Robert Wise’s 1951 version of “The Day The Earth Stood Still” is a science-fiction classic; that’s certainly a word no one will ever apply to this dreadful big-budget remake from Scott Derrickson (“The Exorcism of Emily Rose”), which turns an intelligent and thoughtful film into what might be called a boys’ adventure yarn if that weren’t an insult to both boys and yarn—the latest updating to trash a fifties icon (first “Invaders from Mars,” then “The Blob,” then “Invasion of the Body Snatchers,” now this).

Wise’s film featured a subtle performance by Michael Rennie as Klaatu, the alien who visits earth, along with his formidable robot Gort, to warn its inhabitants of the planetary danger posed by their warlike ways. Derrickson’s stars Keanu Reeves, who’s so tiresomely robotic he should have played Gort, not Klaatu. The original delivered a topical anti-nuclear message in heavy-handed fifties fashion, but still with dramatic skill. The new one is predicated on some general flapdoodle about man killing the earth, but it actually hasn’t an idea in its glossy head; and it becomes as brainless a chase movie as Reeves’s 1996 floppola, “Chain Reaction.” Even sonically it comes in a distant second. Wise’s picture boasted one of Bernard Herrmann’s most memorable scores, with a prominent Theremin part. This one offers music by Tyler Bates that couldn’t be more generically loud and, like the movie itself, bloated.

David Scarpa’s script adds a lot of dreary nonsense at the start to Edmund H. North’s sharp original, having to do with how the alien takes on human form and is questioned by U.S. officials, including a formidable pants-suited female Secretary of Defense (a stand-in for Hillary Clinton?), played stiffly by an obviously uncomfortable Kathy Bates. Klaatu escapes with the help of a scientist named Helen Benson (Jennifer Connelly, totally wasted), who, together with her purportedly sweet stepson Jacob (Jaden Smith, who’s supposed to touch our hearts but instead grates), ferries the fellow about as he reaches the decision that the human race is destroying the earth and the planet must be fumigated of man’s presence so that it can sustain other species. The process of cleansing has something to do with luminous globes that the aliens have been secreting around the world for decades and Klaatu summons from hiding to do their purifying work.

But—wouldn’t you know it?—the alien has a change of heart as a result of his interaction with Helen and Jacob, a talk with her mentor Professor Barnhardt (John Cleese in the old Sam Jaffe role, looking properly bemused at the nonsense around him), and a brief introduction to Bach’s “Goldberg Variations.” He decides to stop the process, which occasions a big, incoherent finale featuring bevies of metallic matter-devouring bugs among a host of other second-rate special effects. Earth apparently survives, though lots of death and destruction have already occurred, if the spread of those insect swarms is any indication.

“The Day The Earth Stood Still” doesn’t work as a sci-fi thriller, but it’s even worse when it tries to inject humanity into the mix. There’s absolutely no emotional reality to the relationships among Klaatu, Helen and Jason, and the alien’s abrupt transformation from destroyer to savior is never made remotely credible, reeking of screenwriting desperation and handled so ineptly that you’d swear a reel of exposition had been dropped in the editing process. Still, it might have been good, dumb fun had it been executed with style. Unfortunately, it’s technically no great shakes, with sloppy CGI work from the usual battalion of graphic artists, unimpressive cinematography by David Tattersall (who arbitrarily switches to hand-held camerawork at some points), and editing by Wayne Wahrman that leaves the picture a shapeless mess, through you have to sympathize with him on the basis of what he had to deal with.

When Klaatu first visited earth, his message was a warning against the nuclear bomb; his return is a bomb of a rather different sort. Wise’s picture has always been remembered for the famous phrase “Klaatu barada nikto.” This one is more like “Klaatu barada crappo.”