Much as been made about the technical accuracy (or lack thereof), mostly by the pedantic types who would argue that Mary Poppins really couldn't fly because the umbrella technology wasn't there yet. While I pity them for failing to enjoy this film for what it is (and wonder what they really do enjoy), I do have to concede they have a point. To illustrate I must discuss a key plot point, and insist you to read no further until you've seen the film.
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Several people have ridiculed the use of the "mysterious force" that wound up pulling Kowalski away from Stone. Of course the screenwriters didn't invent a mysterious force, they just wanted Kowalski to make a sacrifice, wanted a final moment between the two, and thought that was the best way to execute it. While watching I politely suspended my disbelief so I could enjoy the film, but it struck me later how they could have done it better.
Imagine instead they are still tethered together when Stone catches her foot in the parachute lines. Kowalski is floating past and sees the tenuous hold she has. Close-up of his face, close-up of Stone's foot.
"I'm going to pull you off," he concludes, and he begins to unbuckle the tether.
"What are you doing?!" Stone asks.
"When this goes taut, I'll pull you off," he explains as he floats past her, just seconds left now.
"No," she insists, "it'll hold, don't!"
"I can't take that chance," he explains, and he unbuckles. We'll never know if his theory was right, but his sacrifice is all the nobler because of it. You can still have the tense moment, you can still have their conversation as he floats away, and you haven't violated any laws of physics.
So it could have been done better. But it remains important not to be one of the pedantic types. Case in point is the scene where Kowalski returns to the Soviet capsule. My thoughts during that scene were "could that really be him? ... she can't survive that decompression. this is a hallucination ... is this a hallucination? could he be back? ... yeah, i knew it was a hallucination." It is an emotional journey the filmmakers want you to take part in, and one you can't enjoy if you spend the whole time rolling your eyes, only to later come out feeling like an idiot.
So relax, Francis, sit back and enjoy a cinematic moment comparable to when people heard their first THX sounder, or the debut of CinemaScope, or when Dorothy opened a door to a world of color. You can't go back to France in 1895 to experience the thrill of L'arrivée d'un train à La Ciotat and wonder if the train was going to run you over. But Gravity may be the next best thing.