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Did the big bang occur in empty space?

 
 
g day
 
Reply Sat 12 Apr, 2008 08:17 pm
I was pondering the Big Bang model and wondered what is it that allows physicists to predict it didn't happen in already occupied space? Its widely modelled as occuring as the creation event, but I pondered what specific evidence excluses it as just being a pivotal event in a region of already existing spacetime?

If tomorrow a spot just left of Jupiter went pop with say 10 ^ 80 joules of energy - how would someone living 14 billion years later and observing anywhere inside say a 30 - 100 billion lightyear wide shock front - and only able to observe within this shock front be able to say whether it exploded in empty space or already occupied space?

I would presume you still have the CMB, you still have local spacetime expanding with faster recession speeds the further you are from any point of reference - so what factors allows physicists to exclude this possibility and say instead all spacetime was created and expanded as a consequence of the big bang?

I have no bias either way - just curious how we can rule out the Universe being really large, and whether its in flux or steady state excluding that Big Bang type energy events happening periodically in certain localities within it?
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fresco
 
  2  
Reply Sun 13 Apr, 2008 01:06 am
Quote:
so what factors allows physicists to exclude this possibility and say instead all spacetime was created and expanded as a consequence of the big bang?


From a philosophical position....because that would incur the infinite regress of where the "first" space-time came from.
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g day
 
  1  
Reply Sun 13 Apr, 2008 02:21 am
er - regardless - you can't escape an inifinity somewhere...

It doesn't matter if you go endless existence (infinite time), multiverse - infinite spacetime... M-theory or any creation model requires an event - infinite membranes, infinity improbablity in a quantum fluctation, infinite god using some uber-science, infinite luck + something else, infinite complexity - scale invarability extensions to relativity to make all of reality fractal etc...

To me accepting any infinity - and you must choose one - just abstracts the question one level and ends with a purely theoretical framework we little understand and where neither science nor faith can describe the mechanisms involved.
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rosborne979
 
  1  
Reply Mon 14 Apr, 2008 09:22 pm
Re: Did the big bang occur in empty space?
g__day wrote:
I was pondering the Big Bang model and wondered what is it that allows physicists to predict it didn't happen in already occupied space?

I'm not aware of any such prediction or deduction in cosmological theory.

We can't/don't know anything about conditions before/outside the BB. All we know is that our space/time is bounded by the BB.

Where have you seen it stated that a different space/time could not have existed outside/before the BB?
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real life
 
  1  
Reply Mon 14 Apr, 2008 09:29 pm
If space/time were infinite (i.e. had always existed, no beginning point) then entropy would've taken it down by now.

If you say, 'no, maybe it just hasn't been here long enough yet', then you are postulating a beginning point.
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NickFun
 
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Reply Mon 14 Apr, 2008 10:50 pm
Scientists have concluded that space/time expanded faster than the speed of light. If there was already empty space here then that would be impossible.
g day
 
  1  
Reply Mon 14 Apr, 2008 10:52 pm
rosborne979

Actually the cosmological model founded on the Big Bang postulates it actually created space-time, rather than occurred within it - and I was asking why?

We can't readily know anything prior to the Big Bang if you accept it as creating space-time. But my question is why is this perquisite mandatory?

I have no problem with what you are saying and all its implications - except its not at all relevant to my specific question.

I am not sure M-theory doesn't allow it, SuSy certainly would if we could ever get it to a point where it can make a prediction, scale relativity might allow it too.

real life

What is the infinity in space-time was infinite complexity (i.e. rather than saying space-time is quantised into Planck units - say its fractal and there is no limiting scale). Then a metamorphis of scale - even at a 3-brane level - could erase many signs of a different level of relativity. In simpler terms a brane / brane interaction might be partial - not complete - and not invalidate M-theory, relativity, the uncertainty principle nor topological constraints.

You have to be careful of applying laws within the domain to laws about the domain - especially where their could have be a phase change that ushered in new laws.

Example 1 - space-time is expanding, nothing says it must do so slower than light speed.

Relativity only bounds bodies moving within a relativistic framework - not the framework its self stretching according to other dominating laws.

Example 2 - inflation is best modelled as hitting at least 50,000 light speed.

No trouble with relativity because of point 1 and the energy densities where so high we believe the laws of quantum gravity - not relativity - dominated the earliest existence of the universe.

Example 3 - Heisenberg's law of uncertainty can be re-stated any law can be broken in any place for a finite amount of time with a finite certainty.

Wave functions can't work without this. Its the old Schrodinger rules the waves, Heisenberg waives the rules adage.

Too if you want to do frame of existence type rules - then you have to show your rules spans brane / brane interactions and dominates even during quantum gravity frameworks - not just relativistic ones - good luck with that.

In these studies topology itself - far more than force carriers within any fabric of space-time - dominate what can and will occur it seems!

Nickfun

My question was why does that boundary condition exist - why couldn't just 90% or 99.999% of space-time inflate until the energy density fell low enough for the four forces to separate?

Its fine to posit "If there was already empty space here then that would be impossible" - but please explain why - what laws under what framework/s would be dented?

Point two - if only 99.99998% expanded this fast - how could we possibly detected we missed some in the aftermath of so large an explosion?
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NickFun
 
  1  
Reply Sun 20 Apr, 2008 03:55 pm
It's possible that the reality of the big bang is too enormous and complex for our tiny brains to grasp. Even the world's greatest physicists won't conjecture on what was happening BEFORE the big bang.
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OGIONIK
 
  1  
Reply Sun 20 Apr, 2008 04:39 pm
easy, we neither exist or dont exist.

we are in purgatory. this reality is false Razz
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OGIONIK
 
  1  
Reply Sun 20 Apr, 2008 04:39 pm
ill conjecture, nothing at all.
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rosborne979
 
  1  
Reply Sun 20 Apr, 2008 04:42 pm
g__day wrote:
rosborne979

Actually the cosmological model founded on the Big Bang postulates it actually created space-time, rather than occurred within it - and I was asking why?

It postulates that it created it's OWN space-time. The model does not imply that it could not have resulted within ANOTHER space-time.

Can you be more specific about the question you are asking? I'm not sure if you're asking why the model is self-contained, or if you are under the mis-impression that the model makes any type of prediction (or limitation) on what lies outside of the model.
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g day
 
  1  
Reply Mon 21 Apr, 2008 11:17 pm
Why do you need it creating spacetime - its own or anyone elses for that matter.

In layperson's term - why do models of the big bang require it to create spacetime rather than just occurring within already existing spacetime?

Forget about trying to contain any model, and don't get confused by what's outside or limited elsewhere by the model - unless you'd like a flight of fancy.
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Chumly
 
  1  
Reply Mon 21 Apr, 2008 11:27 pm
I guess the presumption is that there was no space-time "before".

But if there was space-time "before", would there not be some evidence of it given that we can assess the Age of the Universe?
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rosborne979
 
  1  
Reply Tue 22 Apr, 2008 06:34 am
g__day wrote:
Why do you need it creating spacetime - its own or anyone elses for that matter.

In layperson's term - why do models of the big bang require it to create spacetime rather than just occurring within already existing spacetime?

Isn't that like asking why E=Mc^2 uses "E" as one of its terms?

(I'm still not sure I understand your question)
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Chumly
 
  1  
Reply Tue 22 Apr, 2008 11:29 am
Maybe he's asking why there could not be have been space-time before there was matter-energy. I thought space-time without matter-energy cannot exist, see here: http://www.physicsforums.com/showthread.php?t=76233
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g day
 
  1  
Reply Tue 22 Apr, 2008 07:16 pm
I'm simply observing any Big Bang model accepts a huge influx of very dense energy that rapidly expands or inflates - affecting spacetime around it rather drastically - and asking why must spacetime be created by that event rather than just be affected by it.

Rosborne979 - no again that's another random connection that has no correlation to the simple question I asked. I am puzzled you seem inable to comprehend such a simple question and preferred to randomly respond to other rather simple questions I didn't ask.

Hence my remaind question what in the Big Bang model precludes spacetime already existing?

Think through my simple example if tomorrow in our universe - say just next to Saturn, 10 ^ 80 joules of energy arrived in a near point form, and rapidly expanded - how would anyone 14 billion years later, observing within the blast radius, be able to tell whether it happened in already pre-occupied spacetime - or whether it actually create spacetime?


Chumly - spacetime, energy and matter interact, but so far as I am aware no respected physicist has proven whether any of these components can pre-date the other or even gone very far to estalish the interactions and show what they do as energy density gets really, really high. The link you mentioned starts with lets just say time and mass are the same bar a constant and see how that effects relativistic fields. Well whoa there fella - that's a mighty big jump to just pull outta anyone pockets isn't it - time and matter are equivalent.
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rosborne979
 
  1  
Reply Tue 22 Apr, 2008 09:22 pm
g__day wrote:
I'm simply observing any Big Bang model accepts a huge influx of very dense energy that rapidly expands or inflates - affecting spacetime around it rather drastically

It isn't affecting spacetime around it, the BB is spacetime.

g__day wrote:
- and asking why must spacetime be created by that event rather than just be affected by it.

Because it's a function of the model. I don't know specifically what part of the mathematics of the model is linked to that assumption, but I was always under the impression that it is a fundamental element of the model. I don't think you can alter that assumption without changing the model so much that it would (be radically different) require a new name, like the Little Bang or something.

g__day wrote:
Rosborne979 - no again that's another random connection that has no correlation to the simple question I asked. I am puzzled you seem inable to comprehend such a simple question and preferred to randomly respond to other rather simple questions I didn't ask.

Because I'm not as smart as you are, but I'm doing my best to answer the question based on my understanding of things. It's not like you're asking me what I had for breakfast. You're asking some obscure question about core cosmological assumptions.
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g day
 
  1  
Reply Mon 28 Apr, 2008 01:00 am
"It isn't affecting spacetime around it, the BB is spacetime."

I can't agree with that statement. You should have said it followed after the initial creation event, spanned several states, existed before relativity became dominant and was involved with the creation of spacetime and all matter and energy in it.

Not it was / is space time.

And I am saying why - why must it be a cause of spacetime, rather than a happening in it? Definitionally why? I know of no science framework or model that absolutely requires this - and am still searching! So its taken as a assumption rather than it evolves as a necessary requirement / outcome - and I am asking why!
0 Replies
 
Terry
 
  2  
Reply Mon 28 Apr, 2008 06:49 pm
If the big bang were an expansion in spacetime rather than of spacetime, you would need to explain how all of the matter/energy happened to get concentrated in one spot prior to the big bang. It would also violate the Copernican Principle since we would have to be at the exact center of the "explosion" to observe the universe expanding uniformly away from us in all directions.

There is a theory (can't recall its name) involving colliding branes which might allow pre-existing spacetime.
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Chumly
 
  1  
Reply Mon 28 Apr, 2008 07:02 pm
If the big bang took place independently of space-time, are you saying there was, or was not matter/energy before the big bang?

If there was matter/energy before the big bang then wouldn't there be a conflict in assessing the age of the universe, as per my Post: 3204939?
 

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