Even though the universe is expanding, it maintains its own average density or steady-state by constantly creating new matter. Several cosmologists today reject this model because it does not accommodate background radiation or the fact that the universe's appearance fluctuates over time.
The steady-state model of the universe was influenced by a film from the 1940s called Dead of Night. The movie was divided into four categories and presented a circular structure such that the ending was similar to the beginning. Following their viewing of this film in 1946, Hermann Bondi, Thomas Gold, and Fred Hoyle questioned if the universe was formed in the same fashion. The debate that ensued eventually led to the steady-state hypothesis.