The film's cascade of debris is a very real possibility. This scenario is known as the Kessler syndrome, named after N.A.S.A. scientist Donald J. Kessler who first proposed the theory in 1978. A cascading Kessler syndrome involving an object the size of the International Space Station would trigger a catastrophic chain-reaction of debris. The orbiting debris field would make it impossible to launch space exploration missions or satellites for many decades.
While filming an aquatic scene, Alfonso Cuarón held his breath along with Sandra Bullock to make sure he wasn't asking too much of her. He soon found he couldn't match her lung capacity.
The opening scene, from the establishing view of Earth to Dr. Stone detaching from the structure, is a single, continuous shot lasting about twelve and a half minutes.
When the script was finalized, Alfonso Cuarón assumed it would take about a year to complete the film, but it took four and a half years.
(At around 3m 50s) In the opening scene, as Kowalski flies very close to the camera, astronauts holding a movie camera and boom mic appear to be reflected in his helmet visor. This is an in-joke by director Alfonso Cuarón. The production crew's "reflections" were added with CGI to make it look like the scene was actually filmed in space, and that the post-production team failed to digitally paint-out those reflections.
Alfonso Cuarón: [Use of long continuous and digitally blended shots] The opening scene and many others as well.