“The Butterfly Effect” is a story written around an idea. The idea, borrowed from chaos mathematics, is that something as small as the flapping of a butterfly’s wings can set into motion the production of a hurricane. Or, as the film puts it, a very small change to the past can completely alter the present. The film earned its R rating for many reasons — pervasive objectionable language, sexual situations, nudity including child pornography, drug use, and severe and sadistic violence including animal abuse and implied child abuse. Don’t put yourself through the trauma of seeing this film.