A mind-bending sci-fi symphony, Stanley Kubrick's landmark 1968 epic pushed the limits of narrative and special effects toward a meditation on technology and humanity. Based on Arthur C. Clarke's story The Sentinel, Kubrick and Clarke's screenplay is structured in four movements. At the Dawn of Man, a group of hominids encounters a mysterious black monolith alien to their surroundings. To the strains of Strauss' Thus Spoke Zarathustra, a hominid discovers the first weapon, using a bone to kill prey. As the hominid tosses the bone in the air, Kubrick cuts to a 21st century spacecraft hovering over the Earth, skipping ahead millions of years in technological development only to imply that man hasn't advanced very far at all psychologically. U.S. scientist Dr. Heywood Floyd (William Sylvester) travels to the moon to check out the discovery of a strange object on the moon's surface: a black monolith. As Floyd touches the mass, however, a piercing sound emitted by the object stops his fellow investigators in their path. Cutting ahead 18 months, impassive astronauts David Bowman (Keir Dullea) and Frank Poole (Gary Lockwood) head toward Jupiter on the space ship Discovery, their only company three hibernating astronauts and the vocal, man-made HAL 9000 computer running the entire ship. When the all-too-human HAL malfunctions, however, he tries to murder the astronauts to cover his error, forcing Bowman to defend himself the only way he can. Free of HAL, and finally informed of the voyage's purpose by a recording from Floyd, Bowman journeys to "Jupiter and Beyond the Infinite," through the psychedelic slit-scan star-gate to an 18th century room, and the completion of the monolith's evolutionary mission. With assistance from special effects expert Douglas Trumbull, Kubrick spent over two years meticulously creating the most "realistic" depictions of outer space ever seen, greatly advancing cinematic technology for a story expressing grave doubts about technology itself. Despite some initial critical reservations that it was too long and too dull, 2001 became one of the most popular films of 1968, underlining the generation gap between young moviegoers who wanted to see something new and challenging and oldsters who "didn't get it." Provocatively billed as "the ultimate trip," 2001 quickly caught on with a counterculture youth audience open to a contemplative (i.e. chemically enhanced) viewing experience of a film suggesting that the way to enlightenment was to free one's mind of the U.S. military-industrial-technological complex.