Are We in the Middle of the Universe?

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Discussion Overview

The discussion revolves around the concept of whether we are located in the middle of the universe, exploring the implications of the universe's shape, the observable limits of light, and the nature of speeds in relativity. Participants engage with theoretical considerations, observational constraints, and the implications of cosmological models.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that if the universe is expanding and we can only see a finite distance, it might give the impression that we are at the center of a spherical universe.
  • Others argue that every observer perceives themselves as being in the center of their observable universe, similar to standing on Earth and seeing a horizon.
  • There is a claim that the universe is infinite beyond certain distances, leading to the idea that it lacks structure beyond those scales.
  • One participant questions the terminology used in describing the observable universe versus the visible universe, suggesting a potential misunderstanding.
  • Some participants discuss the concept of closing speeds in relativity, noting that while closing speeds can exceed the speed of light, relative speeds cannot, leading to a nuanced discussion about the definitions involved.
  • There is a mention of the universe being flat as an approximation, which raises questions about how this fits with the observable spherical nature of the universe.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the shape and structure of the universe, the implications of observable limits, and the nature of speeds in relativity. The discussion remains unresolved, with no consensus on several key points.

Contextual Notes

Limitations include the dependence on definitions of observable versus visible universe, assumptions about the universe's structure, and the complexities of relativistic speeds that are not fully resolved in the discussion.

PrestonMcCall
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Are we in the middle of the universe? I mean, imagine the universe is some sperical or odd shaped three dimensional shape. We can 'see' out to some pint, but is it always a similar distance, making us iin the middle? It makes sense that if the outer edge of the universe is expanding at a rate greater than the speed of light, then we would only be able to see a finite distance and that it would be similar in distance from us? The light ohoton would never reach us from anywhere outside of the area speeding faster than the speed of light.
 
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The shape of the universe is unknown. The best analogy we have is that the universe is a sphere. thus is due to the light reaching us at the same time.
It is hard to tell where )or how large it is) in the universe we are due to this.
cheers, BT
 
Remember that light has only been traveling for ~13/14 billion years. That means we can only see anything that is up to 13/14 billion light years away. This is not limited in any direction, so we see everything 13/14 billion light years away in all directions, giving the appearance of us being in the centre of a sphere.
 
Every observer will see themselves to be in the center of their observable universe, just like when you stand on the surface of the Earth you are in the center of the region defined by your horizon. We don't know, and probably can never know, what is beyond our cosmological horizon.
 
everyone will see as if they are in the middle of the universe because it is infinite..pass 300pc or 300Mpc the universe has no structure
 
Is it theoretically 'allowed' for Mass A and Mass B to have a closing speed that is greater than C? e.g. Mass A is headed towards Mass B with its 'real' speed greater than .5 C, and Mass B is headed towards Mass A with its 'real' speed greater than .5 C.
Likewise for them to have a separating speed greater than C ?
 
No, this is covered in introductory relativity textbooks.
 
From wiki (observable uni)
The visible universe is thus a sphere with a diameter about 93 billion light-years.

Is this a mistake? Aren't they talking about observable not visible? Which visible means what we can see as in the only up to the cmb?
 
Chronos said:
No, this is covered in introductory relativity textbooks.

In a Synchrotron particles, that are each traveling at near the speed of light, are at times traveling towards each other and away from each other at a differential velocity much greater than C. This can't be taking place?
 
  • #10
seto6 said:
everyone will see as if they are in the middle of the universe because it is infinite..pass 300 pc or 300Mpc the universe has no structure

Something without shape or structure can exist? How?
 
  • #11
justwondering said:
Is it theoretically 'allowed' for Mass A and Mass B to have a closing speed that is greater than C? e.g. Mass A is headed towards Mass B with its 'real' speed greater than .5 C, and Mass B is headed towards Mass A with its 'real' speed greater than .5 C.
Likewise for them to have a separating speed greater than C ?

"Closing speed" can exceed c, Relative speed can't.

Closing speed is the apparent respective speed as seen by an observer not sharing a rest frame with either object. For example, if I see a particle coming from my left at 0.75c and one coming from my right at 0.75c, then according to me, the closing speed between the two is 1.5 c

Relative speed is the speed of one object with respect to another as measured from the rest frame of either object. It would be the speed either of the particles measures as the difference of velocity between the two, which would equal 0.96c in our example.

Closing speed is no more "real" than relative speed.
 
  • #12
Calluuuum said:
Remember that light has only been traveling for ~13/14 billion years. That means we can only see anything that is up to 13/14 billion light years away. This is not limited in any direction, so we see everything 13/14 billion light years away in all directions, giving the appearance of us being in the centre of a sphere.

If so, how is it that it is said that the universe is flat ?
 
  • #13
it is flat as an approximation, just like a plain on earth
 
  • #14
Janus said:
"Closing speed" can exceed c, Relative speed can't.

Closing speed is the apparent respective speed as seen by an observer not sharing a rest frame with either object. For example, if I see a particle coming from my left at 0.75c and one coming from my right at 0.75c, then according to me, the closing speed between the two is 1.5 c

Relative speed is the speed of one object with respect to another as measured from the rest frame of either object. It would be the speed either of the particles measures as the difference of velocity between the two, which would equal 0.96c in our example.

Closing speed is no more "real" than relative speed.

No .
 

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