ChatterBank8 mins ago
Size of the actual universe??
The size of the observable universe is bounded by the distance that light has had time to travel to us.
An observer in the Andromeda Galaxy would have a slightly different observable universe to ours and be able to observe objects slightly outside our own range of observation.
However the actual size of the universe is much bigger than this.
An observer at the edge of our observable universe would mostly observe a volume of space completely beyond our range of observation.
My question is....How many of these hypothetical observable universe steps would we have to take before returning to an observable universe which contained our place of origin? How big is the actual universe?
Or alternatively would we never return, meaning that the universe is infinite.
Also if the universe is flat not curved due to inflation how does the above work in a non infinite universe?
Or please explain to me why the above is not valid.
An observer in the Andromeda Galaxy would have a slightly different observable universe to ours and be able to observe objects slightly outside our own range of observation.
However the actual size of the universe is much bigger than this.
An observer at the edge of our observable universe would mostly observe a volume of space completely beyond our range of observation.
My question is....How many of these hypothetical observable universe steps would we have to take before returning to an observable universe which contained our place of origin? How big is the actual universe?
Or alternatively would we never return, meaning that the universe is infinite.
Also if the universe is flat not curved due to inflation how does the above work in a non infinite universe?
Or please explain to me why the above is not valid.
Answers
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Firstly (this is a general discussion; theories and the math behind them takes up to much time and space {no pun}), your initial statement about the size of the Universe implies there is a "size". The fact is that the age and therefore the size of the Universe is dependant on a number of factors, but one of the most significant is the Hubble Constatnt about which there is a lot of disagreement as to it's value. By disagreement I mean the difference between 50 kms/Mpc and 100 kms/Mpc, or 100% of it's estimated value. This means that it's possible, depending on the actual value of H0, that we can never see the original light emitted at the creation event since the universe is expanding faster than the ability of light , at its speed (C) to to reach us.
So, therefore, my answer to your first poser would be... unknown... and unlikely to accomplish your proposition. Secondly... how big? My response would be "When?" We don't know now and can't know when there's no non-speculative way to measure it.
The Universe is not infinite, by any definition that includes a beginning as a component, which the commonly accepted definition of "Big Bang" does.
Lastly, you seem to imply that if the structure of the Universe is one way or the other that somehow inflation would not be part and parcel of whatever the morphology actually is. Big Bang inflation at around 10^-32 to 10^36 seconds is pretty well established mathmatically and the geometry of the universe follows on that event and the true value of Hubble.... A lot of discussion about the geometry, but most likely it's flat in my largely uninformed opinion...
So, therefore, my answer to your first poser would be... unknown... and unlikely to accomplish your proposition. Secondly... how big? My response would be "When?" We don't know now and can't know when there's no non-speculative way to measure it.
The Universe is not infinite, by any definition that includes a beginning as a component, which the commonly accepted definition of "Big Bang" does.
Lastly, you seem to imply that if the structure of the Universe is one way or the other that somehow inflation would not be part and parcel of whatever the morphology actually is. Big Bang inflation at around 10^-32 to 10^36 seconds is pretty well established mathmatically and the geometry of the universe follows on that event and the true value of Hubble.... A lot of discussion about the geometry, but most likely it's flat in my largely uninformed opinion...
Thanks Clanad.
1 I believe that the Hubble constant has been well defined and gives an age of 13.8 billion years to the universe. Since the big bang event was of a finite size and at a specific time, if initial conditions can be estimated, a present size is not an unreasonable concept.
2 The cosmic background radiation takes us back a good way, but it is not reasonable to state that " light " from the big bang has not got here yet because the big bang happened here ( and everywhere else ).
3 There remains my question of how a non infinite but flat universe is possible. I was not implying anything, just trying to understand.
1 I believe that the Hubble constant has been well defined and gives an age of 13.8 billion years to the universe. Since the big bang event was of a finite size and at a specific time, if initial conditions can be estimated, a present size is not an unreasonable concept.
2 The cosmic background radiation takes us back a good way, but it is not reasonable to state that " light " from the big bang has not got here yet because the big bang happened here ( and everywhere else ).
3 There remains my question of how a non infinite but flat universe is possible. I was not implying anything, just trying to understand.
The Hubble constant is much more accurately known now, it used to have an error in excess of 100%. The most widely believed view is that the universe is flat and will reach a stable point. But size is difficult to comprehend in this case, largely because space looks the same no matter you stand. i.e. Everywhere looks like and could be the centre. It is one of the main problems with the big-bang inflation model, along with universe density.
Sorry, this won't be much use because I can't remember where I read it - possibly New Scientist - but I saw an estimate that the observable universe was about 10^-60 (i.e. ten to the power minus sixty) of the full universe. The figure had been derived assuming that large scale anisotropy in the microwave background radiation was caused by quantum fluctuations in the early universe.
I have not heard this figure but it is well accepted that the observable universe is smaller than the actual universe.
This is because the space bertween us at the centre (every place is at the centre of its view) and the edge has expanded since the light was released. So even though theose photons were emitted literally the dawn of time there hasn't been enouth time for their light to reach us.
It is known that gravitationally large objects over the horizon influence the movement of the most distant observable galaxies.
This is because the space bertween us at the centre (every place is at the centre of its view) and the edge has expanded since the light was released. So even though theose photons were emitted literally the dawn of time there hasn't been enouth time for their light to reach us.
It is known that gravitationally large objects over the horizon influence the movement of the most distant observable galaxies.
The size of the observable universe is bounded by the distance that light has had time to travel to us.
Not entirely. We can observe the effects of interactions between forces emanating inside and outside our directly visible range.
An observer in the Andromeda Galaxy would have a slightly different observable universe to ours and be able to observe objects slightly outside our own range of observation.
Yes they would see light up to about three million years prior to and hence what we see along the line of our separation.
However the actual size of the universe is much bigger than this.
Estimated to currently extend 46.5 glys in all directions.
An observer at the edge of our observable universe would mostly observe a volume of space completely beyond our range of observation.
Except for the portion common to our intersecting spheres.
My question is....How many of these hypothetical observable universe steps would we have to take before returning to an observable universe which contained our place of origin? How big is the actual universe?
(46.5/13.7) - 1
Or alternatively would we never return, meaning that the universe is infinite.
Unless you make allowance for arrival at each step proportionately faster in relation to the rate of expansion.
Also if the universe is flat not curved due to inflation how does the above work in a non infinite universe?
The light now arriving from the CMBR originated from a point that at the time of first transparency was more than a thousand times closer, (only 36mlys away).
Or please explain to me why the above is not valid
Something to think about
Not entirely. We can observe the effects of interactions between forces emanating inside and outside our directly visible range.
An observer in the Andromeda Galaxy would have a slightly different observable universe to ours and be able to observe objects slightly outside our own range of observation.
Yes they would see light up to about three million years prior to and hence what we see along the line of our separation.
However the actual size of the universe is much bigger than this.
Estimated to currently extend 46.5 glys in all directions.
An observer at the edge of our observable universe would mostly observe a volume of space completely beyond our range of observation.
Except for the portion common to our intersecting spheres.
My question is....How many of these hypothetical observable universe steps would we have to take before returning to an observable universe which contained our place of origin? How big is the actual universe?
(46.5/13.7) - 1
Or alternatively would we never return, meaning that the universe is infinite.
Unless you make allowance for arrival at each step proportionately faster in relation to the rate of expansion.
Also if the universe is flat not curved due to inflation how does the above work in a non infinite universe?
The light now arriving from the CMBR originated from a point that at the time of first transparency was more than a thousand times closer, (only 36mlys away).
Or please explain to me why the above is not valid
Something to think about
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