Between Earth and Heaven

“Life in space is impossible.” That stark statement of scientific fact is one of the first things to appear on screen in “Gravity,” but before long, it is contradicted, or at least complicated. As our eyes (from behind 3-D glasses) adjust to the vast darkness, illuminated by streaks of sunlight refracted through the Earth’s atmosphere, we detect movement that is recognizably human and hear familiar voices. Those tiny figures bouncing around on that floating contraption — it looks like a mobile suspended from a child’s bedroom ceiling — are people. Scientists. Astronauts. Movie stars. (Sandra Bullock and George Clooney in spacesuits, as Mission Specialist Ryan Stone and Mission Commander Matt Kowalski; Ed Harris, unseen and unnamed, as “Houston” down below).

The defiance of impossibility is this movie’s theme and its reason for being. But the main challenge facing the director, Alfonso Cuarón (who wrote the script with his son Jonás), is not visualizing the unimaginable so much as overcoming the audience’s assumption that we’ve seen it all before. After more than 50 years, space travel has lost some of its luster, and movies are partly to blame for our jadedness. It has been a long time since a filmmaker conjured the awe of “2001: A Space Odyssey” or the terror of “Alien” or captured afresh the spooky wonder of a trip outside our native atmosphere.

Mr. Cuarón succeeds by tethering almost unfathomably complex techniques — both digital and analog — to a simple narrative. “Gravity” is less a science-fiction spectacle than a Jack London tale in orbit. The usual genre baggage has been jettisoned: there are no predatory extraterrestrials, no pompous flights of allegory, no extravagant pseudo-epic gestures. Instead, there is a swift and buoyant story of the struggle for survival in terrible, rapidly changing circumstances. Cosmic questions about our place in the universe are not so much avoided as subordinated to more pressing practical concerns. How do you outrun a storm of debris? Launch a landing module without fuel? Decipher an instruction manual in Russian or Chinese?

It has recently been observed that not all of the film’s answers to these questions are strictly accurate. The course that Stone and Kowalski plot from the Hubble Space Telescope to the International Space Station would apparently not be feasible in real life. (On the other hand, I was relieved to learn that a fire extinguisher really can serve as a makeshift zero-G jetpack. Not a spoiler, just a word to the wise.) Surely, though, the standard for a movie like this one is not realism but coherence. Every true outlaw has a code. The laws of physics are no exception, and Mr. Cuarón violates them with ingenious and exuberant rigor.

The accidental explosion of a communications satellite silences Houston and, what’s worse, sends a blizzard of shrapnel hurtling toward the astronauts. Quite a bit goes wrong. Straps connecting astronauts to the relative security of their spacecraft are severed. Parachute lines foul engines. Fires break out inside vessels, and stuff outside is smashed to pieces. Not everyone survives. All of it — terrifyingly and marvelously — evades summary and confounds expectations. You have to see it to believe it.