Science fiction (or sci-fi) is a film genre that uses speculative, fictional science-based depictions of phenomena that are not fully accepted by mainstream science, such as extraterrestrial lifeforms, spacecraft, robots, cyborgs, interstellar travel, time travel, or other technologies. Science fiction films have often been used to focus on political or social issues, and to explore philosophical issues like the human condition.
Many consider Stanley Kubrick's 2001 A Space Odyssey one of the best sci-fi movies ever made. The film genre called sci-fi had its origins much earlier. The first movies presenting space travel, journeys to the depths of the oceans and the most distant places on Earth, robots, and monsters created in laboratories by mad scientists began at the end of the 19th century. The genre has existed since the early years of silent cinema when Georges Melies' A Trip to the Moon (1902) employed trick photography effects. The next major example (the first feature-length in the genre) was the film Metropolis (1927).