The Steady State theory was a cosmological model developed in 1948 by astronomers Fred Hoyle, Hermann Bondi, and Thomas Gold. It proposed that the universe has no beginning and no end, maintaining a consistent appearance throughout infinite time. The theory served as the primary alternative to the notion of a universe that originated from a single, dense state, becoming the main rival to the model later termed the Big Bang. The Steady State model offered an elegant, perpetual cosmos.
Core Principles of the Steady State Model
The philosophical foundation of the Steady State model rests upon the Perfect Cosmological Principle (PCP), an extension of the standard Cosmological Principle. The standard principle states that the universe is homogenous and isotropic on large scales, meaning it looks the same everywhere in space. The PCP adds the dimension of time, asserting that the universe must appear the same at all times, not just at all places. This means its large-scale properties, such as the average density of matter and the mixture of young and old galaxies, must remain constant forever. This concept required a mechanism to balance the known expansion of the universe, which would otherwise cause the matter density to decrease over time.
The Mechanism of Continuous Creation
To uphold the unchanging nature of the universe as required by the Perfect Cosmological Principle, the Steady State model incorporated the concept of continuous creation. Since observations confirmed the universe was expanding, the density of matter would naturally thin out as space stretched. The theory proposed that new matter must spontaneously appear in the empty space between galaxies to counteract this dilution. This continuous creation of matter, primarily hypothesized as simple hydrogen atoms, was necessary to keep the universe’s average density constant. The required rate was exceedingly minute, estimated to be roughly one hydrogen atom appearing in a volume the size of the Empire State Building over the course of a year. The newly created matter would eventually coalesce, forming new stars and galaxies to replace those that drifted beyond the observable horizon.
The Crucial Conflict: Steady State vs. Big Bang
The Steady State theory championed an eternal, non-evolving cosmos, contrasting sharply with the Big Bang model, which proposed a universe with a finite timeline and a specific moment of origin. The core conflict centered on the universe’s evolution over time. The Steady State model predicted that the distant, ancient universe should look identical to the local, younger universe, displaying a uniform mixture of galaxies. Conversely, the Big Bang model predicted distinct evolution: looking far away means looking back in time, so distant galaxies should appear younger, less structured, and reflect the universe’s changing state.
Observational Evidence that Refuted Steady State
The scientific debate between the two cosmological models was decisively settled by major observational discoveries that directly contradicted the Perfect Cosmological Principle.
Non-Uniform Radio Sources
Radio astronomy surveys first indicated that the distribution of bright, distant radio sources was not uniform. These findings showed that the universe was different in the past than it is now, suggesting clear evolution.
Quasars
The discovery of quasars, which are extremely luminous and distant galactic cores, provided strong evidence against the Steady State model. These objects were found predominantly at great distances, meaning they were common billions of years ago but are rare in the local, modern universe. Their non-uniform distribution demonstrated that the universe was not the same at all times, directly contradicting the theory’s central premise.
Cosmic Microwave Background (CMB)
The final, conclusive blow was the accidental discovery of the Cosmic Microwave Background (CMB) radiation in 1964 by Arno Penzias and Robert Wilson. This faint, uniform radiation permeating all of space was interpreted as the residual heat from an initial, hot, and dense phase of the universe. The CMB could not be adequately explained by the Steady State model, which had only predicted background radiation from scattered starlight. The CMB provided irrefutable evidence that the universe had evolved from a much hotter and denser beginning, marking the end of the Steady State theory as a viable cosmological model.