Radio and movies became popular new forms of mass media in the 1920s that could spread propaganda easily. With more leisure time due to 8 hour work days, people enjoyed new mass leisure activities like sports, movies, and travel. In art, abstract styles like Dadaism and Surrealism depicted nonsensical or fantastical themes to reflect the chaotic state of the world. Modern architecture embraced clean, functional forms using new technologies while literature explored inner thoughts and psychological themes. In physics, Heisenberg's uncertainty principle suggested all natural laws were uncertain, changing views of the world.