Did Inflation Solve the Problem of the Universe's Original Gravity?

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Discussion Overview

The discussion revolves around the role of inflation in relation to the original gravity of the universe and its implications for the Big Bang theory. Participants explore concepts of gravity, escape velocity, and the nature of the singularity, debating whether inflation was necessary to overcome the gravitational forces present at the universe's inception.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants assert that the original gravity of the universe would create a black hole, raising questions about how the universe could have begun under such conditions.
  • There is a suggestion that inflation must have been a mechanism stronger than gravity to allow the universe to begin, with some participants questioning the sufficiency of gravity alone.
  • One participant emphasizes that inflation is not a force but rather an event, which complicates the understanding of its role in overcoming gravity.
  • Another viewpoint introduces the idea that gravity may have acted as a repulsive force due to negative pressure during inflation.
  • A later reply discusses alternative models, such as those proposed by Linde, which suggest starting from a state of eternal inflation rather than a singularity, indicating that the nature of inflation and the initial conditions of the universe are still open questions.
  • One participant challenges the notion of the initial singularity being a black hole, suggesting that the dynamics of the universe's expansion at t = 0 could explain its behavior differently than static black hole solutions.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the relationship between inflation and gravity, with no consensus reached on the necessity of inflation or the nature of the singularity.

Contextual Notes

Participants highlight various assumptions about gravity, inflation, and the initial conditions of the universe, indicating that the discussion is limited by the definitions and interpretations of these concepts.

Macro
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The gravity of the orginal singularity would make it a black hole.
The original gravity of the universe would give it an escape
velocity; the escape velocity of the Big Bang.
In order to get the universe over its gravity there was an inflationary
epoch that rapidly brought the strength of gravity down everywhere
allowing the universe to really begin.

This is the purpose of inflation: to get the universe over its original
gravity.

Anybody want to argue that the universe didn't begin with gravity?
Then Hawking's No Boundary Proposal is violated and the
there really are "Universal Boundaries" or space then No space.
You can't have it both ways Hawking! :-p

Mitch Raemsch
 
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Macro said:
The gravity of the orginal singularity would make it a black hole.

If the singularity were indeed a black hole,then how could the universe (as weknow it) have begun?
Macro said:
The original gravity of the universe would give it an escape
velocity; the escape velocity of the Big Bang.
In order to get the universe over its gravity there was an inflationary
peoch that rapidly brought the strength of gravity down everywhere
allowing the universe to really begin..

But, it becomes more and more difficult to obtain an escape velocity, as the gravity increase, doesn't it?So, there should have been some other mechanism acting at the time, which must have been much stronger than gravity, isn't it?Then, how can the universe begin only with gravity?
 
All that is necessary is for inflation to be a "stronger force" than gravity! :!)

What else is going to get the universe over its own gravity?
 
Macro said:
All that is necessary is for inflation to be a "stronger force" than gravity!

Inflation is not a force.It is an event.
 
As far as I'm aware gravity became a repulsive force under the tremendous negative pressure and for a tiny moment of time caused the inflation.
 
Macro said:
All that is necessary is for inflation to be a "stronger force" than gravity! :!)
What else is going to get the universe over its own gravity?

:!):!):!) God or natural selection! :-p :-p :-p
 
Better still you can follow Linde and others who prefer to start from the "largeness" of eternal inflation rather than the smallness of a singularity. This reverses things so that instead of an explosion of a hot point you get a bubble of cooling in a hot field.

And perhaps even the idea of inflation as a particular kind of state will eventually be replaced by some more general model of dimensional potential.

But certainly, the questions are still open enough that there is room for no singularity. And even inflation could be replaced by something that "looks a little like it" yet is actually quite different under the skin.

Cheers - John McCrone.
 
Macro said:
The gravity of the orginal singularity would make it a black hole.
The original gravity of the universe would give it an escape
velocity; the escape velocity of the Big Bang.
In order to get the universe over its gravity there was an inflationary
epoch that rapidly brought the strength of gravity down everywhere
allowing the universe to really begin.
This is the purpose of inflation: to get the universe over its original
gravity.
Anybody want to argue that the universe didn't begin with gravity?
Then Hawking's No Boundary Proposal is violated and the
there really are "Universal Boundaries" or space then No space.
You can't have it both ways Hawking! :-p
Mitch Raemsch
The initial singularity was not a black hole. Black holes are static solutions to Einstein's equations and the cosmological solution is dynamic. Thus, the fact that the universe did not collapse at t = 0 might be somehow explained by the value of the Hubble parameter (the speed of expansion) which was infinite at t = 0. On the other hand inflation takes place because there is an accelerated expansion of space, mantaining a constant (finite) Hubble parameter at some time after the big-bang.
 

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