Contemporary Cosmologies (Leaving Cert Religious Education): Revision Notes
Contemporary Cosmologies
What is cosmology?
A cosmology provides an explanation for how the universe originated, what it consists of, and how it has developed over time. Unlike ancient cosmologies that relied on mythological stories, modern cosmologies are scientific theories based on observation, mathematics, and physics.
Contemporary cosmologies attempt to answer fundamental questions:
- How did the universe begin?
- What is the universe made of?
- How has it developed over time?
For the Leaving Certificate RE examination, you need to understand two contrasting contemporary cosmologies, describe them thoroughly, and compare their differences.
The Big Bang theory
Background and development
The Big Bang theory is currently the most widely accepted scientific explanation for the universe's origin. The theory was first proposed in the 1920s by Georges Lemaître, a Belgian Catholic priest and physicist, who described the universe's beginning as a "primaeval atom" that underwent expansion.
The term "Big Bang" was originally used dismissively by scientist Fred Hoyle, but it became the standard name for the theory.
Core principles
Key Principles of Big Bang Theory:
The Big Bang theory suggests that:
- The universe originated approximately billion years ago
- Initially, all matter and energy existed in an extraordinarily dense and hot single point
- This point underwent rapid expansion - not an explosion into space, but rather the expansion of space itself
- As expansion occurred, matter began to cool, enabling the formation of stars, galaxies, and eventually planets
- This expansion process continues today, with the universe still growing
Scientific evidence
Three main pieces of evidence support the Big Bang theory, providing strong observational support for this cosmological model:
Scientific Evidence for the Big Bang:
1. Redshift of galaxies (Hubble's Law): Observations show that galaxies are moving away from us, with more distant galaxies moving faster - demonstrating that the universe is expanding.
2. Cosmic Microwave Background Radiation (CMB): Discovered in 1965, this faint radiation represents the "afterglow" remaining from the hot, early universe.
3. Abundance of light elements: The observed proportions of hydrogen and helium in the universe match what the Big Bang theory predicts.
Religious and philosophical implications
Some believers find the Big Bang compatible with the concept of creation ex nihilo (creation from nothing). Pope Pius XII declared in 1951 that it aligned with Catholic teaching.
However, critics argue that the theory still leaves fundamental questions unanswered: what caused the initial expansion, and why does the universe exist at all?
Different people interpret the theory differently - atheists may see it as evidence that the universe can arise without God, while believers may view it as evidence of divine design.
Steady State theory
Background and development
The Steady State theory was proposed in 1948 by scientists Fred Hoyle, Hermann Bondi, and Thomas Gold as an alternative to the Big Bang model. It gained popularity during the mid-20th century but later lost support as new evidence emerged supporting the Big Bang.
Core principles
Core Principles of Steady State Theory:
According to Steady State theory:
- The universe has no beginning and no end - it is eternal and unchanging overall
- While the universe expands, new matter continuously appears to fill the gaps as galaxies move apart
- This maintains a constant density, ensuring the universe always appears roughly the same ("steady state") regardless of time
- This avoids the concept of a singular beginning, which some scientists disliked due to its religious implications
Evidence and challenges
Initially, the theory explained why the universe appears similar in all directions (the cosmological principle). However, the discovery of cosmic microwave background radiation in 1965 provided strong evidence for the Big Bang and contradicted Steady State predictions.
Today, the Steady State theory has very little scientific support, but it remains historically important because it demonstrates that cosmology involves debate and competing ideas.
Religious and philosophical implications
The Steady State theory appeals to some because it avoids questions about creation - if the universe is eternal, no creator is necessary.
However, others see problems with this approach, arguing that it avoids the fundamental question of "why" and offers little sense of purpose or meaning.
Other contemporary models
While the syllabus focuses on two main theories, examiners may expect awareness of other models:
Additional Contemporary Models:
Oscillating Universe theory: Proposes that the universe undergoes endless cycles of expansion (Big Bang) followed by contraction (Big Crunch), with each cycle destroying the previous universe before beginning anew.
Multiverse hypothesis: Suggests our universe is one of many, each potentially having different physical laws and constants. Some view this as explaining fine-tuning without requiring God, whilst others consider it speculative.
Quantum cosmology: Explores how the universe might have emerged from quantum fluctuations - "something from nothing" in physics terms. This represents the frontier of current scientific understanding.
Comparing the theories
| Aspect | Big Bang Theory | Steady State Theory |
|---|---|---|
| Origin | Universe began billion years ago from an extremely dense state | Universe is eternal with no beginning or end |
| Expansion | Universe expands from an initial point and continues expanding today | Universe expands but new matter is constantly created to maintain density |
| Evidence | Strong support from redshift observations, CMB radiation, and light element abundances | Contradicted by evidence, particularly CMB discovery in 1965 |
| Religious implications | Compatible with creation ex nihilo but raises questions about ultimate causation | Removes need for a creator by proposing eternal existence |
| Current status | Widely accepted by the scientific community | Largely rejected but historically significant |
Analysis and significance
Scientific importance
The Big Bang theory succeeds because it aligns with observational evidence and makes predictions that can be tested. Its acceptance demonstrates how scientific theories must be supported by evidence.
The Steady State theory, whilst ultimately disproven, shows that science is not fixed - theories compete and are revised as new evidence emerges.
Philosophical importance
The Big Bang raises profound questions about beginnings and what might have caused the initial expansion. Many theologians see this as compatible with religious faith.
The Steady State theory appeals to those who prefer a universe without a definite beginning, avoiding questions about who or what might have created it.
Theological importance
Critical Understanding: Neither theory proves or disproves the existence of God. Religious believers interpret cosmologies through the lens of faith, whilst atheists interpret them without reference to God.
The debate illustrates how science and religion can be in conflict, dialogue, or seen as complementary, depending on one's interpretation.
Key takeaways
Essential Points to Remember:
- Cosmology definition: Scientific explanation of the universe's origin, structure, and development
- Big Bang essentials: Universe began billion years ago from dense point; supported by redshift, CMB radiation, and light element evidence
- Steady State basics: Proposed eternal universe with continuous matter creation; largely disproven by CMB discovery
- Evidence matters: Scientific theories must be supported by observational evidence, and can be revised or rejected
- Multiple interpretations: Both religious believers and atheists can interpret cosmological theories to support their worldviews