By taking an estimated $24 million at American box offices in its second week, Gladiator skewered the competition easily to hang on to the No 1 spot. But then, the competition is not exactly fighting fit material. In second place is Battlefield Earth, an $80 million adaptation of L. Ron Hubbard's science-fiction novel, starring John Travolta. It took $12 million and will disappear fast. This is the Showgirls of science-fiction. Hubbard, of course, founded Christian Scientology (Travolta is an adherent) and this tale of life in AD3000 is a fitting legacy. Fears that Scientology's reputation for intimidation has affected the critics can be quickly allayed. "It may be a bit early to make such judgments," says The New York Times, "but Battlefield Earth may well turn out to be the worst movie of this century." "It's like taking a bus trip with someone who has needed a bath for a long time," says the Chicago Sun-Times. "It's not merely bad, it's unpleasant in a hostile way." Travolta indulges in the worst overacting of his career. Playing the evil leader of the Psychlos, he sports post-apocalyptic dreadlocks and thin tubes coming out of each nostril, rather like an emergency ward patient. He cackles at his "stupid man animal" subjects and forces them to dig for gold. Why this alien needs gold is never explained. Neither is his decision to educate his most rebellious earthling subject. (Three guesses who leads the overthrow of the Psychlos?) But then the whole project reeks of superstar indulgence. Travolta's official worst film used to be Moment by Moment, the 1978 lulu in which he played a beach bum who falls in love with rich Malibu wife Lily Tomlin. Not any more.