How does the moon help determine the start of Ramadan

Yearly, billions of Muslims across the globe observe the Islamic holy month of Ramadan. The beginning of Ramadan changes each year, and the Islamic faith relies on the Islamic calendar and a crescent moon sighting to determine the exact day it starts. But what if the crescent moon doesn’t appear? And do you do when it does, but you’re in space? Rizwan Arastu, a Muslim scholar, author and the founder of Islamic-Literacy.org, joins The World’s Carol Hills to break down the astronomical aspects of the holy holiday.