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Scotti G

What came before the Big Bang

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1 minute ago, saac said:

I thought that the CMB photons were able to travel unchecked before star formation - the thinning of the fog until it became transparent. Didn't stellar formation then follow ? There was a useful Horizon documentary o this called Cosmic Dawn . I'll see if I can find a link. 

Jim 

Yes the formation of neutral hydrogen let the CMB fee but it was sometime later that stars formed and their UV re-ionized the hydrogen.

Regards  Andrew 

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4 minutes ago, andrew s said:

Yes the formation of neutral hydrogen let the CMB fee but it was sometime later that stars formed and their UV re-ionized the hydrogen.

Regards  Andrew 

So did re ionisation have any impact on subsequent star formation ?    The Horizon video is no longer available on the BBC iPlayer - odd clips are up on YouTube. It's a shame it was watchable albeit suffering from the  repetitive graphic style of the later Horizon documentaries. 

Jim  

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26 minutes ago, saac said:

So did re ionisation have any impact on subsequent star formation ?    The Horizon video is no longer available on the BBC iPlayer - odd clips are up on YouTube. It's a shame it was watchable albeit suffering from the  repetitive graphic style of the later Horizon documentaries. 

Jim  

Simple answer is I don't  know. I will look into my extensive library.  I do know that real data from that era is sparse to say the least.

Regards Andrew 

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1 hour ago, saac said:

I thought that the CMB photons were able to travel unchecked before star formation - the thinning of the fog until it became transparent. Didn't stellar formation then follow ?

 

Yes unchecked, but the "fog" had already just cleared to allw the photons to be unchecked

My (limited and fallable) understanding :
that the time f , at approx. 380,000yrs is called the "time of last scattering" **    because it is when the universe became transparent to photons.  ie. they could travel freely across the universe without bumping into anything (being scatterd by anything) as they were doing in the "fog" of the plasma that existed throughout the universe before that time.

The CMB originated at that time f.
It, the CMB, is visible to us (and anyone else elsewhere !) across and throughout the universe because the photons that constitute it, that background 'noise', are free and able to travel.

ie. the "fog" had already cleared during e to f , just before f,  to allow the CMB to then  be 'seen'.
That CMB noise is thermal noise that started out at 3000K, at f , and has now cooled to 2.7K because of expansion.

** it is also called the "time of recombination" or "of decoupling"
I dont like recombination because that implies that stuff was combined once before and is re- doing it again !,  you see ?

The "dark ages" is the period from f  (well, poetically dark!,  not quite totally dark to human eyes as it still glowed at 3000K for a wee while :) ) until the first stars lit up at time g.

howzat ?

 

Edited by Corncrake
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As a deeply religious person I do not agree with this scientific nonsense of their being nothing and then all of a sudden there was a big bang and the universe was created from the void ....

 

Gospel dictates that there was nothing and then God said "let it be" and all of a sudden the universe was created from the void..

 

Er ! .... hold on a moment ?

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Are theory's of the Universe being nothing but a holographic projection still floating about as this would mean that space was never created and only time came out of the big bang and it is this that dictates what we observe?

Alan 

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1 hour ago, andrew s said:

Simple answer is I don't  know. I will look into my extensive library.  I do know that real data from that era is sparse to say the least.

Regards Andrew 

I picked up "At The Edge of Time - Exploring the Mysteries of Our Universe's First Seconds" by Dan Hooper - I think it was following a review in BBC Sky at Night .  Early days with it but so far I like the way the author doesn't just drop statements as received fact but makes a point to cite evidence.   He has an easy to follow style as well which always helps with this type of subject.  Only covers the first few second though - need to wait for the sequel to find out about stellar formation. :) 

Jim 

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3 hours ago, saac said:

So did re ionisation have any impact on subsequent star formation ?    The Horizon video is no longer available on the BBC iPlayer - odd clips are up on YouTube. It's a shame it was watchable albeit suffering from the  repetitive graphic style of the later Horizon documentaries. 

Jim  

This paper seems to show it does https://www.arxiv-vanity.com/papers/1405.5540/

To quote "Reionization heats the gas and drives it out of the shallow potential wells of low mass halos, affecting especially those below a sharp mass threshold that corresponds to a virial temperature of ∼2×104 K at zreion. The loss of baryons leads to a sharp decline in the star forming activity of early-collapsing systems, which, compounded by feedback from early star formation, empties halos of gas and leaves behind systems where a single old stellar component prevails."

Regards Andrew

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53 minutes ago, andrew s said:

This paper seems to show it does https://www.arxiv-vanity.com/papers/1405.5540/

To quote "Reionization heats the gas and drives it out of the shallow potential wells of low mass halos, affecting especially those below a sharp mass threshold that corresponds to a virial temperature of ∼2×104 K at zreion. The loss of baryons leads to a sharp decline in the star forming activity of early-collapsing systems, which, compounded by feedback from early star formation, empties halos of gas and leaves behind systems where a single old stellar component prevails."

Regards Andrew

Thanks for the link Andrew; so it tapped the brakes so to speak :)   I had read that early star formation was aided by the formation of molecular hydrogen which acted to absorb heat giving gravity the leading edge in collapsing the gas clouds.  It's a fascinating subject for sure and relatively accessible but I guess hard won by those who led the way. 

Jim 

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On 03/06/2020 at 20:44, knobby said:

If God created the universe ... Who created God ? 😂

Same bloke who created science I suppose :D

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On 03/06/2020 at 20:41, Kev M said:

scientific nonsense of their being nothing and then all of a sudden

Ummm, I think there are lots of tongues in aunt sallies' cheeks hereabouts  !

I will not mention discuss in detail the forbidden aspects that these sorts of topics usually descend into,  just say that :-

Science says nothing of the sort !

It is not so presumptuous (as other philosophies are) to know what happened "before" somewhen, let alone that there was a state of nothingness.

It simply and humbly says that  we do not (yet?) know what happened before the Planck time. But after that time then we think the following happened  [insert massive quote of S.H. "A Brief History of Time"+ other refinements]

It is fun to speculate, and that is how science has come to where it is able to banish scary monsters in the greenwood, other human traditions do not even allow speculation.

Edited by Corncrake

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