Comments about "Shape of the universe" in Wikipedia

This document contains comments about the article "Shape of the universe" in Wikipedia

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In the last paragraph I explain my own opinion.

Contents

• 1. Shape of the observable universe
• 2. Curvature of the universe
• 3. Global universe structure
• 3.1 Infinite or finite
• 3.1.1 Bounded or unbounded
• 3.2 Curvature
• 3.2.1 Universe with zero curvature
• 3.2.2 Universe with positive curvature
• 3.2.3 Universe with negative curvature
• 3.2.4 Curvature: open or closed
• 3.2.5 Milne model ("spherical" expanding)
• 4. See also

Introduction

The article starts with the following sentence.

Cosmologists distinguish between the observable universe and the global universe.

The observable universe is not a physical concept.

Since light is observed to have a finite speed, the observable universe can be modeled as a sphere around the Earth with a diameter of 93 billion light-years (8.8×1026 m) and, assuming an isotropic nature, would be similar to any other vantage point.

The question of course is if the second part of this sentence is correct. Most probably it is not.

According to the book Our Mathematical Universe, the shape of the global universe can be explained with three categories:

1. Finite or infinite
2. Flat (no curvature), open (negative curvature) or closed (positive curvature)
3. Connectivity, how the universe is put together, i.e., simply connected space or multiply connected.

The exact shape is still a matter of debate in physical cosmology, but experimental data from various, independent sources (WMAP, BOOMERanG and Planck for example) confirm that the observable universe is flat with only a 0.4% margin of error.

This eliminates accelerated expansion.

1. Shape of the observable universe

As stated in the introduction, there are two aspects to consider:

1. its local geometry, which predominantly concerns the curvature of the universe, particularly the observable universe, and
2. its global geometry, which concerns the topology of the universe as a whole.

The only thing that is of physical interest is the universe as a whole.

2 Curvature of the universe

3. Global universe structure

4. References

4. See also

Following is a list with "Comments in Wikipedia" about related subjects

• Observable Universe Comments

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