What Models Explain the Expansion of the Big Bang?

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Discussion Overview

The discussion revolves around the various models that explain the expansion of the universe as a result of the Big Bang. Participants explore theoretical frameworks and interpretations related to the nature of this expansion, including concepts of infinity and finite space.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant presents four potential models for the expansion of the universe: 1) An expanding infinity, 2) local expansion with an area of non-expansion beyond our range of observation, 3) local expansion with an area of non-expansion in some higher dimension, and 4) finite expansion without anything outside the area of expansion.
  • Another participant expresses a preference for models 1) and 4), linking them to the standard cosmological model (LambdaCDM) and discussing their implications regarding spatial flatness and volume.
  • A different participant suggests that the options presented are not definitive choices but rather directions influenced by observational evidence, emphasizing the role of theory in scientific prediction.
  • One participant raises a question about the comprehension of infinite versus finite concepts, suggesting that laypersons may struggle with the implications of "actual infinity" and the boundaries of finite space.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the models presented, with some favoring specific options while others challenge the framing of these models as choices. The discussion remains unresolved regarding the completeness and validity of the proposed models.

Contextual Notes

There are limitations in the discussion regarding the definitions of infinity and finite space, as well as the implications of the models in relation to observational evidence and theoretical predictions.

Pjpic
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What are the acceptable models to eplain how the big bang is expanding the space of our visible universe? Are these the choices? 1) An expanding infinity 2) local expansion with an area of non-expansion beyond our range of observation 3) local expansion with an an area of non expansion in some higher dimension 4) finite expansion without anything outside the area of expansion. Are the other choices?
 
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I don't know any other possibilities, if I understand the alternatives you present. I personally like 1) and 4). They seem to be the two possibilities you have in the standard cosmological model (LambdaCDM)

Pjpic said:
What are the acceptable models to explain how the big bang is expanding the space of our visible universe? Are these the choices?

1) An expanding infinity
...
4) finite expansion without anything outside the area of expansion
...

Your option 1) would be the LCDM model with Omega=1. Which means spatially flat, and assuming no exotic complications, infinite spatial volume.
Your option 4) would be the LCDM with Omega > 1. A finite spatial volume like the 3D analog of the 2D surface of a balloon with noting inside or outside the 2D surface. An expanding finite volume without anything else---no other space of any dimensionality.

That doesn't cover before the big bang, where there might be a contracting region. but that is not what you were asking about. You were focusing on the expanding space directly connected with what we can see. I think your four possibilities cover all the pictures people have of that. Hope someone will correct me if I am forgetting about something.
 
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They are not choices, merely nudges is the direction observational evidence steers the 'ship' of science. Theory is the term scientists prefer to predict the future course of the 'ship'.
 
I wonder if this is so difficult to comphrehend due to how infinite and finite are defined. Because, to a lay person; it doesn't seem like an "actual infinity" can be increased or that something finite would not have a boundary.
 

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