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The effects of light pollution — human-made light interfering with the view of the stars — is covered in the documentary "The City Dark," which screens Tuesday, April 24, at the Salt Lake City Library's main branch.

The documentary, which uses New York's unnaturally bright nighttime sky as a jumping-off point for its discussion, will screen at 7 p.m. at the library auditorium, 210 E. 400 South, Salt Lake City.

After the screening, Inese Ivans, assistant professor of physics and astronomy at the University of Utah, will answer questions about light pollution and the disappearing night sky.

The screening is free.