2001: A Space Odyssey is a 1968 science fiction film produced and directed by Stanley Kubrick. The screenplay was written by Kubrick and Arthur C. Clarke, and was partially inspired by Clarke's short story "The Sentinel". Clarke concurrently wrote the novel 2001: A Space Odyssey which was published soon after the film was released. The story deals with a series of encounters between humans and mysterious black monoliths that are apparently affecting human evolution, and a voyage to Jupiter tracing a signal emitted by one such monolith found on the Moon. The film is frequently described as an epic, both for its length and scope, and for its affinity with classical epics. The film is structured into four distinct acts. Daniel Richter plays the character "Moonwatcher" in the first act, and William Sylvester plays Dr. Heywood R. Floyd in the second. Keir Dullea (as Dr. David Bowman) and Gary Lockwood (as Dr. Frank Poole) star in the third act as the two astronauts on their voyage to Jupiter on board the spacecraft Discovery One, with Douglas Rain as the voice of the sentient computer HAL 9000 who has full control over their spacecraft. The fourth and final act of the film follows the journey of astronaut David Bowman "beyond the infinite".