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michel123456

Very old view of the Universe

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I was wondering what was the Observable Universe in the old times :

If we were the inhabitants of a young Galaxy, only 600 million years after the Big Bang, what would have been our Observable Universe look like? On the basis of standard cosmology.

Edited by michel123456

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The theory of the big bang goes that the universe started out as an infinitely dense partical or a singularity that for some random reason decided to expand creating all objects that exsist within that sphere of expansion. An early universe would have been much denser than it is today a night sky from planet surface would look very different it would be packed with Nebulae and young stars an incomprihensible amount of energy, rock, ice and other matter would streak through through space coliding with each other constantly in such a packed and chaotic universe Life would not exist long we would be swept back up in the tidal wave of creation that formed us pretty quickly.

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I suspect you are not asking about how stars, galaxies and stuff in general looked like and instead are more interested in the size and range of our observable universe back then.

(From your last discussion of the Big Bang theory here.)

 

Since the suggested "old" time is very close to the Recombination era light would not yet have had enough time to reach us from larger distances so the deep field of observations should have been pitch black, in essence there could only be light reaching us from a little less than 600 million lightyears "appearing" distance. With "appearing" distance" I mean the distance a photon had to travel through space before it could reach us.

 

The Cosmos Calculator don't seem to go that far back, but at ~1 billion years after the Bang our "true" range of our observable universe only reached ~410 million lightyears distant around us. With "true" I mean the actual distance that emitting objects was located from us, when the light we observe now was emitted.

 

The matter emitting the CMBR would appear to be 1 billion lightyears distant but it was less than 100 million lightyears distant when the CMBR was emitted and would be ~3.4 billion lightyears distant when we observe that radiation that took 1 billion years to reach us. This distance of the CMBR is the "proper" range of our observable universe. With "proper" distance I mean the actual distance emitting objects have reached from us now, when we make the observation.

Edited by Spyman

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I suspect you are not asking about how stars, galaxies and stuff in general looked like and instead are more interested in the size and range of our observable universe back then.

 

Please continue. I am also interested about the neighborhood of galaxies. Were they closer?

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Please continue. I am also interested about the neighborhood of galaxies. Were they closer?

 

I defer to Spyman and only comment in support of his explanation, but yes and you can figure for yourself that since the redshift z = 8.6 the surrounding galaxies were about 10 times closer than today on average.

 

The relevant ratio is z+1 = 9.6 or about 10.

 

You are talking about the universe at redshift 8.6 when it was already about 600 million years into its expansion history (correct me if you mean something else.)

 

So the CMB radiation would have a temperature 10 times hotter. Today it is about 2.75 Kelvin. So back then the microwave soup around you would be 27.5 Kelvin. Still pretty cold :-D

 

And objects would be abouty 10 times closer. And the average density of matter in space would be about 1000 times denser.

 

 

Galaxies would still be in the process of forming. People talk about "proto-galaxies". Smaller clumps that would be growing, and merging to form larger clumps. Structure would be in the process of assembling itself. So there could have been more little pieces and fewer big pieces. But if you allow for that qualitative adjustment in your imagination it would be OK to say, I think, that galaxies were 10 times closer.

 

There is one caveat. The Hubble law does not refer to gravitationally bound assemblages of matter, like clusters of galaxies. Our Local Group of galaxies does not participate in the expansion process and so it would not appear to contract as you go back in time. Likewise the Virgo Cluster of galaxies is gravitationally bound. So those distances are stable at least in some average sense.

 

The pattern of expansion does not apply to IMMEDIATE neighbors, like Andromeda a member of our Local Group. It only applies to more distant galaxies which are not bound to us. But that is almost all (the Local Group is only a couple of dozen out of millions, so we can forget about it). We can say that almost all galaxies were 10 times closer back then, than they are today.

Edited by Martin

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Please continue. I am also interested about the neighborhood of galaxies. Were they closer?

Martin said it more elegantly than I can, but YES the Universe was on larger scale more crowded in its early days.

 

There would be fewer galaxies around that had already formed but the building material was there and starting to accumulate in the struggle for domination between gravity and expansion. In close neighborhoods gravity was winning and forming bound systems and structures but on larger distances objects continued to get separated by expansion.

 

The Great Cosmic Battle

The Stelliferous Era

As the Universe reaches its adolescence in the early Stelliferous Era, gravity finally makes some headway against the universal tendencies toward disorganization. During the first billion years, galaxies are created as gravity overcomes the background expansion of the Universe. Gravity also organizes these galaxies into bound clusters and cosmic structures on even larger size scales.

http://www.astrosociety.org/pubs/mercury/0001/cosmic.html

Edited by Spyman

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Reading your link.

 

Small question in the meanwhile: those galaxies are the same that we can observe from Earth today, I suppose.

Edited by michel123456

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A galaxy like UDFy-38135539, from which the light took 13.1 billion years to reach us, is a galaxy that was about ~3 billion lightyears distant when the light we observe now was emitted and it is now thought to be ~30 billions lightyears distant.

(Cosmos Calculator Omega=0.27 Lambda=0.73 Hubble=71 Redshift=8.55)

 

However at that time ~13 billion years ago we would not have been able to observe UDFy-38135539 at its location ~3 billion lightyears distant from us, what we would have been able to see back then is an even older image, from a closer location in a more remote past, of the matter that later became this galaxy.

Edited by Spyman

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Lets continue on the example of a Galaxy 1 billionyear after the BB, so that the cosmos calculator can be used.

 

If I understand correctly, following standard cosmology, an observator in this Galaxy has had a CMBR of 1 billion LY radius, the CMBR has had a temperature 10 times hotter, and the surrounding galaxies observable inside the CMBR radius are were roughly 10 times closer. (edited post)

 

point: The past of an object is also the past of his future.

Syllogism

The Observable Universe of this galaxy (call A) lies totally in her past. Her past is also observable from our place today. This galaxy's past is the part of space from 12 BY and up. For example, a galaxy B, observed from our galaxy A, at a distance of 0,5 BY, should be observable from Earth at a distance of 12,5 BY. The past cone of the distant galaxy is inside our past cone. Correct?

Edited by michel123456

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Are there any possibility to exist any middle life time particles like present exiting proton, neutron and electron in the middle Universe?

But that particles are not existence present Universe.

Electron, Proton and neutron are constant form after inflation period?

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Lets continue on the example of a Galaxy 1 billionyear after the BB, so that the cosmos calculator can be used.

 

If I understand correctly, following standard cosmology, an observator in this Galaxy has had a CMBR of 1 billion LY radius, the CMBR has had a temperature 10 times hotter, and the surrounding galaxies observable inside the CMBR radius are were roughly 10 times closer. (edited post)

No, the galaxy were receiving radiation with an age of 1 billion years that was 10 times hotter than today and all surrounding galaxies both inside and outside of the galaxy's observable horizon were 10 times closer to the observer and each other. Please read my post #3 again.

 

 

point: The past of an object is also the past of his future.

Syllogism

The Observable Universe of this galaxy (call A) lies totally in her past. Her past is also observable from our place today. This galaxy's past is the part of space from 12 BY and up. For example, a galaxy B, observed from our galaxy A, at a distance of 0,5 BY, should be observable from Earth at a distance of 12,5 BY. The past cone of the distant galaxy is inside our past cone. Correct?

No, a distant observer have a different location and as such the past cone of the distant galaxy can only be partially inside our past cone. A distant observer will always be able to see a little further in the direction of the distance separating us than we are at the same time. We might however, depending on difference in time of observation, be able to have a greater view and in our time observe more than the entire field of view which the distant observer had in a more remote past time.

Edited by Spyman

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No, the galaxy were receiving radiation with an age of 1 billion years that was 10 times hotter than today and all surrounding galaxies both inside and outside of the galaxy's observable horizon were 10 times closer to the observer and each other. Please read my post #3 again.

 

 

That is not the point, but reading your post #3 again I read "The matter emitting the CMBR would appear to be 1 billion lightyears distant but (...)". I say it again that is not the point.

 

 

 

No, a distant observer have a different location and as such the past cone of the distant galaxy can only be partially inside our past cone. A distant observer will always be able to see a little further in the direction of the distance separating us than we are at the same time. We might however, depending on difference in time of observation, be able to have a greater view and in our time observe more than the entire field of view which the distant observer had in a more remote past time.

Now that is the point.

Could you please make a diagram of this?

Edited by michel123456

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post-1138-033387800 1289574632_thumb.jpg

 

Thank you, but I don't understand. Where is the Earth today? where is CMBR as seen from Earth? where is CMBR as seen from distant Galaxy A? In any case, I suppose galaxy A cannot be positionned upon the life line of Earth.

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Earth? CMBR? You said twice that it "is not the point".

 

I am sorry but I don't seem to understand, maybe you can explain further and focus on one single question?

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I would like a diagram where I see the Earth, the distant Galaxy, the CMBR as seen from the Earth, and the CMBR as seen from the Galaxy.

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To add the surface of last scattering to the diagram in post 13, wouldn't you just draw a horizontal line almost at the bottom?

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I would like a diagram where I see the Earth, the distant Galaxy, the CMBR as seen from the Earth, and the CMBR as seen from the Galaxy.

post-1138-018480800 1289601729_thumb.jpg

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Nice! Did you do the labeling on that diagram? Ned Wright's cosmology tutorial had some basic diagrams like that, but last time I looked it did not have the labeling with words like "distant galaxy" and "Milkyway".

Ned Wright's diagrams had the teardrop shape lightcones, and the worldlines with little local forward lightcones along them. A light ray worldline passing one of those has to be running parallel to one side or the other of the small local triangle. The plot is with proper time and proper distance. It's a really good tutorial and the diagrams are a great help.

 

But I haven't looked at Wright's UCLA website for quite a while, so I don't know if he has new material. What I think is that you made something responsive and useful by correctly labeling one of his.

In any case thanks for a valuable contribution!

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About CMBR?

Why only long wave eletromagnetic waves are detected?

AT the beginning, it was very high temperature , so very short length eletromagnetic wave would be emitted.

And a little letter, quark gluon plasma reaction occur. We have not done any attempt to detect that wave yet?

Is it difficult to detect very short waves in the background? Any experimental difficulty exist?

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Nice! Did you do the labeling on that diagram? Ned Wright's cosmology tutorial had some basic diagrams like that, but last time I looked it did not have the labeling with words like "distant galaxy" and "Milkyway".

Ned Wright's diagrams had the teardrop shape lightcones, and the worldlines with little local forward lightcones along them. A light ray worldline passing one of those has to be running parallel to one side or the other of the small local triangle. The plot is with proper time and proper distance. It's a really good tutorial and the diagrams are a great help.

 

But I haven't looked at Wright's UCLA website for quite a while, so I don't know if he has new material. What I think is that you made something responsive and useful by correctly labeling one of his.

In any case thanks for a valuable contribution!

Martin you guessed correct, the image is downloaded from Ned Wright's Cosmology Tutorial and then edited with Microsoft Paint.

 

 

----------

 

 

Thank you Spyman. I have stolen your graph to add what I hope is correct.

The added lightcone of the past view from the distant galaxy looks good.

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Are you sure?

Don't play games Michel, the image might be wrong on some small detail or angle but as a crude sketch it's correct.

 

Why don't you get on with it and tell us what is troubling you instead...

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Believe me I don't play games. I just choose a step-by-step procedure in order to avoid misinterpretation. You have already shown that CMBR is not invariant. CMBR was smaller in the past. That's why I spoke about a "small CMBR" and a "large CMBR" in the other thread, that was not understood by some other members of this Forum. I think it is clear to anyone looking at the diagram.

 

Are Galaxies X, Y, Z, observable from Earth, today?

ScreenShot1035.jpg

Edited by michel123456

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