Steady-state model
A now-rejected cosmological model with continuous matter creation.
The steady-state model, also known as steady-state theory, was a cosmological model proposed as an alternative to the Big Bang theory. It holds that the universe is expanding but maintains a constant average density through the continuous creation of matter, adhering to the perfect cosmological principle—the idea that the observable universe looks the same at any time and any place. The model was influential from the 1940s to the 1960s, dividing the astrophysical community, but is now rejected by most cosmologists, astrophysicists, and astronomers due to observational evidence favoring a hot Big Bang cosmology with a finite age.
- field
- Cosmology
- known_for
- Alternative to Big Bang theory; continuous creation of matter; perfect cosmological principle
- earlier_proponent
- William Duncan MacMillan
- status
- Rejected by most cosmologists, astrophysicists, and astronomers
Lore & Background
Similar ideas had been proposed earlier by William Duncan MacMillan, among others. The model posits that the universe has no beginning and no end, requiring matter to be continually created to keep density constant as space expands.
Reader's Guide
The steady-state model was significant as the primary rival to the Big Bang theory during the mid-20th century, forcing cosmologists to refine observational tests. Its clear predictions—such as the uniform distribution of bright radio sources across all distances—allowed it to be disproven when observations showed that quasars and radio galaxies existed only at large distances, implying a changing universe.
Did You Know?
- The steady-state model requires continuous creation of matter to keep the universe's density from decreasing as it expands.
- Bright radio sources such as quasars and radio galaxies were found only at large distances, contradicting the steady-state model's prediction that they would appear throughout the universe.
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