The Core is popcorn entertainment that’s fun without settling for being dumb fun. It’s a movie that provides sufficient scientific explanation for just how six people descend into the earth’s inner core without ruining the gee-whiz kick that comes along with watching them do it.

It’s not to say that this sci-fi disaster movie is without its campy, computer-generated thrills. There is a solar radiation storm that renders the supports of the Golden Gate Bridge no stronger than a spaghetti string and, in a tremendously cheap-looking sequence, the obliteration of Rome. But its script has an easy, unforced wit, an A-list cast playing charming characters and surprising gravity during its inevitable heroic-death moments.

After a group of people inexplicably falls dead to the ground in the opening sequence, the United States fears it was somehow an act of war. Reassurance that it’s not war is enough for them, but not for Dr. Josh Keyes (Aaron Eckhart), a geophysicist they’ve called in to consult on the strange tragedy.

When a flock of dying birds dive-bombs tourists in London’s Trafalgar Square, Keyes concludes the Earth’s liquid outer core has stopped spinning, thereby weakening the electromagnetic field protecting the planet from solar radiation. By engulfing a peach in flame, Keyes explains to the military higher-ups what will happen to the planet in a year as a result.

In Armageddon-esque fashion, though, there is a contingency plan to send a ship to the center of the earth and detonate enough nuclear weapons to jolt the liquid inner core into spinning again. Along for the ride with Keyes are his weapons-specialist friend (Tcheky Karyo), two astronauts (Hilary Swank, Bruce Greenwood), the ship’s creator (Delroy Lindo) and a smug, celebrity scientist with government connections (Stanley Tucci).

For a movie with its fair share of gloom-and-doom moments, The Core is disarmingly funny. At the precise moment when you want Tucci’s character to get knocked out, someone does so. And D.J. Qualls, as a hacker recruited to keep the mission details off the Internet, has one of the best line deliveries this year.

In the predictable scenes when the crew waxes poetic about their mission, at least they do so in low-key terms. Karyo’s character prays to be smart enough not to save the planet, but to save his wife and kids. This lack of machismo works well to the high-pedigree cast, namely Eckhart, whose scruffy, wiseacre charm shines as brightly here as it has in independent dramas.

But while the movie isn’t thumping its chest, it isn’t a chamber piece either. The Core has a crackerjack ticking-clock momentum that builds with a what-could-possibly-go-wrong-next vibe. Director Jon Amiel is aware of the packaged goods that need to be delivered in a movie such as this and even at 130 minutes, The Core rockets forward with efficiency. 

Although the final scientific twist comes so quick and dirty (in the words of one character) that all one can do is just grin and go with it, The Core is a fine example of B-movie storytelling.