In 1948, Sir Hermann Bondi, Sir Thomas Gold and Sir Fred Hoyle proposed the steady state theory of the universe. According to this theory, the universe is eternal and unchanging, with new matter constantly being created at the rate needed to replace the stars, which have used up their fuel and stopped shining, meaning the universe forever remains in a steady state, without a beginning or end.
The steady-state theory was a popular alternative to the Big Bang theory, which stated that the universe began with a massive explosion and had expanded ever since. The steady-state theory solved some problems with the Big Bang theory, such as what caused the explosion and why the universe appeared homogenous on large scales.
However, as time passed and new data was collected, the steady state theory began to fall apart after discovering cosmic microwave background radiation in 1964 significantly blew the steady state theory. The cosmic microwave background radiation is a faint glow of light that fills the universe, and it was discovered that it has the same temperature in all directions. This discovery provided strong evidence in favour of the Big Bang theory, which predicted the existence of this radiation.
Additionally, observations of galaxy redshifts also provided evidence for the Big Bang theory. Redshifts measure how much light stretches from a galaxy, and the observation indicated that the universe was expanding. This was consistent with the Big Bang theory, but it was challenging to explain within the framework of the steady-state theory.
The steady-state theory was an exciting idea popular among scientists in the mid-20th century, but it was later disproved by new evidence. This serves as a reminder that scientific theories are always subject to testing and modification based on new evidence.