Is the Universe infinite?

[StringJunky]

34 minutes ago, Carrock said:

 

"That does mess me up. I thought each portion was finite. Or infinite." - Carrock

Infinity/infinity or infinity-infinity is basically not defined - I was being (too) informal.

Addition and multiplication of infinities is well defined. Using e.g. the denumerable infinity aleph-null,

aleph-null = n+(aleph-null) = n*(aleph-null) =(aleph-null)^n where n (I'm being overcautious) is a finite positive integer and definitely not infinite.

 

So a spatially infinite universe can be considered to be e.g. aleph-null units of finite space or aleph-null units of space each of volume aleph-null units.

 

Thanks. I didn't realise that was the first page or else i wouldn't have asked the question because it was too far back really.

[Dan B.]

14 hours ago, Strange said:

Quote

2. We have to look at the Infinite Universe as an Infinite star.

Except it isn't. It is a collection of stars and galaxies separated by largely empty space

 

Don't you think that on large scale the Universe is homogenous?

It is stated that:

https://en.wikipedia.org/wiki/Friedmann_equations

"The Friedmann equations start with the simplifying assumption that the universe is spatially homogeneous and isotropic, i.e. the cosmological principle; empirically, this is justified on scales larger than ~100 Mpc."

https://en.wikipedia.org/wiki/Cosmological_principle

"Although the universe is inhomogeneous at smaller scales, it is statistically homogeneous on scales larger than 250 million light years. The cosmic microwave background is isotropic, that is to say that its intensity is about the same whichever direction we look at.^[8]"

If the Universe is Infinite, than could it be that a scale of 250ML years is like one grain of sand on Earth?

Hence, don't you agree that on large scale the collections of stars galaxies and space are homogenous?

In this case, why we can't consider it as an Infinite star with a density of:

https://hypertextbook.com/facts/2000/ChristinaCheng.shtml

"The critical density of matter in the universe that separates the two possibilities can be calculated from Einstein's theory. It is now approximately 10⁻³⁰ grams per cubic centimetre. Small though this value maybe, it separates two entirely different futures for the universe"

and a temp of 2.7K?

 

 

 

[Strange]

1 minute ago, Dan B. said:

In this case, why we can't consider it as an Infinite star with a density of:

Because it isn't?

The average density of the universe is much lower than that of a star. 

The average temperature of the universe is much lower than that of a star.

Quote

A star is a luminous sphere of plasma held together by its own gravity.

https://en.wikipedia.org/wiki/Star

The universe is not a star. Simply repeating it will not make it so.

The radiation from stars is not a black body and not of the right temperature.

Also, we have a model that explains exactly why we see a blackbody spectrum with a temperature of 2.7K. Perhaps you would ike to explain exactly what is wrong with that model?

[Carrock]

19 minutes ago, Dan B. said:

...why we can't consider [the universe as having] a temp of 2.7K?

For the same reason you can't consider the universe as having a temp of 1.95K - the cosmic neutrino background temperature.

The CMBR now has the spectrum of black body radiation from a source at 2.7K. It ceased to be in equilibrium at its time of last scattering when its temperature was about 3000K at 380000 years after BB.

The CNBR now has the spectrum of black body radiation from a source at 1.95K. It ceased to be in equilibrium at its time of last scattering when its temperature was a few million K at around 1 second after BB. [neutrino interactions are complicated and this description may not be very accurate.]

So the universe is not in equilibrium. 'spatially homogeneous and isotropic' need not and in this case does not mean in equilibrium.

The CNBR does not have much current effect so it can often be ignored in calculations (but not in calculating critical density). However it has had a major effect and cosmological models have to take it into account.

Strange has addressed the other points you've made. This post is simply an expansion of what I've previously written. I've learned a fair amount about cosmology in this topic.

You now have four temperatures to choose from....

 

 

 

[Dan B.]

1 hour ago, Strange said:

The average density of the universe is much lower than that of a star. 

The average temperature of the universe is much lower than that of a star.

https://en.wikipedia.org/wiki/Star

The universe is not a star. Simply repeating it will not make it so.

Yes, I agree that the Universe is not a star.

I also agree that the density and the temp is much lower than an average star.

But, why a special/unique star can't be in low density and low temp?

Is there any limitation for star density or temp?

However, if you don't like to call it star - then let's keep it under the name - Universe.

 

1 hour ago, Strange said:

The radiation from stars is not a black body and not of the right temperature.

Yes, the radiation from star is not black body.

But that was not my intention.

What about the radiation inside the star or in the  photosphere?

It is stated that it has a black body radiation.

https://en.wikipedia.org/wiki/Black_body#/media/File:Idealized_photosphere.png

"An idealized view of the cross-section of a star. The photosphere contains photons of light nearly in thermal equilibrium, and some escape into space as near-black-body radiation".

But why?

The answer is - thermal equilibrium: "The photosphere contains photons of light nearly in thermal equilibrium".

Therefore, let me ask the following questions:

1. do you agree that if the Universe is in thermal equilibrium its radiation should be black body (or near black body)?

2. If so, what is needed for the Universe to be in thermal equilibrium?

    Do you agree that there is only one solution for that - an Infinite Universe?

 

Edited August 27, 2017 by Dan B.

[Strange]

1 minute ago, Dan B. said:

But, why a special/unique star can't be in low density and low temp?

You need to show (you know: maths and physics) that this is possible rather than just relying on "what if".

2 minutes ago, Dan B. said:

1. do you agree that if the Universe is in thermal equilibrium its radiation should be black body (or near black body)?

It isn't. So the remaining questions are moot

[Dan B.]

O.K.

Let me ask the following:

Based on the BBT we can give an explanation for the Observable Universe - That is clear!

We can justify how a Universe with a radius of 42 BLY had been evolved in time frame of 13.8.

However, it was stated that the real universe is bigger than the observable Universe. 

Some claim that it might be Infinite some might claim that it isn't - However, at least it is very big comparing our tiny observable Universe.

Few questions:

1. Why do we assume now that the Universe could be infinite?

The results from the WMAP show the universe/spacetime to be very nearly flat, at least within very small error bars. A flat universe denotes an infinite universe. Of course it is also possible that an even more accurate methodology may see that flatness as simply the small part of a much larger curvature.

With regards to the BBT

It is stated:

On 19.8.2017 at 9:17 PM, Strange said:

On 19.8.2017 at 9:11 PM, Dan B. said:

3. Why do we still need to use BBT as an explanation for Infinite Universe?

Because it is still the best explanation for all the evidence.

How could it be the best explanation if it can't give an explanation for the real size of our Universe?

So even if the BBT gives perfect explanation to the Observable Universe, how can we ignore the rest of the Universe?

On 22.8.2017 at 7:40 PM, Strange said:

The age of the universe is thought to be 13.8 billion years. Whether it is finite or infinite.

But again - the time frame of 13.8 Billion years gives an explanation for a maximal universe size of 42 BLY. what about the rest?

 

On 22.8.2017 at 3:06 AM, beecee said:

Quote

How a Big Bang which took place 13.8 Billion years ago could affect an infinite Universe?

It doesn't. It describes the evolution of spacetime from 10-43 seconds post t, to what we are able to observe today. If the Universe is infinite, it would always have had to be infinite, and going back in time would just  shorten the distances between any two points, up to around t+10-43 seconds.

If the Universe is infinite, it would always have had to be infinite

Hence do you mean that if the Universe is infinite, it was there infinite time before the BB (So, it age is intinite)?

In the same token, If the Universe is bigger than the Observable Universe could it be that it was there before the BB?

If the Universe was there before the BB, while the BBT doesn't cover its existence, than could it be that there is error in the BBT?

I'm quite confused with that.

 

[Strange]

2 minutes ago, Dan B. said:

How could it be the best explanation if it can't give an explanation for the real size of our Universe?

We can't know how big the universe is because the part outside the observable universe is ... not observable. 

The Big Bang model describes a universe cooling from an early hot dense state. That doesn't say anything about size.

4 minutes ago, Dan B. said:

So even if the BBT gives perfect explanation to the Observable Universe, how can we ignore the rest of the Universe?

Well, we can ignore it because it is not observable (which also means it can have no effect on us).

5 minutes ago, Dan B. said:

But again - the time frame of 13.8 Billion years gives an explanation for a maximal universe size of 42 BLY. what about the rest?

The size of the observable universe (more like 49 billion light years, I think) is determined by how much time light has had to reach us. The rest is too far away for light to have reached us yet. I'm not sure what the problem is.

7 minutes ago, Dan B. said:

If the Universe is infinite, it would always have had to be infinite

Hence do you mean that if the Universe is infinite, it was there infinite time before the BB (So, it age is intinite)?

There isn't really any evidence for "the Big Bang" as an event. All we can talk about is the earliest time our models take us back to. So we can't really say what was before that. But if the universe is [in]finite now then it was [in]finite then.

 

[beecee]

47 minutes ago, Dan B. said:

O.K.

Let me ask the following:

Based on the BBT we can give an explanation for the Observable Universe - That is clear!

We can justify how a Universe with a radius of 42 BLY had been evolved in time frame of 13.8.

However, it was stated that the real universe is bigger than the observable Universe. 

Some claim that it might be Infinite some might claim that it isn't - However, at least it is very big comparing our tiny observable Universe.

With regards to the BBT

It is stated:

How could it be the best explanation if it can't give an explanation for the real size of our Universe?

So even if the BBT gives perfect explanation to the Observable Universe, how can we ignore the rest of the Universe?

But again - the time frame of 13.8 Billion years gives an explanation for a maximal universe size of 42 BLY. what about the rest?

 

If the Universe is infinite, it would always have had to be infinite

Hence do you mean that if the Universe is infinite, it was there infinite time before the BB (So, it age is intinite)?

In the same token, If the Universe is bigger than the Observable Universe could it be that it was there before the BB?

If the Universe was there before the BB, while the BBT doesn't cover its existence, than could it be that there is error in the BBT?

I'm quite confused with that.

 

As per what I said and which you quoted.....

Quote

The results from the WMAP show the universe/spacetime to be very nearly flat, at least within very small error bars. A flat universe denotes an infinite universe. Of course it is also possible that an even more accurate methodology may see that flatness as simply the small part of a much larger curvature

It is still conceivable that a flat universe need not be infinite [a possible torus shape] Either way try thinking of infinity as simply being beyond our ability to measure within any degree of accuracy.

Again we really are unable to determine whether the universe is finite or infinite, but again we can say that the universe, the whole universe, is somewhere between humongously  big and infinite in size and extent...either way, too big for us simple humans to make any real measurable quantities, if even we were able to. Also again, the BB is not a model of how the universe started or was created....It is a descriptive model of how space and time [as we know them] henceforth known as spacetime/universe evolved from a hotter, denser state beginning at around 10-43 seconds after any proposed event.

The rest of the universe beyond the observable universe, as Strange has said, is beyond any causal effect and can have no known effect on our observable sphere.

Edited August 27, 2017 by beecee

[Dan B.]

On 27.8.2017 at 11:37 PM, beecee said:

The rest of the universe beyond the observable universe, as Strange has said, is beyond any causal effect and can have no known effect on our observable sphere.

What is the meaning of: "The rest of the universe beyond the observable universe".

Let's start by understanding the meaning of: "observable universe"

https://en.wikipedia.org/wiki/Observable_universe

"The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects have had time to reach Earth since the beginning of the cosmological expansion."

The word observable used in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected. It refers to the physical limit created by the speed of light itself. Because no signals can travel faster than light, any object further away from us than light could travel in the age of the universe(estimated as of 2015 around 13.799±0.021 billion years^[5]) simply cannot be detected, as they have not reached us yet. In practice, the limit on observation is not 13.799 billion light-years for two reasons.^[10] The first reason is that space itself is expanding, so we can actually detect light from objects that were once close, but are now up to around 45.7 billion light years away (rather than up to 13.799 billion light years away as might be expected).^[10] The second reason is that before the recombination epoch, about 378,000 years after the Big Bang,^{[citation needed]} the Universe was filled with a plasma that was opaque to light, and photons were quickly re-absorbed by other particles, so we cannot see objects from before that time using light or any other electromagnetic radiation. (Gravitational waves and neutrino background would have been unaffected by this, and may be detectable from earlier times.)"

Hence, if I understand it correctly - "observable universe" means the maximal predicted size of the Universe based on its age, space expansion... as estimated by BBT and the speed of light.

We can't really see this Spherical region. We just know that based on the above data by the BBT and the speed light limit, that region is the maximal size of the Universe.

Therefore, it seems to me that as long as the real Universe is in the equal or smaller than the observable universe, it meets the prediction by the BBT.

So how could it be that the rest of the Universe could be bigger than the maximal predicted  spherical region of the Universe (45.7 BLY)?

 

 

 

 

[Strange]

51 minutes ago, Dan B. said:

Hence, if I understand it correctly - "observable universe" means the maximal predicted size of the Universe based on its age, space expansion... as estimated by BBT and the speed of light.

No. It is the size of the universe that is (in principle) observable from Earth. Beyond that is the rest of the universe that can never be observed.

Someone 50 billion light years away will have their own observable universe which overlaps with ours. But most of their observable universe is outside our observable universe. Someone 100 billion light years away will have their own observable universe which doesn't overlap ours and so is outside our observable universe.

 

[beecee]

5 hours ago, Dan B. said:

What is the meaning of: "The rest of the universe beyond the observable universe".

We can't really see this Spherical region. We just know that based on the above data by the BBT and the speed light limit, that region is the maximal size of the Universe.

So how could it be that the rest of the Universe could be bigger than the maximal predicted  spherical region of the Universe (45.7 BLY)?

Bold in your quotes by me: The link you gave yourself, distinctly says "

Quote

 

The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects have had time to reach Earth since the beginning of the cosmological expansion."

The word observable used in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected. It refers to the physical limit created by the speed of light itself."

 

I'm not sure how you can get from that information, that the observable universe is the whole universe which you seem to be saying. Again whether the universe is infinite or finite is still an open question. It is though so big as to defy any attempts we can make to measure it. The finite speed of light assures that. There is no center of the universe from which everything is expanding from: The BB happened everywhere at the same time, remembering that the BB is a model of a universe evolving/expanding from a hotter, denser state, from t+10-43 seconds.

That first quantum/Planck instant and the nature of spacetime and/or the mathematical singularity predicted, is beyond the parameters of the BB. 

[Strange]

5 hours ago, Dan B. said:

"The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects have had time to reach Earth since the beginning of the cosmological expansion."

Lets just look at this again.

It very specifically says that the observable universe is all the matter that can be observed from Earth (because there hasn't been enough time for light from matter further away to reach us). It doesn't say anything about the maximal size of the universe.

It goes on to say:

5 hours ago, Dan B. said:

"any object further away from us than light could travel in the age of the universe(estimated as of 2015 around 13.799±0.021 billion years^[5]) simply cannot be detected"

The same page also says:

Quote

Some parts of the Universe are too far away for the light emitted since the Big Bang to have had enough time to reach Earth, so these portions of the Universe lie outside the observable universe. 

So it explicitly says that there are objects further away than the limit of the observable universe. And therefore the "whole universe" is bigger than the observable universe.

5 hours ago, Dan B. said:

So how could it be that the rest of the Universe could be bigger than the maximal predicted  spherical region of the Universe (45.7 BLY)?

Why shouldn't it be?

Edited September 7, 2017 by Strange

[Dan B.]

Thanks

Correlation between the Universe age and its size:

Let's look at the following diagram:

 

At age of one second - the size of the Universe is just over one light year.

At age of one year - The size of the Universe is less than the size of the Milky Way Galaxy.

At age of 13.8 BL (Today) - What is the size of the Universe? (Is it 92 BLY)?

In the same token, what is the expected maximal size of the Universe with regards to its age (at one second, one Year and today)?

Could it be (for example) that at age of only one year the size of the Universe is over than 100 times the size of the Milky Way or even infinity?

[beecee]

7 minutes ago, Dan B. said:

Thanks

Correlation between the Universe age and its size:

Let's look at the following diagram:

 

At age of one second - the size of the Universe is just over one light year.

At age of one year - The size of the Universe is less than the size of the Milky Way Galaxy.

At age of 13.8 BL (Today) - What is the size of the Universe? (Is it 92 BLY)?

In the same token, what is the expected maximal size of the Universe with regards to its age (at one second, one Year and today)?

Could it be (for example) that at age of only one year the size of the Universe is over than 100 times the size of the Milky Way or even infinity?

https://en.wikipedia.org/wiki/Big_Bang

 

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

Quote

The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point. The distinction between the whole Universe and the part of it that we can see is important. In the figure below, two views of the Universe are shown: on the left for 1 Gyr after the Big Bang, and on the right the current Universe 13 Gyr after the Big Bang (assuming that the Hubble constant is H_o = 50 km/sec/Mpc and the Universe has the critical density.) 

 

[Carrock]

 

From http://www.astro.ucla.edu/~wright/infpoint.html

Quote

 

How can the Universe be infinite if it was all concentrated into a point at the Big Bang?

The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point.

 

As every physically separate observer has a slightly different observable universe, there must be numerous relevant separate points, each of which expands into a finite volume. There are also aleph-one points 'between' each point, each of which expands into a finite volume i.e. aleph-one finite volumes in the post big bang universe.

This isn't possible - see e.g. http://www.scienceforums.net/topic/108435-is-the-universe-infinite/?do=findComment&comment=1008151

I was sad to see the moderators decide by unchallengeable fiat that 'Is the Universe infinite or just really, really big?' is a question which cannot be scientifically discussed, but seeing such a statement by a highly respected physicist is even worse.

 

 

[Mordred]

5 hours ago, Dan B. said:

Thanks

Correlation between the Universe age and its size:

Let's look at the following diagram:

 

At age of one second - the size of the Universe is just over one light year.

At age of one year - The size of the Universe is less than the size of the Milky Way Galaxy.

At age of 13.8 BL (Today) - What is the size of the Universe? (Is it 92 BLY)?

In the same token, what is the expected maximal size of the Universe with regards to its age (at one second, one Year and today)?

Could it be (for example) that at age of only one year the size of the Universe is over than 100 times the size of the Milky Way or even infinity?

 

Alrighty excellent question but not a good approach to trying to attempt an answer. The age of universe estimates will depend on certain key equations which I will include shortly.

However those equations look specifically at the rate of expansion estimates given by the Hubble constant and the evolution of the scale factor. This depends on 3 main components.

1) radiation

2) matter

3) Cosmological constant

so lets take some examples.

WMAP 2013 dataset. parameters Hubble constant 69.8 km/s/Mpc. Lambda 0.72, matter density 0.28

with the above universe age will be 13.753 Gy at present age.

Planck 2013 parameters ubble constant 67.9 km/s/Mpc, Lambda 0.693, matter density 0.307

age with above parameters 13.787

You can look up the latest Planck dataset for the age and the current Hubble constant etc above for the current age value. The Planck papers has this under its archives.

Now here is an easy trick, a quick universe age estimate can be done by a few quick simple steps.

 

Keep in mind This is a rough estimate.....

first assume the Hubble constant is constant during the entire expansion history ( we know this isn't true but its an estimate)

[latex] Age=1/H_0[/latex]

multiply your answer with 3.09*10^19 k/Mpc to get the number of seconds

divide the number of seconds in a year by 3.16*10^7 seconds per year.

A more accurate estimate is achieved by assuming  (correctly) that Hubble constant is only constant in a moment in time everywhere and does in fact change over our expansion history.

So now we need a formula that compares the Hubble value today with the Hubble value at other moments in time.

In order to do this we need to look at how the density of radiation, matter and Lambda evolve over time.

For this it is convenient to associate this to the redshift/distance measures.

[latex]H_z=H_o\sqrt{\Omega_m(1+z)^3+\Omega_{rad}(1+z)^4+\Omega_{\Lambda}}[/latex]

with this formula we can correlate the density evolution of matter, radiation and Lambda as a function of redshift. Anyways I won't take you through all the steps but the formula gets rather complex when your looking for the last formula for age of universe. (if anyone wants the steps then I will just ask)

[latex]t(z)=\int^t_0 dt=H_o^{-1}\int^{\frac{1}{1+z}}_0\frac{dx}{\sqrt{(1-\Omega_0)+\Omega_Rx^{-2}+\Omega_mx^{-1}+\Omega_\Lambda x^2}}[/latex]

this is the age-redshift relation formula

 

 

 

Edited September 9, 2017 by Mordred

[Mordred]

1 hour ago, Carrock said:

 

From http://www.astro.ucla.edu/~wright/infpoint.html

As every physically separate observer has a slightly different observable universe, there must be numerous relevant separate points, each of which expands into a finite volume. There are also aleph-one points 'between' each point, each of which expands into a finite volume i.e. aleph-one finite volumes in the post big bang universe.

This isn't possible - see e.g. http://www.scienceforums.net/topic/108435-is-the-universe-infinite/?do=findComment&comment=1008151

I was sad to see the moderators decide by unchallengeable fiat that 'Is the Universe infinite or just really, really big?' is a question which cannot be scientifically discussed, but seeing such a statement by a highly respected physicist is even worse.

 

 

 

I'm really not sure I understand your argument here.

What is wrong with the possibility of an infinite number of finite "Observable portions". You can have an infinite universe where each observer has its own Observable finite portion. Quite frankly in an infinite universe this statement must be true lol. Seeing as how observable is simply  the radius of shared causality

 

Edited September 9, 2017 by Mordred

[Dan B.]

4 hours ago, Mordred said:

 

Alrighty excellent question but not a good approach to trying to attempt an answer. The age of universe estimates will depend on certain key equations which I will include shortly.

However those equations look specifically at the rate of expansion estimates given by the Hubble constant and the evolution of the scale factor. This depends on 3 main components.

1) radiation

2) matter

3) Cosmological constant

so lets take some examples.

WMAP 2013 dataset. parameters Hubble constant 69.8 km/s/Mpc. Lambda 0.72, matter density 0.28

with the above universe age will be 13.753 Gy at present age.

Planck 2013 parameters ubble constant 67.9 km/s/Mpc, Lambda 0.693, matter density 0.307

age with above parameters 13.787

You can look up the latest Planck dataset for the age and the current Hubble constant etc above for the current age value. The Planck papers has this under its archives.

Now here is an easy trick, a quick universe age estimate can be done by a few quick simple steps.

 

Keep in mind This is a rough estimate.....

first assume the Hubble constant is constant during the entire expansion history ( we know this isn't true but its an estimate)

Age=1/H0

multiply your answer with 3.09*10^19 k/Mpc to get the number of seconds

divide the number of seconds in a year by 3.16*10^7 seconds per year.

A more accurate estimate is achieved by assuming  (correctly) that Hubble constant is only constant in a moment in time everywhere and does in fact change over our expansion history.

So now we need a formula that compares the Hubble value today with the Hubble value at other moments in time.

In order to do this we need to look at how the density of radiation, matter and Lambda evolve over time.

For this it is convenient to associate this to the redshift/distance measures.

Hz=HoΩm(1+z)3+Ωrad(1+z)4+ΩΛ−−−−−−−−−−−−−−−−−−−−−−−−−√

with this formula we can correlate the density evolution of matter, radiation and Lambda as a function of redshift. Anyways I won't take you through all the steps but the formula gets rather complex when your looking for the last formula for age of universe. (if anyone wants the steps then I will just ask)

t(z)=∫t0dt=H−1o∫11+z0dx(1−Ω0)+ΩRx−2+Ωmx−1+ΩΛx2√

this is the age-redshift relation formula

 

Thanks

Great answer.

 

4 hours ago, Mordred said:

first assume the Hubble constant is constant during the entire expansion history ( we know this isn't true but its an estimate)

That is a key issue.

Let me use an example of a car in a motor way.

At any given time we can measure its current speed. But that doesn't give any confidence that this speed was constant forever.

In the same token, 

4 hours ago, Mordred said:

WMAP 2013 dataset. parameters Hubble constant 69.8 km/s/Mpc. Lambda 0.72, matter density 0.28

with the above universe age will be 13.753 Gy at present age.

Planck 2013 parameters ubble constant 67.9 km/s/Mpc, Lambda 0.693, matter density 0.307

age with above parameters 13.787

as all the above parameters might change over time, than by definition (based on the formula) we might get significant change in the calculated age.

Different age means - different size of Universe.

Hence, if I understand it correctly, our Universe might be bigger or smaller than our current expectation.

Edited September 9, 2017 by Dan B.

[Mordred]

Its possible and even likely that further density evolution studies will lead to further changes in age estimates. Usually easiest to follow via different Hubble values. Yes that will also influence universe distance measures ie our observable portion.

The above redshift to expansion  relations above also apply to distance measures. 

Edited September 9, 2017 by Mordred

[Strange]

10 hours ago, Dan B. said:

Let's look at the following diagram:

Just a quick request: when you post an image like that, could you include a link to the source.

The context is sometimes important. For example, the graph seems to be talking about the size of the observable universe, even though it doesn't explicitly say that. The source material may make that clear (or maybe not).

10 hours ago, Dan B. said:

At age of 13.8 BL (Today) - What is the size of the Universe? (Is it 92 BLY)?

The observable universe is about 93 billion light years in diameter: https://en.wikipedia.org/wiki/Observable_universe#Size

[Dan B.]

4 hours ago, Strange said:

Just a quick request: when you post an image like that, could you include a link to the source.

https://medium.com/starts-with-a-bang/how-is-the-universe-bigger-than-its-age-7a95cd59c605

[Strange]

9 minutes ago, Dan B. said:

https://medium.com/starts-with-a-bang/how-is-the-universe-bigger-than-its-age-7a95cd59c605

Thanks!

[Dan B.]

Please look at the following:

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

 

 

It is stated that:

"The size of the box in each view is 78 billion light years. The green circle on the the right is the part of the Universe that we can currently see. In the view on the left, this same part of the Universe is shown by the green circle, but now the green circle is a tiny fraction of the 78 billion light year box, and the box is an infinitesimal fraction of the whole Universe. If we go to smaller and smaller times since the Big Bang, the green circle shrinks to a point, but the 78 billion light year box is always full, and it is always an infinitesimal fraction of the infinite Universe.

Note that the black dots represent galaxies, and the galaxies do not expand even though the separation between galaxies grows with time."

 

At age of 1Gyr all the galaxies were quite close to each other, the density is very high and it looks as homogenous and isotropic Universe.

Therefore, the transient from 1Gyr to 13.0 Gyr is quite simple and logical.

However, let's try to understand the process from 1Yr to 1Gyr (or even from 1sec to 1Gyr).

Please look at the following diagram picture:

http://www.wisegeek.org/what-happened-after-the-big-bang.htm#expanding-universe-after-big-bang

At 1Yr there are no galaxies. The whole Observable mass is concentrated at the size of the Milky way.

Lets call it Early observble Universe.

As there are galaxies all over the Universe, can we assume that there was many (or infinite) spots (at the size of our milky way)  which represents other early observable universes?

If that is correct than I have the following questions:

1. Could it be that there was not just one Big bang but an infinite no. of bangs? (each one set a new observabale Universe)?

2. If so, how could it be that all those bangs started exactly at the same moment?

3. Why they do not collide with each other?

4. How could it be that with so many bangs the Universe had been transformed to its current homogenous and isotropic shape?

 

Edited September 9, 2017 by Dan B.

[Strange]

18 minutes ago, Dan B. said:

Please look at the following diagram picture:

http://www.wisegeek.org/what-happened-after-the-big-bang.htm#expanding-universe-after-big-bang

That is a potentially misleading picture as it implies the universe is a bubble with some sort of void outside.

19 minutes ago, Dan B. said:

As there are galaxies all over the Universe, can we assume that there was many (or infinite) spots (at the size of our milky way)  which represents other early observable universes?

I'm not sure how the first bit of that ("galaxies all over the Universe") is relevant. But there are an infinite number of points that have their own observable universe. There may overlap (if those points are close to us) or not (if they are sufficiently far away). These are not separate "bubble universes"; they are just the volume of space that can be seen from any point.

21 minutes ago, Dan B. said:

1. Could it be that there was not just one Big bang but an infinite no. of bangs? (each one set a new observabale Universe)?

There could be multiple big bangs (there are a class of theories based on this idea) but these do not correspond to different observable universes. The observable universe for someone in the Andromeda galaxy is slightly different from ours (but largely overlaps it) so is not related to another Big Bang. 

I think the rest of your questions also show why that connection is not tenable.

If there are multiple big bangs, then they are probably separated by vast distances in space (and maybe time) and are better described as completely separate universes.