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Warner Bros.
Sandra Bullock as Ryan Stone and George Clooney as Matt Kowalski in "Gravity."

There are two primary definitions of the word gravity. First, there’s the attraction or pull of the Earth’s mass; second, the seriousness of a given situation.

Both are applicable in Sandra Bullock and George Clooney’s new film, “Gravity.”

Clooney stars as astronaut Matt Kowalski, who is a bit of a space cowboy. Bullock is mission specialist Ryan Stone, a no-nonsense scientist. The movie opens with these two engaged in a spacewalk designed to make repairs on the Hubble telescope. All is going well until mission control issues an emergency abort because of space debris rapidly heading their way.

It’s too late. The storm hits and rips through the shuttle, the telescope and members of the crew. Only Kowalski and Stone survive but our mission specialist ends up untethered, floating out into space. Can our space cowboy retrieve her?

Lest you think that’s all that remains of the story, never fear, there are other elements to the plot as these two fight for survival.

While this is clearly Bullock’s movie and the vast majority of face time is hers, Clooney’s character is critical — and both are fabulous. By the way, I should tell you, theirs are the only two faces we see — alive — in the entire film. The very few other characters are only seen as cadavers or simply heard as voices, including Ed Harris delivering the instructions from Houston.

But let’s talk about Bullock. She will undoubtedly be nominated for an Academy Award. Not only is her acting superb, the role is physically taxing, requiring contortion-like interaction with the special effects “green screen” that had to be incredibly difficult. Her range of emotion and quiet desperation in dealing with her demons on Earth and her plight in space — well, she’s remarkable.

One scene almost lost me, however, when I thought the filmmakers were going to sell out and wrap up everything a little too neatly. But, thankfully, my concerns were unfounded and this scene serves the story well.

What did trouble me a bit were the incredible skill and luck it would take to pull off the near miraculous events that are required for our heroine to survive. I mean, we’re talking American knowhow, Russian knowhow and even the ability to utilize the technologies of the Chinese — not to mention the haven and perils of the international space station.

OK, I get it, it’s only a movie. But still ...

It’s a heart-stopper where you have to remind yourself to breathe. Three-and-a-half stars for "Gravity," and it's rated PG-13.