Is the Universe infinite?

[Dan B.]

On 22.8.2017 at 3:24 AM, Strange said:

So an observer half way to the edge of our observable universe would have their own observable universe, and they would see it as having the same age as ours. As far as we know, that will be true wherever you are in the universe.

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The Observable Universe is clear.

However,

1. Infinite Universe vs Observable Universe

    A. Assuming that we could move 1 Trillion Light year away from Earth at any direction (Deep into the Infinite Universe):

          Should we see a similar space view as we see from our current location?

    B. Is there any characteristics change between the two? (CRM, Temp...)

    C.  Can we assume that the Observble Universe is covered by the Infinite Universe?

    D. Is there any edge to the infinite Universe?

 2. Temp - If the temp of the Infinite Universe is identical to the Obseravble Universe:

   A. Can we see it as an example of small oven inside a Huge oven (both at the same temp)?

       If So, by opening the door of the inside oven, Can we decrease its temp?

   B. In the same token. How could the Observable Universe decrease its temp if it is covered by an infinite Universe with the same temp? 

 

 

[Strange]

19 minutes ago, Dan B. said:

The Observable Universe is clear.

However,

1. Infinite Universe vs Observable Universe

    A. Assuming that we could move 1 Trillion Light year away from Earth at any direction (Deep into the Infinite Universe):          Should we see a similar space view as we see from our current location?

That is the assumption but, of course, we can't know. There is no reason to think it would be significantly different but maybe things change very gradually as you move through the universe (gradually, because the observable universe appears completely homogeneous & isotropic).

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    B. Is there any characteristics change between the two? (CRM, Temp...)

We don't know but assume not.

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    C.  Can we assume that the Observble Universe is covered by the Infinite Universe?

Sorry, don't know what that means.

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    D. Is there any edge to the infinite Universe?

No, because it is infinite. (Actually, in current models even a finite universe has no edge.)

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 2. Temp - If the temp of the Infinite Universe is identical to the Obseravble Universe:

   A. Can we see it as an example of small oven inside a Huge oven (both at the same temp)?       If So, by opening the door of the inside oven, Can we decrease its temp?

The trouble with an oven as an analogy is that it implies a source of heat. Also, if they were both at the same temperature then opening the door wouldn't have any effect.

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   B. In the same token. How could the Observable Universe decrease its temp if it is covered by an infinite Universe with the same temp? 

They are both decreasing in temperature in the same way. This is basically the ideal gas law which relates temperature to volume and pressure. As the universe expands it naturally cools (think of an aerosol can, when you release the gas it gets cold - or the opposite when you squeeze a bicycle pump).

 

[Dan B.]

2 hours ago, Strange said:

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   B. In the same token. How could the Observable Universe decrease its temp if it is covered by an infinite Universe with the same temp? 

They are both decreasing in temperature in the same way. This is basically the ideal gas law which relates temperature to volume and pressure. As the universe expands it naturally cools (think of an aerosol can, when you release the gas it gets cold - or the opposite when you squeeze a bicycle pump).

 

1. Aerosol can - Yes, I fully agree that when you release gas it gets cold. However, in order to set it we need to have two different segments of pressure. If the pressure in the can equivalent to the presure outside the can, there will be no gas flow and no gas gets cold. 

2. It seems to me that we do not know how Infinity Universe really works. We might get a severe error by implementing an intuitive finite knowledge on the Infinity.

3. Thermodynamics - Do we have a chapter in thermodynamics which covers the infinity? If not, than it's the time to write it.

 

 

[Strange]

1 hour ago, Dan B. said:

1. Aerosol can - Yes, I fully agree that when you release gas it gets cold. However, in order to set it we need to have two different segments of pressure. If the pressure in the can equivalent to the presure outside the can, there will be no gas flow and no gas gets cold.

Like all analogies, that has limited applicability. It only shows how temperature os related to volume and pressure. 

The universe is expanding but not into anything so the analogy doesn't apply in that sense.

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2. It seems to me that we do not know how Infinity Universe really works. We might get a severe error by implementing an intuitive finite knowledge on the Infinity.

You will certainly get confused if you apply intuitive knowledge of infinity. Scientists do not do that.

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3. Thermodynamics - Do we have a chapter in thermodynamics which covers the infinity? If not, than it's the time to write it.

Is there anything that says it is limited to finite situations?

 

But as you have gone from asking questions to rejecting science, you probably won't get any more answers from me.

[beecee]

7 hours ago, Dan B. said:

However,

1. Infinite Universe vs Observable Universe 

The observable universe is simply that part of the universe that EMR from distant regions has had time to reach us: If the universe is infinite, then by definition it stretches far beyond anything we can or will ever be able to measure. 

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 A. Assuming that we could move 1 Trillion Light year away from Earth at any direction (Deep into the Infinite Universe):

          Should we see a similar space view as we see from our current location?

    B. Is there any characteristics change between the two? (CRM, Temp...)

 

The evidence so far tells us that the universe/spacetime is isotropic and homogeneous, at least for the observable universe and we (scientists that is) have no reason to believe that would not extend everywhere. The CMBR would be the same over there as it is here.

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  C.  Can we assume that the Observble Universe is covered by the Infinite Universe?

    D. Is there any edge to the infinite Universe?

 

Logically the universe as a whole, extends beyond our observable horizon in all directions, and probably to infinite quantities. There are no edges or centers to any reasonable current model of the universe/spacetime, either finite or infinite.

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 2. Temp - If the temp of the Infinite Universe is identical to the Obseravble Universe:

Our assumptions on the isotropic and homogeneous nature of the universe tells us that they should be the same.

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   A. Can we see it as an example of small oven inside a Huge oven (both at the same temp)?

       If So, by opening the door of the inside oven, Can we decrease its temp?

   B. In the same token. How could the Observable Universe decrease its temp if it is covered by an infinite Universe with the same temp? 

 

Analogies while certainly being useful, all have limitations. Your second question is simply physics and as Strange has said, is just the relationship between volume, pressure and temperatures and is evidenced in many ways in our general day to day living..

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2. It seems to me that we do not know how Infinity Universe really works. We might get a severe error by implementing an intuitive finite knowledge on the Infinity

I must admit my understanding of infinite and infinite quantities is lacking somewhat and I was advised back in the thread to read up on this topic which I intend to do. In the meantime my limited research so far tells me that infinity exist when relevant quantities are stretched far beyond what we will ever be capable of measuring and/or knowing: I am certainly more comfortable with that definition so far. Remember even when cosmologists speak of a physical BH singularity, or the BB singularity, they are not automatically inferring infinite quantities, although such singularities may lead to infinite quantities.

I welcome any comment from any reputable source as to the validity or otherwise of what I have posted above...any errors, alterations and/or corrections?

Edited August 23, 2017 by beecee

[Mordred]

Interesting discussipn so far. 

I would like to note in regards to thermodynamics and the oven mentioned above.

Under the classical ideal gas laws treat all thermodynamics as a homogeneous and isotropic fluid with adiabatic ( no inflow or outflow of energy) expansion. 

Now think about the observable universe and lets assume the above isn't true but instead we have a surrounding universe that isn't of the same temperature as the observable portion state.

As you approach the further regions of our observable universe the temperature will have a gradiant, depending on the temp variation.

So no longer homogeneous and isotropic...

Our observations agree strongly that this isn't the case and the immediate regions (regions of shared causality overlap) outside our observable portion will be roughly the same thermodynamic state.  Beyond regions of possible shared causality overlaps we simply will never know.

Edited August 24, 2017 by Mordred

[Carrock]

There's an analogy used in this thread that I feel has been stretched to breaking point, with some posters confused by its departure from actual cosmology.

This is the analogy with a classical container whose gaseous contents remain in thermal equilibrium and cool as it expands, and that the CMBR is the same as the equilibrium radiation associated with a temperature of 2.7K.

After the time of last coupling, if the universe doubles in size, the energy of each photon is halved since the wavelength has doubled due to the expansion of space and its energy is hc/wavelength i.e. its energy is inversely proportional to the size of the universe.

Non relativistic matter has kinetic energy= (1/2)mv^2. If the universe doubles in size each particle has its velocity halved since it travels twice the distance in unit time. However because of the v^2 term its energy is quartered i.e. its energy is inversely proportional to the square of the size of the universe.

Other interactions e.g. gravitational soon swamp the effect of expansion on non relativistic matter.

There is an exception, the neutrino, which is ordinary matter travelling at relativistic speed, which complicates things.

The temperature of the cosmic neutrino background radiation (with similar caveats as above) is estimated to be about 1.95K.

https://en.wikipedia.org/wiki/Cosmic_neutrino_background provides interesting info.

The CMBR at 2.7K and the CNBR at 1.95K are not in equilibrium in the sense that there is negligible interaction to even out any perturbation induced since the time of last coupling.

While these temperatures, especially the CMBR, are very useful in calculations, neither is applicable in some calculations involving equilibrium thermodynamics.

 

 

[Airbrush]

On ‎8‎/‎23‎/‎2017 at 5:42 AM, Dan B. said:

......Assuming that we could move 1 Trillion Light year away from Earth at any direction (Deep into the Infinite Universe):

          Should we see a similar space view as we see from our current location?

The universe, or as I prefer to call it "our big bang", out at a distance of a Trillion LY is about 21 times the distance to the edge of our observable universe (big bang).  It could look a little different, or very different, at that distance.  How would it look at a great distance, like a googol LY out?  No way of telling because even though our big bang is homogeneous and isotropic out to 46 Billion LY, that does not mean it will look that way from a viewpoint a googol LY away.

Edited August 24, 2017 by Airbrush

[Dan B.]

On 24.8.2017 at 5:17 AM, Mordred said:

Interesting discussipn so far. 

I would like to note in regards to thermodynamics and the oven mentioned above.

Under the classical ideal gas laws treat all thermodynamics as a homogeneous and isotropic fluid with adiabatic ( no inflow or outflow of energy) expansion. 

Now think about the observable universe and lets assume the above isn't true but instead we have a surrounding universe that isn't of the same temperature as the observable portion state.

As you approach the further regions of our observable universe the temperature will have a gradiant, depending on the temp variation.

So no longer homogeneous and isotropic...

Our observations agree strongly that this isn't the case and the immediate regions (regions of shared causality overlap) outside our observable portion will be roughly the same thermodynamic state.  Beyond regions of possible shared causality overlaps we simply will never know.

Now that we know that our Universe is infinite, homogeneous and isotropic, let's take it one step further.

Could it be that the CRM and all other measurements are simple reflections from this infinite Universe?

In order to verify it:

The Observable Universe is just a very tiny piece with regards to the Infinity Universe. 

Let's assume that we could set our whole observable Universe in an oven, what would be the outcome of its thermodynamics?

Could it be that based on its density, its temp in this kind of oven should be exactly 2.7K?

Could it be that a black body radiation is just a reflection of this infinite Universe and we might discover it in this oven?

Edited August 25, 2017 by Dan B.

[Strange]

1 minute ago, Dan B. said:

Now that we know that our Universe is infinite, homogeneous and isotropic, let's take it one step further.

We don't know it is infinite.

1 minute ago, Dan B. said:

Could it be that the CRM and all other measurements are a simple feedback from this infinite Universe?

By definition, we can only measure things from our observable universe.

2 minutes ago, Dan B. said:

Let's assume that we could set our whole observable Universe in an oven, what would be the outcome of its thermodynamics?

It depends on the temperature of that oven.

2 minutes ago, Dan B. said:

Could it be that based on its density, its temp in this kind of oven should be exactly 2.7K?

Why? We have a model that explains the temperature. What is your alternative explanation?

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Could it be that a black body radiation is just a reflection of this infinite Universe and we might discover it in this oven?

It is a characteristic of the OBSERVABLE universe. We are causally disconnected from the rest of the universe. So, no.

[Mordred]

to start with whether the universe or finite is irrelevant to this question, secondly adiabatic literally means no inflow or outflow of energy or temperature.

 Think about that with regards to your ovenx  x posted with Strange

Edited August 25, 2017 by Mordred

[Dan B.]

1 hour ago, Strange said:

1 hour ago, Dan B. said:

Let's assume that we could set our whole observable Universe in an oven, what would be the outcome of its thermodynamics?

It depends on the temperature of that oven

Well, the Oven itself does not contribute any heat. There is no heater inside. It is used as an isolator. No heat gets in and no heat goes out.

Hence, without the galaxy or stars Its temp is virtually 0 K.

However, in order to simplify the question -

If we could set only the Milky Way in an Oven, what might be its temp?

In other words, if we can close the Milky way heat radiation in an Oven, what might be the average temp?

 

 

 

Edited August 25, 2017 by Dan B.

[Strange]

1 hour ago, Dan B. said:

Well, the Oven itself does not contribute any heat. There is no heater inside. It is used as an isolator. No heat gets in and no heat goes out.

Then it isn't an oven.

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If we could set only the Milky Way in an Oven, what might be its temp?

In other words, if we can close the Milky way heat radiation in an Oven, what might be the average temp?

That is irrelevant. We can observe the light from our and other galaxies. It is not a black body spectrum. For that you need a uniformly heated gas or plasma.

But I think the answer is that it is about 1 million degrees. So you won't find much help there.

[Dan B.]

17 hours ago, Strange said:

We can observe the light from our and other galaxies. It is not a black body spectrum.

 

What is a Black Body ?

A black body is an ideal body which allows the whole of the incident radiation to pass into itself ( without reflecting the energy ) and absorbs within itself this whole incident radiation (without passing on the energy).

1. So could it be that an infinite object as an infinite Universe meets this expression?

2. An Infinite Universe could also be considered to an infinite Star. We know that a star has an internal black body radiation.

    So, if a star has an internal black body radiation, why an infinite star (as an infinite Universe) couldn't have that kind of radiation? 

If that is correct, than the black body radiation of Universe proves that our Universe must be infinite

 

 

 

 

L

[Strange]

A star does not have a black body spectrum. So an infinite number of stars wouldn't either. 

[Dan B.]

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

A star or planet often is modeled as a black body, and electromagnetic radiation emitted from these bodies as 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.

28 minutes ago, Strange said:

A star does not have a black body spectrum. So an infinite number of stars wouldn't either. 

Not Infinite number of stars but one Infinite star.

Edited August 26, 2017 by Dan B.

[Carrock]

1 hour ago, Dan B. said:

If that is correct, than the black body radiation of Universe proves that our Universe must be infinite

Which cosmic background radiation do you think is relevant?

The neutrino background at 1.95K or the microwave background at 2.7K?

IIRC the neutrino time of last scattering was about one second after BB and the photon(microwave) time of scattering 300 thousand years.

Expansion lowered their temperature after last scattering but these particles were never again in equilibrium.

Perturbations and blocking after last scattering will never be smoothed out.

4 minutes ago, Dan B. said:

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

A star or planet often is modeled as a black body, and electromagnetic radiation emitted from these bodies as 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.

Again these photons are no longer in thermal equilibrium when they've left the sun. The sun heats one side of objects on earth, but not the other.

The black body radiation you're referring to here is radiation from a black body, not radiation inside a black body.

[Dan B.]

5 minutes ago, Carrock said:

The black body radiation you're referring to here is radiation from a black body, not radiation inside a black body.

It seems to me that you are missing the point.

The Internal radiation inside a star (or inside the  photosphere) is a Black body radiation.

Therefore, as small portion of this radiation is ejected out - it carries the black body signature.

If the Inside radiation was not a black body then by definition it can't be a black body radiation as it goes out.

[Carrock]

22 hours ago, Dan B. said:

Let's assume that we could set our whole observable Universe in an oven, what would be the outcome of its thermodynamics?

Could it be that based on its density, its temp in this kind of oven should be exactly 2.7K?

Could it be that a black body radiation is just a reflection of this infinite Universe and we might discover it in this oven?

I was referring to this and the fact that the CMBR at 2.7K and the CNBR at 1.95K are not now and never again will be in equilibrium with themselves or each other.

Black body radiation is generated by a body in thermal equilibrium. Once the radiation leaves or is decoupled it is no longer in equilibrium.

You're avoiding the question of whether you think the universe is a black body at 2.7K or 1.95K or neither.

[Dan B.]

35 minutes ago, Carrock said:

You're avoiding the question of whether you think the universe is a black body at 2.7K or 1.95K or neither.

1. I claim that CMB in an Infinity Universe should carry a black body spectrum.

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

 The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K.

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

35 minutes ago, Carrock said:

Black body radiation is generated by a body in thermal equilibrium. Once the radiation leaves or is decoupled it is no longer in equilibrium.

The radiation in an Infinite star does not leave the star. Therefore, as long as the radiation is located inside the Infinite star, it is in thermal equilibrium.

Hence, we get it as a black body radiation.

If the Universe was not infinite, than the radiation had to leave the Universe.

In this case, once the radiation leaves or is decoupled it is no longer in equilibrium and it has no black body spectrum.

That proves that the universe is Infinite

Edited August 26, 2017 by Dan B.

[Mordred]

DanB radiation and matter has flow rates, this applies to baryon accoustic oscillations. A starter up on this topic is the Jeans instability equations for hydrodynamic flows.

Speed limits of radiation through spacetime and mediums apply here.

This directly relates to the Causality relations of the particle horizon, Cosmological event horizon and our Observable universe.

And no, thermodynamic data including any produced by radiation do not prove our universe is infinite.  Under theory yes, but under observation indeterminant. It can still swing either way 

Edited August 26, 2017 by Mordred

[Phi for All]

3 hours ago, Dan B. said:

1. I claim that CMB in an Infinity Universe should carry a black body spectrum.

!

Moderator Note

Welcome to the Speculations section. Please read the special rules for this section, and provide as much evidence as you can to support your position.

 

[StringJunky]

On 15/08/2017 at 3:22 AM, Carrock said:

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

 

If infinity is without limit then infinity/x (but not infinity) = infinity. i can't see how it can be anything else. I'm no mathematician but is that not so?

[Strange]

4 hours ago, Dan B. said:

1. I claim that CMB in an Infinity Universe should carry a black body spectrum.

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

The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K.

You can claim that. But to be taken seriously you need to provide some justification; ideally based on known physics. Without that, your claim is just hot air.

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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.

5 hours ago, Dan B. said:

Therefore, as small portion of this radiation is ejected out - it carries the black body signature.

If the Inside radiation was not a black body then by definition it can't be a black body radiation as it goes out.

Here is a graph of the light from the sun: https://en.wikipedia.org/wiki/Sunlight#/media/File:Solar_spectrum_en.svg

Note that: 

1) It departs significantly from a black body

2) The black body spectrum it approximates is about 5800K, not 2.7K

So this cannot possibly be the source of the CMB.

[Carrock]

 

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

1 hour ago, StringJunky said:

If infinity is without limit then infinity/x (but not infinity) = infinity. i can't see how it can be anything else. I'm no mathematician but is that not so?

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.

 

Edited August 26, 2017 by Carrock
Removed offtopic line