Here's the meaning behind Gravity's "Houston in the blind" term. Gravity tells the very stressful story of two astronauts - played by Sandra Bullock and George Clooney - who are left stranded in space when debris destroys their space shuttle. The pair have to work together to overcome the seemingly hopeless situation and Gravity plays like an intense survival movie in outer space.
Gravity was an ambitious project that took years to get off the ground, and several actresses were considered for the role of Ryan Stone, including Angelina Jolie and Natalie Portman (Thor: Love and Thunder). Robert Downey Jr. was also considered for the Matt Kowalski role before moving on to other projects. Gravity would go on to become a big hit worldwide and grossed over $700 million. It also received rave reviews for both Bullock's performance and the impressive visual effects. Alfonso Cuarón would also win the Best Director Academy Award for Gravity in 2014.
Part of what makes Gravity such a harrowing thriller is it's attention to realism, including a complete lack of sound in space. While Cuarón has admitted the movie isn't intended to be a documentary and he used dramatic license several times, Gravity was noted for its scientific accuracy. This also includes the technical jargon, such as the line "Houston in the blind," which is repeated a number of times throughout the story.
This term is used in Gravity after Stone and Kowalski lose contact with NASA ground control and have no way of knowing if anybody can hear them. They keep transmitting regardless, with "Houston in the blind" meaning they're transmitting in the hope somebody is listening, even if they can't hear them in return. In addition to the terminology being correct, it also underlines the isolation of the stranded astronauts as they try to figure out a way to survive.
Thankfully Gravity ends on a happy note - at least for one of the main characters. "Houston in the blind" has since become a popular term from the movie, and Gravity's success would lead to more space set thrillers such as Ridley Scott's The Martian and Life. While Gravity is incredibly unlikely to receive a sequel - and nor should it - it did receive a short film companion in Aningaaq, which revolves around the Inuit fisherman that Ryan Stone talks to over the radio, though they can't understand one another. This short provides a fun alternate take on the emotional scene.