Alien (film) disguise imaginative poverty". In a 1980 episode of "Sneak Previews" discussing science fiction films of the 1950s and 1970s, critics Gene Siskel and Roger Ebert were critical of "Alien". Ebert called it "basically just an intergalactic haunted house thriller set inside a spaceship" and one of several science fiction pictures that were "real disappointments" compared to "Star Wars", "Close Encounters of the Third Kind", and "", though he did compliment the early scene of the "Nostromo" crew exploring the alien planet as showing "real imagination". However, the film later made it onto Ebert's "Great Movies" list, where he gave it
Bell's spaceship paradox proper time in the momentary frame, and the momentary velocity is given by The mathematical treatment of this paradox is similar to the treatment of Born rigid motion. However, rather than ask about the separation of spaceships with the same acceleration in an inertial frame, the problem of Born rigid motion asks, "What acceleration profile is required by the second spaceship so that the distance between the spaceships remains constant in their proper frame?" In order for the two spaceships, initially at rest in an inertial frame, to maintain a constant proper distance, the lead spaceship must have a lower