What existed before the big bang?

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In summary, the conversation discusses different theories and models regarding the origin of the universe. Some suggest that time and space emerged with the big bang and the concept of "before" is irrelevant, while others propose the idea of a cyclical universe or multiple universes. There are also discussions about the limitations of using general relativity to predict the earliest stages of the big bang and the need for a theory of quantum gravity. Ultimately, there is no clear answer to the question of how the universe came into existence, and it may not be a question that can be answered by science.
  • #36
hellfire said:
You might be interested in this.

Yes! I knew of that paper! it is a strange offbeat paper because it USES the cushioning effect of LQG repulsive gravity (which I personally tend to think as having a good chance of being real) to

cushion the collision of two imaginary objects (which I personally tend to think are pure fantasy)

so it is in a way like "a real toad in an imaginary garden"

this was how a poet once defined what a poem does.

I didnt want to mention that paper----which I think is the exception that proves the rarity of crossover. there is ALMOST no crossover between loop cosmology and braneworlds----and the one exception that one knows about (both you and I) is this strange paper where loop gravity is the quantum padding between two branes so they don't even have to touch when they collide and rebound

In case anyone is reading and hasnt seen this paper that hellfire was referring to:

http://arxiv.org/abs/hep-th/0407115
Loop Quantum Gravity and the Cyclic Universe
Martin Bojowald, Roy Maartens, Parampreet Singh
6 pages, 4 figures; v2: minor changes to match PRD version
Phys.Rev. D70 (2004) 083517
"Loop quantum gravity introduces strong non-perturbative modifications to the dynamical equations in the semi-classical regime, which are responsible for various novel effects, including resolution of the classical singularity in a Friedman universe. Here we investigate the modifications for the case of a cyclic universe potential, assuming that we can apply the four-dimensional loop quantum formalism within the effective four-dimensional theory of the cyclic scenario. We find that loop quantum effects can dramatically alter the near-collision dynamics of the cyclic scenario. In the kinetic-dominated collapse era, the scalar field is effectively frozen by loop quantum friction, so thatthe branes approach collision and bounce back without actual collision.
 
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  • #37
Perhaps Mathmatically Zero is the answer. Negative would not be possible implying "before". But that for reasons yet to be discovered zero became positive and BOOM! the universe started with a singularity that was unstable. Perhaps there are a million, million billion zeros each second in this and other diamensions of non-reality that stay stable and no booms, along with other million, million billion zeros becoming unstable.
 
  • #38
Before and after our BB

time traveller d said:
i all ways wonder this. what existed before the big bang?

What else than an ever existing swinging " Infinity-verse" ?:smile:
 
  • #39
I am prejudiced in favor of the net zero energy universe model - it preserves causality, IMO.
 
  • #40
before and after our bb

Chronos said:
I am prejudiced in favor of the net zero energy universe model - it preserves causality, IMO.
To me N.Z.E.U.M. preserves incomprehensibility. Symmetry is elegant and beautiful, but isn't like throwing away the baby and the bathwater? Is N.Z.E.U.M. the only way (if it really is?) to preserve causality?
"If you are to describe the 'truth', leave elegance to the taylor."
(Albert Einstein)
 
  • #41
I admit believing NZE is necessary to preserve causality in an FRW universe.
 
  • #42
Before and after the BB

Chronos said:
I admit believing NZE is necessary to preserve causality in an FRW universe.
To me belief seems like a 'well' adapted boundary/frontier. Interest in what is behind or beyond seems to stop there. I don't want to live in such a prison.
 
  • #43
Possible Pre Big Bang Scenarios

time traveller d said:
i just came up with a theory. another universe. maybe when a
universe ends it explodes in a big bang and creates another universe. what do you guys think?

My understanding is that experts like Hawking describe three posible scenarios. 1) The big bang singularity, whatever its cause, or lack thereof, began as a unique event with "creation of everything out of nothing" which jibbed well with othrodox Christians because of the the book of Hebrews says something akin to "it is by faith that we believe God created everything that is seen from what is not seen" and was interpreted by orthodox theologians as meaning creation 'ex nihilo' (out of nothing)

the second scenario is that some other universe existed, with unknown properties and collapsed into a black hole time of effect until so much "stuff" was packed into the singularity that it exploded into the big bang.

Scenario three is that the universe is in a continuous oscillation of collapsion. expansion with infinite big bangs/big crunches. But this teory is kind of pooched if the new data on universal expansions is correct that the expansion rate is actually accelerating, meaning that the universe will never collapse regardless of <> omega mass (or whatever it's called, fravity of the total mass of the universe overcoming the inertia of the expansion) On the other hand, until we know why the expansion is accelerating, its kind of illogical to assume that the acceleration is permanent; perhaps there will, for some reason, be an eventually deceleration. Until there is more data, such theories require almost as much blind faith as religion (no snub intended)
 

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