Brit Marling wanted William Mapother because she had been haunted by his performance in En la habitación (2001). Mapother agreed to make the film for $100 a day.
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.
Director Mike Cahill began shooting the film in his hometown, with a single HD camcorder, before he even acquired any funding.
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, in which Rhoda sees tree blossoms dancing in the air, due to the pull of Earth 2's gravity, but the scene did not work and was deleted from the final print.