Please explain the statement "the big bang happened everywhere at once"

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Discussion Overview

The discussion centers around the phrase "the big bang happened everywhere at once," exploring its implications and interpretations within the context of cosmology. Participants delve into the nature of space-time, the Big Bang theory, and the philosophical aspects of the universe's origin, with a focus on theoretical and conceptual understandings rather than definitive conclusions.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Philosophical

Main Points Raised

  • Some participants argue that the Big Bang represents a moment in time rather than a specific point in space, emphasizing that all points in the universe were equivalent at the beginning.
  • Others propose that the Big Bang theory is an abstract construct that describes the universe's expansion from a hot, dense state, suggesting that questions about "where" it happened are not applicable.
  • A participant notes the distinction between the Big Bang theory and the singularity, explaining that the singularity is a mathematical concept where physical laws break down, not a location in space.
  • Some express confusion about how a universal event could occur simultaneously across infinite space, questioning the intuition behind such a concept.
  • One participant highlights the philosophical implications of the Big Bang, suggesting that it raises questions about the nature of existence and the universe's origins.
  • Another participant mentions the role of inflation in cosmology, indicating that it alters the understanding of the Big Bang and may avoid the singularity traditionally associated with it.
  • There is a discussion about the potential for redefining the Big Bang to explore earlier states of the universe, although some express skepticism about the practicality of this approach.

Areas of Agreement / Disagreement

Participants exhibit a range of views on the interpretation of the Big Bang and its implications, with no consensus reached on the nature of the event or its philosophical ramifications. Disagreements persist regarding the understanding of space-time and the significance of the singularity.

Contextual Notes

Some statements reflect assumptions about the nature of space and time that may not be universally accepted. The discussion includes references to mathematical concepts and theoretical frameworks that are not fully resolved, indicating limitations in the current understanding of cosmological events.

  • #151
"the comoving frame coordinate system"... an expanding system of coordinates, very interesting, I'm looking into this... I think many questions will be answered. Thanks, Ken G!
 
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  • #152
If the Universe in now flat, it must also be infinite. If it is infinite now, it must have always been infinite, even at that singularity at time zero.

Please see the thread: Big Bang Singularity.
 
  • #153
Buzz Bloom said:
If it is infinite now, it must have always been infinite, even at that singularity at time zero.

No, this is not correct. The singularity at "time zero" is not part of spacetime, so it is meaningless to ask whether or not the universe was spatially infinite there. (Also, the model in which this singularity appears is not the actual Big Bang model used in cosmology; that model leaves it open what came before the inflationary era, and does not make any claims about an initial singularity.)
 
  • #154
PeterDonis said:
No, this is not correct. The singularity at "time zero" is not part of spacetime, so it is meaningless to ask whether or not the universe was spatially infinite there.

Hi PeterDoris::

Thank you for you comment.

I am OK with the concept that the singularity is not part of spacetime, but that would also imply it is not a point either, wouldn't it?

I also understand that the current thinking about the singularity is that in first Planck time (5.4 x 10^-44 secs) of the universe, a General Relativity (GR) model would have to be replaced by some currently unspecified quantum model. However, my comment is about extraolating the geometry of the spacetime of an infinite GR model to time zero. This extrapolation would not not result in a point; the spacetime would remain infinite.

I started a thread on this point and my impression of the consensus of the responses there seem to agree with the above point of view. Please see
Big Bang Singularity.
 
  • #155
Buzz Bloom said:
...that would also imply it is not a point either, wouldn't it?
Correct, and this is exactly what was already explained to you in the other thread. "Singulaity" does not mean "point" except in the phrase "this is the point where the math model breaks down" in which case it mean "place" not a dimensionless point.
 

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