As people across the globe stay home to stop the spread of the new coronavirus, the air has cleaned up, albeit temporarily. Smog stopped choking New Delhi, one of the most polluted cities in the world, and India's getting views of sights not visible in decades. Nitrogen dioxide pollution in the northeastern United States is down 30%. Rome air pollution levels from mid-March to mid-April were down 49% from a year ago. Stars seems more visible at night.