First some backstory. The 1951 film, "The Day the Earth Stood Still," was a surprising hit, touching a public nerve at the dawn of the nuclear age. Shot in black and white, it told a seamless story of an extra-terrestrial, Klaatu, played by Michael Rennie, who lands his spacecraft on the Washington Mall. There is panic and an aggressive military response as tanks and soldiers surround the ship. The world watched in disbelief as Klaatu emerges from the enormous silver disk, followed by Gort, a giant robot.

First some backstory. The 1951 film, "The Day the Earth Stood Still," was a surprising hit, touching a public nerve at the dawn of the nuclear age. Shot in black and white, it told a seamless story of an extra-terrestrial, Klaatu, played by Michael Rennie, who lands his spacecraft on the Washington Mall. There is panic and an aggressive military response as tanks and soldiers surround the ship. The world watched in disbelief as Klaatu emerges from the enormous silver disk, followed by Gort, a giant robot.

Klaatu's arrival sets in motion a lean narrative wherein he makes known his wish to meet with the world's leaders to explain that he represents a confederation of planets who have become disturbed by Earth's warlike history, their concern heightened by the recent invention of the atomic bomb.

The film proves to be a cautionary tale, and even given its low-tech hardware and low-budget special effects it creates and sustains a riveting tension. When first released, kids especially loved the film and for weeks afterward went about muttering, "Gort. Klaatu. Barada. Nickto." If that sounds like nonsense, well, you had to be there.

And now comes the remake of this classic sci-fi film that has substituted environmental collapse for atomic bombs. Fair enough. But beyond that, the changes made to the original Edmund H. North screenplay have leached most of the drama out of what could have been an engaging and intelligent adaptation.

Whereas the 1951 Klaatu was urbane, even speaking with an Oxford accent, Keanu Reeves' Klaatu is stiff and unemotional, seeming almost robotic. If in the opening set-up he hadn't been operated on to remove a bullet, the suspicion would have lingered that he was all circuit boards and wires.

Perhaps more egregious, at no time throughout the film does the Earth stand still, an event central to the original movie. In the 1951 film, the people of Earth ask for a demonstration that Klaatu possesses powers that could destroy the earth. At exactly noon Klaatu stops the earth's rotation for mere minutes. Globally, all comes to a standstill. It's an eerie scene as people stand outside their cars stunned, others are trapped in trains and elevators. No one is hurt, yet this event has its intended consequence. Klaatu is now taken very seriously.

The remake, regrettably, skips over this moment and focuses instead on an uneven chase that seems cobbled together with Klaatu and Dr. Helen Benson (Jennifer Connelly), an astrobiologist, and her son Jacob (Jaden Smith), running from the police and the military. At this point the film seems directionless, and whatever tension was created is undermined. As well, there are scenes that seem superfluous, tacked on without purpose.

The art of making good sci-fi resides in the screenwriter's ability to craft speculative fiction involving science and technology in an imaginative way while constructing a narrative that has compelling characters and creates a strong sense of verisimilitude. As a genre it's elusive. Some might argue that defining science fiction is impossible. We don't know exactly what it is; yet we know it when we see it. Though sci-fi films have, as a rule, been on the perimeter of Hollywood filmmaking for decades, there have been more than a few that have captivated enthusiastic mainstream audiences. The "Star Wars" franchise is a good example. "Blade Runner" another. These films were highly imaginative, the stories complex and even thrilling.

Sadly, "The Day the Earth Stood Still" should have been a remarkable remake. The premise of an alien arriving from the stars to warn us that a confederation of ETs will not permit Earth to become an environmental catastrophe is filled with promise. For reasons known only to the filmmakers, as germane as it seems, this issue was allowed to be sidelined, whereas in the original film mutually assured destruction was central.

This remake was a big-budget effort with strong actors. It should have been excellent. But once again, it all comes down to the story. Why the director and the screenwriter were unable to see the script's flaws is surprising. But then once in the middle of a project, perhaps it's the forest for the trees.