The Cyclic Universe: Exploring the Idea of a Repeating Cosmos

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In summary: I was reading that the universe will repeat after its done. http://seedmagazine.com/content/article/a_cyclic_universe/I'm exceedingly skeptical of cyclic universe models. First, they definitely seem to be at odds with our current observations, in that it doesn't look like our universe will ever collapse in on itself. Second, in their most naive incarnations, they completely violate our understanding of entropy.I'm much more partial to ideas related to quantum fluctuations leading to the births of new universes. Yes it will, and I already answered this in the previous 5 or so repeats :biggrin:There is no evidence that supports this comment.
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  • #2
Yes it will, and I already answered this in the previous 5 or so repeats :biggrin:

The big question is, will it be different.
 
  • #3
byron178 said:
I was reading that the universe will repeat after its done. http://seedmagazine.com/content/article/a_cyclic_universe/
I'm exceedingly skeptical of cyclic universe models. First, they definitely seem to be at odds with our current observations, in that it doesn't look like our universe will ever collapse in on itself. Second, in their most naive incarnations, they completely violate our understanding of entropy.

I'm much more partial to ideas related to quantum fluctuations leading to the births of new universes.
 
  • #4
Skaperen said:
Yes it will, and I already answered this in the previous 5 or so repeats :biggrin:
There is no evidence that supports this comment.
 
  • #5
May be it's like this ,the universe is expanding from an infinitely small size to an infinitely large size and there was no beginning and there will be no end. i mean may be the big bang is still happening and we are all inside it and it will be happening! can this be true?
 
  • #6
shashankac655 said:
May be it's like this ,the universe is expanding from an infinitely small size to an infinitely large size and there was no beginning and there will be no end. i mean may be the big bang is still happening and we are all inside it and it will be happening! can this be true?
Basically, if you have any matter or radiation in the universe at all, then extrapolating back into the past, General Relativity says that everything had to be concentrated at one point sometime in the finite past.

Though we don't expect that General Relativity is completely accurate here, this does say that something interesting had to occur to produce our region of space-time at some point in the finite past. The ideas for what that could be are rather varied, but it can't have simply been a universe that has been expanding smoothly forever.
 
  • #7
bapowell said:
There is no evidence that supports this comment.

There is no evidence to refute it, either. The point is, how can we know. And if there is repeating, does it repeat exactly, or are we just referring to the theory that space will eventually collapse and bang out again (and are those 2 concepts even different things). If it repeats exactly as before, how can we ever possibly know. And what happens to the cone of influence. At this point, it's all wild conjecture and fun.
 
  • #8
Skaperen said:
There is no evidence to refute it, either. The point is, how can we know. And if there is repeating, does it repeat exactly, or are we just referring to the theory that space will eventually collapse and bang out again (and are those 2 concepts even different things). If it repeats exactly as before, how can we ever possibly know. And what happens to the cone of influence. At this point, it's all wild conjecture and fun.

It is wild conjecture and it is neither fun nor the right way to go about things. Claiming "there's no evidence to refute this!" before speculating whatever you want is not appropriate. This is a science forum, speculation should be based on evidence and current understanding.

As has been highlighted there is no good evidence that the universe will eventually experience a http://en.wikipedia.org/wiki/Big_Crunch" [Broken]. Discussing the available evidence for and against is perfectly reasonable, assuming one to be true then discussing how it could work is fallacious as it puts the cart before the horse. Without knowing the mechanism by which something could occur it is unreasonable to merely assume a mechanism.
 
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  • #9
Skaperen said:
There is no evidence to refute it, either. The point is, how can we know. And if there is repeating, does it repeat exactly, or are we just referring to the theory that space will eventually collapse and bang out again (and are those 2 concepts even different things). If it repeats exactly as before, how can we ever possibly know. And what happens to the cone of influence. At this point, it's all wild conjecture and fun.

There are 2 major problems with the cyclical Universe cosmological model.

Firsty, the model assumes a classical spacetime contractionary preiod - current observations rule out a contracting Universe now, and at any point in the future. Expansion continues until final entropy and heat death.
Secondly, A cyclical classical spacetime does not resolve the singularity, and as far as I am aware does not contain any modification to the EFE that results in a "cycle" and allows unification of QG and classical GR - theory still breaks down at the Planck scale.

In my humble opinion LQC is a far more elegant solution, this assumes we are on a current "bounce" from a previously contracting classical spacetime or from random quantum fluctuations. For me LQC is a more elegant solution as the quantum effect of gravity can modify classical GR to cause a "bounce" without need for the current "bounce" entering a future contraction period. Thus LQC requires less caveats and is more observationally accurate than a cyclical theory.
 
  • #10
Skaperen said:
There is no evidence to refute it, either.
Except for the fact that the vast, vast majority of unevidenced assertions are wrong. Every once in a while you may come across a correct one, but those instances are quite rare.
 
  • #11
Skaperen said:
There is no evidence to refute it, either.
Perhaps. But you said "Yes it will" happen, and I'm simply pointing out that there is no evidence to support this assertion. If there is no evidence pointing definitively in either direction, then we simply don't know the answer. Why not just say that?
 
  • #12
Cosmo Novice said:
There are 2 major problems with the cyclical Universe cosmological model.

Firsty, the model assumes a classical spacetime contractionary preiod - current observations rule out a contracting Universe now, and at any point in the future.

Penrose's CCC doesn't require a recontraction.
 
  • #13
bcrowell said:
Penrose's CCC doesn't require a recontraction.

Ah yes. I am not overly familiar with this cosmological model so I will look further into this.

Many thanks for the information, do you happen to have any Arxiv or similar references? If not I will search for the relevant material.
 
  • #14
bcrowell said:
Penrose's CCC doesn't require a recontraction.
True, but Penrose's CCC also has no physical justification. It's an idea without any physical mechanism whatsoever that suggests it is in any way plausible, and what we know about quantum gravity (that horizons have actual, physical sizes that have real meaning) strongly indicates that it isn't possible.
 
  • #15
Cosmo Novice said:
Ah yes. I am not overly familiar with this cosmological model so I will look further into this.

Many thanks for the information, do you happen to have any Arxiv or similar references? If not I will search for the relevant material.
I wouldn't recommend it. As ideas go, this one belongs in the crackpot bin. To give you a rough idea of just how bad CCC is, in order to claim evidential support for it by looking at the CMB, Penrose and his co-author, Gurzadyan, mistook the word "random" to mean "uncorrelated". It turns out that the correlations on the CMB are what the entire field of CMB science is all about, and not knowing about statistical correlations is just plain sad.
 
  • #16
Cosmo Novice said:
Ah yes. I am not overly familiar with this cosmological model so I will look further into this.

Many thanks for the information, do you happen to have any Arxiv or similar references? If not I will search for the relevant material.

He wrote a popular-level book about it: Cycles of Time: An Extraordinary New View of the Universe. I learned a lot from the book that was interesting and that remains important and valid regardless of whether CCC is right.
 

1. What is the cyclic universe theory?

The cyclic universe theory posits that our universe goes through cycles of expansion and contraction, with each cycle starting anew after the previous one ends. This theory suggests that the universe has no beginning or end, but instead has existed in an endless series of cycles.

2. How does the cyclic universe theory differ from the Big Bang theory?

The Big Bang theory proposes that the universe began with a single massive explosion, while the cyclic universe theory suggests that the universe has been cycling through periods of expansion and contraction for eternity. Additionally, the cyclic universe theory allows for the possibility of multiple universes, while the Big Bang theory focuses solely on our own universe.

3. What evidence supports the cyclic universe theory?

Some evidence that supports the cyclic universe theory includes the observation of cosmic microwave background radiation, which is believed to be leftover energy from the previous cycles of the universe. Additionally, the theory has been mathematically modeled and found to be consistent with our current understanding of physics.

4. How does the cyclic universe theory address the concept of time?

The cyclic universe theory suggests that time is cyclical and has no beginning or end. It also proposes that time is not linear, but instead repeats itself in each cycle. This idea challenges our traditional understanding of time as a linear progression.

5. What are some potential implications of the cyclic universe theory?

If the cyclic universe theory is proven to be true, it would have significant implications for our understanding of the origin and fate of the universe. It would also challenge our concept of time and the idea of a singular beginning or end. Additionally, it could have implications for the existence of other universes and the possibility of eternal existence.

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