Exploring the Observable Universe After GRB090429b

[Lookup]

Hi all...my first post to this forum and my first question might seem pedestrian to you frequent posters and academics.
As the description of this GRB states it happened 520 million years after the big bang.
My question is if the big bang happened everywhere at once would this event simply be at the edge of the OBSERVABLE universe which continues ad infinitum beyond GRB090429B? Or does the universe beyond this GRB simply exist as nothingness? A question no doubt which defies credible answer but asks a logical question.
I will be very interested to hear your opinions and comments on this.
Many thanks,
Stu

 

[zhermes]

My question is if the big bang happened everywhere at once would this event simply be at the edge of the OBSERVABLE universe which continues ad infinitum beyond GRB090429B? Or does the universe beyond this GRB simply exist as nothingness>

As you hint, this is a very complicated question.

This GRB is at the edge of the observable universe. We don't know if the universe is infinite in size or not, but either way its definitely very very big. Even at such a short time after the big-bang, the universe was very large. For GRB090429B, the 'observable universe' would have only been a few hundred million light years large, but the 'whole' universe would have been tremendously larger (though causally disconnected). This applies for us as-well. Although the 'observable' (and thus causally connected) universe ends at about 13.7 Gyr from us, we believe the modern universe extends significantly farther.

I hope that helps answer your question. I'm not entirely clear on what you mean by, 'universe beyond this GRB simply exist as nothingness'.

 

[Lookup]

Thank you for indulging my lay perspective zhermes for I am neither a physicist nor astronomer rather an interested observer.
What I meant by "nothingness" might be better described as "unknown".
My interpretation comes from Hawking describing the big bang as something which happened everywhere at once. From that I gathered it meant it emanated from an infinite singularity. No doubt my interpretation may lack but let's say I were a viewer in the galaxy (or whatever that object may be) where the GRB happened (and somehow survived) and was also privvy to telescopes such as we have, would our Milky Way to the GRB viewer ALSO BE on the edge of the observable universe and be 520 million years after the big bang? I am of course speaking about the GRB 13.14 bly hence since, as you described, the "observabale universe" on the GRB 13.14 bly ago would have been relegated to 520 mly. Hope I've explained it adequately.
Lastly, does science believe the "nothingness or unknown" consists of the perimeter of the big bang heading outwards (defined for simplicity) or would it be populated by an infinite number of galaxies and other phenomena.
Many of the periodicals on this topic are either couched in language and terminologies that are extremely hard to interpret for the average inquisitive person and are like reading double dutch.
Thanks,
Stu

 

[zhermes]

What I meant by "nothingness" might be better described as "unknown".

We believe the universe to be quite homogenous and uniform. Every region is more or less like the others, and certainly governed by the same laws. There is nothing special about the location where(/when) we perceive the horizon of our observable universe... we simply cannot see farther.

My interpretation comes from Hawking describing the big bang as something which happened everywhere at once. From that I gathered it meant it emanated from an infinite singularity.

That's not quite right. The big bang happened everywhere because it was something that happened to (all of) the universe itself, which defines the 'where' in everywhere. It doesn't matter if the universe is infinite (and thus the big bang occurred across an infinite amount of space), or not. If the universe was small and finite at the big bang, it still would have happened across the entire universe, and thus everywhere.

would our Milky Way to the GRB viewer ALSO BE on the edge of the observable universe and be 520 million years after the big bang? I am of course speaking about the GRB 13.14 bly hence since, as you described, the "observabale universe" on the GRB 13.14 bly ago would have been relegated to 520 mly.

No, the GRB viewer would not be able to see the Milky-way, because the milky way would be significantly farther away than 520 mly, which is the extend of the universe which he/she can see.
At the same spatial position where the GRB occured, but 'now' (i.e. 13.7 gyr after the big bang), the GRB observer would see the milky-way, ~13.1 gyr ago (i.e. ~520 mly after the big bang).

Lastly, does science believe the "nothingness or unknown" consists of the perimeter of the big bang heading outwards (defined for simplicity) or would it be populated by an infinite number of galaxies and other phenomena.

A galaxy is a particular object within the universe. A collection of gas, stars, dark matter, etc etc---nothing special. The universe is everything. Space. Time. The collection of all galaxies. Etc. There isn't "nothing/unknown outside the universe" because there is no outside of the universe. The universe thus doesn't expand into anything, it just gets bigger---this is something that fundamentally can not be visualized by a person, but can only be understood conceptually or via mathematics.

 

[Lookup]

Thank you zhermes for your patient and thorough reply. It helps me tremendously. I can now visualize that if one were to travel 13.14 bly to GRB090429b at light speed, when one arrived there the limit of the observable universe under today's criteria from there would be 13.14 bly distant and so on hence the "observable universe".
Lastly, any recommendations on literature which simplifies such topics in the fashion you describe?
My last post on this topic as I don't want to belabour the issue.

 

[Cosmo Novice]

Thank you zhermes for your patient and thorough reply. It helps me tremendously. I can now visualize that if one were to travel 13.14 bly to GRB090429b at light speed, when one arrived there the limit of the observable universe under today's criteria from there would be 13.14 bly distant and so on hence the "observable universe".
Lastly, any recommendations on literature which simplifies such topics in the fashion you describe?
My last post on this topic as I don't want to belabour the issue.

There are some interesting threads on these forums regarding the sort of questions you are asking. The furthest point we can see in out OU (Observable Universe) is a temporal edge, in that only photons who have had time to travel to us we can actually see. Although if we could (as a thought experiment) instantly travel to the furthest point we could see and looked out into space, we would essentially see the same thing. (The universe is the same in all directions, which is also called isotropy and homogenity)

The big bang was the beggining of everything - including time and space, so it did not expand into a pre-existing space, the bang included the space. Its is important to conceptualise that the space between galaxies and stars etc. (traditional space) is also part of the expansion process.

If you find this sort of thing interesting then the infinite/not infinite and topology threads are very interesting.

 

[zhermes]

Thank you zhermes for your patient and thorough reply. It helps me tremendously. I can now visualize that if one were to travel 13.14 bly to GRB090429b at light speed, when one arrived there the limit of the observable universe under today's criteria from there would be 13.14 bly distant and so on hence the "observable universe".
Lastly, any recommendations on literature which simplifies such topics in the fashion you describe?
My last post on this topic as I don't want to belabour the issue.

Glad I could help. I think Cosmo Novice's reply is your best bet. I can't think of many other appropriate resources.

 

[marcus]

Even though the thread has been well answered and satisfactorily concluded I will add a note. The estimated redshift was z = 9.4.

Here is the technical article's summary page:
http://arxiv.org/abs/1105.4915
A Photometric Redshift of z ~ 9.4 for GRB 090429B
click on "pdf" to get the whole thing.

They don't actually measure the distance, or the lookback time. They measure the redshift, by looking at the spectrum of the afterglow (the light spread out to show its rainbow of different wavelengths). So in some sense 9.4 is the "real" number and the lightyears are just something estimated from that using a model of the universe that has been developed and refined over the years using much other data.

To convert that 9.4 into more familiar stuff, google "wright calculator" or "cosmo calculator" and type the number 9.4 into the z-box.

http://www.astro.ucla.edu/~wright/CosmoCalc.html

You will see the estimates using the standard model. The light travel time of 13.14 billion years.

The original distance from us when the star exploded: 2.99 billion lightyears.
The distance now (how far the remnants of the explosion are from us today): 31.1 billion lightyears.

The calculator gives the distance as it was back then (when light was emitted) under the heading of "angular size distance". That is where you will see the figure of 2.99 billion light years.

The ratio of now/then distances is always z+1. That is, distances in the universe have expanded by a factor of 9.4+1 = 10.4 during the time the light was in transit. You can check that 31.1/2.99 = 10.4.

This z+1 factor is the same factor by which the wavelengths of the light have been increased.