<p>The arguments against this are that it doesn't match what we currently see in the evolution of our universe.</p>
<p>The current best &quot;concordance model&quot; in cosmology (a.k.a. the <a href="https://en.wikipedia.org/wiki/Lambda-CDM_model" rel="nofollow noreferrer">Lambda-CDM model</a>) is based on an expansion from an initially small, hot state, following the Friedmann equations. The best-fitting parameters of this model (using observations of the cosmic microwave background, the distances and redshifts of Type Ia supernovae, the primordial abundances of deuterium and helium, the motions of objects in galaxies and clusters of galaxies, the large scale structure in the universe, and others) suggest that the universe is spatially flat (Euclidean) and is now expanding at an accelerating rate.</p>
<p>In the context of the Lambda-CDM model, there is no observational evidence that would support the notion that the universal expansion will slow down and reverse.</p>
<p>There are of course problems with the Lambda-CDM model - the most important of which, in my view, is growing evidence that the universe is not homogeneous on quite large scales (an assumption baked in to the model) and this might lead to problems in interpreting the observations. No doubt you could invent other models, or extensions to the Lambda-CDM model that would allow the various properties of dark matter and energy to change in time such that the universe did collapse.</p>

CC BY-SA 4.0
2022-04-11T11:25:34.970Z
Guess I'll need to do some heavier reading. Seems to me that entropy should become a dominant factor over time, that acceleration can't continue forever, and that a hot state a singularity) couldn't have sat there for eternity and then in a moment expanded without cause.
J H
CC BY-SA 4.0
2022-04-10T10:43:40.197Z
2022-04-10T10:43:40.197Z
ProfRob
<p>What are the arguments against a perpetual universe, i.e. one that expands from a singularity, like we observe with ours, then suffers from terminal entropy, collapses back upon itself before reaching a new state of singularity, then experiences a new big bang? Wash, rinse, repeat for eternity.</p>
<p>It makes sense as a layman, but when I mention to others I'm told it's been refuted--yet I've never heard any actual refutations.</p>
<p>Thanks.</p>

CC BY-SA 4.0
2022-04-10T15:28:34.647Z
Does this answer your question? [Has the Big Crunch been ruled out?](https://astronomy.stackexchange.com/questions/32107/has-the-big-crunch-been-ruled-out)
WarpPrime
<cosmology><universe><entropy>
Time & The Big Bang
J H
# Time & The Big Bang

(Asked by: username_0 on 2022-04-10)

What are the arguments against a perpetual universe, i.e. one that expands from a singularity, like we observe with ours, then suffers from terminal entropy, collapses back upon itself before reaching a new state of singularity, then experiences a new big bang? Wash, rinse, repeat for eternity.

It makes sense as a layman, but when I mention to others I'm told it's been refuted--yet I've never heard any actual refutations.

Thanks.

**Tags:** cosmology, universe, entropy

> **Comments:**
> **username_1**: Does this answer your question? [Has the Big Crunch been ruled out?](https://astronomy.stackexchange.com/questions/32107/has-the-big-crunch-been-ruled-out)  

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## 1 answers

### Answer by username_2 on 2022-04-10. Score: 0

The arguments against this are that it doesn't match what we currently see in the evolution of our universe.

The current best "concordance model" in cosmology (a.k.a. the [Lambda-CDM model](https://en.wikipedia.org/wiki/Lambda-CDM_model)) is based on an expansion from an initially small, hot state, following the Friedmann equations. The best-fitting parameters of this model (using observations of the cosmic microwave background, the distances and redshifts of Type Ia supernovae, the primordial abundances of deuterium and helium, the motions of objects in galaxies and clusters of galaxies, the large scale structure in the universe, and others) suggest that the universe is spatially flat (Euclidean) and is now expanding at an accelerating rate.

In the context of the Lambda-CDM model, there is no observational evidence that would support the notion that the universal expansion will slow down and reverse.

There are of course problems with the Lambda-CDM model - the most important of which, in my view, is growing evidence that the universe is not homogeneous on quite large scales (an assumption baked in to the model) and this might lead to problems in interpreting the observations. No doubt you could invent other models, or extensions to the Lambda-CDM model that would allow the various properties of dark matter and energy to change in time such that the universe did collapse.

> **Comments:**
> **username_0**: Guess I'll need to do some heavier reading. Seems to me that entropy should become a dominant factor over time, that acceleration can't continue forever, and that a hot state a singularity) couldn't have sat there for eternity and then in a moment expanded without cause.  

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