Cyclic models

Definition

Cyclic models are theoretical frameworks in cosmology that propose the universe undergoes an infinite series of expansions and contractions, leading to a repetitive cycle of big bangs and big crunches. This concept challenges traditional views of a singular, linear progression of time and cosmological events, suggesting instead that the universe is eternally renewing itself through these cycles.

5 Must Know Facts For Your Next Test

1. Cyclic models suggest that the universe goes through infinite cycles, alternating between expansion and contraction phases.
2. One implication of cyclic models is that each cycle may lead to different physical laws or constants due to changes in conditions during each phase.
3. The concept offers potential resolutions to issues such as the flatness problem and the horizon problem by providing an alternative explanation for cosmic uniformity.
4. Cyclic models can involve different mechanisms for the transitions between expansions and contractions, such as scalar fields or modifications to gravity.
5. Some variants propose that each cycle could erase all previous information, while others suggest that some aspects of each cycle could persist into future iterations.

Review Questions

• How do cyclic models differ from traditional models of cosmology regarding the nature of time and cosmic events?
  • Cyclic models differ significantly from traditional cosmological models by suggesting that time is not linear but rather cyclical, where the universe experiences endless sequences of expansion and contraction. While traditional models often posit a singular beginning with the Big Bang followed by continuous expansion, cyclic models introduce the idea that this process repeats infinitely. This perspective fundamentally alters our understanding of cosmic history, proposing that past cycles may influence future states of the universe.
• Evaluate the implications of cyclic models on our understanding of entropy and cosmic evolution.
  • Cyclic models pose intriguing implications for entropy and cosmic evolution, as they challenge the conventional understanding dictated by the second law of thermodynamics. In a traditional framework, entropy tends to increase over time, leading to a 'heat death' scenario. However, cyclic models suggest that each cycle might reset or redefine conditions, allowing for new beginnings while potentially preserving some order from previous cycles. This invites deeper inquiry into how entropy operates in a non-linear timeline and how it shapes cosmic structures through successive cycles.
• Synthesize how cyclic models can offer solutions to key cosmological problems while posing new questions about the nature of the universe.
  • Cyclic models present innovative solutions to fundamental cosmological problems like the flatness and horizon problems by proposing that repetitive cycles allow for uniform conditions across vast expanses of time. However, this cyclical nature raises new questions regarding what happens to physical laws across different cycles and how information or matter persists—or fails to persist—throughout these transformations. By challenging existing paradigms, cyclic models invite further exploration into the fabric of reality itself, urging us to reconsider notions like causality and existence within an ever-repeating universe.

Related terms

Big Bang: The prevailing cosmological model explaining the origin of the universe, proposing it began from a singular point and has been expanding ever since.

Big Crunch:

A hypothetical scenario in which the expansion of the universe eventually reverses, leading to a collapse back into a singularity.

Entropy:

A measure of disorder or randomness in a system, often associated with the second law of thermodynamics, which states that entropy tends to increase over time.