The scene where Brit Marling leaves prison was achieved by getting Marling to pose as a yoga instructor and enter and leave the prison for real.
Brit Marling wanted William Mapother because she had been haunted by his performance in In the Bedroom (2001). Mapother agreed to make the film for $100 a day.
The film came about out of conversations between Brit Marling and Mike Cahill about what it might be like to meet yourself.
Filmed in and around New Haven, Connecticut - Mike Cahill's hometown. Cahill knew that by filming there he would be able to call on favors from family and friends, helping keep costs down. This is particularly true of the car crash that is an integral part of the film. One of Cahill's friends is a police officer who was able to shut down some roads to allow for filming.
The Williams's house is actually director Mike Cahill's mother's house.
One of two drama films released in 2011 where the appearance of a new planet in Earth's vicinity is of major importance to the characters and plot. The other one is Melancholia (2011).
Director Mike Cahill began shooting the film in his hometown, with a single HD camcorder, before he even acquired any funding.
Towards the end of the film, Rhoda is in her room making her bed, grooming a bouquet of flowers and placing them on a vase. These flowers are called Chrysanthemum 'Clara Curtis' that bloom during the final days of summer and throughout autumn until the first frost. Later on is noted that four months have passed and its winter.
No mention is made of the effect that the vicinity of Earth 2 may have on Earth 1's gravity. A special effects scene was shot where Rhoda sees tree-blossom dancing in the air due to Earth 2's gravity pull, but the scene did not work and was deleted from the final print.
When Rhoda speaks with United Space Ventures CEO Keith Harding, Harding makes an off-beat comment that his headmaster once told him "you will either become a millionaire or go to jail". This is a reference to Richard Branson, who was told the same thing by his headmaster at school and also owns a pioneering civilian space travel company.
The word Rhoda writes on Purdeep's hand is "FORGIVE".
More shots of Rhoda and her identical copy meeting at the end were shot for coverage, like one where the women approach each other without talking, but it was not used.