Infinite Universe: Can It Ever End?

In summary, it is unlikely that an infinite Universe could ever end, either in space or in time, according to the current understanding of general relativity. However, there is still much to be explored and discovered in the realm of quantum gravity that may shed new light on the potential fate of the Universe.
  • #1
Einstein's Cat
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2
Could an infinite Universe ever end?
 
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  • #2
No. By definition.
 
  • #3
Einstein's Cat said:
Could an infinite Universe ever end?

If by "end" you mean "end in space", then obviously not, as DaveC426913 pointed out.

If by "end" you mean "end in time", i.e., "come to an end", then according to GR, no; any spatially infinite universe must keep expanding forever.
 
  • #4
PeterDonis said:
If by "end" you mean "end in time", i.e., "come to an end", then according to GR, no; any spatially infinite universe must keep expanding forever.

I didn't know that. Care to elucidate?
 
  • #5
Hornbein said:
Care to elucidate?

There are no solutions in the FRW family of spacetimes that are spatially infinite and recollapse; all of the spatially infinite solutions expand forever. The only solutions that recollapse are spatially finite (closed universes--but not even all of those recollapse, some, with positive cosmological constant, expand forever).
 
  • #6
PeterDonis said:
If by "end" you mean "end in space", then obviously not, as DaveC426913 pointed out.

If by "end" you mean "end in time", i.e., "come to an end", then according to GR, no; any spatially infinite universe must keep expanding forever.
I'm not sure that's true. You could have universe with a negative cosmological constant and open curvature that recollapses. However, it might not "end" in the sense that quantum gravity might demonstrate that something happens after the recollapse.
 
  • #7
Chalnoth said:
You could have universe with a negative cosmological constant and open curvature that recollapses.

Hm, yes, you're right. (I think a flat universe could also recollapse with a negative cosmological constant.) AFIAK, nobody has proposed that such a model might describe our actual universe, so it would not be relevant in a practical sense, but as a matter of theory, yes, such a model could be spatially infinite and recollapse.

Chalnoth said:
it might not "end" in the sense that quantum gravity might demonstrate that something happens after the recollapse.

Yes, agreed; this would be true of closed models that recollapse as well.
 

Related to Infinite Universe: Can It Ever End?

1. What is the concept of an infinite universe?

The concept of an infinite universe is based on the idea that the universe is boundless and has no end. This means that there is no limit to the size or extent of the universe, and it continues to expand infinitely in all directions.

2. Is there any evidence to support the idea of an infinite universe?

There is currently no conclusive evidence to prove or disprove the concept of an infinite universe. However, many theories in physics and cosmology, such as the inflationary model of the universe, suggest that the universe may indeed be infinite.

3. Can an infinite universe ever end?

Based on our current understanding of the universe, it is unlikely that an infinite universe will ever come to an end. This is because an infinite universe does not have a boundary or edge, and therefore, there is no way for it to reach an end.

4. How does the concept of an infinite universe affect our understanding of time?

The concept of an infinite universe has a significant impact on our understanding of time. In an infinite universe, time is also infinite and has no beginning or end. This means that events can occur infinitely in the past and future, and the concept of a beginning of the universe is not applicable.

5. What are the implications of an infinite universe for the search for extraterrestrial life?

If the universe is truly infinite, it means that there are an infinite number of stars, planets, and galaxies, and therefore, the likelihood of other forms of life existing in the universe increases significantly. However, the vastness and infinite nature of the universe also present challenges in detecting and communicating with any potential extraterrestrial life forms.

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