Oscillating Universe Theory Notes

The oscillating universe is a combination of the big crunch and the big bang.
Big crunch occurs when the universe expands and eventually reverses, then collapses causing the formation of a singularity.

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Once the universe reverses and attains the point of singularity, another universe will be born.

1. The suggestion that the universe would collapse on its own after it reached its full expansion violates some current laws of physics, such as the postulated existence of dark energy.
2. The currently postulated end of the universe is by big freeze or heat death.

The theory attempts to describe a cyclical cosmos where each end of expansion leads to a new beginning.
Dark energy, which drives accelerated expansion, presents a challenge to a universe that would eventually re-collapse.
The observed fate of the universe is often discussed in terms of a possible big freeze/heat death, rather than a guaranteed re-collapse.
Related ideas: a turning point in expansion (turnaround) and a subsequent contraction that leads to a new singularity and birth of another universe (big bounce).

Singularity concept: as the cycle progresses toward a turnaround or bounce, certain physical quantities diverge.
- Density: \rho \to \infty
- Temperature: T \to \infty
Turnaround and bounce conditions (conceptual):
- Turnaround (from expansion to contraction) occurs when the scale factor's rate of change vanishes: \dot{a}(t{turn}) = 0\,, with eventual contraction if \ddot{a}(t{turn}) < 0.
- Bounce (from contraction to expansion) occurs when the scale factor reaches a minimum and begins to increase: \dot{a}(t{bounce}) = 0\,, with \ddot{a}(t{bounce}) > 0.
Basic cosmology form (conceptual, often used in discussions of expansion):
- The Friedmann–Lemaître–Robertson–Walker (FLRW) line element in simple flat space can be written as: ds^2 = -c^2 dt^2 + a(t)^2 d\mathbf{x}^2\,.
- The dynamics of the scale factor a(t) encode the expansion and contraction history of the universe.
Conceptual timeline in the oscillating model:
- Expansion → turnaround → contraction → singularity → big bang (new expansion) → repeat.

Links to Big Bang theory: oscillating model builds on expansion from a primordial state and a prior contraction history.
Dark energy and cosmic fate: current observations of accelerated expansion challenge a simple re-collapse scenario, favoring a possible end-state like a big freeze rather than a cyclic contraction.
Philosophical and practical implications: if cycles occur, questions arise about entropy buildup, information retention across cycles, and whether physical laws permit infinite cycles.

Philosophical: cyclic cosmos prompts reflection on the nature of time, causality, and the ultimate fate of cosmic structures.
Practical: understanding cyclic models informs our interpretation of cosmological data (supernova distances, cosmic microwave background) and the role of dark energy in shaping future evolution.

Oscillating Universe Theory posits a cycle of expansion and contraction with repeated formation of singularities (turning points) that seed new universes via big bangs (big bounce).
Big crunch is the contraction phase leading to a singularity, and it is proposed to trigger a new big bang, initiating another universe.
Richard Tolman was a major proponent, coining the term "big bounce" for the birth of a new universe.
Major drawbacks include conflicts with current physics (notably dark energy) and the tendency in standard cosmology toward a big freeze/heat death rather than a guaranteed re-collapse.
Mathematical intuition involves turning points of the scale factor a(t) and the behavior of density and temperature approaching singularities, with simple representations such as \rho \to \infty and ds^2 = -c^2 dt^2 + a(t)^2 d\mathbf{x}^2 to frame expansion.