We see so many big-budget science-fiction spectacles — so many painstakingly realized fantasy worlds and lavishly rendered alien landscapes and environments, inhabited by extravagantly imagined extraterrestrial species, with fantastic spacecraft and starships traveling through hyperspace and all manner of wormholes, nebulae and so forth.

Yet simple weightlessness, though no more exotic than the space shuttle, remains among the most fascinating, captivating effects in any Hollywood production of recent years.

It’s an effect put to mesmerizing use by Alfonso Cuarón in his action thriller Gravity, starring Sandra Bullock and George Clooney as astronauts on a space walk that goes terribly wrong.

Gorgeous, nerve-wracking, literally awesome, Gravity takes us to a world much nearer than Duncan Jones’ Moon, nearer even than the layer of satellites that our mobile phones and GPS devices talk to every day: only about 350 miles away, in the low Earth orbit of the Hubble Space Telescope. Roughly the distance from Los Angeles to San Francisco — but oh, that’s far enough.

Far enough for the Earth to be not a location, but a silent third character in what is largely a simple, relentless two-character survival story.

The familiar blue-and-green orb looms large in the background or reflected in space-suit visors. It is home, a place of life, of connections — so close, yet so inaccessible.

My family and I saw the IMAX documentary Hubble 3D a few years back, depicting the 2009 Atlantis space-shuttle mission to repair and upgrade the Hubble telescope. Not many live-action cinematic experiences need or benefit from the third dimension, but a documentary about astronauts is one that does.

Gravity opens with a mission of exactly this sort, with Bullock’s Dr. Ryan Stone, an elite medical engineer and novice astronaut, and Clooney’s Matt Kowalsky, a veteran space monkey, equipping the telescope with some new gadgets. The imagery in Cuarón’s celebrated opening shot — a full 13 minutes with no visible cuts — feels very much of a piece with what I remember of Hubble 3D.

Yet there’s nothing documentary-like about this opening shot, or about Gravity generally, as there is at times about, say, Ron Howard’s Apollo 13. The elaborately choreographed movements of the astronauts and the camera itself, gliding and roving around the space-suited figures, the shuttle and the telescope, alternating between tight close-ups, long shots and everything in between, is too artful, too obviously liberated from the limitations and exigencies of documentary filmmaking.

We’ve gotten accustomed to the idea that filmmakers, using computer graphics, can put anything at all on the screen. Certainly Gravity makes extensive use of digital effects — and it shows. As astonishing as that opening shot is, one assumes it was assembled from a blend of multiple film elements and computer-generated imagery, with seams hidden through digital trickery.

And when catastrophe strikes, and Stone and Kowalsky are thrown into chaos, the scale of the disaster — and the graceful, inexorable physics of so many bits of debris spinning and flying in the weightless vacuum of space — could only be simulated in virtual space.

Yet when Stone, at the end of an extended crisis, sheds her suit inside a space station, rotating in space in a fetal position as she recovers, then glides through the passages of the station, pushing off the walls, the effect is breathtakingly persuasive as well as beautiful. (Shrewdly, she wears a pixie cut that doesn’t betray the weight of her hair.)

Then there’s the almost unbearably vertiginous sequence in which the original crisis sends Stone spinning off into space. As she flips head over heels (in a manner of speaking, "over" having no meaning in space), sunlight and shadow play over her in relentless succession, every second a miniature day and night on the tiny planet (the root meaning of "planet" is "wanderer") that is her body.

The crushing isolation in this sequence, in which Stone has no bearings except for a fleeting glimpse of the Earth every second or so, borders on the existential. Michael Collins, who orbited the moon by himself while Neil Armstrong and Buzz Aldrin descended to the moon’s surface, has stoutly denied ever feeling like "the loneliest man in the universe." In this sequence, above all, Stone might be the loneliest woman in the universe.

Recent Hollywood films depicting characters facing crisis or bereavement have suffered from a striking absence of any religious awareness. While Gravity has no pretensions of depth, it does a bit better in this regard.

In a landing module, Stone contemplates a holy card depicting the patron of travelers, St. Christopher, while reflecting that if she dies, "no one will pray for my soul." This isn’t the concern of a pious believer, for she adds plaintively, "I’d say a prayer for myself … but no one ever taught me how."

Later, there’s a sequence in a Chinese vessel with an analogous shot of a little smiling Buddha statue. These grace notes point collectively to the human religious impulse or instinct, the thirst for transcendence, more than the religious background of any character, onscreen or implied. Stone’s isolation and disconnection isn’t just physical, but personal, social, even spiritual. A return to Earth means perhaps a chance to reconnect with her own humanity.

These thoughtful moments are brief respites in what is largely a nail-bitingly tense series of crises and hairsbreadth survival gambits.

Gravity is a popcorn action thriller, not a philosophical art film, as the movie-star presence of Bullock and Clooney attests.

To that end, Clooney plays squarely to his strengths, providing mood relief as a bantering, self-deprecating pro whose drollery and flirting repartee mask a touching chivalry and even heroism. He knows it’s Bullock’s film, and he does his job, no more and no less.

Bullock shines in a demanding role, projecting intelligence, desperation, vulnerability, angst and inner strength. Her novice status invites the viewer to identify with her, making the journey that much more harrowing.

Very few effects-driven Hollywood movies in recent years have offered anything visually groundbreaking or novel. The ones that have — Avatar, Inception, Life of Pi — have done so through fantastic or surreal imagery.

Gravity is something almost unheard of these days: a movie that shows us something new, set in the universe we live in.

Steven D. Greydanus is the Register’s film critic and creator of Decent Films.

He is studying for the permanent diaconate for the Archdiocese of Newark, New Jersey.

Caveat Spectator: Much intense peril and some brief graphic, disturbing images; some strong language; a sequence in which the heroine strips to modest underthings (close-fitting tank top and shorts). Fine for older teens and up.