Jonathan Nolan worked on the script for four years. To learn the scientific aspects, he studied relativity at the California Institute of Technology. He was pessimistic about the Space Shuttle program ending and how NASA lacked financing for a human mission to Mars, drawing inspiration from science-fiction films with apocalyptic themes, such as WALL-E (2008) and Avatar (2009). Jeff Jensen of Entertainment Weekly said: "He set the story in a dystopian future ravaged by blight, but populated with hardy folk who refuse to bow to despair." His brother Christopher had worked on other science fiction scripts but decided to take the Interstellar script and choose among the vast array of ideas presented by Jonathan and Thorne. He picked what he felt, as director, he could get "across to the audience and hopefully not lose them," before he merged it with a script he had worked on for years on his own. Christopher kept in place Jonathan's conception of the first hour, which is set on a resource depleted Earth in the near future. The setting was inspired by the Dust Bowl that took place in the United States during the Great Depression in the 1930s. He revised the rest of the script, where a team travels into space, instead. After watching the 2012 documentary The Dust Bowl for inspiration, Christopher contacted the director, Ken Burns, and the producer, Dayton Duncan. They granted him permission to use some of their featured interviews in Interstellar.