The multiverse is the hypothetical set of all universes.[1][a] Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "flat universes", "other universes", "alternate universes", "multiple universes", "plane universes", "parent and child universes", "many universes", or "many worlds". One common assumption is that the multiverse is a "patchwork quilt of separate universes all bound by the same laws of physics."[2]
The concept of multiple universes, or a multiverse, has been discussed throughout history, including Greek philosophy. It has evolved and has been debated in various fields, including cosmology, physics, and philosophy. Some physicists argue that the multiverse is a philosophical notion rather than a scientific hypothesis, as it cannot be empirically falsified. In recent years, there have been proponents and skeptics of multiverse theories within the physics community. Although some scientists have analyzed data in search of evidence for other universes, no statistically significant evidence has been found. Critics argue that the multiverse concept lacks testability and falsifiability, which are essential for scientific inquiry, and that it raises unresolved metaphysical issues.
Max Tegmark and Brian Greene have proposed different classification schemes for multiverses and universes. Tegmark's four-level classification consists of Level I: an extension of our universe, Level II: universes with different physical constants, Level III: many-worlds interpretation of quantum mechanics, and Level IV: ultimate ensemble. Brian Greene's nine types of multiverses include quilted, inflationary, brane, cyclic, landscape, quantum, holographic, simulated, and ultimate. The ideas explore various dimensions of space, physical laws, and mathematical structures to explain the existence and interactions of multiple universes. Some other multiverse concepts include twin-world models, cyclic theories, M-theory, and black-hole cosmology.
The anthropic principle suggests that the existence of a multitude of universes, each with different physical laws, could explain the asserted appearance of fine-tuning of our own universe for conscious life. The weak anthropic principle posits that we exist in one of the few universes that support life. Debates around Occam's razor and the simplicity of the multiverse versus a single universe arise, with proponents like Max Tegmark arguing that the multiverse is simpler and more elegant. The many-worlds interpretation of quantum mechanicsand modal realism, the belief that all possible worlds exist and are as real as our world, are also subjects of debate in the context of the anthropic principle.
History of the concepteditAccording to some, the idea of infinite worlds was first suggested by the pre-Socratic Greek philosopher Anaximander in the sixth century BCE.[3] However, there is debate as to whether he believed in multiple worlds, and if he did, whether those worlds were co-existent or successive.[4][5][6][7]
The first to whom we can definitively attribute the concept of innumerable worlds are the Ancient Greek Atomists, beginning with Leucippus and Democritus in the 5th century BCE, followed by Epicurus (341–270 BCE) and Lucretius (1st century BCE).[8][9][7][10][11][12] In the third century BCE, the philosopher Chrysippus suggested that the world eternally expired and regenerated, effectively suggesting the existence of multiple universes across time.[11] The concept of multiple universes became more defined in the Middle Ages.[citation needed]
The American philosopher and psychologist William James used the term "multiverse" in 1895, but in a different context.[13]
The concept first appeared in the modern scientific context in the course of the debate between Boltzmann and Zermelo in 1895.[14]
In Dublin in 1952, Erwin Schrödinger gave a lecture in which he jocularly warned his audience that what he was about to say might "seem lunatic". He said that when his equations seemed to describe several different histories, these were "not alternatives, but all really happen simultaneously".[15] This sort of duality is called "superposition".
Search for evidenceeditIn the 1990s, after recent works of fiction about the concept gained popularity, scientific discussions about the multiverse and journal articles about it gained prominence.[16]
Around 2010, scientists such as Stephen M. Feeney analyzed Wilkinson Microwave Anisotropy Probe(WMAP) data and claimed to find evidence suggesting that this universe collided with other (parallel) universes in the distant past.[17][18][19]However, a more thorough analysis of data from the WMAP and from the Planck satellite, which has a resolution three times higher than WMAP, did not reveal any statistically significant evidence of such a bubble universe collision.[20][21] In addition, there was no evidence of any gravitational pull of other universes on ours.[22][23]
In 2015, an astrophysicist may have found evidence of alternate or parallel universes by looking back in time to a time immediately after the Big Bang, although it is still a matter of debate among physicists.[24] Dr. Ranga-Ram Chary, after analyzing the cosmic radiation spectrum, found a signal 4,500 times brighter than it should have been, based on the number of protons and electrons scientists believe existed in the very early universe. This signal—an emission line that arose from the formation of atoms during the era of recombination—is more consistent with a universe whose ratio of matter particles to photons is about 65 times greater than our own. There is a 30% chance that this signal is noise, and not really a signal at all; however, it is also possible that it exists because a parallel universe dumped some of its matter particles into our universe. If additional protons and electrons had been added to our universe during recombination, more atoms would have formed, more photons would have been emitted during their formation, and the signature line that arose from all of these emissions would be greatly enhanced. Chary himself is skeptical:
Many other regions beyond our observable universe would exist with each such region governed by a different set of physical parameters than the ones we have measured for our universe.[24]
— Ranga-Ram Chary, "USA Today"Chary also noted:[25]
Unusual claims like evidence for alternate universes require a very high burden of proof.[25]
— Ranga-Ram Chary, "Universe Today"The signature that Chary has isolated may be a consequence of incoming light from distant galaxies, or even from clouds of dust surrounding our own galaxy.[25]
Proponents and skepticseditModern proponents of one or more of the multiverse hypotheses include Lee Smolin,[26] Don Page,[27]Brian Greene,[28][29] Max Tegmark,[30] Alan Guth,[31]Andrei Linde,[32] Michio Kaku,[33] David Deutsch,[34]Leonard Susskind,[35] Alexander Vilenkin,[36]Yasunori Nomura,[37] Raj Pathria,[38] Laura Mersini-Houghton,[39] Neil deGrasse Tyson,[40] Sean Carroll[41] and Stephen Hawking.[42]
Scientists who are generally skeptical of the concept of a multiverse or popular multiverse hypotheses include Sabine Hossenfelder,[43] David Gross,[44]Paul Steinhardt,[45][46] Anna Ijjas,[46] Abraham Loeb,[46] David Spergel,[47] Neil Turok,[48] Viatcheslav Mukhanov,[49] Michael S. Turner,[50] Roger Penrose,[51] George Ellis,[52][53] Joe Silk,[54] Carlo Rovelli,[55]Adam Frank,[56] Marcelo Gleiser,[56] Jim Baggott[57]and Paul Davies.[58]
Arguments against multiverse hypotheseseditIn his 2003 New York Times opinion piece, "A Brief History of the Multiverse", author and cosmologist Paul Davies offered a variety of arguments that multiverse hypotheses are non-scientific:[59]
For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there is an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification. Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence, it requires the same leap of faith.
— Paul Davies, "A Brief History of the Multiverse", The New York TimesGeorge Ellis, writing in August 2011, provided a criticism of the multiverse, and pointed out that it is not a traditional scientific theory. He accepts that the multiverse is thought to exist far beyond the cosmological horizon. He emphasized that it is theorized to be so far away that it is unlikely any evidence will ever be found. Ellis also explained that some theorists do not believe the lack of empiricaltestability and falsifiability is a major concern, but he is opposed to that line of thinking:
Many physicists who talk about the multiverse, especially advocates of the string landscape, do not care much about parallel universes per se. For them, objections to the multiverse as a concept are unimportant. Their theories live or die based on internal consistency and, one hopes, eventual laboratory testing.
Ellis says that scientists have proposed the idea of the multiverse as a way of explaining the nature of existence. He points out that it ultimately leaves those questions unresolved because it is a metaphysical issue that cannot be resolved by empirical science. He argues that observational testing is at the core of science and should not be abandoned:[60]
As skeptical as I am, I think the contemplation of the multiverse is an excellent opportunity to reflect on the nature of science and on the ultimate nature of existence: why we are here. ... In looking at this concept, we need an open mind, though not too open. It is a delicate path to tread. Parallel universes may or may not exist; the case is unproved. We are going to have to live with that uncertainty. Nothing is wrong with scientifically based philosophical speculation, which is what multiverse proposals are. But we should name it for what it is.
— George Ellis, "Does the Multiverse Really Exist?", Scientific AmericanPhilosopher Philip Goff argues that the inference of a multiverse to explain the apparent fine-tuning of the universe is an example of Inverse Gambler's Fallacy.[61]
Stoeger, Ellis, and Kircher[62]: sec. 7 note that in a true multiverse theory, "the universes are then completely disjoint and nothing that happens in any one of them is causally linked to what happens in any other one. This lack of any causal connection in such multiverses really places them beyond any scientific support".
In May 2020, astrophysicist Ethan Siegel expressed criticism in a Forbes blog post that parallel universes would have to remain a science fiction dream for the time being, based on the scientific evidence available to us.[63]
Scientific American contributor John Horgan also argues against the idea of a multiverse, claiming that they are "bad for science."[64]
TypeseditMax Tegmark and Brian Greene have devised classification schemes for the various theoretical types of multiverses and universes that they might comprise.
Max Tegmark's four levelseditCosmologist Max Tegmark has provided a taxonomyof universes beyond the familiar observable universe. The four levels of Tegmark's classification are arranged such that subsequent levels can be understood to encompass and expand upon previous levels. They are briefly described below.[65][66]
Level I: An extension of our universeeditA prediction of cosmic inflation is the existence of an infinite ergodic universe, which, being infinite, must contain Hubble volumes realizing all initial conditions.
Accordingly, an infinite universe will contain an infinite number of Hubble volumes, all having the same physical laws and physical constants. In regard to configurations such as the distribution of matter, almost all will differ from our Hubble volume. However, because there are infinitely many, far beyond the cosmological horizon, there will eventually be Hubble volumes with similar, and even identical, configurations. Tegmark estimates that an identical volume to ours should be about 1010115meters away from us.[30]
Given infinite space, there would be an infinite number of Hubble volumes identical to ours in the universe.[67] This follows directly from the cosmological principle, wherein it is assumed that our Hubble volume is not special or unique.
Level II: Universes with different physical constantseditIn the eternal inflation theory, which is a variant of the cosmic inflation theory, the multiverse or space as a whole is stretching and will continue doing so forever,[68] but some regions of space stop stretching and form distinct bubbles (like gas pockets in a loaf of rising bread). Such bubbles are embryonic level I multiverses.
Different bubbles may experience different spontaneous symmetry breaking, which results in different properties, such as different physical constants.[67]
Level II also includes John Archibald Wheeler's oscillatory universe theory and Lee Smolin's fecund universes theory.
Level III: Many-worlds interpretation of quantum mechanicseditSchrödinger's cat in the many-worlds interpretation, where a branching of the universe occurs through a superposition of two quantum mechanical statesHugh Everett III's many-worlds interpretation (MWI) is one of several mainstream interpretations of quantum mechanics.
In brief, one aspect of quantum mechanics is that certain observations cannot be predicted absolutely. Instead, there is a range of possible observations, each with a different probability. According to the MWI, each of these possible observations corresponds to a different "world" within the Universal wavefunction, with each world as real as ours. Suppose a six-sided dice is thrown and that the result of the throw corresponds to observablequantum mechanics. All six possible ways the dice can fall correspond to six different worlds. In the case of the Schrödinger's cat thought experiment, both outcomes would be "real" in at least one "world".
Tegmark argues that a Level III multiverse does not contain more possibilities in the Hubble volume than a Level I or Level II multiverse. In effect, all the different worlds created by "splits" in a Level III multiverse with the same physical constants can be found in some Hubble volume in a Level I multiverse. Tegmark writes that, "The only difference between Level I and Level III is where your doppelgängersreside. In Level I they live elsewhere in good old three-dimensional space. In Level III they live on another quantum branch in infinite-dimensional Hilbert space."
Similarly, all Level II bubble universes with different physical constants can, in effect, be found as "worlds" created by "splits" at the moment of spontaneous symmetry breaking in a Level III multiverse.[67] According to Yasunori Nomura,[37]Raphael Bousso, and Leonard Susskind,[35] this is because global spacetime appearing in the (eternally) inflating multiverse is a redundant concept. This implies that the multiverses of Levels I, II, and III are, in fact, the same thing. This hypothesis is referred to as "Multiverse = Quantum Many Worlds". According to Yasunori Nomura, this quantum multiverse is static, and time is a simple illusion.[69]
Another version of the many-worlds idea is H. Dieter Zeh's many-minds interpretation.
Level IV: Ultimate ensembleeditThe ultimate mathematical universe hypothesis is Tegmark's own hypothesis.[70]
This level considers all universes to be equally real which can be described by different mathematical structures.
Tegmark writes:
Abstract mathematics is so general that any Theory Of Everything (TOE) which is definable in purely formal terms (independent of vague human terminology) is also a mathematical structure. For instance, a TOE involving a set of different types of entities (denoted by words, say) and relations between them (denoted by additional words) is nothing but what mathematicians call a set-theoretical model, and one can generally find a formal systemthat it is a model of.
He argues that this "implies that any conceivable parallel universe theory can be described at Level IV" and "subsumes all other ensembles, therefore brings closure to the hierarchy of multiverses, and there cannot be, say, a Level V."[30]
Jürgen Schmidhuber, however, says that the set of mathematical structures is not even well-definedand that it admits only universe representations describable by constructive mathematics—that is, computer programs.
Schmidhuber explicitly includes universe representations describable by non-halting programs whose output bits converge after a finite time, although the convergence time itself may not be predictable by a halting program, due to the undecidability of the halting problem.[71][72][73] He also explicitly discusses the more restricted ensemble of quickly computable universes.[74]
Brian Greene's nine typeseditThe American theoretical physicist and string theorist Brian Greene discussed nine types of multiverses:[75]
QuiltedThe quilted multiverse works only in an infiniteuniverse. With an infinite amount of space, every possible event will occur an infinite number of times. However, the speed of light prevents us from being aware of these other identical areas.InflationaryThe inflationary multiverse is composed of various pockets in which inflation fields collapse and form new universes.Duration: 10 seconds.0:10Animation showing the multiple brane universes in the bulkBraneThe brane multiverse version postulates that our entire universe exists on a membrane (brane) which floats in a higher dimension or "bulk". In this bulk, there are other membranes with their own universes. These universes can interact with one another, and when they collide, the violence and energy produced is more than enough to give rise to a Big Bang. The branes float or drift near each other in the bulk, and every few trillion years, attracted by gravity or some other force we do not understand, collide and bang into each other. This repeated contact gives rise to multiple or "cyclic" Big Bangs. This particular hypothesis falls under the string theory umbrella as it requires extra spatial dimensions.
The Omniverse holds everything that can be accessed through progressive powersets of any particular base universe (or "reality") within itself. It is the limit of archverse recursion - this can be the first limit ordinal ω, or a much higher transfinite, depending on the level of recursion considered.
In a sense, it can indeed be argued to contain "all of Reality", but only in the sense that those below it observe it to be as such. The inhabitants of a universe, for instance, can posit the existence of a multiverse containing every possible state their universe could be in, and a megaverse allowing for looser laws of physics, and a gigaverse allowing for even fewer restrictions, but the limit of this application must be at the omniverse if they wish to stay within the concept of "things that are real". Thus, alternate omniverses in each others' relative Paradox Space contain things that cannot be mapped from one sense of "reality" to another.
Not many entities or civilizations can achieve or even fathom exiting the Omniverse, either being denied access to the exterior by Creator or Destroyer, or simply not being advanced enough to jump through an infinite amount of spaces. However, it has been done by many highly advanced civilizations, and even some small teams, such as Satoru's crew.
The only trait every single thing within the Omniverse share is that it exists. How it exists varies in countless ways.
The term "omniverse" was coined by Mark Gruenwald. It has been popularized by the composer-writer Sun Ra. Roger Penrose has spoken of the "omnium".
Beyond the OmniverseThe Omniverse exists in the surrounding emptiness known as The Outside, a void of virtual nothingness. Whatever may lie outside of these concepts is simply referred to as Beyond, one of the many iterations contained by Transcendentem.
Two Godverses orbit the Omniverse, one belonging to Creator, and one to Destroyer.
The Omniverse, the three Godverses and The Outsideare what makeup the Barrel, the local monocosm
The Omniverse holds everything that can be accessed through progressive powersets of any particular base universe (or "reality") within itself. It is the limit of archverse recursion - this can be the first limit ordinal ω, or a much higher transfinite, depending on the level of recursion considered.
In a sense, it can indeed be argued to contain "all of Reality", but only in the sense that those below it observe it to be as such. The inhabitants of a universe, for instance, can posit the existence of a multiverse containing every possible state their universe could be in, and a megaverse allowing for looser laws of physics, and a gigaverse allowing for even fewer restrictions, but the limit of this application must be at the omniverse if they wish to stay within the concept of "things that are real". Thus, alternate omniverses in each others' relative Paradox Space contain things that cannot be mapped from one sense of "reality" to another.
Not many entities or civilizations can achieve or even fathom exiting the Omniverse, either being denied access to the exterior by Creator or Destroyer, or simply not being advanced enough to jump through an infinite amount of spaces. However, it has been done by many highly advanced civilizations, and even some small teams, such as Satoru's crew.
The only trait every single thing within the Omniverse share is that it exists. How it exists varies in countless ways.
The term "omniverse" was coined by Mark Gruenwald. It has been popularized by the composer-writer Sun Ra. Roger Penrose has spoken of the "omnium".
Beyond the OmniverseThe Omniverse exists in the surrounding emptiness known as The Outside, a void of virtual nothingness. Whatever may lie outside of these concepts is simply referred to as Beyond, one of the many iterations contained by Transcendentem.
Two Godverses orbit the Omniverse, one belonging to Creator, and one to Destroyer.
The Omniverse, the three Godverses and The Outsideare what makeup the Barrel, the local monocosm
The multiverse is the hypothetical set of all universes.[1][a] Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "flat universes", "other universes", "alternate universes", "multiple universes", "plane universes", "parent and child universes", "many universes", or "many worlds". One common assumption is that the multiverse is a "patchwork quilt of separate universes all bound by the same laws of physics."[2]
The concept of multiple universes, or a multiverse, has been discussed throughout history, including Greek philosophy. It has evolved and has been debated in various fields, including cosmology, physics, and philosophy. Some physicists argue that the multiverse is a philosophical notion rather than a scientific hypothesis, as it cannot be empirically falsified. In recent years, there have been proponents and skeptics of multiverse theories within the physics community. Although some scientists have analyzed data in search of evidence for other universes, no statistically significant evidence has been found. Critics argue that the multiverse concept lacks testability and falsifiability, which are essential for scientific inquiry, and that it raises unresolved metaphysical issues.
Max Tegmark and Brian Greene have proposed different classification schemes for multiverses and universes. Tegmark's four-level classification consists of Level I: an extension of our universe, Level II: universes with different physical constants, Level III: many-worlds interpretation of quantum mechanics, and Level IV: ultimate ensemble. Brian Greene's nine types of multiverses include quilted, inflationary, brane, cyclic, landscape, quantum, holographic, simulated, and ultimate. The ideas explore various dimensions of space, physical laws, and mathematical structures to explain the existence and interactions of multiple universes. Some other multiverse concepts include twin-world models, cyclic theories, M-theory, and black-hole cosmology.
The anthropic principle suggests that the existence of a multitude of universes, each with different physical laws, could explain the asserted appearance of fine-tuning of our own universe for conscious life. The weak anthropic principle posits that we exist in one of the few universes that support life. Debates around Occam's razor and the simplicity of the multiverse versus a single universe arise, with proponents like Max Tegmark arguing that the multiverse is simpler and more elegant. The many-worlds interpretation of quantum mechanicsand modal realism, the belief that all possible worlds exist and are as real as our world, are also subjects of debate in the context of the anthropic principle.
History of the concepteditAccording to some, the idea of infinite worlds was first suggested by the pre-Socratic Greek philosopher Anaximander in the sixth century BCE.[3] However, there is debate as to whether he believed in multiple worlds, and if he did, whether those worlds were co-existent or successive.[4][5][6][7]
The first to whom we can definitively attribute the concept of innumerable worlds are the Ancient Greek Atomists, beginning with Leucippus and Democritus in the 5th century BCE, followed by Epicurus (341–270 BCE) and Lucretius (1st century BCE).[8][9][7][10][11][12] In the third century BCE, the philosopher Chrysippus suggested that the world eternally expired and regenerated, effectively suggesting the existence of multiple universes across time.[11] The concept of multiple universes became more defined in the Middle Ages.[citation needed]
The American philosopher and psychologist William James used the term "multiverse" in 1895, but in a different context.[13]
The concept first appeared in the modern scientific context in the course of the debate between Boltzmann and Zermelo in 1895.[14]
In Dublin in 1952, Erwin Schrödinger gave a lecture in which he jocularly warned his audience that what he was about to say might "seem lunatic". He said that when his equations seemed to describe several different histories, these were "not alternatives, but all really happen simultaneously".[15] This sort of duality is called "superposition".
Search for evidenceeditIn the 1990s, after recent works of fiction about the concept gained popularity, scientific discussions about the multiverse and journal articles about it gained prominence.[16]
Around 2010, scientists such as Stephen M. Feeney analyzed Wilkinson Microwave Anisotropy Probe(WMAP) data and claimed to find evidence suggesting that this universe collided with other (parallel) universes in the distant past.[17][18][19]However, a more thorough analysis of data from the WMAP and from the Planck satellite, which has a resolution three times higher than WMAP, did not reveal any statistically significant evidence of such a bubble universe collision.[20][21] In addition, there was no evidence of any gravitational pull of other universes on ours.[22][23]
In 2015, an astrophysicist may have found evidence of alternate or parallel universes by looking back in time to a time immediately after the Big Bang, although it is still a matter of debate among physicists.[24] Dr. Ranga-Ram Chary, after analyzing the cosmic radiation spectrum, found a signal 4,500 times brighter than it should have been, based on the number of protons and electrons scientists believe existed in the very early universe. This signal—an emission line that arose from the formation of atoms during the era of recombination—is more consistent with a universe whose ratio of matter particles to photons is about 65 times greater than our own. There is a 30% chance that this signal is noise, and not really a signal at all; however, it is also possible that it exists because a parallel universe dumped some of its matter particles into our universe. If additional protons and electrons had been added to our universe during recombination, more atoms would have formed, more photons would have been emitted during their formation, and the signature line that arose from all of these emissions would be greatly enhanced. Chary himself is skeptical:
Many other regions beyond our observable universe would exist with each such region governed by a different set of physical parameters than the ones we have measured for our universe.[24]
— Ranga-Ram Chary, "USA Today"Chary also noted:[25]
Unusual claims like evidence for alternate universes require a very high burden of proof.[25]
— Ranga-Ram Chary, "Universe Today"The signature that Chary has isolated may be a consequence of incoming light from distant galaxies, or even from clouds of dust surrounding our own galaxy.[25]
Proponents and skepticseditModern proponents of one or more of the multiverse hypotheses include Lee Smolin,[26] Don Page,[27]Brian Greene,[28][29] Max Tegmark,[30] Alan Guth,[31]Andrei Linde,[32] Michio Kaku,[33] David Deutsch,[34]Leonard Susskind,[35] Alexander Vilenkin,[36]Yasunori Nomura,[37] Raj Pathria,[38] Laura Mersini-Houghton,[39] Neil deGrasse Tyson,[40] Sean Carroll[41] and Stephen Hawking.[42]
Scientists who are generally skeptical of the concept of a multiverse or popular multiverse hypotheses include Sabine Hossenfelder,[43] David Gross,[44]Paul Steinhardt,[45][46] Anna Ijjas,[46] Abraham Loeb,[46] David Spergel,[47] Neil Turok,[48] Viatcheslav Mukhanov,[49] Michael S. Turner,[50] Roger Penrose,[51] George Ellis,[52][53] Joe Silk,[54] Carlo Rovelli,[55]Adam Frank,[56] Marcelo Gleiser,[56] Jim Baggott[57]and Paul Davies.[58]
Arguments against multiverse hypotheseseditIn his 2003 New York Times opinion piece, "A Brief History of the Multiverse", author and cosmologist Paul Davies offered a variety of arguments that multiverse hypotheses are non-scientific:[59]
For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there is an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification. Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence, it requires the same leap of faith.
— Paul Davies, "A Brief History of the Multiverse", The New York TimesGeorge Ellis, writing in August 2011, provided a criticism of the multiverse, and pointed out that it is not a traditional scientific theory. He accepts that the multiverse is thought to exist far beyond the cosmological horizon. He emphasized that it is theorized to be so far away that it is unlikely any evidence will ever be found. Ellis also explained that some theorists do not believe the lack of empiricaltestability and falsifiability is a major concern, but he is opposed to that line of thinking:
Many physicists who talk about the multiverse, especially advocates of the string landscape, do not care much about parallel universes per se. For them, objections to the multiverse as a concept are unimportant. Their theories live or die based on internal consistency and, one hopes, eventual laboratory testing.
Ellis says that scientists have proposed the idea of the multiverse as a way of explaining the nature of existence. He points out that it ultimately leaves those questions unresolved because it is a metaphysical issue that cannot be resolved by empirical science. He argues that observational testing is at the core of science and should not be abandoned:[60]
As skeptical as I am, I think the contemplation of the multiverse is an excellent opportunity to reflect on the nature of science and on the ultimate nature of existence: why we are here. ... In looking at this concept, we need an open mind, though not too open. It is a delicate path to tread. Parallel universes may or may not exist; the case is unproved. We are going to have to live with that uncertainty. Nothing is wrong with scientifically based philosophical speculation, which is what multiverse proposals are. But we should name it for what it is.
— George Ellis, "Does the Multiverse Really Exist?", Scientific AmericanPhilosopher Philip Goff argues that the inference of a multiverse to explain the apparent fine-tuning of the universe is an example of Inverse Gambler's Fallacy.[61]
Stoeger, Ellis, and Kircher[62]: sec. 7 note that in a true multiverse theory, "the universes are then completely disjoint and nothing that happens in any one of them is causally linked to what happens in any other one. This lack of any causal connection in such multiverses really places them beyond any scientific support".
In May 2020, astrophysicist Ethan Siegel expressed criticism in a Forbes blog post that parallel universes would have to remain a science fiction dream for the time being, based on the scientific evidence available to us.[63]
Scientific American contributor John Horgan also argues against the idea of a multiverse, claiming that they are "bad for science."[64]
TypeseditMax Tegmark and Brian Greene have devised classification schemes for the various theoretical types of multiverses and universes that they might comprise.
Max Tegmark's four levelseditCosmologist Max Tegmark has provided a taxonomyof universes beyond the familiar observable universe. The four levels of Tegmark's classification are arranged such that subsequent levels can be understood to encompass and expand upon previous levels. They are briefly described below.[65][66]
Level I: An extension of our universeeditA prediction of cosmic inflation is the existence of an infinite ergodic universe, which, being infinite, must contain Hubble volumes realizing all initial conditions.
Accordingly, an infinite universe will contain an infinite number of Hubble volumes, all having the same physical laws and physical constants. In regard to configurations such as the distribution of matter, almost all will differ from our Hubble volume. However, because there are infinitely many, far beyond the cosmological horizon, there will eventually be Hubble volumes with similar, and even identical, configurations. Tegmark estimates that an identical volume to ours should be about 1010115meters away from us.[30]
Given infinite space, there would be an infinite number of Hubble volumes identical to ours in the universe.[67] This follows directly from the cosmological principle, wherein it is assumed that our Hubble volume is not special or unique.
Level II: Universes with different physical constantseditIn the eternal inflation theory, which is a variant of the cosmic inflation theory, the multiverse or space as a whole is stretching and will continue doing so forever,[68] but some regions of space stop stretching and form distinct bubbles (like gas pockets in a loaf of rising bread). Such bubbles are embryonic level I multiverses.
Different bubbles may experience different spontaneous symmetry breaking, which results in different properties, such as different physical constants.[67]
Level II also includes John Archibald Wheeler's oscillatory universe theory and Lee Smolin's fecund universes theory.
Level III: Many-worlds interpretation of quantum mechanicseditSchrödinger's cat in the many-worlds interpretation, where a branching of the universe occurs through a superposition of two quantum mechanical statesHugh Everett III's many-worlds interpretation (MWI) is one of several mainstream interpretations of quantum mechanics.
In brief, one aspect of quantum mechanics is that certain observations cannot be predicted absolutely. Instead, there is a range of possible observations, each with a different probability. According to the MWI, each of these possible observations corresponds to a different "world" within the Universal wavefunction, with each world as real as ours. Suppose a six-sided dice is thrown and that the result of the throw corresponds to observablequantum mechanics. All six possible ways the dice can fall correspond to six different worlds. In the case of the Schrödinger's cat thought experiment, both outcomes would be "real" in at least one "world".
Tegmark argues that a Level III multiverse does not contain more possibilities in the Hubble volume than a Level I or Level II multiverse. In effect, all the different worlds created by "splits" in a Level III multiverse with the same physical constants can be found in some Hubble volume in a Level I multiverse. Tegmark writes that, "The only difference between Level I and Level III is where your doppelgängersreside. In Level I they live elsewhere in good old three-dimensional space. In Level III they live on another quantum branch in infinite-dimensional Hilbert space."
Similarly, all Level II bubble universes with different physical constants can, in effect, be found as "worlds" created by "splits" at the moment of spontaneous symmetry breaking in a Level III multiverse.[67] According to Yasunori Nomura,[37]Raphael Bousso, and Leonard Susskind,[35] this is because global spacetime appearing in the (eternally) inflating multiverse is a redundant concept. This implies that the multiverses of Levels I, II, and III are, in fact, the same thing. This hypothesis is referred to as "Multiverse = Quantum Many Worlds". According to Yasunori Nomura, this quantum multiverse is static, and time is a simple illusion.[69]
Another version of the many-worlds idea is H. Dieter Zeh's many-minds interpretation.
Level IV: Ultimate ensembleeditThe ultimate mathematical universe hypothesis is Tegmark's own hypothesis.[70]
This level considers all universes to be equally real which can be described by different mathematical structures.
Tegmark writes:
Abstract mathematics is so general that any Theory Of Everything (TOE) which is definable in purely formal terms (independent of vague human terminology) is also a mathematical structure. For instance, a TOE involving a set of different types of entities (denoted by words, say) and relations between them (denoted by additional words) is nothing but what mathematicians call a set-theoretical model, and one can generally find a formal systemthat it is a model of.
He argues that this "implies that any conceivable parallel universe theory can be described at Level IV" and "subsumes all other ensembles, therefore brings closure to the hierarchy of multiverses, and there cannot be, say, a Level V."[30]
Jürgen Schmidhuber, however, says that the set of mathematical structures is not even well-definedand that it admits only universe representations describable by constructive mathematics—that is, computer programs.
Schmidhuber explicitly includes universe representations describable by non-halting programs whose output bits converge after a finite time, although the convergence time itself may not be predictable by a halting program, due to the undecidability of the halting problem.[71][72][73] He also explicitly discusses the more restricted ensemble of quickly computable universes.[74]
Brian Greene's nine typeseditThe American theoretical physicist and string theorist Brian Greene discussed nine types of multiverses:[75]
QuiltedThe quilted multiverse works only in an infiniteuniverse. With an infinite amount of space, every possible event will occur an infinite number of times. However, the speed of light prevents us from being aware of these other identical areas.InflationaryThe inflationary multiverse is composed of various pockets in which inflation fields collapse and form new universes.Duration: 10 seconds.0:10Animation showing the multiple brane universes in the bulkBraneThe brane multiverse version postulates that our entire universe exists on a membrane (brane) which floats in a higher dimension or "bulk". In this bulk, there are other membranes with their own universes. These universes can interact with one another, and when they collide, the violence and energy produced is more than enough to give rise to a Big Bang. The branes float or drift near each other in the bulk, and every few trillion years, attracted by gravity or some other force we do not understand, collide and bang into each other. This repeated contact gives rise to multiple or "cyclic" Big Bangs. This particular hypothesis falls under the string theory umbrella as it requires extra spatial dimensions.
The Omniverse holds everything that can be accessed through progressive powersets of any particular base universe (or "reality") within itself. It is the limit of archverse recursion - this can be the first limit ordinal ω, or a much higher transfinite, depending on the level of recursion considered.
In a sense, it can indeed be argued to contain "all of Reality", but only in the sense that those below it observe it to be as such. The inhabitants of a universe, for instance, can posit the existence of a multiverse containing every possible state their universe could be in, and a megaverse allowing for looser laws of physics, and a gigaverse allowing for even fewer restrictions, but the limit of this application must be at the omniverse if they wish to stay within the concept of "things that are real". Thus, alternate omniverses in each others' relative Paradox Space contain things that cannot be mapped from one sense of "reality" to another.
Not many entities or civilizations can achieve or even fathom exiting the Omniverse, either being denied access to the exterior by Creator or Destroyer, or simply not being advanced enough to jump through an infinite amount of spaces. However, it has been done by many highly advanced civilizations, and even some small teams, such as Satoru's crew.
The only trait every single thing within the Omniverse share is that it exists. How it exists varies in countless ways.
The term "omniverse" was coined by Mark Gruenwald. It has been popularized by the composer-writer Sun Ra. Roger Penrose has spoken of the "omnium".
Beyond the OmniverseThe Omniverse exists in the surrounding emptiness known as The Outside, a void of virtual nothingness. Whatever may lie outside of these concepts is simply referred to as Beyond, one of the many iterations contained by Transcendentem.
Two Godverses orbit the Omniverse, one belonging to Creator, and one to Destroyer.
The Omniverse, the three Godverses and The Outsideare what makeup the Barrel, the local monocosm
The Omniverse holds everything that can be accessed through progressive powersets of any particular base universe (or "reality") within itself. It is the limit of archverse recursion - this can be the first limit ordinal ω, or a much higher transfinite, depending on the level of recursion considered.
In a sense, it can indeed be argued to contain "all of Reality", but only in the sense that those below it observe it to be as such. The inhabitants of a universe, for instance, can posit the existence of a multiverse containing every possible state their universe could be in, and a megaverse allowing for looser laws of physics, and a gigaverse allowing for even fewer restrictions, but the limit of this application must be at the omniverse if they wish to stay within the concept of "things that are real". Thus, alternate omniverses in each others' relative Paradox Space contain things that cannot be mapped from one sense of "reality" to another.
Not many entities or civilizations can achieve or even fathom exiting the Omniverse, either being denied access to the exterior by Creator or Destroyer, or simply not being advanced enough to jump through an infinite amount of spaces. However, it has been done by many highly advanced civilizations, and even some small teams, such as Satoru's crew.
The only trait every single thing within the Omniverse share is that it exists. How it exists varies in countless ways.
The term "omniverse" was coined by Mark Gruenwald. It has been popularized by the composer-writer Sun Ra. Roger Penrose has spoken of the "omnium".
Beyond the OmniverseThe Omniverse exists in the surrounding emptiness known as The Outside, a void of virtual nothingness. Whatever may lie outside of these concepts is simply referred to as Beyond, one of the many iterations contained by Transcendentem.
Two Godverses orbit the Omniverse, one belonging to Creator, and one to Destroyer.
The Omniverse, the three Godverses and The Outsideare what makeup the Barrel, the local monocosm
The multiverse is the hypothetical set of all universes.[1][a] Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "flat universes", "other universes", "alternate universes", "multiple universes", "plane universes", "parent and child universes", "many universes", or "many worlds". One common assumption is that the multiverse is a "patchwork quilt of separate universes all bound by the same laws of physics."[2]
The concept of multiple universes, or a multiverse, has been discussed throughout history, including Greek philosophy. It has evolved and has been debated in various fields, including cosmology, physics, and philosophy. Some physicists argue that the multiverse is a philosophical notion rather than a scientific hypothesis, as it cannot be empirically falsified. In recent years, there have been proponents and skeptics of multiverse theories within the physics community. Although some scientists have analyzed data in search of evidence for other universes, no statistically significant evidence has been found. Critics argue that the multiverse concept lacks testability and falsifiability, which are essential for scientific inquiry, and that it raises unresolved metaphysical issues.
Max Tegmark and Brian Greene have proposed different classification schemes for multiverses and universes. Tegmark's four-level classification consists of Level I: an extension of our universe, Level II: universes with different physical constants, Level III: many-worlds interpretation of quantum mechanics, and Level IV: ultimate ensemble. Brian Greene's nine types of multiverses include quilted, inflationary, brane, cyclic, landscape, quantum, holographic, simulated, and ultimate. The ideas explore various dimensions of space, physical laws, and mathematical structures to explain the existence and interactions of multiple universes. Some other multiverse concepts include twin-world models, cyclic theories, M-theory, and black-hole cosmology.
The anthropic principle suggests that the existence of a multitude of universes, each with different physical laws, could explain the asserted appearance of fine-tuning of our own universe for conscious life. The weak anthropic principle posits that we exist in one of the few universes that support life. Debates around Occam's razor and the simplicity of the multiverse versus a single universe arise, with proponents like Max Tegmark arguing that the multiverse is simpler and more elegant. The many-worlds interpretation of quantum mechanicsand modal realism, the belief that all possible worlds exist and are as real as our world, are also subjects of debate in the context of the anthropic principle.
History of the concepteditAccording to some, the idea of infinite worlds was first suggested by the pre-Socratic Greek philosopher Anaximander in the sixth century BCE.[3] However, there is debate as to whether he believed in multiple worlds, and if he did, whether those worlds were co-existent or successive.[4][5][6][7]
The first to whom we can definitively attribute the concept of innumerable worlds are the Ancient Greek Atomists, beginning with Leucippus and Democritus in the 5th century BCE, followed by Epicurus (341–270 BCE) and Lucretius (1st century BCE).[8][9][7][10][11][12] In the third century BCE, the philosopher Chrysippus suggested that the world eternally expired and regenerated, effectively suggesting the existence of multiple universes across time.[11] The concept of multiple universes became more defined in the Middle Ages.[citation needed]
The American philosopher and psychologist William James used the term "multiverse" in 1895, but in a different context.[13]
The concept first appeared in the modern scientific context in the course of the debate between Boltzmann and Zermelo in 1895.[14]
In Dublin in 1952, Erwin Schrödinger gave a lecture in which he jocularly warned his audience that what he was about to say might "seem lunatic". He said that when his equations seemed to describe several different histories, these were "not alternatives, but all really happen simultaneously".[15] This sort of duality is called "superposition".
Search for evidenceeditIn the 1990s, after recent works of fiction about the concept gained popularity, scientific discussions about the multiverse and journal articles about it gained prominence.[16]
Around 2010, scientists such as Stephen M. Feeney analyzed Wilkinson Microwave Anisotropy Probe(WMAP) data and claimed to find evidence suggesting that this universe collided with other (parallel) universes in the distant past.[17][18][19]However, a more thorough analysis of data from the WMAP and from the Planck satellite, which has a resolution three times higher than WMAP, did not reveal any statistically significant evidence of such a bubble universe collision.[20][21] In addition, there was no evidence of any gravitational pull of other universes on ours.[22][23]
In 2015, an astrophysicist may have found evidence of alternate or parallel universes by looking back in time to a time immediately after the Big Bang, although it is still a matter of debate among physicists.[24] Dr. Ranga-Ram Chary, after analyzing the cosmic radiation spectrum, found a signal 4,500 times brighter than it should have been, based on the number of protons and electrons scientists believe existed in the very early universe. This signal—an emission line that arose from the formation of atoms during the era of recombination—is more consistent with a universe whose ratio of matter particles to photons is about 65 times greater than our own. There is a 30% chance that this signal is noise, and not really a signal at all; however, it is also possible that it exists because a parallel universe dumped some of its matter particles into our universe. If additional protons and electrons had been added to our universe during recombination, more atoms would have formed, more photons would have been emitted during their formation, and the signature line that arose from all of these emissions would be greatly enhanced. Chary himself is skeptical:
Many other regions beyond our observable universe would exist with each such region governed by a different set of physical parameters than the ones we have measured for our universe.[24]
— Ranga-Ram Chary, "USA Today"Chary also noted:[25]
Unusual claims like evidence for alternate universes require a very high burden of proof.[25]
— Ranga-Ram Chary, "Universe Today"The signature that Chary has isolated may be a consequence of incoming light from distant galaxies, or even from clouds of dust surrounding our own galaxy.[25]
Proponents and skepticseditModern proponents of one or more of the multiverse hypotheses include Lee Smolin,[26] Don Page,[27]Brian Greene,[28][29] Max Tegmark,[30] Alan Guth,[31]Andrei Linde,[32] Michio Kaku,[33] David Deutsch,[34]Leonard Susskind,[35] Alexander Vilenkin,[36]Yasunori Nomura,[37] Raj Pathria,[38] Laura Mersini-Houghton,[39] Neil deGrasse Tyson,[40] Sean Carroll[41] and Stephen Hawking.[42]
Scientists who are generally skeptical of the concept of a multiverse or popular multiverse hypotheses include Sabine Hossenfelder,[43] David Gross,[44]Paul Steinhardt,[45][46] Anna Ijjas,[46] Abraham Loeb,[46] David Spergel,[47] Neil Turok,[48] Viatcheslav Mukhanov,[49] Michael S. Turner,[50] Roger Penrose,[51] George Ellis,[52][53] Joe Silk,[54] Carlo Rovelli,[55]Adam Frank,[56] Marcelo Gleiser,[56] Jim Baggott[57]and Paul Davies.[58]
Arguments against multiverse hypotheseseditIn his 2003 New York Times opinion piece, "A Brief History of the Multiverse", author and cosmologist Paul Davies offered a variety of arguments that multiverse hypotheses are non-scientific:[59]
For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there is an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification. Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence, it requires the same leap of faith.
— Paul Davies, "A Brief History of the Multiverse", The New York TimesGeorge Ellis, writing in August 2011, provided a criticism of the multiverse, and pointed out that it is not a traditional scientific theory. He accepts that the multiverse is thought to exist far beyond the cosmological horizon. He emphasized that it is theorized to be so far away that it is unlikely any evidence will ever be found. Ellis also explained that some theorists do not believe the lack of empiricaltestability and falsifiability is a major concern, but he is opposed to that line of thinking:
Many physicists who talk about the multiverse, especially advocates of the string landscape, do not care much about parallel universes per se. For them, objections to the multiverse as a concept are unimportant. Their theories live or die based on internal consistency and, one hopes, eventual laboratory testing.
Ellis says that scientists have proposed the idea of the multiverse as a way of explaining the nature of existence. He points out that it ultimately leaves those questions unresolved because it is a metaphysical issue that cannot be resolved by empirical science. He argues that observational testing is at the core of science and should not be abandoned:[60]
As skeptical as I am, I think the contemplation of the multiverse is an excellent opportunity to reflect on the nature of science and on the ultimate nature of existence: why we are here. ... In looking at this concept, we need an open mind, though not too open. It is a delicate path to tread. Parallel universes may or may not exist; the case is unproved. We are going to have to live with that uncertainty. Nothing is wrong with scientifically based philosophical speculation, which is what multiverse proposals are. But we should name it for what it is.
— George Ellis, "Does the Multiverse Really Exist?", Scientific AmericanPhilosopher Philip Goff argues that the inference of a multiverse to explain the apparent fine-tuning of the universe is an example of Inverse Gambler's Fallacy.[61]
Stoeger, Ellis, and Kircher[62]: sec. 7 note that in a true multiverse theory, "the universes are then completely disjoint and nothing that happens in any one of them is causally linked to what happens in any other one. This lack of any causal connection in such multiverses really places them beyond any scientific support".
In May 2020, astrophysicist Ethan Siegel expressed criticism in a Forbes blog post that parallel universes would have to remain a science fiction dream for the time being, based on the scientific evidence available to us.[63]
Scientific American contributor John Horgan also argues against the idea of a multiverse, claiming that they are "bad for science."[64]
TypeseditMax Tegmark and Brian Greene have devised classification schemes for the various theoretical types of multiverses and universes that they might comprise.
Max Tegmark's four levelseditCosmologist Max Tegmark has provided a taxonomyof universes beyond the familiar observable universe. The four levels of Tegmark's classification are arranged such that subsequent levels can be understood to encompass and expand upon previous levels. They are briefly described below.[65][66]
Level I: An extension of our universeeditA prediction of cosmic inflation is the existence of an infinite ergodic universe, which, being infinite, must contain Hubble volumes realizing all initial conditions.
Accordingly, an infinite universe will contain an infinite number of Hubble volumes, all having the same physical laws and physical constants. In regard to configurations such as the distribution of matter, almost all will differ from our Hubble volume. However, because there are infinitely many, far beyond the cosmological horizon, there will eventually be Hubble volumes with similar, and even identical, configurations. Tegmark estimates that an identical volume to ours should be about 1010115meters away from us.[30]
Given infinite space, there would be an infinite number of Hubble volumes identical to ours in the universe.[67] This follows directly from the cosmological principle, wherein it is assumed that our Hubble volume is not special or unique.
Level II: Universes with different physical constantseditIn the eternal inflation theory, which is a variant of the cosmic inflation theory, the multiverse or space as a whole is stretching and will continue doing so forever,[68] but some regions of space stop stretching and form distinct bubbles (like gas pockets in a loaf of rising bread). Such bubbles are embryonic level I multiverses.
Different bubbles may experience different spontaneous symmetry breaking, which results in different properties, such as different physical constants.[67]
Level II also includes John Archibald Wheeler's oscillatory universe theory and Lee Smolin's fecund universes theory.
Level III: Many-worlds interpretation of quantum mechanicseditSchrödinger's cat in the many-worlds interpretation, where a branching of the universe occurs through a superposition of two quantum mechanical statesHugh Everett III's many-worlds interpretation (MWI) is one of several mainstream interpretations of quantum mechanics.
In brief, one aspect of quantum mechanics is that certain observations cannot be predicted absolutely. Instead, there is a range of possible observations, each with a different probability. According to the MWI, each of these possible observations corresponds to a different "world" within the Universal wavefunction, with each world as real as ours. Suppose a six-sided dice is thrown and that the result of the throw corresponds to observablequantum mechanics. All six possible ways the dice can fall correspond to six different worlds. In the case of the Schrödinger's cat thought experiment, both outcomes would be "real" in at least one "world".
Tegmark argues that a Level III multiverse does not contain more possibilities in the Hubble volume than a Level I or Level II multiverse. In effect, all the different worlds created by "splits" in a Level III multiverse with the same physical constants can be found in some Hubble volume in a Level I multiverse. Tegmark writes that, "The only difference between Level I and Level III is where your doppelgängersreside. In Level I they live elsewhere in good old three-dimensional space. In Level III they live on another quantum branch in infinite-dimensional Hilbert space."
Similarly, all Level II bubble universes with different physical constants can, in effect, be found as "worlds" created by "splits" at the moment of spontaneous symmetry breaking in a Level III multiverse.[67] According to Yasunori Nomura,[37]Raphael Bousso, and Leonard Susskind,[35] this is because global spacetime appearing in the (eternally) inflating multiverse is a redundant concept. This implies that the multiverses of Levels I, II, and III are, in fact, the same thing. This hypothesis is referred to as "Multiverse = Quantum Many Worlds". According to Yasunori Nomura, this quantum multiverse is static, and time is a simple illusion.[69]
Another version of the many-worlds idea is H. Dieter Zeh's many-minds interpretation.
Level IV: Ultimate ensembleeditThe ultimate mathematical universe hypothesis is Tegmark's own hypothesis.[70]
This level considers all universes to be equally real which can be described by different mathematical structures.
Tegmark writes:
Abstract mathematics is so general that any Theory Of Everything (TOE) which is definable in purely formal terms (independent of vague human terminology) is also a mathematical structure. For instance, a TOE involving a set of different types of entities (denoted by words, say) and relations between them (denoted by additional words) is nothing but what mathematicians call a set-theoretical model, and one can generally find a formal systemthat it is a model of.
He argues that this "implies that any conceivable parallel universe theory can be described at Level IV" and "subsumes all other ensembles, therefore brings closure to the hierarchy of multiverses, and there cannot be, say, a Level V."[30]
Jürgen Schmidhuber, however, says that the set of mathematical structures is not even well-definedand that it admits only universe representations describable by constructive mathematics—that is, computer programs.
Schmidhuber explicitly includes universe representations describable by non-halting programs whose output bits converge after a finite time, although the convergence time itself may not be predictable by a halting program, due to the undecidability of the halting problem.[71][72][73] He also explicitly discusses the more restricted ensemble of quickly computable universes.[74]
Brian Greene's nine typeseditThe American theoretical physicist and string theorist Brian Greene discussed nine types of multiverses:[75]
QuiltedThe quilted multiverse works only in an infiniteuniverse. With an infinite amount of space, every possible event will occur an infinite number of times. However, the speed of light prevents us from being aware of these other identical areas.InflationaryThe inflationary multiverse is composed of various pockets in which inflation fields collapse and form new universes.Duration: 10 seconds.0:10Animation showing the multiple brane universes in the bulkBraneThe brane multiverse version postulates that our entire universe exists on a membrane (brane) which floats in a higher dimension or "bulk". In this bulk, there are other membranes with their own universes. These universes can interact with one another, and when they collide, the violence and energy produced is more than enough to give rise to a Big Bang. The branes float or drift near each other in the bulk, and every few trillion years, attracted by gravity or some other force we do not understand, collide and bang into each other. This repeated contact gives rise to multiple or "cyclic" Big Bangs. This particular hypothesis falls under the string theory umbrella as it requires extra spatial dimensions.
The Omniverse holds everything that can be accessed through progressive powersets of any particular base universe (or "reality") within itself. It is the limit of archverse recursion - this can be the first limit ordinal ω, or a much higher transfinite, depending on the level of recursion considered.
In a sense, it can indeed be argued to contain "all of Reality", but only in the sense that those below it observe it to be as such. The inhabitants of a universe, for instance, can posit the existence of a multiverse containing every possible state their universe could be in, and a megaverse allowing for looser laws of physics, and a gigaverse allowing for even fewer restrictions, but the limit of this application must be at the omniverse if they wish to stay within the concept of "things that are real". Thus, alternate omniverses in each others' relative Paradox Space contain things that cannot be mapped from one sense of "reality" to another.
Not many entities or civilizations can achieve or even fathom exiting the Omniverse, either being denied access to the exterior by Creator or Destroyer, or simply not being advanced enough to jump through an infinite amount of spaces. However, it has been done by many highly advanced civilizations, and even some small teams, such as Satoru's crew.
The only trait every single thing within the Omniverse share is that it exists. How it exists varies in countless ways.
The term "omniverse" was coined by Mark Gruenwald. It has been popularized by the composer-writer Sun Ra. Roger Penrose has spoken of the "omnium".
Beyond the OmniverseThe Omniverse exists in the surrounding emptiness known as The Outside, a void of virtual nothingness. Whatever may lie outside of these concepts is simply referred to as Beyond, one of the many iterations contained by Transcendentem.
Two Godverses orbit the Omniverse, one belonging to Creator, and one to Destroyer.
The Omniverse, the three Godverses and The Outsideare what makeup the Barrel, the local monocosm
The Omniverse holds everything that can be accessed through progressive powersets of any particular base universe (or "reality") within itself. It is the limit of archverse recursion - this can be the first limit ordinal ω, or a much higher transfinite, depending on the level of recursion considered.
In a sense, it can indeed be argued to contain "all of Reality", but only in the sense that those below it observe it to be as such. The inhabitants of a universe, for instance, can posit the existence of a multiverse containing every possible state their universe could be in, and a megaverse allowing for looser laws of physics, and a gigaverse allowing for even fewer restrictions, but the limit of this application must be at the omniverse if they wish to stay within the concept of "things that are real". Thus, alternate omniverses in each others' relative Paradox Space contain things that cannot be mapped from one sense of "reality" to another.
Not many entities or civilizations can achieve or even fathom exiting the Omniverse, either being denied access to the exterior by Creator or Destroyer, or simply not being advanced enough to jump through an infinite amount of spaces. However, it has been done by many highly advanced civilizations, and even some small teams, such as Satoru's crew.
The only trait every single thing within the Omniverse share is that it exists. How it exists varies in countless ways.
The term "omniverse" was coined by Mark Gruenwald. It has been popularized by the composer-writer Sun Ra. Roger Penrose has spoken of the "omnium".
Beyond the OmniverseThe Omniverse exists in the surrounding emptiness known as The Outside, a void of virtual nothingness. Whatever may lie outside of these concepts is simply referred to as Beyond, one of the many iterations contained by Transcendentem.
Two Godverses orbit the Omniverse, one belonging to Creator, and one to Destroyer.
The Omniverse, the three Godverses and The Outsideare what makeup the Barrel, the local monocosm