Interpretations of 2001: A Space Odyssey machines". Kubrick was also confronted with the fact that, during the production of the film, the US and USSR had agreed not to put any nuclear weapons into outer space by signing the Outer Space Treaty. Alexander Walker in a book he wrote with Kubrick's assistance and authorisation, states that Kubrick eventually decided that as nuclear weapons the bombs had "no place at all in the film's thematic development", now being an "orbiting red herring" which would "merely have raised irrelevant questions to suggest this as a reality of the twenty-first century". In the Canadian TV documentary "2001 and Beyond",
Technologies in 2001: A Space Odyssey adviser for the film. "2001" accurately presents outer space as not allowing the propagation of sound, in sharp contrast to other films with space scenes in which explosions or sounds of passing spacecraft are heard. "2001" portrayal of weightlessness in spaceships and outer space is also more realistic. Tracking shots inside the rotating wheel providing artificial gravity contrast with the weightlessness outside the wheel during the repair and Hal disconnection scenes. (Scenes of the astronauts in the "Discovery" pod bay, along with earlier scenes involving shuttle flight attendants, depict walking in zero-gravity with the help of velcro-equipped shoes labeled "Grip