Roughly 5,000 stars are visible from Earth, but you've never seen most of them. If you live in a city, you may not see any of them. Filmmakers Gavin Heffernan and Hurun Mehmedinovic let us glimpse the wonders of space with their sweeping long-exposure photos and time-lapse videos that reveal the cosmos in all its glory.

Light pollution brightening the night sky in populated areas, or skyglow, is why urbanites often see nothing but darkness when they look up. Skyglow increases exponentially each year as the world's metropolitan areas grow and grow and grow. Research has linked light pollution to everything from disrupted sleep patterns to the death of migratory birds. Although people may realize they see fewer and fewer stars, it's rarely given much consideration. Mehmedinovic, who was born in Bosnia, remembers the first time he realized he hadn't seen a star.

"When I came to the US and landed in Phoenix, it took me a while to realize I couldn't see the stars at all," he says.