I start this timeline with a fixed idea: a world without Islam would not be quite different than our world. Thus, this timeline pretends delving the questions about geopolitical scenaries, historical migrations and European imperialism/colonialism for developing the roots and questions about our world. This timeline is opposed to Clash of Civilizations' theory and begins from Graham E. Fuller conception in "World without Islam".
I attached some ideas that I answered to an user from this wiki:
1) The Umayyad and Abbasid(until 9th century) Caliphates represents de facto a restoration of the "Darius' Empire". I mean, this empires were a centralized monarchies in opposition of the Sasanian feudal monarchy. So, I propose a transformation of the Sasanian Empire in a centralized monarchy after a brief civil war: the Pahlavian Empire. This empire would be a "Darius' Empire" similar to Umayyad/Abbasid Caliphates but Mazdaist and the consequences in the Roman Empire of Constantiple would be very similar. As in the case of the Abbasid Caliphate, this empire breakdown in 9th century and will be disestablished after the Turk conquest of Ctesiphon in 11th century.
2) The Roman Empire would survive as a Greek Empire like in the real timeline. They would suffer Persian invasions instead of Arab invasions, but also Turk invasions since 11th century. I have to recognize that Constantinople issue is not easy. In my opinion I have two options: (a) the Hellenization of the Turks installed in Anatolia as a kind of "turcopoles" that will be essential for the restoration of Constantinople power in Anatolia and the Mediterranian after the 14th century (plus the fact that Constantinople would not have been taken by the Crusaders in 1204); (b) the emergence of a Turkish Empire centered in Crimea and expanded until Kyrgyzstan that would be adherent of a syncretic monotheistic religion with Tengrist roots or maybe Nestorian. Anyway, I used both and the Eastern Roman Empire will be survive until 19th century with the emergences of nationalisms.
3) Actually, a intervention of the Moors in the Visigothic kingdom during the litigium of Witiza's sons against Ruderic as in the real timeline would be possible to succeed, because the main motivation wasn't religious. The religiousity may cause the differences between the Catholic Europe and the Moorish Africa. Moorish would be adherent to a different kind of Christianity that don't believe in the Trinity and don't recognize Pope's authority (like the circumcellions in 4th century). However, Carthage remains Catholic due to its intense Romanization and Norman conquest in by Roger I in c.1091 (as in the real timeline). Iberian Peninsula will suffered a similar "Reconquista" (but as a struggle between Catholics and Moorish) that results as we know.
4) The Crusades would exist because the Seljukian Turks would invade Holy Land as in the real timeline. In addition, the Crusades were a first exemple of Western imperialism (as Israel today) and was an exit for the Frankish over-population in 11th-12th centuries.
5) Islamic Golden Age: this would exist but not as a continuous based on the religion. While Europe was in the Dark Ages, it would be a Persian Renaissance (but Mazdaist) and a Moorish Golden Age. A Coptic Egypt (until 9th century under Persian administration) and a Greek Pentapolis would be the nexus between Western Moors and Eastern Romans and Persians. The Mediterranean would be geopolitically divided in North-West (Catholic Europe with Germanic roots) vs. South-West (Moorish Africa) and East (Egypt, Persia and Roman Empire).
6) Yes, chaos theory is an issue I haven't had much in mind. However, of course I have done changes between relation of the non-existence of Islam: cases of Catalonia, Quebec, Yiddishland, Lusatia, Romania, Bulgaria, Bessarabia, Bosnia, Serbia, Arabia, Turkey, Greece, Tibet, Armenia. But I recognize that I did conservatives changes for the understanding of the allegory. Anyway, this is all a distraction.
7) That's an important issue as I've appointed in (2). However, I think this classical conception of the trade routes is wrong: while the emergence of the Ottoman empire was one of the causes, much less was the only. Henry the Navigator did his travels before the fall of Constantinople. It's the same case of the Castilian conquest of the Canaries.
If anybody is interested to participae, please, contact with me! Thanks!