In our Multiverse journey we’ve passed down a long road through Friedman’s expanding Universe, inflationary cosmology, quantum mechanics, superstring theory and even thermodynamics. What combines all of these concepts is that they’ve come to our attention through physical laws. Some of the considered theories have been confirmed to an extraordinary level of precision, while others remain hypothetical mathematical constructions providing conceptually elegant solutions to some profound questions about the laws governing our Universe. Now we will go the other way around and shall be concerned with two Multiverse ideas that are not so physically dependent, albeit our previous considerations can also play a significant role in the following discussions. These two are combined in one chapter of Brian Greene’s book “The Hidden Reality”, but I’ve decided to separate them out as, from my perspective, they are quite independent. This time we shall be talking about artificially created universes which might have arisen either if an extremely powerful civilization were to produce necessary conditions for generating another Big Bang or if an entire universe could be mimicked by an overwhelmingly sophisticated computer.
Let us begin by considering the first concept. Is it possible to generate such extreme conditions for a Big Bang to occur? We do not know for sure, but we can give it a thought and see where it gets us. If we take into account the Big Bang model which physicists were focused on before the idea of inflation took its place, we see that if we reverse the flow of time, everything in the Universe we are aware of should have been compressed to a smaller and smaller volume with higher and higher density reaching an infinite value at the moment of the Bing Bang. Physicists now know with a pretty high level of confidence that the mass of everything within our cosmological horizon is roughly 10 to the 55 grams. So in this case we have to compress an unimaginable amount of matter into a vanishingly small volume, which seems to be completely unachievable. And if we take into account that energy values close to the Big Bang were immensely high, we come to a magnitude of roughly 10 to the 65 power. The existence of that initial material is just taken as a given in the Big Bang model with no explanations. Moreover, even if we somehow manage to achieve this, another important question arises: how could we generate a bang? This is a very important question since the Big Bang is not an explosion happening somewhere in space, it’s an explosion that generates both space and time themselves. This is where inflation seems to play a great supporting role.
Energy needed for the outward rush of space, which happened, according to the inflationary model, when the Universe was 10 to the negative 35 seconds old, is way lower and, what’s also important, with inflationary cosmology we do explain the emergence of matter which will later become stars, galaxies and everything our Universe consists of. Recall that inflation occurs when the inflaton field reaches a high energy state which then drops down to a lower state. When this lower energy state of the inflaton field is reached, the tremendous amount of energy accumulated during the inflation period decays into elementary particles. This explains where all the material for complex structures in the Universe comes from. The next question that might come to your mind is what is the source of the inflaton energy?
This source happens to be gravity. Even though we tend to think that gravity does one thing, pulls massive objects, according to Einstein’s equations it can also be repulsive. Such repulsive gravity is responsible for that rapid expansion of space at the beginning. Since inflation starts when inflaton field is in its high energy state, the expanded space also possesses an inflaton field with high energy, so the more space is filled with this field the more energy it possesses. Great, now we know that inflationary model provides a natural way to overwhelmingly increase the value of energy. But in this case we have another question which would replace the original one – where does gravity take its energy from? This question is much better explicable and we can make headway out of it. In the presence of gravity you have an exhaustless reservoir of energy. Suppose you are jumping off a plane and are falling down under the force of gravity. While you are falling down your kinetic energy is constantly increasing. In any normal situation your energy will stop increasing when you smash into the ground. But if a hypothetical thing called a wormhole is placed in a way that one of its ends happens to be located just above the ground and another one somewhere in the atmosphere, you could use it to increase your kinetic energy indefinitely. With that said, we can depict a picture where the inflaton field gets huge amount of potential energy given by gravity, and this, in turn, increases the amount of energy within expanded space. This energy will then decay into elementary particles, so it becomes clear that the inflationary model does not require initial material for the later production of complex structures such as stars and galaxies, this material is generated at the end of the inflation period.
All the inflationary idea needs as a given is the small amount of initial energy which would start the process of inflation. According to calculations this would be a small speck of space 10 to the negative 26 centimeters in size and its mass would be roughly 10 grams. Such an infinitesimal grain would then experience a violent expansion such that its size will become bigger than our observable Universe in a fraction of a second.
The main remaining question in our discussion is whether or not the inflaton field actually exists. We freely use this notion in our calculations but contrary to the electromagnetic field or gravitational field we can only speculate about its existence for now. But let’s suppose that it actually exists and that we will even manage to control it as we can control the electromagnetic field. Will we really become gods able to create entire universes? And if we do, shouldn’t we care that expanding space created by our own hands will swallow this Universe where we live?
According to Alan Guth and his colleagues the answer to the second question is promising. Pressure does a thing here. If an inflaton grain will be created in a lab it will possess positive energy and negative pressure. And it will be surrounded by the space in our lab which possesses inflaton field with its pressure of either zero or a very small value. Generally, zero does not make much sense, but here our artificial inflaton grain’s pressure is negative which is clearly less than zero. This difference in pressure will not allow the grain to expand into outer space, so our lab will be safe. But this will not stop the expansion of the grain. Because of the difference in pressure our expanding grain will separate out from our Universe and will expand independently. Yes, you’ve got it right; in this case our grain becomes a new independent universe.
Ok, this is all good, we see that we need not be afraid of the fate of our Universe, but could we then say that we have created a new universe and became gods? The answer to this question is unsatisfying – we will not have a chance to even confirm that we’ve succeeded. After our inflaton grain will separate out from our Universe, we will lose any connection with it and it will be just a deep gravitational void which will look like a black hole in our lab. Unlike this cat, we will be put aside from our own work.
More importantly, Guth and his team figured out that for initiating the process of inflation we need an extremely strong push. So strong that there is only one hypothetical entity which would be capable to exert it – a white hole, the reverse of a black hole. And there is no hint at the moment that such entities exist. The initiating of inflation can also be done through the process of quantum tunneling, but its probability is so infinitesimally small that you can wait billions of years until it happens. To conclude, with an artificially initiated Big Bang, we can say that we understand quite a lot about this process, but, more probably, it is impossible, or we have to pass a long, long road until we reach the point.
With that out of the way, let’s see what we can achieve with the notion of a computationally modeled universe.
Sometimes people get so sick that they experience some sorts of hallucinations. When this happens our notion of reality could vary significantly. If our perception of reality is so dependent upon our internal conditions, how could we be sure that we know something and that this something actually corresponds to reality, without it being biased by procedures developed in the process of evolution? One of my friends once argued that mathematics could contain any truth since it is merely a human-constructed procedure that might not be applicable for any other civilization. Moreover, she was arguing that the very concept of truth does not make much sense. We are not going to dig in deep into mathematics just yet since it will be the main concept of my next article, but as for the second question, it is central to epistemology – the branch of philosophy concerned with the nature and scope of knowledge. It is well presented in a number of movies among those are “The Matrix”, “The Thirteenth Floor”, “Vanilla Sky” to name but a few. So how could we know that our reality isn’t generated in a way similar to The Matrix?
One important thing that I should mention here is that this point of view, according to which there could be no actual truth or that what we perceive as truth is generated computationally or in any other artificial way, can certainly lead us into complete bewilderment which would be followed by a consciousness crash. For in this case the degree of our distrust rises indefinitely compelling us to doubt in our possibility of deductive reasoning even in the one that led us to this conclusion! I’m not going to dig deep into the details but you can see that in this case even unassailable truths about, for example, musical tones that construct a consistent melody may fall out from our perception. Let’s not fall too deep into conceptual details and have a look at how likely it is that a human brain, or an entire universe, are simulated.
The question as to whether or not the human brain can be computationally simulated is a very complicated one since the workings of the brain is a highly unexplored area in science. But let’s consider the eye’s retina, which is one of the most studied parts of human brain. A specialist in artificial intelligence Hans Moravec made his calculations and estimated that a computationally modeled retina performing a million operations per second could be as useful as our biological retina. To model an entire brain our computer would need to perform roughly 10 to the 17th operations a second according to these estimates. The most powerful computers of our age can reach 10 to the 15th operations a second, so there is no doubt that we will reach the necessary point in the next couple of decades. Of course, this does not imply that artificial intelligence is going to succeed that fast, but almost everybody would agree that eventually the power of our computer systems will exceed our biological limits.
These are certainly modern age questions but their roots go into antiquity. Great thinkers such as Plato and Aristotle, Descartes and Kant, Nietzsche and Freud, Wittgenstein and Turing were thinking about the aspects that make our brains capable of perceiving reality the way they do throughout the human history. There are plenty of theories concerned with the workings of the brain, but we will focus on three of them which are relevant to our discussion. The first one is physicalism which states that any subjective matter of our experience is necessarily based on the unique condition of a brain, such as the location of molecules and their interactions with each other. Another branch of the philosophical theories of mind called functionalism states that it is not necessary what the stuff in our brains is made of. Instead, the only important thing is the processes and functions that take place while we are obtaining some knowledge or using that knowledge for making a statement of any kind. In this sense, it does not matter whether these processes and functions take place inside the physical substance of a brain or they are generated by using electronic signals simulated on a powerful computer. The third one called dualism goes against both previous concepts advocating independent mental and physical substances. As you might guess, we shall be concerned mostly with functionalism since it provides a way of incorporating the idea of a simulated reality. According to this concept, it would not make any difference whether the process of generating a thought takes place in a physical brain consisting of neurons and synapses or if it were to be simulated with an appropriate electrical network.
We are not concerned here with artificial minds that require a body through which it will operate, namely a robot that we are quite familiar with from the movies such as “Bladerunner”, “Star Wars”, “I, Robot” and many more. Here our concern would be with programmed games such as “The Sims”, “Second Life” and the like. The history of computer games, which dates back only a few decades, shows that their similarity with our own world increases dramatically. It is quite imaginable that one day the environment of these games will reach the point of being completely indistinguishable from our own environment. Will the inhabitants of such a world possess some sort of consciousness? And if they did, would they know that they inhabit an artificial world? Our previous estimations concerned with computer power needed for simulating a human brain could be incorporated into a model of our entire civilization. Taking a rough estimate of the number of people who have ever existed on the planet Earth we come to a rough conclusion that our computer would need to perform 10 to the 35th operations a second. With our present day computers we can estimate that it would be achievable with an Earth-sized computer, which would presumably perform 10 to the 33rd – 10 to the 42nd operations a second. Even with the lowest estimate here we see that the computational power of all the people ever existed on our planet could be achieved within a couple of minutes with an Earth-sized computer.
Of course, to generate not only human minds but to combine them with everything else we, humans, deal with this number will get far larger, but we were concerned here only with present day computational capabilities, and if we have a look into the possibility of developing a quantum computer, it can increase the computational power up to an overwhelming degree. Moreover, there are some ways to diminish the necessary computational power. The inhabitants of a universe like ours will never notice the artificial nature of their universe if it shows its inconsistencies beyond their cosmological horizon, so everything located beyond it could be taken away. There are also a lot of people who aren’t interested in various concepts, for example mathematics, physics, politics, literature, music or any other, so according to the previous performance of a subject necessary computational power could be sufficiently diminished. Consequently, a well developed program not taking into account those places where it is not necessary for it to operate properly could still simulate a universe without losing its credibility for the inhabitants.
Comparing both our concepts of this article we inevitably come to the conclusion that initiating a big bang that would generate a new universe is very hard to do and may even be completely unachievable. But the question of simulating new environments is far more reachable and has to do with new computational technologies whose capacity becomes higher and higher with time. So it’s not even a question whether or not our descendants will manage to create a simulated world, we are already doing this. The question here is how realistic a simulated world could be. The most important thing to realize is that if we ever manage to simulate an environment with reasonable inhabitants we won’t stop. For what can be more interesting than coming home from your workplace push a button on your computer which would generate a distinct universe in a couple of minutes. Once we succeed, we will generate more and more universes with their own reasonable inhabitants, so eventually the number of people and all the animals on our planet would fade out in comparison with the number of our artificially simulated creatures. In this case, we are getting to the main point of our conversation which would signalize that we ourselves are inhabitants of such a simulated universe. You might say that we are again coming to that pointless conclusion which increases our distrust in everything, but if you think about it, it does not take away our possibility for the comprehension of a generic reality which, in this case, surely admits the possibility of simulated universes in one of which we happened to live.
Now, if we indeed live in a simulated universe how could we confirm this to be true? It surely depends on the “simulator” himself since he can surely denote his existence if he wants to. But it is more likely that he (or she or whoever) won’t do it. Most probably, they would have used their knowledge of the laws of physics to generate our universe. This is saying that they would have used some initial calculations to determine the behavior of any constituent of the universe they simulate up to elementary particles. But this inevitably leads to the conclusion that they must use approximate methods of calculations for elementary particles since these particles, according to our own calculations, always change some values. To obtain an exact number of a constantly changing parameter requires a calculation with the precision of an infinite number of decimal places. We have our established laws of physics which work perfectly but what if one day their predictions start to diverge from experimental results? Of course, the most probable explanation would imply that we need a new theory capable to explain this divergence, but there is a possibility that at some point even some of our basic equations such as F = ma would diverge from experimental data. In this case, the possibility of our Universe being artificially simulated could not be ruled out.
Now we came to the end of this story but I cannot resist providing my own thoughts. The possibility of such a computationally modeled universe depends extremely explicitly upon the question of whether or not it is possible to simulate a human mind. I believe that with the modern understanding of human consciousness and modern physical theories we cannot do it. This belief is based on the information obtained from two books written by Roger Penrose about 20-25 years ago. The books are “The Emperor’s New Mind” and “Shadows of the Mind”. The main reasons behind the idea of impossibility of simulating a reasonable object possessing some sort of mind is based on various concepts such as Gödel’s incompleteness theorem and mathematical non-computability so I encourage all the interested readers to put these books into their lists.