The observable Universe and its shape

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Discussion Overview

The discussion revolves around the shape of the observable universe, exploring analogies such as the surface of a balloon, the implications of cosmic expansion, and the nature of curvature in cosmological models. Participants delve into theoretical considerations, observational implications, and the limitations of current understanding regarding the universe's geometry.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that the universe can be likened to the surface of a balloon, expanding as the balloon inflates, suggesting that traveling in a straight line would eventually return one to the starting point.
  • Others argue that while this analogy is useful for understanding expansion, it is imperfect and does not accurately represent the universe's actual shape or structure.
  • There is a claim that the observable universe is a sphere, but this is contested as it may not reflect the true nature of the universe beyond what is observable.
  • Some participants note that the curvature of the observable universe appears consistent with flatness, while others highlight that evidence supports multiple geometries, including spherical and flat models.
  • Discussions include the implications of dark energy on curvature and the potential for measuring spatial curvature, with varying opinions on whether flatness should be considered the null hypothesis.
  • Participants discuss the nature of free parameters in cosmological models, debating whether curvature should be treated as a free parameter or a necessary aspect of the model derived from General Relativity.
  • There is a contention regarding the interpretation of the universe's expansion, with some asserting that it does not originate from a central point, challenging the notion of a spherical shape.
  • One participant emphasizes that the universe is conceptualized as "everywhere," lacking measurable shape, size, or center, which complicates the understanding of its geometry.

Areas of Agreement / Disagreement

Participants express a range of views on the shape and curvature of the universe, with no consensus reached. Disagreements persist regarding the validity of the balloon analogy, the implications of curvature, and the interpretation of expansion dynamics.

Contextual Notes

Limitations include the dependence on analogies that may not fully capture the complexities of cosmic geometry, as well as unresolved questions about the nature of curvature and its implications for cosmological models.

  • #61
Droidriven said:
From whatever vantage point you are in at the time.
Yes, but 'frame of reference' is the usual term
 
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  • #62
Droidriven said:
I think you're improperly editing the posts you are quoting, make sure the

if I do this correctly the 'Lol, you did it again, look at your post.' will be missing.
 
  • #63
tobyr65 said:
if I do this correctly the 'Lol, you did it again, look at your post.' will be missing.
You got it, you just needed to the first quote tab with my username and post to be at the beginning of my post, then my entire post after that and a quote tab on the end and my whole post would display.

You don't see a "quote" button or a "reply" button under everyone's posts? Are you using PC/mobile browser or a mobile app to view the forum?

Anyway, this is off topic, I'm just trying to help save the confusion of quoting everyone and everyone quoting you.
 
  • #64
Droidriven said:
You don't see a "quote" button or a "reply" button under everyone's posts? Are you using PC/mobile browser or a mobile app to view the forum?

Anyway, this is off topic, I'm just trying to help save the confusion of quoting everyone and everyone quoting you.

I see them, I first used the reply but was told to use the info/help to do it right. That said to use the quote button which I do. But then I was deleting all but the quote part I wanted and leaving the bracketed, back slash QUOTE at the end. So to be clear I should leave in the beginning bracketed content and the end bracketed content?
 
  • #65
tobyr65 said:
I see them, I first used the reply but was told to use the info/help to do it right. That said to use the quote button which I do. But then I was deleting all but the quote part I wanted and leaving the bracketed, back slash QUOTE at the end. So to be clear I should leave in the beginning bracketed content and the end bracketed content?
Yes, leave the first quote bracket with the username, post number and member ID number inside the bracket, then the quoted post with a quote bracket on the end.
 
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  • #66
Droidriven said:
Yes, leave the first quote bracket with the username, post number and member ID number inside the bracket, then the quoted post with a quote bracket on the end.
And what is this reply do?
 
  • #67
tobyr65 said:
And what is this reply do?
Quote quotes, reply just replies

Now, back to topic
 
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  • #68
rootone said:
We do know that our observable universe is spherical and the centre of it is somewhere between your eyeballs.
Droidriven said:
From whatever vantage point you are in at the time.

To be as exact as I can be: The observable universe is a sphere centered between the average location of all your sensors looking outwards from your position in time looking backwards.
 
  • #69
Everybody: the observable universe is not positively "spherical" in the sense of having positive curvature. The curvature of the observable universe is zero to within a percent, making it consistent with flatness. The universe *does* have spherical symmetry, on account of global isotropy.
 

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