Steady State Theory

In cosmology, the Steady State theory (also known as the Infinite Universe theory or continuous creation) is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory (known, usually, as the standard cosmological model). In steady state views, new matter is continuously created as the universe expands, so that the perfect cosmological principle is adhered to.

The steady state theory of Bondi and Gold was inspired by the circular plot of the film Dead of Night, which they had watched together. Theoretical calculations showed that a static universe was impossible under general relativity, and observations by Edwin Hubble had shown that the universe was expanding. The steady state theory asserts that although the universe is expanding, it nevertheless does not change its appearance over time (the perfect cosmological principle); it has no beginning and no end.
The theory requires that new matter must be continuously created (mostly as hydrogen) to keep the average density of matter equal over time. The amount required is low and not directly detectable: roughly one solar mass of baryons per cubic megaparsec per year or roughly one hydrogen atom per cubic meter per billion years, with roughly five times as much dark matter. Such a creation rate, however, would cause observable effects on cosmological scales.

An aesthetically unattractive feature of the theory is that the postulated spontaneous new matter formation would presumably need to include deuterium, helium, and a small amount of lithium, as well as regular hydrogen, since no mechanism of nucleosynthesis in stars or by other processes accounts for the observed abundance of deuterium and helium-3. (In the Big Bang model, primordial deuterium is made directly after the "bang," before the existence of the first stars).