As if underscoring their film’s essential witlessness, the folks at Marvel Entertainment have inexplicably missed the opportunity to make a splash by opening “Thor: The Dark World” on a Thursday. But repackaging a Norse god as an alien superhero takes chutzpah, not humor (unless you count the Viking ship that serves as his spacecraft), and movie studios have yet to lose money by assuming that their audiences have the intellectual discernment of newborns. So if the multiple idiocies on view strike you as neither here nor there, it’s probably because your eyeballs are too busy recoiling from the onslaught of disorienting 3-D effects, or else too distracted by the title character’s Popeye arms and really big mallet.

Natalie Portman, playing the astrophysicist Jane Foster, certainly is. Ever since meeting her hammer-swinging hero (Chris Hemsworth) two years ago in “Thor,” Jane has been pining to subject the rest of his tool belt to scientific study. (Careful there, Jane; his mythological namesake was closely associated with fertility.)

An opportunity arises when she’s invaded by an alien substance known as Aether (like the red weed in “War of the Worlds,” only more floaty) and whisked into a conflict between Thor and the Dark Elves. Newly emerged from hibernation and dead set on sucking every last bit of light from the universe — the screenwriters see no reason to tell us why — the Elves and their leader, Malekith (an unrecognizable Christopher Eccleston) are disappointing villains. Mostly, they just suck up the budget for fancy wigs and fancier contact lenses.