As anyone familiar with Earth Hour knows, the idea of getting people to collectively shut off their lights is a nice idea, but difficult to execute. And even with 100% participation, a city is never going to look this dark, even during a disaster. So how did Cohen make these incredible images? The process is almost as amazing as the finished work:
Cohen’s method is original and precise and harkens back to the methodologies employed by early 19th century photographers like Gustave Le Grey. He photographs the world’s major cities, seeking out views that resonate for him and noting the precise time, angle, and latitude and longitude of his exposure. As the world rotates around its axis the stars that would have been visible above a particular city move to deserts, plains, and other places free of light pollution. By noting the precise latitude and angle of his cityscape, Cohen is able to track the earth’s rotation to places of atmospheric clarity like the Mojave, the Sahara, and the Atacama desert. There he sets up his camera to record what is lost to modern urban dwellers.
Incredible, right?! Lesser humans would probably be content to recreate the starscapes in Photoshop or some other computer program, but Cohen's process makes the work that much more beautiful.