Infinite Universe: What does it mean?

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Discussion Overview

The discussion centers on the implications of an infinite universe, particularly in relation to the observable universe and the nature of matter and energy beyond its limits. Participants explore definitions and conceptual frameworks surrounding the finite versus infinite nature of the universe, including cosmological models and their geometrical interpretations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants express uncertainty about the implications of an infinite universe, particularly regarding the existence of matter and energy beyond the observable universe.
  • One participant suggests that if the universe is infinite, it would imply that matter/energy exists at distances greater than the observable universe, while another counters that "infinite" should not be conflated with "really, really large."
  • There is a proposal that matter/energy may extend beyond the observable universe with similar density, although this is contested by others who emphasize the lack of certainty in such assumptions.
  • A hypothetical model (Option D) is introduced, questioning whether an off-center observable universe could exist within a finite universe, leading to discussions about the implications of a center in the universe.
  • Another participant argues against the possibility of a center in the universe, citing the Cosmological Principle, which suggests that the universe is homogeneous and isotropic.
  • Concerns are raised about the implications of assuming a center in relation to the structure of the universe, with some participants expressing confusion over how finite and unbounded concepts apply to an open universe.

Areas of Agreement / Disagreement

Participants generally disagree on the implications of an infinite universe, particularly regarding the existence and distribution of matter beyond the observable universe. There is no consensus on the nature of the universe's geometry or the validity of the proposed models.

Contextual Notes

Participants acknowledge that definitions and assumptions play a critical role in the discussion, and there is an emphasis on the limitations of current knowledge regarding the universe's structure and extent.

  • #31
marcus said:
... The Hubble radius is just a handle on the speed of expansion of distances. Expansion speed is proportional ...

Can I just confirm, if something sent a signal today, & it was greater than the Hubble radius from us, could it reach us?
 
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  • #32
Lino said:
Can I just confirm, if something sent a signal today, & it was greater than the Hubble radius from us, could it reach us?

Yes! and there is a nice reason! The Hubble radius is reciprocal to the percentage rate of distance growth, so as the growth rate declines the Hubble radius increases.

It is not a physical distance between definite things, so it is to subject to cosmological metric expansion. But it can increase.

So it can REACH OUT AND GATHER IN light which may be struggling to reach us but being carried slowly back by the expansion of distance.

If the light starts out a little bit outside the Hubble radius TODAY, and at first is being swept slowly back, it still may be inside TOMORROW'S Hubble radius.

Once a flash of light is safely within the Hubble radius it is home free, it will eventually make it.
 
  • #33
marcus said:
Yes! and there is a nice reason! ...
Wow! Thank you ... it reads correctly & sense-aguilie (?), but I need to think about it :)

Thanks Marcus.
 

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