The facts are that the lowest framerate that can be used to make the pictures move is 16 FPS but the more, the better and smoother the movie gets. Thomas Edison believed that the optimal framerate should be 46 FPS, however, the cameras and projectors were not that fast and the film on which the movies were shot was expensive, to 46 FPS was too much. Most silent movies were filmed with around 14-26 FPS but projected in the cinema in speeds varying from 22 to 26 FPS. When movies started to include sound, the footage couldn't be sped up anymore, so the average projection speed of 24 FPS was selected to be the standard and from then on, every movie was shot in 24 FPS and projected in 24 FPS.
Later the thing that kept the 24 FPS as a standard was the fact, that people got used to it and our brains coded this speed as the movie speed. If you look at a movie shot with for example 48 FPS, like The Hobbit, it looks "unnatural" and not like a movie, but like a telenovela.
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