Typically, physics says this isn't allowed. A person in either system would view a person in one with an opposite arrow as getting younger, from his or her own perspective. Well - Schulman uses reasoning, first proposed by physicists John Wheeler and Robert Feynman, to show that the system would have normal transmission and reception of light, which would help. Viewing possibilities are definitely greater for a big budget movie version of Crichton's Timeline , but a celluloid depiction of Schulman's timeline should be less expensive to make-just run an already made film backwards. He's piled speculation upon speculation.
Physics thrives on teasing apart outrageous and delicious paradoxes.
That's how real science is done. Although this is a novel conceptual view of time in a macroscopic system, a localized region in the universe would have to be observed for new physical laws to prevail. Our assumptions are that the laws do not change depending upon your location in the universe. If that's a pun, all the better. Copyright 2000, The American Physical Society.