How do we know the real size of the space in the Universe? Is it finite or infinite?

[Dandav]

Unfortunately, I couldn't find real answer for this question.

After long thinking, there is a possibility that the answer was always there Infront of our eyes.

That answer is called CMBR.

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

The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe

So, it is all about Microwave radiation.

What is Microwave?

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

Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz, 

Microwaves are non-ionizing radiation, which means that microwave photons do not contain sufficient energy to ionize molecules or break chemical bonds, or cause DNA damage, as ionizing radiation such as x-rays or ultraviolet can.^[25] The word "radiation" refers to energy radiating from a source and not to radioactivity. The main effect of absorption of microwaves is to heat materials;

All warm objects emit low level microwave black-body radiation, depending on their temperature, so in meteorology and remote sensing, microwave radiometers are used to measure the temperature of objects or terrain.^[17] The sun^[18] and other astronomical radio sources such as Cassiopeia A emit low level microwave radiation which carries information about their makeup,

Hence, All warm objects (including any star, warm Pulsar, BH, planet and moon) emit low level microwave black-body radiation

There are billions of objects just in our MW galaxy. 

Each object emits low level microwave black-body radiation

If we could set the MW galaxy in a some sort of a giant oven, that microwave black-body radiation could stay there and eventually heat the entire giant oven while keeping the black body radiation.

In the same token, we could set any nearby galaxy in a similar oven and get also there a black-body radiation in its CMBR.

There is no limitation for the oven size.

Therefore, we can set each nearby galaxy in an oven so their external walls would touch our galaxy' oven.

Let's assume that we have 9 ovens in the same size touching each other.

If we will eliminate the internal walls of those ovens, we would get a 9 times bigger oven while keeping the black-body radiation in the CMBR.

There are billions of galaxies in the observable universe. Hence, if we could keep all of them in a single oven it will still keep the black-body radiation in the CMBR.

However, once we eliminate the oven, we would lose the black-body radiation in the CMBR.

Now, let's assume that the space in the universe has only three real dimensions and it is infinite, while the number of the galaxies is finite.

In this case, as the number of the galaxies is limited and therefore, there is a limit for the size of the oven.

Hence, once we eliminate the oven (around all the finite galaxies in the Infinite space universe), there won't be a black-body radiation in its CMBR.

However, if the number of the galaxies is also infinite and they are located in the whole infinite space universe, then it is clear that even without placing it in an oven it would still keep the black-body radiation in the CMBR.

We currently estimate that "The CMB is landmark evidence of the Big Bang theory for the origin of the universe. "

However, in this case, there must be some sort of curvature in the universe. In other words, the space in this kind of universe must be limited or finite and therefore, there is no need for infinite galaxies to fill all of that finite space. A finite number of galaxies could still keep the black-body radiation in the CMBR (In a finite space universe - without an oven) .

conclusions:

There are two possibilities to maintain the black-body radiation in the CMBR:

1.  Finite space Universe - There must be a curvature in the Universe and therefore it has a limited / finite space. In this case finite no. of galaxies should be good enough to maintain the black-body radiation in the CMBR (without a need to place them all in an oven)

2. Infinite space Universe - There is no curvature in the Universe and therefore its space is infinite. In this case, the number of the galaxies must also be infinite to maintain the black-body radiation in the CMBR ((without a need to place them all in an oven).

If I understand it correctly, so far, we didn't observe any sort of curvature in our Universe.

Therefore, could it be that the second choice might be the correct one?

Edited November 19 by Dandav

[Dandav]

In the following article it is stated:

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

• If Ω = 1, the universe is flat.
• If Ω > 1, there is positive curvature.
• If Ω < 1, there is negative curvature.

 

Infinite or finite

One of the unanswered questions about the universe is whether it is infinite or finite in extent. For intuition, it can be understood that a finite universe has a finite volume that, for example, could be in theory filled with a finite amount of material, while an infinite universe is unbounded and no numerical volume could possibly fill it. Mathematically, the question of whether the universe is infinite or finite is referred to as boundedness. An infinite universe (unbounded metric space) means that there are points arbitrarily far apart: for any distance d, there are points that are of a distance at least d apart. A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other. The smallest such d is called the diameter of the universe, in which case the universe has a well-defined "volume" or "scale"

 

Final results of the Planck mission, released in 2018, show the cosmological curvature parameter, 1 − Ω = Ω_K = −Kc²/a²H², to be 0.0007±0.0019, consistent with a flat universe.^[15] (i.e. positive curvature: K = +1, Ω_K < 0, Ω > 1, negative curvature: K = −1, Ω_K > 0, Ω < 1, zero curvature: K = 0, Ω_K = 0, Ω = 1).

Universe with zero curvature 

In a universe with zero curvature, the local geometry is flat. The most familiar such global structure is that of Euclidean space, which is infinite in extent. Flat universes that are finite in extent include the torus and Klein bottle. Moreover, in three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 are non-orientable. These are the Bieberbach manifolds. The most familiar is the aforementioned 3-torus universe.

 

Hence, based on the measurements the universe is flat and therefore it must be infinite in its extent.

In other words, there is very high possibility that we are living in a universe with infinite volume / space.

Therefore, the following choice should be the correct one:

On 11/19/2024 at 10:29 AM, Dandav said:

2. Infinite space Universe - There is no curvature in the Universe and therefore its space is infinite. In this case, the number of the galaxies must also be infinite to maintain the black-body radiation in the CMBR ((without a need to place them all in an oven).

Could it be that the current BBT can't fit into that kind of infinite space universe?

If so, why we do not try to find an updated version for the BBT theory or even a new theory for our current real infinite space universe?

Edited November 22 by Dandav

[Dandav]

We wish to believe that the Universe is finite in its size and therefore we should observe some curvature in the universe that we can observe (that is also called "local geometry), but unfortunately, the universe doesn't cooperate with this expectation.

The curvature is zero.

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

Local geometry: This relates to the curvature of the universe, primarily concerning what we can observe.

Global geometry: This pertains to the universe's overall shape and structure.

On 11/22/2024 at 8:55 AM, Dandav said:

Final results of the Planck mission, released in 2018, show the cosmological curvature parameter, 1 − Ω = Ω_K = −Kc²/a²H², to be 0.0007±0.0019, consistent with a flat universe

 

On 11/22/2024 at 8:55 AM, Dandav said:

In a universe with zero curvature, the local geometry is flat. The most familiar such global structure is that of Euclidean space, which is infinite in extent.

Therefore, I would assume that what we have observed in the Local geometry is what we have and it is also correct for the Global geometry.

In other words, let's assume that the Global geometry of the universe is infinite in its size and try to understand the real meaning of this discovery.

Edited November 24 by Dandav

[LaurieAG]

20 hours ago, Dandav said:

In other words, let's assume that the Global geometry of the universe is infinite in its size and try to understand the real meaning of this discovery.

Therefore the visible universe, which we cannot see beyond in any empirical way, is a spherical boundary for our physical universal models that may actually be more accurately a cubic model, but we can never test it.

This might explain why the ratio of All matter (dark and Visible) over Visible matter equals 2*pi +/- 1.1% using both the WMAP and PLANCK ΛCDM percentage density figures. And also why twice the ratio of Everything (Dark energy and Matter) divided by Visible matter equals 2*pi squared +/-3%. Please note that the overdensity constant Δ c as used in Virial mass, is 100 for ΛCDM but 200 (double) for your stock standard galaxy and a sphere in a cube occupies around 54% of the total volume. Dark energy and Dark matter are mere phantoms of our restricted universal viewpoint and the limitations of our scientific process.

Quote

This definition is not universal, however, as the exact value of Δ c depends on the cosmology. In an Einstein–de Sitter model, it is assumed that the density parameter is due to matter only, where Ω m = 1 . Compare this to the currently accepted cosmological model for the universe, ΛCDM model, where Ω m = 0.3 and Ω Λ = 0.7 ; in this case, Δ c ≈ 100 (at a redshift of zero; with increased redshift the value approaches the Einstein-de Sitter value and then drops to a value of 56.65 for an empty de Sitter universe). Nevertheless, it is typically assumed that Δ c = 200 for the purpose of using a common definition, also giving the correct one-digit rounding for a long period 1090 > z > 0.87, and this is denoted as r 200 for the virial radius and M 200 for the virial mass.

https://en.wikipedia.org/wiki/Virial_mass#Virial_radius

Edited November 25 by LaurieAG

[Dandav]

On 11/25/2024 at 5:08 AM, LaurieAG said:

Therefore the visible universe, which we cannot see beyond in any empirical way, is a spherical boundary for our physical universal models that may actually be more accurately a cubic model, but we can never test it.

Thanks for this important message about the Viral theorem:

It is stated:

In astrophysics, the virial mass is the mass of a gravitationally bound astrophysical system, assuming the virial theorem applies. In the context of galaxy formation and dark matter halos, the virial mass is defined as the mass enclosed within the virial radius rvir of a gravitationally bound system, a radius within which the system obeys the virial theorem.

The virial radius of a gravitationally bound astrophysical system is the radius within which the virial theorem applies. It is defined as the radius at which the density is equal to the critical density ρc of the universe at the redshift of the system, multiplied by an overdensity constant Δc:

where ρ(<rvir) is the halo's mean density within that radius,

Hence, they discuss about the virial radius & mass of a gravitationally bound astrophysical system and about density.

The key question is how do we know what is the viral mass of the entier global geometry of the universe or its size.

We can easily understand the "observable" Universe radius. It is about 46 BLY:

https://www.britannica.com/video/universe/-203957

since the universe is only about 13.8 billion years old and light takes time to travel through space, then regardless of what direction we look, we see light that's been traveling, at most, 13.8 billion years. So it's logical to think that the observable universe must then be 2 times 13.77 equals 27.5 billion light years across, but it's not. That's because over time, space has been expanding, so the distant objects that gave off that light 13.8 billion years ago have since moved even farther away from us. Today, those distant objects are a bit more than 46 billion light years away. Multiply times 2, and you get 93 billion light years, the diameter of the observable universe.

let's just say that the observable universe is stupendously big, but the whole universe, as far as we can tell, is a lot bigger. Space is most likely infinite, or at least it doesn't have an edge, though the difference between those is another story unto itself.

Therefore, based on this article the space of the global geometry universe is most likely infinite and it has no edge.

However, we need to understand if we operate the viral theorem only on the Finite observable Universe (local geometry) or on the infinite universe (Global geometry).

In order to answer that question let's start with the local Geometry (visible universe -whatever we can see today).

Let's also assume the following:

We can observe a galaxy A1 at a distance of 10 BLY away from us.

Let's assume that at this moment there are people over there looking at our direction. 

It is clear that they should see our milky way with a similar view that we see in their direction (which means: same density of matter, and same zero curvature).

Therefore, if they would look at the other direction (away from our location), it is expected that they should also see the same view: same density of matter, and same zero curvature.

They could also set a viral theorem around them and get the same result as we get around our galaxy.

We can add and claim that a person in A1 should see a galaxy A2 (at the other direction from us) that is located at a distance of 10 BLY from its location.

In the same token, as A1 can't see any curvature around it, then also A2 can't see any curvature.

Therefore, there is a direct line between our galaxy to A2 and the distance should be 20 BLY.

Without a curvature, we can go on with that line up and add more galaxies up to the infinity.

Hence, if we wish to use the viral theorem, then at any location in this infinite line, the density should be similar as it is in our location (while the curvature is zero).

Therefore, as the universe is most likely infinite then it is most likely that its total mass is also infinite.

This understanding was already clear to me at the first stage of this discussion by using the black body radiation in the CMBR. 

On 11/19/2024 at 10:29 AM, Dandav said:

2. Infinite space Universe - There is no curvature in the Universe and therefore its space is infinite. In this case, the number of the galaxies must also be infinite to maintain the black-body radiation in the CMBR ((without a need to place them all in an oven).

Let's make it clear:

An infinite Universe with a finite matter can't technically maintain the  black-body radiation in the CMBR.

Therefore, if we are ready to accept the idea that the universe is infinite and it doesn't have an edge, then we have to accept the idea that it MUST be full with infinite matter (while the density is more or less constant all over the infinite universe)

 

Edited November 26 by Dandav

[LaurieAG]

But unfortunately we cannot test that so we make up Dark things that must be made of something we haven't discovered yet.

[Dandav]

3 hours ago, LaurieAG said:

But unfortunately we cannot test that so we make up Dark things that must be made of something we haven't discovered yet.

I fully agree with you that we must base our understanding only on something that we have tested and discovered.

1. Curvature - We have clearly discovered in 2018 that the curvature of the visible universe is ZERO. This is real data. Therefore, it is a severe mistake to claim that the universe is limited in its size (Radius of 13 BLY or even 46 BLY)

Therefore, the zero-curvature discovery tells us that the Universe is most likely infinite or at least it Doesn't have an edge:

https://www.britannica.com/video/universe/-203957

10 hours ago, Dandav said:

Space is most likely infinite, or at least it doesn't have an edge.

2. CMBR -  The CMBR is real data and its black-body radiation is very clear to us. As I have already explained, there are two possibilities for the CMBR to keep its Black body radiation:

On 11/19/2024 at 10:29 AM, Dandav said:

conclusions:

There are two possibilities to maintain the black-body radiation in the CMBR:

1.  Finite space Universe - There must be a curvature in the Universe and therefore it has a limited / finite space. In this case finite no. of galaxies should be good enough to maintain the black-body radiation in the CMBR (without a need to place them all in an oven)

2. Infinite space Universe - There is no curvature in the Universe and therefore its space is infinite. In this case, the number of the galaxies must also be infinite to maintain the black-body radiation in the CMBR ((without a need to place them all in an oven).

If I understand it correctly, so far, we didn't observe any sort of curvature in our Universe.

As the Universe Space is most likely infinite, or at least it doesn't have an edge then by definition the second choice is the correct one:

"There is no curvature in the Universe and therefore its space is infinite. In this case, the number of the galaxies must also be infinite to maintain the black-body radiation in the CMBR ((without a need to place them all in an oven)."

Hence, as the density of mass must be equal everywhere (more or less), the number of galaxies in the real infinite universe must be infinite in order to maintain the black-body radiation in the CMBR ((without a need to place them all in an oven - or have an edge to the universe).

The understanding that the space of the universe is infinite without an edge and it is also full with galaxies is realistic as it bases on two clear tested observations.

On the other hand, as long as we didn't discover or tested any curvature in the universe, the claim that the universe is finite in its size (only the observable universe size) is clearly not realistic.

Edited November 27 by Dandav

[LaurieAG]

Once a sphere gets large enough its surface becomes 'flat' relative to the sensitivity of our measurement system +/-. As our measurement system gets more accurate the spherical model gets 'flatter' so we still can't say what's beyond the sphere.

Now Universal Relative Density/Specific Gravity (SG) is a dimensionless constant https://en.wikipedia.org/wiki/Relative_density

Quote

defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.

So if we use Visible Matter as the reference material we find that the Relative Density of the total universal matter (equals the spherical transformation 2*pi) and the Relative Density of the total universal Energy + Matter is 2* pi squared (equals the spherical transformation squared) without requiring any dark unknown components.

[Dandav]

5 hours ago, LaurieAG said:

As our measurement system gets more accurate

I hope that you fully confirm that based on the observation made in 2018, the curvature of the Universe is ZERO.

On 11/22/2024 at 8:55 AM, Dandav said:

inal results of the Planck mission, released in 2018, show the cosmological curvature parameter, 1 − Ω = Ω_K = −Kc²/a²H², to be 0.0007±0.0019, consistent with a flat universe.^[15] (i.e. positive curvature: K = +1, Ω_K < 0, Ω > 1, negative curvature: K = −1, Ω_K > 0, Ω < 1, zero curvature: K = 0, Ω_K = 0, Ω = 1).

Universe with zero curvature 

In a universe with zero curvature, the local geometry is flat.

If you still don't agree with this observation then please offer the updated observation.

If you accept it, then you have to agree that the current curvature of the visible universe is zero without any hesitation!

It is a severe mistake to claim that our current measurement system isn't accurate enough and feel free to twist the observation as we like.

If someone would tell you that Elephant can fly to the Moon but unfortunately our current measurement system is not accurate enough to detect them, would you accept it as real science?

Sorry, a real theory must be base only on the CURRENT observation!!!

Never the less, if the measurement system would get more accurate in the future and we would discover a curvature in the universe, then upon this discovery we would update the theory.

Therefore, as long as we observe a zero curvature then it is our obligation to accept it as is even if we don't like it.

Do you think that the following understanding is incorrect?

https://www.britannica.com/video/universe/-203957

On 11/26/2024 at 9:14 PM, Dandav said:

Space is most likely infinite, or at least it doesn't have an edge,

As the understanding that the Space is most likely infinite or at least it doesn't have an edge is based on the current observation, then why we can't consider it as real possibility?

5 hours ago, LaurieAG said:

Once a sphere gets large enough its surface becomes 'flat' relative to the sensitivity of our measurement system +/-. As our measurement system gets more accurate the spherical model gets 'flatter' so we still can't say what's beyond the sphere.

Would you kindly estimate the minimal size of the universe sphere?

If you can't say what is the minimal size of the Universe or what's beyond its sphere, then how do you know that your current theory can fit into this unknown universe size?

 

5 hours ago, LaurieAG said:

Now Universal Relative Density/Specific Gravity (SG) is a dimensionless constant https://en.wikipedia.org/wiki/Relative_density

Quote

defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.

So if we use Visible Matter as the reference material we find that the Relative Density of the total universal matter (equals the spherical transformation 2*pi) and the Relative Density of the total universal Energy + Matter is 2* pi squared (equals the spherical transformation squared) without requiring any dark unknown components.

Sorry, I don't understand how the Relative density, also called specific gravity can help us to understand the real size of the universe?

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

Relative density, also called specific gravity,^[1][2] is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nearly always measured with respect to water at its densest (at 4 °C or 39.2 °F); for gases, the reference is air at room temperature (20 °C or 68 °F). The term "relative density" (abbreviated r.d. or RD) is preferred in SI, whereas the term "specific gravity" is gradually being abandoned

Did you had the chance to read the following limitation?

Limitations

Specific gravity (SG) is a useful concept but has several limitations. One major issue is its sensitivity to temperature since the density of both the substance being measured and the reference changes with temperature, affecting accuracy.^[12] It also assumes materials are incompressible, which isn't true for gasses or some liquids under varying pressures.^[13] It doesn't provide detailed information about a material’s composition or properties beyond density.^[14] Errors can also occur due to impurities, incomplete mixing, or air bubbles in liquids, which can skew results.^[15

Don't you agree that in the open universe the temp could be higher or lower than "room temperature"

Edited November 28 by Dandav

[Dandav]

With regards to the number density of photons in the CMBR:

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

The CMB contains the vast majority of photons in the universe by a factor of 400 to 1;^[12]: 5 the number density of photons in the CMB is one billion times (10⁹) the number density of matter in the universe. 

Let's focus on the following message - the number density of photons in the CMB is one billion times (10⁹) the number density of matter in the universe. 

If I understand it correctly, they discuss about the number density of matter in the local universe (visible Universe)

If so, the number density of photons in the CMB can't be due to the matter in our local universe as it is higher by 10^9 then number density of matter in this universe.

The only solution for that is that the number density of photons in the CMB is due to the matter in the global geometry universe (the infinite universe)

That gives us a brief indication for the vast matter in the geometry /infinite universe.

Actually, if my understanding is correct, and the CMBR is based on the photons that comes from the Infinite galaxies in the Infinite Global geometry Universe, then those photons should come at a very high redshift.

Therefore, I wonder if there is any possibility for us to isolate each photon and detect its redshift in order to estimate the location of its source.

Edited November 28 by Dandav

[Dandav]

13 hours ago, Dandav said:

the number density of photons in the CMB is one billion times (10⁹) the number density of matter in the universe. 

I thought again about this discovery.

As the local universe contributes only 1 / 10^9 from the CMBR Photons, then we can claim that this ratio also represents the energy / temp contribution of the local universe.

The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K.^[4] 

2.72548 K / 10^9 = 2.72548 * 10^-9 K = 0.00000000272548 K

Hence, based on the photon discovery / understanding, our local / visible universe contributes only 0.00000000272548 K in the CMBR while the global geometry universe contributes:

2.72548 K -  0.00000000272548 K = 2.72547.... K

I wonder if this outcome is realistic.

Edited November 28 by Dandav

[OceanBreeze]

13 hours ago, Dandav said:

I thought again about this discovery.

As the local universe contributes only 1 / 10^9 from the CMBR Photons, then we can claim that this ratio also represents the energy / temp contribution of the local universe.

The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K.^[4] 

2.72548 K / 10^9 = 2.72548 * 10^-9 K = 0.00000000272548 K

Hence, based on the photon discovery / understanding, our local / visible universe contributes only 0.00000000272548 K in the CMBR while the global geometry universe contributes:

2.72548 K -  0.00000000272548 K = 2.72547.... K

I wonder if this outcome is realistic.

This "outcome" is total nonsense, the same as 90% of this thread.

The main reason I say that is because you are confusing galactic black body radiation with the CMB radiation!

All mentions of the “universe” in the following post refer to the known (observable) universe.

Dark matter + Dark Energy make up more than 90% of the Mass/Energy density of the universe.

The CMB has absolutely nothing to do with the black body radiation given off by galaxies, dust clouds, or any other matter in the universe!

I don’t have time to correct all of the nonsense in this thread, all I can do is post the correct information and numbers, Based on E=mc^2: (feel free to check my numbers against any source and report any discrepancy you find, I will appreciate any corrections that are verifiable)

The average density of Ordinary Matter in the known universe is about 0.2 hydrogen atoms per cubic meter. This is equal to a Mass Density of about 3.3474E−28 kg / cubic meter. This is estimated to be about 4% of the universe's total mass density. The equivalent Energy Density  = 3.0085E-11 J / cubic meter.

Dark matter forms about 22% of the universe (as per estimates), which gives an average Mass Density of about 1.8411E-27 kg / cubic meter. Dark Matter Energy Density = 1.6547E-10 J / cubic meter.

Ratio of dark matter / ordinary matter = 5.5, Ratio of ( dark matter + ordinary matter ) / ordinary matter = 6.5

The remaining 74% of the universe consists of dark energy, which has an an estimated average Energy Density of 5.5658E-10 J / cubic meter. Corresponding equivalent Mass Density is 6.1928E−27 kg / cubic meter.

Total density of the universe: Energy = 7.52177E-10 J / cubic meter,  Mass = 8.369E-27 kg / cubic meter

While the CMB contains the vast majority of photons in the universe, by a factor of 400 to 1;  (there are about 2 billion photons for every hydrogen atom) the CMB photons only account for a negligible fraction of the mass-energy budget of the universe (about 0.01%).

The energy density of the CMB is 0.260 eV/cm3 (4.17E−14 J / cubic meter), about 411 photons / cubic centimeter.  Compare that to the total Energy Density of the universe of 7.52177E-10 J / cubic meter. Equivalent Mass Density of the CMB = 4.6398E-31 kg / cubic meter, compared to the total mass density of the universe of  8.369E-27 kg / cubic meter.

Repeating for emphasis:

The CMB has absolutely nothing to do with the black body radiation given off by galaxies, dust clouds, or any other matter in the observable universe!

All of the photons in the CMB came from the Recombination Epoch which occurred when the universe was about  378000 years old. At a present Temperature of 2.725 K, the CMB photons have a redshift  z ~ 1100. This means they originated when the entire universe had a temperature of 3000 K and had a radius of only about 41.8 Mlyr (46 billion Lyr / 1100).

The Hubble constant, H ~ 21 km/s per million LY, and the formula to calculate age is Age (t)=1/H, = (1E6/21) (Lyr/km) x sec = 47,620 x 9.46E12 seconds = 4.5E17 sec = 14.3E9 years.

Because of the expansion of the universe, the presently accepted radius of the universe is about 46 billion lyr.

Hopefully, this clears up at least some of the misconceptions in this thread!

 

[Dandav]

10 hours ago, OceanBreeze said:

Because of the expansion of the universe, the presently accepted radius of the universe is about 46 billion lyr.

Thanks for your answers.

So far, I didn't get an answer to my following question:

How do we know the real size of the space in the Universe? Is it finite or infinite?

Now I understand that we have to distinguish between the local geometry universe to the global geometry universe:

 

On 11/24/2024 at 8:20 AM, Dandav said:

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

Local geometry: This relates to the curvature of the universe, primarily concerning what we can observe.

Global geometry: This pertains to the universe's overall shape and structure.

Do you think that they have the same size?

In the following article it is stated:

https://www.britannica.com/video/universe/-203957

On 11/26/2024 at 9:14 PM, Dandav said:

Space is most likely infinite, or at least it doesn't have an edge

Do you accept this message?

Please be aware that in 2018 we have detected that the curvature of the local universe is ZERO.

Therefore, do you agree that the global geometry universe must be bigger than the local geometry universe?

However, how big it could be?

Any idea about the minimal size / radius of the global geometry universe?

Does it have an edge?

Edited November 29 by Dandav

[OceanBreeze]

14 hours ago, Dandav said:

Thanks for your answers.

So far, I didn't get an answer to my following question:

How do we know the real size of the space in the Universe? Is it finite or infinite?

Now I understand that we have to distinguish between the local geometry universe to the global geometry universe:

There is no “global geometry universe”.  There are scientists (and crackpots) who are trying to use information about the local geometry of the observable universe to deduce something about a proposed global geometry of a proposed global universe. I sum it all up this way: “A global geometry universe is nothing more than the proposition that there is a global geometry universe”

All we have is an imaginary sphere, expanding at the speed of light, which serves as a mathematical boundary to the “observable universe”.

We don't know anything about outside this region, since the Universe has a finite age, and information can't travel faster than the speed of light.

As for an infinite universe, there is a lot of speculation but nothing more.

When cosmologists say the universe seems flat, all they are saying is it displays Euclidean geometry. It is not flat like a pizza! There are a number of finite geometries that have flat Euclidean geometry. Flatness may be an indication the observable universe may expand forever (speculation) and either become infinite in size (speculation) or maybe it already is infinite in size (more speculation). Nobody can give you a more definite answer to that (at least nobody who isn’t a crackpot)!

Speculation about infinities is a sure way to give yourself a headache. If a headache is what you want, be my guest and speculate away.

[engcat]

That question is not unanswered. The word "curvature" means acceleration. It is proven that the universe is "accelerating," so there is indeed positive "curvature."  In theory there are 3 options, but in real world only one of those three is observed, positive curvature.

[OceanBreeze]

16 hours ago, engcat said:

That question is not unanswered. The word "curvature" means acceleration. It is proven that the universe is "accelerating," so there is indeed positive "curvature."  In theory there are 3 options, but in real world only one of those three is observed, positive curvature.

I agree that if any curvature is seen in graphical analysis, it generally does mean acceleration.

Let me ask you what does it mean to have Zero curvature?

We can determine the spatial curvature of the universe by use of the Density Parameter,  Ω which is the average density of the universe divided by the critical density.

    If Ω = 1, means Zero curvature and Euclidean geometry; (parallel lines never cross). The universe is Flat and presently expanding but may contract in the future.

    If Ω > 1, there is positive curvature and Elliptic geometry (“Parallel” lines do cross at a single point). The universe is closed, with a finite future.

    If Ω < 1, there is negative curvature and hyperbolic geometry,(parallel lines are geodesic and approach each other asympotically but do not cross). The universe is open and expands forever.

 

I have already calculated the average density of the universe in my previous post but I will repeat it here: Total average density of the universe: Energy = 7.52177E-10 J / cubic meter,  Mass = 8.369E-27 kg / cubic meter.

All I need to determine the value of the density parameter, Ω, is the value of the critical density of the universe.

I just need to solve this equation for ρc where ρc is the critical density, H is the Hubble “constant”,(70 km/s/Mpc) and G is Newton’s Gravitational Constant (6.6743E-11 N∙ m^2 / kg^2). Should be a piece of cake!( Ρc)😆

Ρc = 3H^2 / 8 π G

Ρc = 0.588E-36 / G ∙ s^2 = 8.81E-27 kg / cubic meter

That is very close to my calculated average mass density of 8.369E-27 kg / cubic meter

So, the density parameter, Ω = (8.369E-27 kg / cubic meter) / (8.81E-27 kg / cubic meter) ~ 0.95

That is very close to 1 considering my rough calculation and rounding off.

I am going to take the liberty of calling the density parameter close enough to 1 to claim a flat universe with zero curvature that is expanding. Notice this calculation says nothing about the acceleration of that expansion; the accelerated expansion of the universe was determined through observations of distant supernovae and redshift of distant galaxies. Initially it was not mathematically calculated and came as quite a surprise to scientists studying the cosmos.

No doubt there are even more surprises in store as the question about the ultimate fate of the universe is still unanswered.

[Dandav]

On 12/5/2024 at 1:26 AM, OceanBreeze said:

Let me ask you what does it mean to have Zero curvature?

The answer is very clear:

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

Universe with zero curvature 

In a universe with zero curvature, the local geometry is flat. The most familiar such global structure is that of Euclidean space, which is infinite in extent. Flat universes that are finite in extent include the torus and Klein bottle. Moreover, in three dimensions, there are 10 finite closed flat 3-manifolds, of which 6 are orientable and 4 are non-orientable. These are the Bieberbach manifolds. The most familiar is the aforementioned 3-torus universe.

Direct measurements of the Universe curvature by critical density:

On 12/5/2024 at 1:26 AM, OceanBreeze said:

We can determine the spatial curvature of the universe by use of the Density Parameter,  Ω which is the average density of the universe divided by the critical density.

If Ω = 1, means Zero curvature and Euclidean geometry; (parallel lines never cross). The universe is Flat and presently expanding but may contract in the future.

Based on your calculation you have found that Ω is very close to 1:

On 12/5/2024 at 1:26 AM, OceanBreeze said:

That is very close to my calculated average mass density of 8.369E-27 kg / cubic meter

So, the density parameter, Ω = (8.369E-27 kg / cubic meter) / (8.81E-27 kg / cubic meter) ~ 0.95

That is very close to 1 considering my rough calculation and rounding off.

In the following articale it is stated:

https://map.gsfc.nasa.gov/universe/uni_matter.html

WMAP determined that the universe is flat, from which it follows that the mean energy density in the universe is equal to the critical density (within a 0.5% margin of error). This is equivalent to a mass density of 9.9 x 10^-30 g/cm³, which is equivalent to only 5.9 protons per cubic meter.

I hope that we accept the WMAP observation based on " the mean energy density in the universe is equal to the critical density" that the universe is flat within a 0.5% margin of error (based o your calculation within a 0.05 margin).

In the following article it is stated:

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

Final results of the Planck mission, released in 2018, show the cosmological curvature parameter, 1 − Ω = Ω_K = −Kc²/a²H², to be 0.0007±0.0019, consistent with a flat universe.^[15] (i.e. positive curvature: K = +1, Ω_K < 0, Ω > 1, negative curvature: K = −1, Ω_K > 0, Ω < 1, zero curvature: K = 0, Ω_K = 0, Ω = 1).

As of 2024, current observational evidence suggests that the observable universe is spatially flat with an unknown global structure.

Therefore, As of today, current observational evidence suggests that the observable universe is spatially flat with zero curvature.

Once we accept the observation, then we should also agree that "In a universe with zero curvature, the local geometry is flat. The most familiar such global structure is that of Euclidean space, which is infinite in extent.

However, as we refuse to accept the idea that the universe could be infinite then let's verify what could be the reasons that the universe isn't infinite in its size:

1.  Positive curvature like the Earth:

"The universe as a whole could have many different shapes, each of which have different properties. One of the most important properties is called curvature. The Earth, which is a sphere-like shape, has positive curvature."

Therefore, although we don't observe any curvature in our visible universe, they think that somehow there is a curvature (but we just don't detect it yet).

It is like an ant on Earth looking around. It is very clear that the Earth surface is flat from her point of view.

However, we can easily detect the curvature of Earth. In an open sea view it might be 10Km or even 1Km. let's agree on 10Km.

Earth's circumference is about 40,000 Km.

Therefore, the ratio is 1 to 4,000.

circumference = 2*3.14*R

Therefore, the ration between the radius of the none observable curvature volume to the observable curvature volume is 4,000^3 = 6.4 10^10.

Therefore, if we use the Earth surface flatness as an example for the curvature in the visible universe, we should also agree that the real universe volume should be bigger by 6.4 10^10 from our expectation.

2. Temperature fluctuations that appear in the Cosmic Microwave Background

https://map.gsfc.nasa.gov/universe/uni_matter.html

The angular size of the temperature fluctuations that appear in the Cosmic Microwave Background. Our Universe was very uniform in the early stages of the hot Big Bang, but not perfectly uniform. ..

These fluctuations have a particular spectrum: hotter or colder by a certain amount on specific distance scales. In a flat Universe, those scales appear as they are, while in a curved Universe, those scales would appear larger (in a positively curved Universe) or smaller (in a negatively curved Universe). Based on the apparent sizes of the fluctuations we see, from the Planck satellite as well as other sources, we can determine that the Universe is not only flat, but it’s flat to at least a 99.6% precision

This tells us that if the Universe is curved, the scale on which its curved is at least ~250 times larger than the part of the Universe that’s observable to us, which is already ~92 billion light-years in diameter.

Therefore, based on this idea the radius of the real universe is 250 times then the radius of the visible universe.

Hence the real universe volume should be bigger by 250^3 = 15,625,000 then the visible universe.

3. The apparent angular separations between galaxies that cluster at different epochs throughout the Universe

The fact that we see a null result, particularly if we combine it with the cosmic microwave background results, gives us an even more stringent constraint: the Universe is flat to within ~99.75% precision.

In other words, if the Universe isn’t curved — for example, if it’s really a hypersphere (the four-dimensional analogue of a three-dimensional sphere) — that hypersphere has a radius that’s at least ~400 times larger than our observable Universe

Therefore, based on this idea the radius of the real universe is 400 times then the radius of the visible universe.

Hence the real universe volume should be bigger by 400^3 = 64,000,000 then the visible universe.

4. . "curvature" means acceleration

On 12/4/2024 at 8:57 AM, engcat said:

That question is not unanswered. The word "curvature" means acceleration. It is proven that the universe is "accelerating," so there is indeed positive "curvature."  In theory there are 3 options, but in real world only one of those three is observed, positive curvature.

Can you please prove it by real article and show the ratio between the curvature to the acceleration?

5. Error in the observation

https://map.gsfc.nasa.gov/universe/uni_matter.html

WMAP determined that the universe is flat, from which it follows that the mean energy density in the universe is equal to the critical density (within a 0.5% margin of error)

So, there is an error of 0.5% in the radius.

That ratio is relevant to 1 to 200.

Therefore, based on this idea the radius of the real universe is 200 times then the radius of the visible universe.

Hence the real universe volume should be bigger by 200^3 = 8,000,000 then the visible universe.

On 11/29/2024 at 11:43 AM, OceanBreeze said:

Because of the expansion of the universe, the presently accepted radius of the universe is about 46 billion lyr.

As of 2024, current observational evidence suggests that the observable universe is spatially flat.

Any kind of fluctuations or error means oscillation. Therefore, it could be positive or negative.

Hence, if in one section of the universe the oscillation is positive then technically, in other section it might be negative.

In other words, if in one section the universe the radius gets a positive curvature and on other section of the radius it has a negative curvature then the total curvature of the radius is zero.

Therefore, by average, the statistical fluctuations / error / oscillation might end with a flat / infinite radius.

Hence, the chance that the radius of the real universe is infinite (or at least very...very big) is significantly higher than the current assumption / hope that it is only 46 BLY.

Let me ask you the following:

1. why do we refuse to accept the observation as is and the real meaning of zero curvature and flat universe?

2. What is more important: Observation or theory?

3. Even if we prefer the theory, then why the expansion can't work also in the infinite / close to infinite or at least bigger than the observable universe?

4. Why do we prefer to claim that the global structure of the universe is unknown and do not even try to verify its minimal volume?

Edited December 10 by Dandav