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Unformatted text preview: theorists would tell us to abandon the very notion of reality when considering phenomena at the scale of particles, atoms or even molecules. This seems rather hard to take, especially when we are also told that quantum behaviour rules all phenomena, and that even large-scale objects, being built from quantum ingredients, are themselves subject to the same quantum rules. Where does quantum non-reality leave off and that physical reality that we actually seem to experience begin to take over? Present-day quantum theory has no satisfactory answer to this question. My own viewpoint concerning this (and there are many other viewpoints) is that present-day quantum theory is not quite right, and that as the objects under consideration get more massive then the principles of Einstein’s general relativity begin to clash with those of quantum mechanics, and a notion of reality that is more in accordance with our experiences will begin to emerge. The reader should, however, be warned: quantum mechanics, as it stands, has no accepted observational evidence against it, and all such modifications remain speculative. Moreover, even general relativity, involving, as it does, the idea of a curved space-time, itself diverges from the notions of reality we are used to. Whether we look at the universe either at to address tHe nature oF realitY we need to understand its connection to consciousness and matHematics the quantum scale or across the vast distances over which the effects of general relativity become clear, then, the common-sense reality of chairs, tables and other material things would seem to dissolve away, to be replaced by a deeper reality inhabiting the world of mathematics. Our mathematical models of physical reality are far from complete, but they provide us with schemes that model reality with great precision – a precision enormously exceeding that of any description that is free of mathematics. There seems every reason to believe that these already remarkable schemes will be improved upon and that even more elegant and subtle pieces of mathematics will be found to mirror reality with even greater precision. Might mathematical entities inhabit their own world, the abstract Platonic world of mathematical forms? It is an idea that many mathematicians are comfortable with. In this scheme, the truths that mathematicians seek are, in a clear sense, already “there”, and mathematical research can be compared with archaeology; the mathematicians’ job is seek out these truths as a task of discovery rather than one of invention. To a mathematical Platonist, it is not so absurd to seek an ultimate home for physical reality within Plato’s world. This is not acceptable to everyone. Many philosophers (and others) would argue that mathematics consists merely of idealised mental concepts, and, if the world of mathematics is to be regarded as arising ultimately from our minds, then we have reached a circularity: our minds arise from the functioning of our physical brains, and the very precise physical laws that underlie that functioning are grounded in the mathematics that requires our brains for its existence. My own position is to avoid this immediate do we live in a computer simulation? NICK BOSTROM SCIENCE has revealed much about the world and our position within it. Generally, the findings have been humbling. The Earth is not the centre of the universe. Our species descended from brutes. We are made of the same stuff as mud. We are moved by neurophysiological signals and subject to a variety of biological, psychological and sociological influences over which we have limited control and little understanding. One of our remaining sources of pride is technological progress. Like the polyps that over time create coral reefs, the many generations of humans that have come before us have built up a vast technological  | NewScientist | 00 Month 2006 infrastructure. Our habitat is now largely one of human making. The fact of technological progress is also in a sense humbling. It suggests that the most advanced technology we have today is extremely limited and primitive compared with what our descendants will have. If we extrapolate these expected technological advances, and think through some of their logical implications, we arrive at another humbling conclusion: the “simulation argument”, which has caused some stir since I published it three years ago. The formal version of the argument requires some probability theory, but the underlying idea can be grasped without mathematics. It starts with the assumption that future civilisations will have enough computing power and programming skills to be able to create what I call “ancestor simulations”. These would be detailed simulations of the simulators’ predecessors – detailed enough for the simulated minds to be conscious and have the same kinds of experiences we have. Think of an ancestor simulation as a very realistic virtual reality environment, but one where the brains inhabiting the world are themselves part of the simulation. The simulation argument makes no assumption about how long it will take to develop this capacity. Some futurologists think it will happen within the next 50 years. But even if it takes10 million years, it makes no difference to the argument. Let me state what the conclusion of the argument is. The conclusion is that at least one of the following three propositions must be true: 1 Almost all civilisations at our level of development become extinct before becoming technologically mature. 2 The fraction of technologically mature civilisations that are interested in creating ancestor simulations is almost zero. 3 You are almost certainly living in a computer simulation. How do we reach this conclusion? Suppose first that the first proposition is false. Then a significant fraction of civilisations at our level of development eventually become technologically mature. Suppose, too, that the second proposition is false. Then a significant fraction of these civilisawww.newscientist.com paradox by allowing the Platonic mathematical world its own timeless and locationless existence, while allowing it to be accessible to us through mental activity. My viewpoint allows for three different kinds of reality: the physical, the mental and the Platonic-mathematical, with something (as yet) profoundly mysterious in the relations between the three. We do not properly understand why it is that physical behaviour is mirrored so precisely within the Platonic world, nor do we have much understanding of how conscious mentality seems to arise when physical material, such as that found in wakeful healthy human brains, is organised in just the right way. Nor do we really understand how it is that consciousness, when directed towards the understanding of mathematical problems, is capable of divining mathematical truth. What does this tell us about the nature of physical reality? It tells us that we cannot properly address the question of that reality without understanding its connection with the other two realities: conscious mentality and the wonderful world of mathematics. ● Roger Penrose is Emeritus Rouse Ball Professor of Mathematics at the University of Oxford and author of The Road to Reality: A complete guide to the laws of the universe (Alfred A. Knopf/Jonathan Cape, 2004) tions run ancestor simulations. Therefore, if both one and two are false, there will be simulated minds like ours. If we work out the numbers, we find that there would be vastly many more simulated minds than nonsimulated minds. We assume that technologically mature civilisations would have access to enormous amounts of computing power. So enormous, in fact, that by devoting even a tiny fraction to ancestor simulations, they would be able to implement billions of simulations, each containing as many people as have ever existed. In other words, almost all minds like yours would be simulated. Therefore, by a very weak principle of indifference, you would have to assume that you are probably one of these simulated minds rather than one of the ones that are not simulated. Hence, if you think that propositions one and two are both false, you should accept the third. It is not coherent to reject all three. www.newscientist.com Baroness susan greenField rudolpH metzger The next fifty years hold the real prospect that we might finally reveal the secrets behind prime numbers. Primes, the other indivisible numbers like 17 and 23, are the atoms of mathematics. Every other number is built by multiplying these atomic numbers together. Mathematicians have wrestled for two thou t thousand years to understand how Nature chose thhousand years to understand how Nature chose thsand years to understaure chose these enigmatic numbers. As you count higf mathematics. Every other number is built by multiplying these atomic numbers together. Mathematicians have wrestled fopredict whereit seems impossible to predictr two thousand years to undh the universe of numbers, it seems impossible to predict whereit seems impossible to predict where you are going to find the next prime. They appear as wild as lottery ticket numbers there fore. 135 The discovery of life elsewhere in the Universe would be the most significant breakthrough, cultural orientation. Within our solar system, forms of life may now, or may have existed earlier, on Mars, most likely in rather simple through a study a study of the chemistry of plane of the chemistry of planets and primitive unicellular forms of this ve existed earlier, on Mars, most likely in ratherikely in rather simple through a study of the chemistry of plane simple through a study of the chemistry of planets and primitive unicellular forms of this or that. The discovery of life elsewhere in the Universe woor that. The discovery of life elsewhere in the Universe would be the most significant breakthrough, cultural orientation. Within our solar system, forms breakthrough, cultural orientation. Within of life may most likely in rather simple through a study of the chemistry of planets and primitive unicellular forms the other no way. 155 Baroness Susan Greenfield Fullerian Professor of Physiology Oxford University Rudolph Metzger is Professor of Really Advanced Stuff University of Nowhere It should be emphasised that the simulation argument does not show that you are living in a simulation. The conclusion is simply that at least one of the three propositions is true. It does not tell us which one. In reality, we don’t have much specific information to tell us which of the three propositions might be true. In this situation, it might be reasonable to distribute our credence roughly evenly between them. Let us consider the options in a little more detail. Proposition one is straightforward. For example, maybe there is some technology that every advanced civilisation eventually develops and which then destroys them. Let us hope this is not the case. Proposition two requires that there is a strong convergence among all advanced civilisations, such that almost none of them are interested in running ancestor simulations. One can imagine various reasons that may lead civilisations to make this choice. Yet for proposition two to be true, virtually all civilisations would have to refrain. If this were true, it would be an interesting constraint on the future evolution of intelligent life. The third possibility is philosophically the most intriguing. If it is correct, you are almost certainly living in a computer simulation that was created by some advanced civilisation. What Copernicus and Darwin and latter-day scientists have been discovering are the laws and workings of the simulated reality. These laws might or might not be identical to those operating at the more fundamental level of reality where the computer that is running our simulation exists (which, of course, may itself be a simulation). In a way, our place in the world would be even humbler than we thought. What kind of implications would this have? How should it change the way you live your life? Your first reaction might think that if three is true, then all bets are off and you would go crazy. To reason thus would be an error. Even if we are in a simulation, the best methods of predicting what will happen next are still the familiar ones – extrapolation of past trends, scientific modelling and common sense. To a first approximation, if you thought you were in a simulation, you should get on with your life in much the same way as if you were convinced that you were leading a non-simulated life at the “bottom” level of reality. If we are in a simulation, could ever know for certain? If the simulators don’t want us to find out, we probably never will. But if they choose to reveal themselves, they could certainly do so. Another event that would let us conclude with a high degree of confidence that we are in a simulation is if we ever reach a point when we are about to switch on our own ancestor simulations. That would be very strong evidence against the first two propositions, leaving us only with the third. Nick Bostrom is the director of the Future of Humanity Institute at the University of Oxford 00 Month 2006 | NewScientist |  ...
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