I have found the multiverse subject extremely enticing, as it provided me a way to reflect upon my existence and forced me to question everything. In this article I want to share and explain from different perspectives (scientific, theological, fictional, philosophical) the four different levels of multiverses suggested by scientists and astronomers.
We usually think of our universe as a vast nearly endlessly expanse that contains every star, galaxy in existence. But, what if there is more than one universe? Could it be that we live in a multiverse?
Our universe as we know, originated from a huge explosion that is known as the big bang. In the first split second after the big bang the universe underwent a fast expansion, known as the cosmic inflation. Our universe in the last 13.7 billion years have expanded enormously from the size of
an atom and its keep expanding since then. There was a time when the universe was expanding so rapidly that the parts of it were moving away from each other faster than the speed of light.
Why we might be living in a Multiverse?
In ancient times it was believed that the earth is the center of the universe and other planets revolves around it, later on, we discovered that our earth revolves around the Sun which is part of the solar system, and our solar system was found to be a part of the Milky Way galaxy. By further observations scientists learnt that our universe is composed with other billions of such galaxies, each galaxy containing billions of stars. We can only see a small portion of the entire universe, known as the observable universe, which has a diameter of 93 billion light years and the radius of approximately 46 billion light years.
According to modern theories of particle physics there might be other parallel universes like ours in the vast collection of universes so called multiverse. Scientists have started taking the idea of parallel universes very seriously in the past years and the majority of cosmologists today agree with the concept of a multiverse, which is the idea that our universe might not be the only one of its kind. There are number of theories about what the multiverse could be and there are four different perspectives of looking at them.
Level I — The Quilted Multiverse
There isn’t one single multiverse hypothesis, cosmologist Max Tegmark has proposed four different types of multiverse that might exist. The quilted universes model is predicted by the theory of inflation developed by Alan Guth and Andrei Linde, which suggests that the space itself is not just big but is infinite in size. Beyond the range of our telescopes are other regions of space, those regions are a type of parallel universes with the same physical laws and constants, some identical to ours while some very different from ours, and there is a probability for one of those parallel universes being identical to ours.
From scientific point of view, we are just a configuration of different particles, and according to science matter can be arranged only in finite ways and afterwards it tends to repeat itself. Based on the same idea according to Dr Tegmark an identical Hubble space to ours should be around 10 to the 10¹¹⁸, beyond that it must repeat, which means there might another you in another universe. However, we cannot observe those regions of space with our current technology, the farthest that we can observe is about 42 billion light years, which is the distance that light has been able to travel to us since the big bang happened. This quilted multiverse model is not really a theory, but rather a prediction, because it is predicted by the theory of inflation, and it agrees with the data provided by the cosmologists.
For example, Einstein’s general theory of relativity is not a theory anymore, it was in the past, but it has been proved and tested, and now scientists take it very seriously and use it as a scientific model in order to make sense of the events, even though it predicts lots of things which cannot be tested or observed, such as what happens if you fall inside a black hole. Hence, this model makes sense from scientific perspective, which requires logic and nature to make sense of the events. Even though this model is not a scientific model yet, as it is not testable, and we don’t have any observational evidences to prove this model, but it is predictable. For a theory to be scientific, you don’t have to observe everything that it predicts, but be able to observe only one thing that it predicts. Therefore, the lack of evidence for the existence of something, is not the evidence for the lack of something.
Level II — Inflationary Multiverse
The level I multiverse model was complicated to comprehend, the level II model forces us to open our imagination to infinite possibilities. The second model is based on the idea of infinite bubble universes, known as the inflationary multiverse model. In order to understand this model it is necessary to understand how the theory of inflation works, which tells us how the big bang occurred. The inflationary multiverse model suggests that the universe is infinite in size, and according to the theory of cosmic inflation the big bang that created our universe may not have been a onetime event, instead it could have happened again and again and going on forever
known as eternal inflation. As you are reading this sentence, there might be another big bang happening out in the cosmos, giving births to other universes or bubble universes. Our universe is part of one of those infinite bubbles, which is filled with matter deposited by the energy field that drove inflation, a process that would continue eternally. We will never get to those bubbles even if we travel at the speed of light. The bubbles vary not only in the initial conditions but also in aspects of nature with different space-time dimensions and different physical constants.
This model is not scientific either, as it lacks observable evidences. This idea of the multiverse is sounder from a theological perspective, where all the natural laws can be broken. Much of modern theology tries to address the questions concerning our existence on this planet. Since theology doesn’t require any observational evidences in order to make sense of the events.
Theists can easily argue that God is the creator and sustainer of the entire universe. Being omnipotent and omniscient God has the power to control everything. Hence, God decided to create not one universe but many, as God would be the one who created space and time, the inflation and the big bang. According to theism, once you have a transcendence source of everything, space and time, matter and energy, then God is free to create any type physical reality he wants. Therefore, theology can agree with this concept more than science, as science require evidence, unlike theology.
Level III — Quantum Universe
The third level multiverse model, is known as quantum many worlds, which is the most controversial type. This quantum multiverse model concentrates on the idea of quantum mechanics, and is very different from the first two models. Quantum mechanics works on probabilities, it states that there are a range of possible observations, each with a different probability. In order to be clear, if in this universe you are reading this paper, in another quantum
universe you might be reading a different paper, in yet another universe you got offered a job, or perhaps in many you don’t exist at all. This idea tells us that there are an infinite number of universes, with infinite number of possible outcomes, where random quantum processes splits the universe into multiple copies. At every point, a new universe is being created.
This model makes more sense from fictional point of view, as there are no limits to the realms, events can make sense or not, one can either obey the logic or defy it. I am firmly unconvinced by this theory, it is still fictional to me, as I believe that we do not have established the analysis about how the quantum thinking would describe this observation. Quantum physics is the
science that attempts to explain phenomena which cannot be explained by science and physics. This is why perhaps scientists love the quantum world idea as it explains mathematically things which are not observable.
I believe that we do not understand the quantum physics completely yet. In order to understand quantum mechanics it is very important to understand how quantum mechanics would link up with the observation. The link between quantum mechanics and the observation is still missing.If the ideas which makes sense mathematically are linked up with the observation, then perhaps it can enhance our understanding for the quantum multiverse. Nevertheless, there needs to be done more research on this theory in order to understand it completely which will require more time from physicists.
Level IV- Brane Multiverse
The level I, II and III varies from each other but they are governed by the same natural fundamental laws. Moving to the fourth level multiverse, which revolves around string theory, is called the brane multiverse. This model suggests that universes can differ not only in shape, but also in different laws of physics. The brane multiverse theory suggests that there can be more dimensions than three. We live in a four dimensional universe including time, but in brane multiverse, our four dimensional universe lives on a membrane, or brane, that is embedded with more than four dimensions. The idea here is that our membrane is not the only one, there might be other membranes. Existing outside of space and time, they are almost impossible to visualize.
This model is the most unclear and sounds crazy to me. It is definitely not a scientific model, as String theory is not a complete theory yet. I would see this model more from a philosophical point of view, where observational evidences are not required, one can use logic to make sense of the
events. I strongly believe that the brane multiverse hypothesis has high probability to fall under scientific realm in the near future, as the brane multiverse model has the chance of being experimentally tested based on string theory under shortest time frame.
String theory states that the space is made up of tiny little filaments known as strings which vibrates at different patterns, and according to scientists this proposal might be tested at the LSG (large hadron collider).
There is no doubt that the concept remains science fiction for now, however the lack of scientific proof should not be the reason to stop questioning. Hence, it is important for the concept of parallel universes to be explored completely, even though they lack observational evidences. One way can be to work on the multiverse theories which have highest chances of being tested in the shortest period of time frame.
I can confidently conclude, none of the multiverse models mentioned above are scientific models and remains unproven for now, as they lack observational evidences, but this should not stop science to investigate further on these ideas. I am eager to find out what the next big discovery will be in the multiverse hypothesis.
What do you think?
I’d love to hear your thoughts. Comment below to share your ideas and insight about the multiverse theory.