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Yes more questions about BB


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Just a few questions around Big Bang that are niggling me.

First off why microwaves? So my understanding is at the big bang the then universe was filled with light. Then the said universe expanded rapidly due to "expansion", this stretched that birght light into microwaves which we see today as the Cosmic Microwave Background. But surely expansion was quite simply huge and very rapid. Should expansion not of stretched the light beyond microwaves? Should we not be looking at Cosmic Amplitude Modulation Background?

Second the singularity would it not in theory at least have been the mother of black holes? If so could it bang? I know black holes it seems can evaporate but could an escape velocity be reached that would allow them to bang?

Thirdly in the brief instant before expansion should the early universe just not of collapsed back on itself? I guess you could say at this point no matter had been created so no gravity, but it was filled with energy and arent energy and mass interchangeable? doesnt all mass exert gravity?

And lastly im sure we have all seen the deep field pics of the earliest objects we can see, those 2 pixel smudges described as the early clouds of gases before the formation of stars and galaxies. And then been wowed as accompanying text explains how through spectroscopy has analysed light passing through them to determine they are formed of pure hydrogen and hellium. But wait how can there be light passing through? where does this light come from? surely these 13.5 billion year old gassious clouds are before stars? for light to pass through them then this would indicate the light is further away and therefore more ancient than the clouds but how?

Thats it for now i think.

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1) The CMB is an artifact of a universe that was about 380,000 years old. Prior to this time, the universe consisted of an "energetic soup" that would not allow the free passage of photons (ie. it was opaque). As the 'soup' expanded and cooled it reached a point whereupon the photons became free from matter and we had light. These early photons have been red-shifted by the cosmological expansion and appear predominantly as microwaves today.

2) Not much known detail about the early universe but whatever it was it looks very much like it went bang.

3)Not if the bang was big enough.

4)If the clouds are not on the edge of the observable Universe then light would pass through them.

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Just some ideas. 

1-Microwaves because ... The universe became transparent some 370.000 years after the big bang and inflation, when photons stopped being constantly reabsorbed and re-emitted. It's the expansion from between age 300000 and now which stretched the radiation of that era into the microwave range.

2-There was no singularity. If the universe is infinitely large now, it was infinitely large before, all the way back to the big bang. Every part of the universe was smaller once. Our locally observable universe too. 

3-There was no time before the big bang. Nothing could have happened before it. The big bang is supposed to be the point when time and space come into existence.

4-No idea here.

Well, I hope at least a word or two are somewhat true.

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'There was no time before the big bang.' This needs a qualification, maybe. The dimension we now perceive as time did, perhaps, come into being at the BB. This does not mean that other dimensions did not exist outside that one. It is no good saying 'before' the BB because 'before' is a term which only makes sense within our present concept of time. So according to the BB there was no 'before' but that does not prevent there from being an 'outside' of the dimensions we know.

To put it more simply, the BB is a scientifc theory which works with all that we can see. It does not preclude the possibility that there are things (eg dimensions) which we cannot see. The BB is not a theory of everything. It is a theory of everything we can see. Don't ask it to do the impossible.

Olly

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O.k thanks for the replies but i think ive confused the situation by using the wrong word, "expansion" instead of using "inflation". Im aware that there was no time before the big bang. What i was asking was should the early universe not of collapsed on itself in the trillionth of a trillionth of a second between the big bang and "inflation"?.

Im also aware that inflation stretched the wavelength of early light into the microwaves we see throughout the universe today. But what i was asking was given the enormous stretch "inflation" that took place why was the light not stretched further? i.e into radio wavelengths, AM wavelengths being the longer of these?

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What i was asking was should the early universe not of collapsed on itself in the trillionth of a trillionth of a second between the big bang and "inflation"?.

Im also aware that inflation stretched the wavelength of early light into the microwaves we see throughout the universe today. But what i was asking was given the enormous stretch "inflation" that took place why was the light not stretched further? i.e into radio wavelengths, AM wavelengths being the longer of these?

This Ethan Siegal article may help: Why Didn't the universe Collapse into a Black Hole?

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At risk of repeating previous answers...

1. Why microwaves: because it's a red-shifted black-body spectrum of the radiation at about 380,000 years after the Big Bang. Prior to that time the universe was hot enough to be opaque, so we don't get any of that.

2. Why not a black hole. Because general relativity says otherwise. The metric is changing: this is different form the conditions under which black holes are predicted. You can't calculate a Schwarzschild radius for the early universe.

3. Why no recollapse. General relativity gives three options: eventual recollapse, accelerating expansion, or exact balance (expansion without acceleration). Which you have depends on the amount of mass that's present. There isn't enough for recollapse.

4. Clouds of pure hydrogen and helium. Not to be confused with images of the earliest galaxies. Clouds have been detected which consist of gas that has not been through stellar fusion - in that respect they are primordial. But they've stayed that way for a long time, and are not the oldest or most distant objects that can be observed. These clouds can therefore be detected thanks to light from more distant objects shining through them.

Inflation is a separate issue. It occurred over an extremely short period of time, and did not give rise to the microwave background. It did however "stretch" quantum fluctuations in the initial universe, and these stretched features are observed as slight variations in the temperature of the microwave background. 

Edited by acey
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Knight cheers havent had a chance to read in depth yet but looks interesting.

O.k still a little confuesed as i thought Infaltion took place some 10-32 after the big bang which i thought was a few trillionths of a second. But either way i still dont see how that explains why the stretch of light from inflation was limited to microwaves and not to radio waves? I must be missing something.

Well the amount of mass present is surely the current amount of mass in the universe as everything we currently see must of been contained in that pre-inflation universe even if in the guise of pure energy. Surely as that universe was still who knows how ridiculousy small it should of collapsed?

Not confusing early galxies for cloud of dust at all.  http://www.popularmechanics.com/science/space/deep/spotted-gas-clouds-from-the-early-universe-older-than-metals-themselves-6554368

quote: "However, while these findings are more validation for the big bang theory, the researchers say that the existence of these pure clouds means they might have to rethink how the universe recycles material. The material in the pure clouds was made minutes after the big bang, but surprisingly, avoided pollution for roughly two billion years"

Soagain if these clouds are pure and created just minutes into the big bang then what is it "behind and back in time" that is lighting and allowing us to determine their makeup?

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O.k still a little confuesed as i thought Infaltion took place some 10-32 after the big bang which i thought was a few trillionths of a second. But either way i still dont see how that explains why the stretch of light from inflation was limited to microwaves and not to radio waves? I must be missing something.

There were no free photons in the early universe. It is thought that the first free photons came into being when the universe was 380,000 yrs old.

These primordial photons have not been around long enough to 'stretch' into radio waves. The CMB was predicted in the 1940's and forgotten about for twenty years. The inflationary era of the universe pre-dates free photons.

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At risk of repeating previous answers... :) :)

>> "O.k still a little confuesed"

Yes, you are still confusing inflation and expansion

 > "as i thought Infaltion took place some 10-32 after the big bang which i thought was a few trillionths of a second.

Yes, quite right, near enough,
 and it was all over, done and dusted a teensy weensy fraction of a second later.
Long _long_ before your 'bright light" that ended up as the CMB was created.

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, tear here
Inflation (exponential) was the reason the universe is so smooth that we see today
 ( you might not think it with lumpy planets and big galaxy clusters and things, but on the grand scale it is too smooth to have been created with anything other than some form of exponential inflation )
Not a consideration, yet, in the matter of the CMB and its wavelength because what will later be the CMB has not yet started.
The universe at that tiny time is just a glob of energy which has yet to go through some decoupling events before it can give rise to quarks and then protons and stuff.
oh, and Higgs fields and strong and weak and electromagnetic fields.
Heck, there can be no wavelengths yet cos electromagnetism has not yet decoupled from the um well lets just call them the others ( call them the Grand Unified Things :) )
, , , , , , un-tear here

Wind the movie on by 380,000 years
Yes 380,000y, _well _past _inflation _time,
the universe is now cool enough (about 3000K ) to allow non ionised stuff to exist and allow the free passage of photons
NOW we can consider the light that gave rise to the CMB.

That glowing hot 3000K blackbody universe was now _expanding_ ( slowly, ever so slowly compared the the inflation all that long time ago)
In the 13By ( give or take ) since, the universe has now had time to cool to 2.7K (give or take) and we can see that 2.7K blackbody as microwaves.
Yes, it will expand some more till the CMB will not be microwaves any more, it will be a very very cold very long wave radio waves.
Just wait a while :) everybody will then be talking about the CRB * :)

Tiki, Ruud, and Acey have already said all that though !!!!!!!!!!

* actually, dont think I have seen that CRB term used before, dont suppose I can get any kudos for being the first to coin it ? !

Edited by Ptarmigan
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http://www.popularmechanics.com/science/space/deep/spotted-gas-clouds-from-the-early-universe-older-than-metals-themselves-6554368

Soagain if these clouds are pure and created just minutes into the big bang then what is it "behind and back in time" that is lighting and allowing us to determine their makeup?

Second paragraph of article:

"The clouds aren’t the oldest celestial objects astronomers can see—they’re from about two billion years after the big bang, and astronomers have spotted parts of the universe that date to less than one billion years after the event."

There's your answer.

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  • 2 months later...

The clouds are visable at 13.5b years with our best known tech, who is to say that it is definative in a 100 years we could be looking back 15b years or more and what if you was at a point today 10b years from here?

The visable universe is the known universe and that is all we know so far.

the BB is just a theory along with expansion, relativity, string & many many others in truth we know very little and what we do know is always changing but that's physics.

we have way more questions than answers and even einstein would be the first to tell you the theory of relativity in incomplete.

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