Undergrad The observable Universe and its shape

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SUMMARY

The discussion centers on the shape and expansion of the universe, using the balloon analogy to explain its properties. Participants clarify that while the observable universe appears spherical, its actual shape may be flat or have other geometries, as supported by current cosmological evidence. The universe does not have a measurable thickness, and concepts like curvature and expansion are discussed in relation to General Relativity. The conversation emphasizes that the universe is likely infinite, with no defined edges or centers, challenging traditional notions of shape and size.

PREREQUISITES
  • Understanding of General Relativity and its implications on cosmology
  • Familiarity with the balloon analogy in explaining cosmic expansion
  • Knowledge of observable universe concepts and light travel time
  • Basic grasp of cosmological parameters like curvature and density
NEXT STEPS
  • Research the implications of General Relativity on cosmic shape and expansion
  • Explore the balloon analogy and its limitations in cosmological discussions
  • Study the evidence for the flatness of the universe and its implications
  • Investigate the concept of infinity in cosmology and its philosophical implications
USEFUL FOR

Astronomers, cosmologists, physics students, and anyone interested in understanding the complexities of the universe's shape and expansion dynamics.

  • #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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