Center of the Universe: What Again

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Discussion Overview

The discussion revolves around the concept of the universe's size and whether it has a physical center. Participants explore the implications of the observable universe's diameter, the nature of observation, and the potential for differing views of the universe based on directionality.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant notes the universe's estimated diameter of about 95 billion light years and questions the implications of this measurement suggesting a physical center, despite claims that there is no center to the universe.
  • Another participant emphasizes the term "observable universe," suggesting that since we can see in all directions, we are at the center of the observable part.
  • Several participants question whether the distance to the extremes of our view is uniform in all directions, speculating that if it is, it could imply a central position for Earth.
  • One participant argues that the laws of physics suggest the observable universe should have the same diameter in all directions, reinforcing the idea of a uniform observable universe.
  • Another participant points out that there are limits to how far we can see due to the beginning of time and the nature of light, which complicates the understanding of the universe's edges.
  • A participant references the Cosmic Microwave Background (CMB) and its uniform redshift, suggesting that it provides evidence for a consistent observable universe across all directions.
  • One participant draws an analogy between the observable universe and the observable Earth, suggesting that while individual perspectives differ, they are all centered on the observer's location.

Areas of Agreement / Disagreement

Participants express differing views on whether the observable universe implies a center, with some arguing for a central position based on observation and others asserting that the universe lacks a physical center. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants highlight limitations in current observational technology and the historical context of the universe's formation, which may affect interpretations of the observable universe's structure.

trainman2001
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I've recently read that the universe is now estimated to be about 95 billion light years in diameter. This was based on what we now can observe (Hubble Deep Field for example), what is estimated to be seen with new technology (James Webb) and an estimate of what's beyond that which we can't yet image. That being said, doesn't the word "diameter" imply a physical center? I've read many of the threads about how there is NO center to the universe as we now understand it, and then I read a description of the SIZE of the universe implying a physical shape with the normal attributes of shapes about which we are familiar. And then I get completely confused. Furthermore, the latest graphic images that depict the arrangement of local groups, clusters and super clusters again show a universe that is physical with a definable center. Could someone please help me grasp this apparent inconsistency? And that's not even getting into when we do visualize the extremes of our universe, what's beyond that edge.
 
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The word observable has been left, i.e., it should "the observable universe". Since we can see in all directions, we are at the centre of the part of the universe that we can observe.
 
Is that true? Is the distance to the extremes of our view the same in all directions? If so, then I guess we are the center of the universe. Some people have always acted like they were. Perhaps they were right all along. We haven't taken a deep field view looking in all directions I don't believe. I know it's been done twice looking in the Northern Hemisphere and then in the Southern. Perhaps it should be done in many directions and see what the numbers show regarding the farthest viewed galaxies.
 
trainman2001 said:
Is that true? Is the distance to the extremes of our view the same in all directions? If so, then I guess we are the center of the universe. Some people have always acted like they were. Perhaps they were right all along. We haven't taken a deep field view looking in all directions I don't believe. I know it's been done twice looking in the Northern Hemisphere and then in the Southern. Perhaps it should be done in many directions and see what the numbers show regarding the farthest viewed galaxies.

There is no reason to expect our view to extend to different distances in different directions. While we haven't taken a Hubble deep field quality image of the entire sky (it would take something like 10 million years), we have taken plenty of other surveys and our knowledge of the laws of physics appears to hold in all directions. These laws tell us that the observable universe should have the same diameter in all directions and that the diameter is approximately 95 billion light years.
 
There is a limit to how far we can see, it's not based on technology, it's because there was a beginning of time. As you look further out into space, you look backwards in time. There was a time before light could move freely, and then even more time where there was nothing interesting being created.
 
We have a full sky map of the CMB and found it to have a virtually identical redshift of about 1090 in every direction, A redshift of 1090 corresponds to a proper distance of about 46 billion light years and is a view of the observable universe when it was only a few hundred thousand years old. Only a neutrino or gravitational wave detector can possibily 'see' anything more distant than CMB photons [which are the most ancient of all photons in the universe]. We are still working on those.
 
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trainman2001 said:
Is that true? Is the distance to the extremes of our view the same in all directions? If so, then I guess we are the center of the universe. Some people have always acted like they were. Perhaps they were right all along. We haven't taken a deep field view looking in all directions I don't believe. I know it's been done twice looking in the Northern Hemisphere and then in the Southern. Perhaps it should be done in many directions and see what the numbers show regarding the farthest viewed galaxies.

The situation is similar to standing on the surface of the Earth. The distance to the horizon is the same in all directions (assuming no trees, mountains, etc.). The part of the Earth that you see out to the horizon constitutes the "observable Earth". My "observable Earth" is different from your "observable Earth", but they are both circular regions centered on where we are standing.
 

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