Steady state theory

Definition

Steady state theory is a cosmological model that posits the universe is eternal and unchanging on a large scale, with new matter continuously created to maintain a constant density as the universe expands. This theory contrasts with the Big Bang model, suggesting that while the universe evolves, it does so without a beginning or end, leading to an unchanging average appearance over time.

5 Must Know Facts For Your Next Test

1. Steady state theory was first proposed by Fred Hoyle, Thomas Gold, and Hermann Bondi in 1948 as an alternative to the Big Bang theory.
2. The theory suggests that as the universe expands, new matter is created to fill in the gaps left behind, keeping the overall density constant.
3. One of the main criticisms of steady state theory is its inability to explain observed phenomena like the cosmic microwave background radiation.
4. Observational evidence supporting the expansion of the universe, such as Hubble's Law and redshift measurements, challenges the steady state model.
5. The steady state theory has largely fallen out of favor in contemporary cosmology due to overwhelming evidence for the Big Bang model.

Review Questions

• Compare and contrast steady state theory with the Big Bang theory in terms of their views on the universe's evolution.
  • Steady state theory argues that the universe is eternal and unchanging on average, continuously creating new matter as it expands. In contrast, the Big Bang theory posits that the universe began from a hot, dense state and has been evolving since its inception about 13.8 billion years ago. While steady state maintains a constant density throughout expansion, the Big Bang emphasizes a dynamic history leading to an ever-cooling universe.
• Evaluate why observational evidence like Hubble's Law poses challenges to steady state theory.
  • Hubble's Law demonstrates that galaxies are receding from us at velocities proportional to their distances, suggesting a uniform expansion of the universe. This observation contradicts steady state theory, which cannot account for a dynamically changing universe. Instead, steady state insists on continuous matter creation to keep density constant, but does not provide a framework for understanding varying distances and speeds of distant galaxies.
• Assess how discoveries like cosmic microwave background radiation have influenced our understanding of cosmology and led to a preference for one model over another.
  • The discovery of cosmic microwave background radiation provided strong evidence for the Big Bang theory, indicating that our universe had a hot, dense beginning followed by expansion. This finding contradicted steady state theory, which does not predict such relic radiation from an unchanging cosmos. As more observational data aligned with the Big Bang model and contradicted steady state predictions, cosmologists increasingly favored the former, reshaping our understanding of cosmic evolution.

Related terms

Hubble's Law: A principle that states that the recessional velocity of galaxies is directly proportional to their distance from us, supporting the idea that the universe is expanding.

Cosmic Microwave Background Radiation: The afterglow radiation from the Big Bang, serving as evidence for the universe's hot, dense origin and providing critical support for the Big Bang theory.

Redshift: The phenomenon where light from distant galaxies is shifted to longer wavelengths, indicating that those galaxies are moving away from us, which supports the expanding universe concept.