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Muslim engineers in the Islamic world made a number of innovative industrial uses of hydropower, and early industrial uses of tidal power and wind power, fossil fuels such as petroleum, and early large factory complexes (tiraz in Arabic). The industrial uses of watermills in the Islamic world date back to the 7th century, while horizontal-wheeled and vertical-wheeled water mills were both in widespread use since at least the 9th century. A variety of industrial mills were being employed in the Islamic world, including early fulling mills, gristmills, hullers, sawmills, ship mills, stamp mills, steel mills, sugar mills, tide mills and windmills. By the 11th century, every province throughout the Islamic world had these industrial mills in operation, from al-Andalus and North Africa to the Middle East and Central Asia. Muslim engineers also invented crankshafts and water turbines, employed gears in mills and water-raising machines, and pioneered the use of dams as a source of water power, used to provide additional power to watermills and water-raising machines. Such advances made it possible for industrial tasks that were previously driven by manual labour in ancient times to be mechanized and driven by machinery instead in the medieval Islamic world. The transfer of these technologies to medieval Europe had an influence on the Industrial Revolution.

At what point was the use of watermills common in the Muslim World?
Answer: 9th century
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Witnesses believe that a "little flock" go to heaven, but that the hope for life after death for the majority of "other sheep" involves being resurrected by God to a cleansed earth after Armageddon. They interpret Revelation 14:1–5 to mean that the number of Christians going to heaven is limited to exactly 144,000, who will rule with Jesus as kings and priests over earth. Jehovah's Witnesses teach that only they meet scriptural requirements for surviving Armageddon, but that God is the final judge. During Christ's millennial reign, most people who died prior to Armageddon will be resurrected with the prospect of living forever; they will be taught the proper way to worship God to prepare them for their final test at the end of the millennium.

Jehovah Witnesses interrupted Revelation 14:1-5 to limit heaven goers to exactly what number?
Answer: 144,000
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Historians estimate that between the advent of Islam in 650CE and the abolition of slavery in the Arabian Peninsula in the mid-20th century, 10 to 18 million sub-Saharan Black Africans were enslaved by Arab slave traders and transported to the Arabian Peninsula and neighboring countries. This number far exceeded the number of slaves who were taken to the Americas. Several factors affected the visibility of descendants of this diaspora in 21st-century Arab societies: The traders shipped more female slaves than males, as there was a demand for them to serve as concubines in harems in the Arabian Peninsula and neighboring countries. Male slaves were castrated in order to serve as harem guards. The death toll of Black African slaves from forced labor was high. The mixed-race children of female slaves and Arab owners were assimilated into the Arab owners' families under the patrilineal kinship system. As a result, few distinctive Afro-Arab black communities have survived in the Arabian Peninsula and neighboring countries.

Who enslaved these people?
Answer:
Arab slave traders