<1> Dialogue with the View that the Universe has an End
<2> Dialogue with the Idea That the Universe Is Finite in Time
<3> Dialogue with the Finite Theory of the Universe Deduced from a Three-Dimensional Torus Structure
<4> Dialogue with the View that "Space is a Physical Entity, Distinct from 'Nil,'" or with the View that "Nil has No Spatial Expanse"
<5> Dialogue with the Finite Theory of the Universe Based on Spatial Curvature
<6> Dialogue with the Finite Nature of Cosmic Space: Perspectives on Expansion and Contraction




<1> Dialogue with the View that the Universe has an End

According to the book titled "Is there an 'End' to the Universe?" (*1), the latest scientific views suggest that the universe has a finite end.

<Quotation> Our universe, which originated from the chaos of the Big Bang within the vast emptiness of the Mother Universe, will eventually reach a state of eternal silence known as the Big Whimper, around the 100th power of the cosmic year. <Unquote> (p.13, translated by me)

The author of the book, Nobuo Yoshida, does not explicitly state whether the expanse of this Mother Universe is finite or infinite.

However,

Even if the expanse of the Mother Universe is finite, assuming the infinity and eternity of the "entire" universe, it does not necessarily imply the existence of only one Mother Universe. Therefore, even if one Mother Universe were to become "silent" in a "Big Whimper," other Big Bangs could occur in other Mother Universes. By assuming the possibility of other Big Bangs, the 'entire' Universe would not come to an end as a whole. Only a small part of the infinite universe may come to an end. Therefore, the infinite 'entire' universe as a whole will not come to an end.

Conversely, if we assume that the expanse of the Mother Universe is infinite, even if "our universe" were to experience the eternal silence known as the Big Whimper, there might still be other universes within the infinite whole, or new ones might be born.

However, according to the author of the book, while the possibility of countless universes being born can be suggested, mere ideas are insufficient. No leading theory has been developed yet to convincingly support this notion and gain the consensus of many physicists. he also emphasize that without a concrete, computable model, a theory cannot be regarded as a serious argument in the field of physics.

Regardless of whether the Mother Universe is finite or infinite, based on the aforementioned reasoning, the "entire" universe would logically avoid complete "silence." Only a small portion of the infinite universe may come to an end. Therefore, the infinite "entire" universe as a whole will not come to an end.

(*1) Nobuo Yoshida. Uchu Ni Owari Wa Arunoka: [Is There an End of the Universe? - From its birth to '10 hundredth power years' later, as depicted by the latest cosmology]. Kodansha, 2019.

<2> Dialogue with the Idea That the Universe Is Finite in Time

The "whole" universe is considered to be infinite in time (*). While the notion of the universe having beginnings in space and time may appear to contradict infinite time, this apparent contradiction can be reconciled through a multi-layered time model. According to this model, the finite universe that originated with the Big Bang is seen as a part of an infinite "whole" universe.

First, (1) I will explain that the whole universe is infinite in time, and then (2) I will explain the multilayered time model.

(1) To simplify the conclusion, the whole universe encompasses "nil" (Close-to-absolute nil I) with infinite spatial extent. As it remains unchanged and continues to exist, it endures infinitely in time. Therefore, the whole universe exists infinitely in time.

The explanation of the whole universe as a premise is as follows:
In essence, the whole universe consists of both "nil" and "thing." "Nil" can be further categorized into "Close-to-absolute nil" and "relative nil," both of which are perceptible entities and thus part of "existence."

In other words, the whole universe = everything comprises "Close-to-absolute nil I" + "Close-to-absolute nil II" + "thing" (including "relative nil = relative thing").

('Close-to-absolute nil I' refers to that which can solely be recognized through words and possesses spatial expanse.)
("Close-to-absolute nil II" refers to the subset of nil that can solely be recognized through words and lacks expanse.)
('Relative nil' is synonymous with 'relative thing' and denotes entities imperceptible by certain beings through their senses alone. For instance, ultraviolet light is imperceptible to humans through their five senses, yet it exists. (However, it can be detected through measuring instruments, etc.))
("Thing" encompasses entities whose existence is perceptible, excluding for convenience "Close-to-absolute nil I and II." It includes both "relative nil" and "relative thing.")

(Close-to-absolute nil I and II are considered existences since they can be perceived through words.)

Now, let us delve into the explanation of 'Close-to-absolute nil I' and its infinite existence in time.

Close-to-absolute nil I represents 'nil that can only be grasped through words and possesses spatial expanse.' Its spatial expanse stems from being devoid of all 'things' within space. ('Thing' encompasses not only objects but also phenomena such as radio waves, light, smells, and energy.) Therefore, it does not encompass any 'thing' whatsoever. Even if we assume the expansion, contraction, or distortion of space, we require a field (space) capable of accommodating and encompassing such transformations. In essence, Close-to-absolute nil I lacks any transformative elements and thus remains unchanged. From another perspective, it can be considered a foundational field in which "things" can be placed, as all "things" have been eliminated from it in advance. Its perpetual state of non-change implies that it continues to exist unaltered and never disappears, hence rendering it infinite in time.

The explanation for the infinite spatial expanse of Close-to-absolute nil is as follows:

When we consider a certain territory, we implicitly acknowledge the existence of something beyond that territory. Infinite space encompasses both the inside and outside of a given territory. 'Close-to-absolute nil I' exists within and beyond that territory, with an infinite expanse that extends inward and outward (this is because all 'things' have been removed from within and outside the territory, respectively). Therefore, if we designate a certain territory as the universe, the entire universe, encompassing the inside and outside of that territory, extends infinitely, and 'Close-to-absolute nil I' also extends infinitely.

As a result, 'Close-to-absolute nil I', serving as the backdrop for the existence of 'things', spreads infinitely like an expansive background, existing in infinite time.

Furthermore, this demonstrates that the notion of a 'temporal beginning and end of the whole universe (everything)' is a linguistic error. It reveals its impossibility.

(2) Multi-Layered Time Model:

In the limited universe that originated with the Big Bang, the concept of a beginning of time is assumed. (*)

This assumption aligns with the temporal infinity of the whole universe in the multilayered time model.

In other words, we can postulate the beginning of a particular layer of time in relation to the spatial and temporal infinity of 'Close-to-absolute nil I'.

For instance, by using a stopwatch and varying the speed of time progression (faster or slower than usual) for clarity, we can observe the existence of multiple time layers within a single time. Thus, within an infinite time, there can be additional time layers, including their respective beginnings and ends. Time can exhibit a multilayered nature.

Moreover, since the whole universe is infinite and eternal, the occurrence of the Big Bang does not necessarily represent a singular event. It is worth considering the possibility of the existence of multiple universes.

(*)My understanding and limitations regarding the definition of 'time' discussed here are as follows:

Time: The duration between moments.
Moment: A specific point in time when something 'exists'.
Point in time: A singular moment in time.
Duration: The difference, change, or continuation between moments.

Regarding time, anything beyond these aspects is currently not well understood for me. (as of May 2023).

(*) The Big Bang Theory suggests a beginning of time: Katsuhiko Sato. Sotaisei-riron ni Okeru Jikan to Uchu no Tanjyo [The Birth of Time and the Universe in Relativity]. Design of Space-Time. 2007. http://umdb.um.u-tokyo.ac.jp/DKankoub/Publish_db/2006jiku_design/satou.html, (ref 2023-5-2).

<3> Dialogue with the Finite Theory of the Universe Deduced from a Three-Dimensional Torus Structure

A three-dimensional torus structure is formed by connecting a two-dimensional torus (a ring-shaped surface resembling a doughnut) to the top, bottom, left, and right sides of a rectangle, and it is said that the front and rear sides are also connected. Unlike the two-dimensional case, where the distant edges are connected, the distant surfaces in a three-dimensional torus are connected, resulting in a continuous world where going straight in any direction leads to circling back around.

It is important to note that the analogy of a doughnut shape is only used to illustrate the concept, as the structure itself has no curvature. In other words, space is connected to space without any bending or warping. (Reference: Takahiko Matsubara, Uchu ha Mugen ka Yu-Genka [Is the Universe Infinite or Finite?], Kobunsha 2019)

Now, there is a notion that the universe has such a three-dimensional torus structure and that its expanse is finite.

However, even if the region of the universe we inhabit possesses a three-dimensional torus structure, the "whole" universe remains infinite. Alternatively, the proposition that the "whole" universe is a three-dimensional torus structure and therefore finite is incorrect.

Firstly, even if we assume that a three-dimensional torus structure is a physically possible finite structure, it must still be encompassed within an infinite space defined by the XYZ axes. This implies that the entire universe is infinite. In other words, being a finite three-dimensional structure, it would exist within the infinite expanse of the XYZ axes, and conversely, the XYZ axes would extend beyond the boundaries of the three-dimensional torus structure and further.

Furthermore, the three-dimensional torus structure is described as a loop-like structure without bends, meaning it is connected without any bending in the up-down, left-right, and front-back directions. This loop-like nature restricts one from surpassing a certain point, resulting in continuous circling. In other words, even if one were to travel "straight ahead" within this structure, they would be unable to surpass a particular point due to the looping effect, endlessly circling without reaching a new destination. Such a loop structure is conceivable if our universe is programmed in such a way. However, even if the universe we inhabit follows a three-dimensional torus structure with this looping characteristic, the whole universe remains infinite because it encompasses areas beyond the looping point, including the regions "beyond" its structural expanse, even if they are considered "Nil."

By the way, since the whole universe is infinite, it is plausible that multiple universes with three-dimensional torus structures and multiple universes without such structures exist concurrently.

<4> Dialogue with the View that "Space is a Physical Entity, Distinct from 'Nil,'" or with the View that "Nil has No Spatial Expanse"

I acknowledge the existence of 'nothing' (referred to as 'Close-to-absolute nil II') that lacks spatial expanse within the realm of language. However, there is also 'Close-to-absolute nil' (referred to as 'Close-to-absolute nil I') that encompasses a spatial expanse by removing not only objects but also all 'things' such as waves, light, and energy from space. This 'Close-to-absolute nil I' must exist as a distinct entity alongside 'Close-to-absolute nil II'. (Even if we consider the possibility of space being physically distorted, there must be a background that allows and encompasses this distortion, and 'Close-to-absolute nil I' serves as that background. Thus, space can exhibit a multi-layered nature. In essence, a layer that remains unchanged as a background can coexist with one or more layers that undergo change.)

In other words, it is plausible to posit that space, with its physical characteristics, extends with 'Close-to-absolute nil I' as its background, thereby creating a multi-layered structure. If space lacks physical characteristics and does not contain any 'thing', it is equivalent to 'Close-to-absolute nil I'.

An example that illustrates the concept of space being multi-layered can be found in the realm of virtual reality. The virtual space within a computer exists as a singular reality, while the world we inhabit serves as the background for that virtual space.

Another example (although it may not fully support the claim) is that of a container used in an experiment. If there is a distinction between the space within the container and the space in the laboratory, it could indicate a multi-layered structure of space. In this case, the space within the container and the space in the laboratory can coexist in multiple layers, with only the space within the container undergoing physical changes while the other remains unchanged.

In summary, there exist two forms of 'nil': those with spatial expanse and those without. It is a cognitive error to assume that the absence of space in a part of 'nil' represents the entirety of 'nil'. There exists a type of 'nil' that encompasses spatial expanse, which coexists with 'Close-to-absolute nil II' that lacks spatial expanse.

<5> Dialogue with the Finite Theory of the Universe Based on Spatial Curvature

The finite theory of the universe based on spatial curvature is described in Takahiko Matsubara's book "Uchu ha Mugen ka Yu-Genka [Is the Universe Infinite or Finite?]" (Kobunsha, 2019).

According to Matsubara's explanation:

"If it can be proven that spatial curvature is uniformly positive throughout the actual universe, then we can conclude that the universe is finitely closed. In such a case, the question of whether the universe extends indefinitely would be resolved. If you were to travel in a straight line within this universe, you would eventually return to your starting point, and space would not extend indefinitely." (Translation by me)

However, even if we assume that space is curved, traveling straight ahead would take us through that closed space and beyond, extending infinitely in any direction.

This can be understood by examining the misperception that arises when we "travel straight" on Earth. Normally, if we walk straight on Earth's surface, we eventually return to our starting point due to the Earth's spherical shape. This creates the misconception that if we were to travel straight "truly," we would return to our original location.

The following explanation clarifies the nature of this misconception:

In reality, we are not traveling straight. When we walk straight on Earth's surface, we are actually traveling "in accordance with the curvature of the Earth," rather than in a truly straight line.

If we were to travel truly straight, we would gradually depart from the Earth's surface and eventually travel through space.

Similarly, if we were to travel "truly" straight through space, we would not follow the curvature of space and thus continue beyond the confines of the closed space into an infinite expanse.

The question of whether we can travel without following the bends in space, assuming the existence of such bends, and the question of whether there is a space beyond where we can travel without following the bends are two distinct issues.

In conclusion, even if the universe in which we reside is finite and closed in terms of spatial dimensions, there exists an infinite expansion beyond its boundaries.

<6> Dialogue with the Finite Nature of Cosmic Space: Perspectives on Expansion and Contraction

One theory regarding the finiteness of the universe, based on the Big Bang theory and other related theories, suggests that cosmic space is finite and experiences both expansion and contraction.

In this view, the limit of the universe's expansion is determined by the "critical mass" of matter. If the amount of matter exceeds the critical mass, a phenomenon opposite to the Big Bang occurs, leading to the universe contracting back to a singular point. On the other hand, if the amount of matter is below the critical mass, the universe's expansion continues indefinitely (Toshifumi Futamase, "Zukai Zatsugaku Uchu-ron" [Illustrated Miscellaneous Cosmology], Natsumesha, 2002, p. 100).

However, whether space expands or contracts, the whole universe exists as a background, encompassing "nothingness" or "nil", and because it includes "nothingness", its expanse is infinite. (For further exploration of 'nil' and the infinity of the whole universe, please refer to 'About Infinity' [https://www.jcstation.info/e.infinity.htm]).

It is important to emphasize that the universe in which we reside is merely a part of the whole universe. Even if it were to reach an endpoint through a contraction known as the Big Crunch, other universes must exist and persist somewhere within the infinite expanse of the whole universe.