Understanding the Big Bounce Theory - Josh Habka

In the big bounce theory, the universe repeatedly expands and contracts into a new "big bang", seesawing back and forth in a massively big-picture timeline.
Understanding the Big Bounce Theory - Josh Habka

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  1. Concept of the Big Bounce Theory:
    • The Big Bounce Theory proposes that the universe undergoes cycles of expansion and contraction, with each contraction leading to a new "big bang," creating a cyclical timeline on a massive scale.
  2. Variations of the Bounce:
    • There are various versions of the Big Bounce, including periodic bounces and one-time events. Some physicists argue for an infinite cycle, reintroducing the idea of cyclic cosmology, where key parameters oscillate from cycle to cycle.
  3. Verification of the Theory:
    • While the Big Bounce Theory is supported by significant evidence and research, it has not been definitively proven as the ultimate cause of the universe's origins.
  4. Mechanism of the Bounce:
    • During a bounce, the universe collapses to a singularity, where classical physics breaks down, and then rebounds into expansion. This cyclical process challenges traditional views of the universe's beginning and end.
  5. Challenges to the Big Bang Theory:
    • Unlike the Big Bang Theory, which struggles to explain the universe's state before the expansion, the Big Bounce proposes a continuous cycle of contractions and expansions, avoiding the need for a singularity.
  6. Inflation and Quantum Effects:
    • Inflationary models help reconcile the rapid expansion of the early universe with its observed uniformity by smoothing out quantum irregularities. These models suggest that each bounce starts with the remnants of the previous cycle, rather than from a singular point.
  7. Supporting Evidence and Observations:
    • The contraction phase of ekpyrotic scenarios aligns with observational data and can produce density fluctuations compatible with cosmic microwave background observations, leading to the formation of separate universes with distinct physical laws.

In the big bounce theory, the universe repeatedly expands and contracts into a new "big bang", seesawing back and forth in a massively big-picture timeline.

There are a few potential versions of bounce - some that are periodic, others that only bounce once. Some physicists suggest this bounce may be infinite, reinstating the cyclic cosmology first proposed in the 1930s. B795(2019) 666-672 The combination of (non-singular) intervals of ekpyrotic contractions with (non-singular) classical bouncing leads naturally to a new cyclic universe theory, where Hubble parameters, energy density, and temperature periodically swing, but with scale factors growing exponentially from cycle to cycle.

Is the Big Bounce Theory True?


While significant evidence and research supports the Big Bounce Theory, it has not been proven to be the ultimate cause of the origins of the universe.

In a bounce, the Universe collapses to a singularity, where Einstein's gravity theory, General Relativity, breaks down. Eventually, the Universe collapses into the singularity, and bounces start growing again. For instance, Einstein's theory of general relativity predicted that if any large object in space suddenly collapses, it would consume itself, vanishing at a point that is infinitely small and dense, known as a singularity.

Many physicists have studied the Big Bang as an origin emerging from oblivion. The problem with this theory is that it does not explain what existed prior to the Big Bang or what caused it to expand. By far, the most popular theory is inflation, which is the idea that the cosmos expanded in size within the first few seconds of its birth with the bang.

Inflation helps to close the gap between explosions and the uniformity we observe today: Space expanded so quickly that it flattened all of the irregularities that would occur because of quantum effects at the time of the big bang. On the left side of this picture, you can see the very brief moments of inflation, which many physicists think balances the randomized effects of early quantum fluctuations. There is a dense point of an infinite temperature without dimensions called the singularity.

Instead of the Big Bang, the event is thought to have been the Big Bounce, a point in time when the Universe slowly shrinks towards a surprisingly, but not infinitely, small point, bounced back up into an expansion. Each new inflationary period would start with the remains of a previous period of expansion, not with the singularity. An expansion might be followed in the distant future by a collapse, followed by another rebound.

What Robert Brandenberger and Ziwei Wang found is that the contraction of ekpyrotic would allow for all of this to align, which would also match the observations of today.

There are three basic ideas in this model of cycles, which are different from the usual single big bag theory. These models are significant because they can produce an almost scale-invariant spectrum of the Super Hubble density fluctuations, fully compatible with observations from the cosmic microwave background. These bubbles are then closed off from one another, effectively becoming separate universes with their physical laws.

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