Could the Early Universe Have Collapsed into Black Holes?

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Discussion Overview

The discussion centers around the question of whether the early universe could have collapsed into black holes, exploring concepts related to density, expansion, and the implications of general relativity. The scope includes theoretical considerations and conceptual clarifications regarding the nature of the early universe and black holes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses skepticism about the possibility of the early universe being more compact than a black hole, questioning how it could expand under such high density.
  • Another participant emphasizes that the expansion of the universe is a mathematical prediction of general relativity, which allows for spacetimes that expand from dense states.
  • A different viewpoint highlights that the symmetry of matter distribution in the early universe leads to expansion, contrasting it with the spherical symmetry of black holes that results in static spacetimes.
  • One participant clarifies that the early universe should not be thought of as a black hole, describing it instead as a unique case of quantum phenomena.
  • A later reply acknowledges the helpfulness of the previous explanation, indicating engagement with the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the early universe and its relationship to black holes, with no consensus reached on whether the early universe could have collapsed into black holes.

Contextual Notes

Participants note the importance of mathematical predictions from general relativity and the implications of symmetry in matter distribution, but the discussion does not resolve the complexities surrounding these concepts.

Constantin
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I can't imagine an object more compact than a black hole for a certain radius and personally don't think it makes sense. Yet for earlier stages of the Universe, without a variable c , it gets far more compact than a black hole.

Shouldn't major parts of the early universe simply collapse into black holes when such a density is present ? I mean for such a density the escape velocity would be far higher than c for major parts of the Universe, so how could it keep expanding ?
And yes I did see explanations like, the space itself was expanding, but it doesn't sound convincing.

Please let me know your thoughts.
Thank you
 
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Constantin said:
And yes I did see explanations like, the space itself was expanding, but it doesn't sound convincing.
Presumably you've seen this page? Anyway, the issue isn't whether verbal descriptions sound convincing to our intuitions, it's a mathematical matter of what is actually predicted by the equations of general relativity, and in this case you can find spacetimes that satisfy these equations everywhere that expand from such dense states.
 
I think what it really comes down to is the symmetry of the matter distribution. The early universe is expanding not just because we say so, but because that's what general relativity says will happen if you fill the universe with a uniform and isotropic energy density. In this case, there is no spatial curvature, but there is still a dramatic effect on spacetime by way of the time coordinate -- the universe expands!

On the other hand, a black hole exhibits spherical symmetry. In this case general relativity gives you a static spacetime with the well known event horizon.

I think the main point of confusion is that people often imagine the big bang as some singular point of high energy density. In fact, cosmology has nothing to say about The Big Bang itself, and most cosmologists use the term "big bang" to refer to the earliest moments in the expansion history of our observable part of the universe. These earliest moments are most accurately described by a uniformly expanding space with a homogeneous energy density.
 
The very early universe was not a black hole. It was a unique case of quantum weirdness.
 
bapowell, thank you for your answer. It is very helpful.
 

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