By Christopher Pacetta,New York Daily News

In the new sci-fi comedy “The Hitchhiker’s Guide to the Galaxy,” earthlings and aliens travel across great expanses of time and space. But the longest journey was simply getting the movie into theaters.

The long-awaited big screen version of Douglas Adams’ cult classic landed Friday – after a quarter century, three directors, two major studios and Adams’ death.

The film follows an unsuspecting everyman named Arthur Dent (Martin Freeman of “The Office”), who must use an omnipotent “guide book” to make his way through a comically absurd universe after the Earth is demolished to make room for an intergalactic highway.

First appearing in England as a six-part radio series in March 1978, “Hitchhiker’s” hip, ironic humor drew immediate comparisons to “Monty Python’s Flying Circus.” It quickly became a hit and was later adapted into a worldwide best-selling novel.

But Adams wanted to see his blockbuster on the big screen. He began writing a screenplay in the early ’80s. Universal Studios bought the development rights and signed director Ivan Reitman, who had done “Meatballs” and “Stripes.”

“(Adams) moved out to Hollywood after the Universal deal,” says Robbie Stamp, executive producer of “Hitchhiker’s” and Adams’ close friend. “He turned in a very big script, with every guide entry in it and it basically didn’t work.”

Reitman decided instead to gamble on another sci-fi comedy script, “Ghostbusters,” effectively banishing “Hitchhiker’s” into what insiders call “development hell.”

Still, the franchise flourished. Adams kept writing “Hitchhiker’s” books, and the story became a BBC-TV show, a video game, an album and even a stage play.

A decade later, Disney purchased the rights to the script, signed “Meet the Parents” director Jay Roach and even hinted at Jim Carrey for a starring role.

The momentum would be short-lived. Early one May morning in 2001, while jogging on a treadmill at a Santa Barbara gym, Adams had a fatal heart attack.

“It was a total shock,” says Stamp. “As far as the film went, things ground to a halt.”

Stamp says he spoke with Adams’ family before deciding to go ahead.

“I think they felt that if we could get a movie off the ground, it would be a great vindication for Douglas,” says Stamp.

Screenwriter Karey Kirkpatrick, who wrote the animated comedy “Chicken Run,” was brought in to polish the script. “After I read it, I immediately called and said that I didn’t know if I could do it,” he says. “It was really original … I wasn’t sure that I could quite pick up where he left off.”

After Roach convinced Kirkpatrick to give it a shot, he decided he wanted only to produce the movie, not direct. The team scrambled to find a replacement. Their first choice, “Being John Malkovich” creator Spike Jonze, was unavailable. But Jonze suggested Garth Jennings, a music video director known for his visually inventive work for such artists as Blur and REM.

“At first, I said to my agent, “Please don’t send me that script,’ ” says Jennings. “I grew up loving the material and I was concerned that it would be Hollywoodized. But they sent it anyway and I realized it had that lovely sense of wonder and fun.”

Zooey Dechanel, who co-stars with Freeman, Mos Def and Sam Rockwell, says picking an English director was the right move. “It’s something that very much belongs to England,” she says. “‘Hitchhiker’s’ is like a national treasure there.”

And Adams contributes more than his wit and style to the movie. Before he died, a computer scan was taken of his head allowing filmmakers to construct certain digital set pieces based on his features.

“He is in this movie a tremendous amount,” says Stamp. “It’s fused with his spirit.”