Which of 4 Universe Scenarios Do You Believe In?

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In summary, the current experimental data allows for four scenarios for the universe: closed but expanding forever, closed ending in a finite time by Big Rip, open and expanding forever, or open ending by Big Rip. However, we do not yet know the makeup or behavior of dark energy, making it difficult to determine which scenario is most likely. Belief should not play a role in scientific discussions, and while Einstein had good intuition, he also made mistakes. His belief in a steady state universe and rejection of the Copenhagen Interpretation of quantum mechanics were disproven by further evidence. The universe's past and future eternity, as well as the validity of the cosmic darwinism theory, are still unknown and should not be held onto until further evidence is
  • #1
Dmitry67
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I assume that current experimantal data allows to exclude only some scenarios, for example, closed Universe: Big Bang->Big Cranch

We know that Universe is almost flat, but we don't know if it is closed or open. We also don't know how 'strong' the Dark Energy is: is it just a Cosmological constant or Quintessence.

It gives 4 scenarios compatible with the current experimantal data:
1. Closed but expanding forever
2. Closed, ends in a finite time by Big Rip
3. Open, expanding forever
4. Open, ends by Big Rip.

What is your favourite one you believe in?

P.S. I know there is a special case with a flat universe, but I don't know, in case of Quintessence or Cosmological constant if it flat now is it flat forever, or curvature becomes negative when universe expands and becomes more and more dominated by the Dark Energy?
 
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  • #2
Dmitry67 said:
I assume that current experimantal data allows to exclude only some scenarios, for example, closed Universe: Big Bang->Big Cranch
Not necessarily. We don't yet know the makeup of the dark energy, and until we do, we can't say much definitive about the future expansion of our universe.

However, the trend so far is that it seems likely to continue expanding forever, driven by the dark energy, and thus any small deviations from flatness won't matter one bit.

Dmitry67 said:
We know that Universe is almost flat, but we don't know if it is closed or open. We also don't know how 'strong' the Dark Energy is: is it just a Cosmological constant or Quintessence.
Well, we know very accurately how "strong" it is. What we don't know is how it changes with time.

Dmitry67 said:
What is your favourite one you believe in?
Belief in these matters is silly. The real world is a certain way. We don't yet know all of the precise details of that. But attaching ourselves to one or another option before the evidence is in just biases the results.

Dmitry67 said:
P.S. I know there is a special case with a flat universe, but I don't know, in case of Quintessence or Cosmological constant if it flat now is it flat forever, or curvature becomes negative when universe expands and becomes more and more dominated by the Dark Energy?
The curvature doesn't change with time. It's just a part of the initial conditions. But its effect is diluted by the expansion as [tex]1/a^2[/tex]. If the dark energy continues to dilute more slowly than this, as it has done so far, then the effects of the curvature will continue to decrease with time.
 
  • #3
Chalnoth said:
Belief in these matters is silly.

No, like Einstein said "I don't believe that God plays dice"
Was it silly?
 
  • #4
Dmitry67 said:
No, like Einstein said "I don't believe that God plays dice"
Was it silly?

It is silly to draw an analogy between an out of context comment and the scientific method. As Chalnoth says, belief does not come into science: the 'correct' theory is the one that matches the observational evidence best, not the one that you 'believe' most.
 
  • #5
Dmitry67 said:
No, like Einstein said "I don't believe that God plays dice"
Was it silly?
Pretty much, especially since he was fundamentally wrong on the question of reality to which he was referring at the time.
 
  • #6
Ha! He called the cosmological constant his biggest mistake - et voila - he was actually right, it is non-zero!

He said "I don't believe that God plays dice" - and Copenhagen Interpretation is less and less popular, in QM we are discussing here Bohmian (deterministic) or MWI (deterministic), but you can find only few threads about the CI

He believed in the Universe existed for eternity, and now look - we are discussing the eternal inflation/cosmic darwinism scenarions.

He had very good intuition!
 
  • #7
Dmitry67 said:
Ha! He called the cosmological constant his biggest mistake - et voila - he was actually right, it is non-zero!
Except it still was a pretty darned big mistake on his part, because he attempted to use the cosmological constant to balance the expansion so that there could be a steady state universe. This approach was roundly disproven by Hubble's observation of the expansion. The fact that the cosmological constant appears to be non-zero (we don't yet know for sure) doesn't make this a non-mistake.

Dmitry67 said:
He said "I don't believe that God plays dice" - and Copenhagen Interpretation is less and less popular, in QM we are discussing here Bohmian (deterministic) or MWI (deterministic), but you can find only few threads about the CI
Except here he was, if I remember correctly, attempting to find a hidden variable theory, an attempt which wholly failed.

Look, Einstein was a really great physicist, who completely transformed our view of how the world works. But like every scientist, he made mistakes. Taking somebody at their word just because of who they are or what they have done is a huge mistake.

Dmitry67 said:
Ha! He called the cosmological constant his biggest mistake - et voila - he was actually right, it is non-zero!
Except it still was a pretty darned big mistake on his part, because he attempted to use the cosmological constant to balance the expansion so that there could be a steady state universe. This approach was roundly disproven by Hubble's observation of the expansion. The fact that the cosmological constant appears to be non-zero (we don't yet know for sure) doesn't make this a non-mistake.

Dmitry67 said:
He believed in the Universe existed for eternity, and now look - we are discussing the eternal inflation/cosmic darwinism scenarions.
Eternal inflation is eternal into the future, not the past. Cosmic Darwinism is generally considered to be extremely unlikely. In any case, we just don't know whether or not the universe is eternal into the past, and it's foolish to hold too strongly to one or another option until the evidence is in.
 

1. What are the four universe scenarios?

The four universe scenarios are the Big Bang model, the Steady State model, the Inflationary model, and the Multiverse theory.

2. Which universe scenario is the most widely accepted by scientists?

The Big Bang model is the most widely accepted scenario among scientists. It is supported by a large body of evidence, including the cosmic microwave background radiation and the observed expansion of the universe.

3. Can you explain the Inflationary model in simple terms?

The Inflationary model proposes that the universe underwent a rapid period of expansion in the first fraction of a second after the Big Bang. This expansion occurred at a much faster rate than the current expansion of the universe, and is thought to explain some of the observed properties of the universe today.

4. What is the Multiverse theory?

The Multiverse theory suggests that our universe is just one of many universes that exist, each with its own set of physical laws and properties. This theory is still highly debated and has not been proven.

5. Is it possible to prove which universe scenario is correct?

At this time, it is not possible to definitively prove which universe scenario is correct. Each scenario has its own supporting evidence and limitations, and scientists continue to research and gather data to better understand the origin and nature of the universe.

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