SANTIAGO, Chile (AP) — Chile’s Atacama Desert is one of the darkest spots on earth, a crown jewel for astronomers who flock from around the world to study the origins of the universe in this inhospitable desert along the Pacific coast. A rare confluence of factors makes the Atacama an ideal home for some of the world’s biggest ground-based astronomical projects — dry climate , high altitude and, crucially, isolation from the light pollution of civilization. “It’s a perfect cocktail for