Analysis Since the earliest centuries of Islamic history, jurists have differed slightly over the correct method of declaring the beginning of Ramadan, arguing global sighting by witnesses is sufficient for all Muslims, and exceptionally allowing local sightings due to geographical communication constraints - astronomical calculations have been permitted after sightings have been attempted, usually reserved for individuals. However, it is important not to ignore process from all of these discussions - something I will address in the next section. If we look at the large corpus of legal works authored under the aegis of these four schools of law, we will find that every method currently followed, in Britain or elsewhere, is discussed. Relying on astronomical calculations, for example, is an opinion of a tiny minority of scholars who obliged sighting should first take place and if it was not possible due to cloudiness, then calculations could be used. Most scholars rejected this minority opinion, claiming there was an ijma on the obligation of sighting. Global sighting, meaning following a sighting from a faraway land, has been upheld as the strongest opinion of the Hanafi and Hanbali schools, and, according to some, the Maliki school. Local sighting, meaning each locality following its own sightings, has been seen as the strongest opinion of the Shafi'i school, and, according to some, the Malikis. Regarding the number of witnesses required, three positions emerge: Some classical jurists argue if the sky is clear, a large number of people are required to have seen the moon as the sighting of a few people on a clear night is inherently suspicious given most observers did not see it. This is the insight of the Hanafi legal school (al-Mawsu'ah al-fiqhiyyah al-kuwaytiyyah, c.v. "Khabar," vol. 19, p. 16.) Some Maliki texts also indicate this. If the sky is overcast, some jurists stipulated two witnesses for a valid sighting, treating it akin to establishing a fact in court. This is the strongest position of the Maliki school (al-Mawsu'ah al-fiqhiyyah al-kuwaytiyyah, c.v. "Khabar," vol. 19, p. 17). Others accepted a single witness, treating the sighting as a religious report. This is the strongest position of the Shafi'i and Hanbali schools, who stipulate this whether the sky is overcast or clear, and of the Hanafi school, who only stipulate this if the sky is overcast (al-Mawsu'ah al-fiqhiyyah al-kuwaytiyyah, c.v. "Khabar," vol. 19 pp. 16-17). In all cases, they require individuals to be morally upright. The question arises, who will determine whether a group sighting is large enough on a clear night? Who will decide whether a witness is upright or not? Who will determine the number of witnesses required on an overcast night? Official Judgement of the Caliph/Imam The commencement of Ramadan is not a private matter for individuals to determine or declare themselves. Individuals are only allowed to raise possible sightings to the appropriate authority who will then consider whether to accept or reject the sighting and will determine which conditions to consider to declare the beginning of Ramadan and Eid. This is why books of Islamic law discuss cases where an individual is sure they sighted the new moon, but the judge does not agree, should such a person fast? The commonly stated answer is that such a person does fast. However, this only applies to the person in question; everyone else is to await the official judgement on the matter.  This is the opinion of all four schools of law, who differ only on whether such a person must expiate for consciously violating the fast, or not. The responsibility for making these judgements is that of the Imam or Caliph. This has been agreed upon by all the classical scholars. It is the process that the Muslims applied historically. The differences that arose related to conveying the decision in a short period of time across vast distances. Where this was not possible one saw local sightings.  Since 1924 when the Ottoman caliphate was destroyed and nation states emerged, the conflicting and disputes over Ramadan and Eids have magnified. This is the process that works of sacred law attest to. The communal nature of Ramadan and Eid cannot be realised if a society is divided over when it starts and finishes the month. This process prevents that from happening - especially in an age where global communications communicate decisions instantaneously. Islamic scholarship was categorical on this point - the fifth-century Ash'ari and Shafi'i jurist and theologian Imam al-Juwayni for instance notes the importance of Khilafah in these matters: وَقَدْ تَقَرَّرَ مِنْ دِينِ الْأُمَّةِ قَاطِبَةً أَنَّ الْغَرَضَ مِنَ الْإِمَامَةِ جَمْعُ الْآرَاءِ الْمُشَتَّتَةِ، وَارْتِبَاطُ الْأَهْوَاءِ الْمُتَفَاوِتَةِ، وَلَيْسَ بِالْخَافِي عَلَى ذَوِي الْبَصَائِرِ أَنَّ الدُّوَلَ إِنَّمَا تَضْطَرِبُ بِتَحَزُّبِ الْأُمَرَاءِ، وَتَفَرُّقِ الْآرَاءِ، وَتَجَاذُبِ الْأَهْوَاءِ، وَنِظَامُ الْمُلْكِ، وَقِوَامُ الْأَمْرِ بِالْإِذْعَانِ، وَالْإِقْرَارُ لِذِي رَأْيٍ ثَابِتٍ لَا يَسْتَبِدُّ، وَلَا يَنْفَرِدُ، بَلْ يَسْتَضِيءُ بِعُقُولِ الْعُقَلَاءِ، وَيَسْتَبِينُ بِرَأْيِ طَوَائِفِ الْحُكَمَاءِ، وَالْعُلَمَاءِ، وَيَسْتَثْمِرُ لُبَابَ الْأَلْبَابِ، فَيَحْصُلُ مِنِ انْفِرَادِهِ الْفَائِدَةُ الْعُظْمَى فِي قَطْعِ الِاخْتِلَافِ، وَيَتَحَقَّقُ بِاسْتِضَاءَتِهِ اسْتِثْمَارُ عُقُولِ الْعُقَلَاءِ.  "It is an established matter in the deen of all the ummah collectively that the objective of the Imama (Sahih al-Muslim leadership) is to unite scattered views and to bind incongruous inclinations.  It is not hidden from the people of insight that the stability of polities are shaken by the partisanship of rulers, the diversity of views, and the mutual pull of various desires.  The proper organisation and strength of a dominion requires submission to and affirmation of one person of established decision, who does not rule by his opinion alone and become despotic but seeks illumination from the wise, the intelligent and the learned.  In this way, his singularity achieves the greatest benefit of resolving difference and his consultation of the learned bring the fruits of the multiplicity of wise intellects." (Imam al-Juwayni, Ghiyath al-Umam, pp.172-3) Conclusion The issue of moonsighting illustrates the purpose of the central acts of Islam that make up its five pillars. Each of these upholds not some personal faith of individuals, but the very polity to which these individuals belong. The detailed rules of the prayers, fasting, hajj and zakat provide guidance and clarity on how a community is to be formed which importantly requires an Imam or Caliph - something the prophet (saw) showed how to establish during his mission in Mecca visible in Medina. If the community finds itself in discord and disarray, its members can only blame themselves for not having established the Caliphate as they were instructed. References Al-Mawsu'ah al-fiqhiyyah al-kuwaytiyyah Al-Juwayni, Ghiyath al-Umam