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Offline Michael Gentry

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Where did the big bang occur?
« on: 26/03/2011 19:30:03 »
Michael Gentry asked the Naked Scientists:
   
Do we know where our universe started - ie where the "big bang" occured?  If so where in the sky is it?  If not will we ever be able to find?

What do you think?
« Last Edit: 26/03/2011 19:30:03 by _system »


 

Offline JMLCarter

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Where did the big bang occur?
« Reply #1 on: 27/03/2011 02:17:00 »
The big bang occurred 8-9 billion years ago, says current thinking [this was in error, see later post, is 13.75billion].

The explosion that was the big bang became the universe, so if you want to know where it is now, take a look around. "Why can't we see it?" you ask, the answer is we can.

If you want to know where it started, which is supposedly at the centre of the universe, then note firstly that
1) Light itself first formed some time after, and it was even later before it could escape the core, so we cannot "see" back to the original explosion.
2) Astronomy is examining older and older light from more distant and fainter stars. As it does so it is looking back in time nearer to light that was first formed close to the time of the big bang.



It must be said that there is some uncertainty, and what I would consider to be a couple of holes in the theory, i.e. dark matter (no-one knows what that is, and how it has impacted expansion) and dark energy (yep, you guessed, no-one know what that is either).
« Last Edit: 28/03/2011 19:43:01 by JMLCarter »
 

Offline Madidus_Scientia

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Where did the big bang occur?
« Reply #2 on: 27/03/2011 06:26:41 »
The big bang was an expansion of space itself, so the big bang occured everywhere.
 

Offline imatfaal

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Where did the big bang occur?
« Reply #3 on: 28/03/2011 14:14:17 »
As MadSci said - it was everywhere, this is why we can see the afterglow from every direction (cosmic microwave background radiation).  The big bang as a name was given by a detractor and it continues to confuse and confound many years later

And the generally accepted timescale is 13.75 billion years give or take a hundred million years. 

And I am not so sure about JMLC's comments on the formation of light.  Light/EMR will, I think, have existed from the moment of decoupling of the weak and the electromagnetic ie after about one million-millionth of a second.  We cannot see any further back than the era of last scattering - which is when the universe stopped being an opaque sea of charged ions, electrons, and radiation ie after about 400,000 years.  The only chance of seeing any evidence of the universe before the era of last scattering is by using a detection technique that does not rely of electromagnetic radiation (neutrinos, gravity waves etc) - these are decades/centuries into the future.
« Last Edit: 28/03/2011 14:23:48 by imatfaal »
 

Offline JMLCarter

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Where did the big bang occur?
« Reply #4 on: 28/03/2011 19:39:41 »
apologies 13.75 billion as you say. Yes universe is only a small proportion larger than observable universe, 3% or something.
 

Offline Michael Gentry

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Where did the big bang occur?
« Reply #5 on: 07/04/2011 09:02:16 »
I understand that in theory we could build a three dimensional model/map of the Universe. It would be roughly spherical and the Milky Way would be about half way from the centre. If this is case I believe that we would be able to consult this map and point to a spot in the sky and say " the centre of the Universe lies in that direction". It does not seem unreasonable to add "where the big bang occurred".
 

Offline Madidus_Scientia

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Where did the big bang occur?
« Reply #6 on: 07/04/2011 13:01:32 »
Why would the milky way be half way from the center?
 

Offline JMLCarter

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Where did the big bang occur?
« Reply #7 on: 08/04/2011 01:59:02 »
It may not seem unreasonable but it is not strictly correct. A fairly subtle point of understanding.
The big bang created space, before the big bang there was no "where".
Or to put it another way, if you stretch an elastic band, where does it start stretching? (OK, no explosion in this analogy, but it could still help).

Also "If the observable universe is smaller than the entire universe (in some models it is many orders of magnitude smaller), one cannot determine the global structure by observation: one is limited to a small patch."

The observable universe is 93billion light years across, and on that scale looks more or less the same in every direction.
 

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Where did the big bang occur?
« Reply #7 on: 08/04/2011 01:59:02 »

 

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