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Hong Kong

University of Durham
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United Kingdom

University of Sussex

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United Kingdom

Writing - Commentary

In Search of the Multiverse




                        The cosmos contains more than one universe, to the point that every possible form a universe can take exists for certain. This is the main idea of John Gribbin’s book, In Search of the Multiverse. The Multiverse is literally a setting containing many universes, and Gribbin argues that it truly exists. Although they might contradict common sense, those arguments are certainly not nonsense and warrants serious attention. Yet are they conclusive to prove the Multiverse’s existence?

The Multiverse from Quantum Mechanics

                        The Multiverse idea’s birth is related to quantum mechanics, a topic the author explains in the first chapter. In quantum mechanics, particular properties like position and velocity are uncertain. For example: small particles can take two different paths simultaneously, but only if we do not watch them travel those paths. Two exclusive outcomes can occur at the same time, in a superposition. These situations defy common sense. Yet the different quantum interpretations created to cope with these uncertainties are even more eccentric.

                        Such quantum interpretations of natural mysteries eventually inspired the development of the initial form of the Multiverse idea. In the 1950’s, a man called Hugh Everett proposed an interesting perspective: when we make a decision, our world splits into several similar ones. In one world, we follow the option that we chose. However, in the other worlds' near-identical versions of us would follow other possible options or outcomes. As such, there will be countless different universes. This was the so-called Many-World Interpretation, which will eventually lead to the modern Multiverse theory.

Arguments for the Multiverse

                        The Multiverse explicitly places our universe as just one part of a much larger landscape. Why should we assume this to be so in the first place? Gribbin’s explanation is that our universe has many constant properties (like the speed of light) which can easily be different. Because the probability of our universe having different values for natural constants is very high, our universe must be just one of many existing universes, each having natural constants of various values. This justifies the existence of the Multiverse.

                        Far from being an isolated, nonsensical idea, the modern Multiverse theory is intertwined with other scientific concepts like thermodynamics and cosmology. Together they can form a comprehensive picture of our cosmological setting, as well as our own universe.

                        For thermodynamics, the infinity of space means that parts of the Multiverse can fluctuate from the normal pattern of matter: from order to disorder. While the rest of the Multiverse is in a state of disorder, the fluctuations accumulate order and matter. This creates the conditions for forming an independent universe. Because of infinite space, there is an appreciable probability that such fluctuations do occur. With time, we have a Multiverse. Also, because time is typically associated with the disorder-order flow, the Multiverse theory implies that time only exists in each individual universe fluctuation.

                        Given that a Multiverse perspective changes the identity of our universe (as well as how it was created), the Multiverse theory is closely linked to cosmology. The central point of this relationship is inflation, which was created along with a great explosion of matter that we call the Big Bang.

                        It is a well-known fact that the universe is expanding. Yet not all parts of space expand uniformly. Some expand quicker, some slower. Over time the patches expanding faster will eventually dominate space, and the cycle repeats as fluctuations occur again (this is called Eternal Inflation). Such differential expansion for the patches leads to space bubbles with specific combinations of natural constants. These bubbles then develop into individual universes. Note that each bubble is essentially isolated from all other universe bubbles.

                        Thermodynamics and cosmology both accommodates the Multiverse idea, supporting it to an appreciable extent. Yet that is not the end of the list of evidence provided. Additional backing comes from an interesting source that is the String Theory.

                        The String Theory is a set of theories that attempt to explain the universe (or the Multiverse, for that matter) as vibrating strings. Supporters have touted it as the right description of the universe mainly because it includes gravity, although the jury is still out on whether the theory is correct. Nevertheless, it appears that the Multiverse idea can be linked to the String Theory. In String Theory, space has not just four but eleven dimensions. We only see four because the remaining seven were compacted. Calculations have suggested that there are 10^500 possible ways of compacting dimensions.  That would yield 10^500 different universes, in what has been named the Cosmic Landscape. This Cosmic Landscape is actually the String Theory’s version of the Multiverse.

                        With String Theory, the author’s list of evidence for the Multiverse ends, but the book does not finish with it yet. Gribbin takes a brief look at a way of doubting the authenticity of our universe, and by extension the Multiverse.

A Simulated Universe?

                        Some argue that our universe is actually a simulation created by other civilizations. They say it is easier to create a simulation of a universe, rather than having a real one form in nature. Hence the probability that our universe is a simulation is overwhelming. Gribbin counters by showing that an infinite universe requires infinite data to simulate; they would need infinite memory space in their computer. This is clearly impossible, either for a universe or Multiverse. Then Gribbin argues for another view: it is actually more probable for universes to naturally form rather than being simulations.

                        Black holes are collapsed stars that suck and trap matter, yet such matter are not destroyed and exist somewhere. As such, some speculated that black holes transport matter into another dimension, creating a new universe bubble with slightly different natural constants. Eventually the new universe generates black holes and transports matter into new universe bubbles, again with slightly different natural constants.

                        Here is the punch line: universes with the right natural constants to generate carbon make more black holes. These universes thus create more new universe bubbles. Eventually they outcompete other carbon-less universes with less black holes, so that the Multiverse is populated with universes with the constants that are just right for producing carbon, and hence black holes and universes. This is evolution for universes, where those that makes the most black holes, and so more offspring universes, are selected. In addition, because life requires carbon, universes that are good for black holes are also good for life.

                        If civilizations do succeed in modifying black holes, which is impossible by our standards, then they can arguably alter universe propagation. They can make “designer universes”. However, the initial conditions of the Multiverse for universe reproduction are self-driven; no designer was needed.

                        Gribbin concludes by stating that the fact that we exist is the best evidence for the Multiverse. Our own universe is not a lucky combination of natural constants suitable for life. It is just one of many possible combinations that exist in a multi-universe landscape known as the Multiverse.

Intriguing yet Inconclusive

                        The idea of the Multiverse is intriguing to me. It resembles science fiction (at times another word for nonsense), but it more or less fits with certain scientific works, past and present. If proven correct, the theory shall radically alter our perspective of the cosmos that we live in. Yet at the present, I cannot say that there is conclusive evidence for the Multiverse’s existence.

                        Recall the argument that our universe, with its life-friendly natural constants, can probably exist only if it is just one of many in the Multiverse. Gribbin used it as one way to justify the Multiverse’s existence. Yet however improbable an outcome, it does not mean it’s impossible, just like the improbable fluctuations from disorder to order. As far as I am concerned, we might be precisely living in a universe with an improbable, but possible, combination of natural constants. This is not to say the justification is unreasonable. It is just not very strong.

                        String Theory offers relatively more concrete ground, but nevertheless shaky. Simply put, we are uncertain about accuracy of The String Theory. It is currently still being developed, and it is far from universally accepted. As such, to seriously use String Theory to lend credibility to the Multiverse is inappropriate. It can compliment other supporting evidence at most, but String Theory certainly cannot be a main factor until it is sufficiently supported.

                        As for the rest of the evidence (on thermodynamic and cosmological aspects) in book, I say they are merely compatible with the Multiverse theory, because we cannot prove them for now. Fluctuations results in ordered space pockets in a sea of disorder, or space pockets that expand faster. Yet do they actually result in new universes? We may never know for sure, either due to our limited lifespan or the impossibility of establishing contact between universes.

                        As such, Gribbin’s arguments to prove the Multiverse’s existence are insufficient. The direct way to prove the Multiverse theory is to exchange something, like matter or energy, between another universe and our own. However, there is no way to accomplish this to date. Therefore, the theory either needs to be further developed or for advancements in other fields to bolster it.

                        Authenticity aside, applying evolution to universes is also intriguing. The prospect of natural selection of universes with variable constants illustrates the probabilistic nature of evolution. An entity that is most suited for replication shall eventually outnumber those that are less capable. Evolution is simply a consequence of probability, which should settle any doubt on evolution.

                        I am not against the Multiverse theory. I think it is most interesting from both a scientific and philosophical perspective; it can change the identity of various things, including humans. Yet it is also a theory that is extremely difficult both to prove and falsify, so I shall take a wait-and-see approach for now (with eager impatience).


                                                                                                                                                                  Mike Ko
                                                                                                                                                                  ( 1,642 words )


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