NEW YORK—If you, me and every person and thing in the cosmos were actually characters in some giant computer game, we would not necessarily know it. The idea that the universe is a simulation sounds more like the plot of “The Matrix,” but it is also a legitimate scientific hypothesis. Researchers pondered the controversial notion Tuesday at the annual Isaac Asimov Memorial Debate here at the American Museum of Natural History.
Moderator Neil deGrasse Tyson, director of the museum’s Hayden Planetarium, put the odds at 50-50 that our entire existence is a program on someone else’s hard drive. “I think the likelihood may be very high,” he said. He noted the gap between human and chimpanzee intelligence, despite the fact that we share more than 98 percent of our DNA. Somewhere out there could be a being whose intelligence is that much greater than our own. “We would be drooling, blithering idiots in their presence,” he said. “If that’s the case, it is easy for me to imagine that everything in our lives is just a creation of some other entity for their entertainment.”
Virtual minds
A popular argument for the simulation hypothesis came from University of Oxford philosopher Nick Bostrum in 2003, when he suggested that members of an advanced civilization with enormous computing power might decide to run simulations of their ancestors. They would probably have the ability to run many, many such simulations, to the point where the vast majority of minds would actually be artificial ones within such simulations, rather than the original ancestral minds. So simple statistics suggest it is much more likely that we are among the simulated minds.And there are other reasons to think we might be virtual. For instance, the more we learn about the universe, the more it appears to be based on mathematical laws. Perhaps that is not a given, but a function of the nature of the universe we are living in. “If I were a character in a computer game, I would also discover eventually that the rules seemed completely rigid and mathematical,” said Max Tegmark, a cosmologist at the Massachusetts Institute of Technology (MIT). “That just reflects the computer code in which it was written.”
Furthermore, ideas from information theory keep showing up in physics. “In my research I found this very strange thing,” said James Gates, a theoretical physicist at the University of Maryland. “I was driven to error-correcting codes—they’re what make browsers work. So why were they in the equations I was studying about quarks and electrons and supersymmetry? This brought me to the stark realization that I could no longer say people like Max are crazy.”
Room for skepticism
Yet not everyone on the panel agreed with this reasoning. “If you’re finding IT solutions to your problems, maybe it’s just the fad of the moment,” Tyson pointed out. “Kind of like if you’re a hammer, every problem looks like a nail.”And the statistical argument that most minds in the future will turn out to be artificial rather than biological is also not a given, said Lisa Randall, a theoretical physicist at Harvard University. “It’s just not based on well-defined probabilities. The argument says you’d have lots of things that want to simulate us. I actually have a problem with that. We mostly are interested in ourselves. I don’t know why this higher species would want to simulate us.” Randall admitted she did not quite understand why other scientists were even entertaining the notion that the universe is a simulation. “I actually am very interested in why so many people think it’s an interesting question.” She rated the chances that this idea turns out to be true “effectively zero.”
Such existential-sounding hypotheses often tend to be essentially untestable, but some researchers think they could find experimental evidence that we are living in a computer game. One idea is that the programmers might cut corners to make the simulation easier to run. “If there is an underlying simulation of the universe that has the problem of finite computational resources, just as we do, then the laws of physics have to be put on a finite set of points in a finite volume,” said Zohreh Davoudi, a physicist at MIT. “Then we go back and see what kind of signatures we find that tell us we started from non-continuous spacetime.” That evidence might come, for example, in the form of an unusual distribution of energies among the cosmic rays hitting Earth that suggests spacetime is not continuous, but made of discrete points. “That’s the kind of evidence that would convince me as a physicist,” Gates said. Yet proving the opposite—that the universe is real—might be harder. “You’re not going to get proof that we’re not in a simulation, because any evidence that we get could be simulated,” said David Chalmers, a professor of philosophy at New York University.
Life, the universe and everything
If it turns out we really are living in a version of “The Matrix,” though—so what? “Maybe we’re in a simulation, maybe we’re not, but if we are, hey, it’s not so bad,” Chalmers said.“My advice is to go out and do really interesting things,” Tegmark said, “so the simulators don’t shut you down.”
But some were more contemplative, saying the possibility raises some weighty spiritual questions. “If the simulation hypothesis is valid then we open the door to eternal life and resurrection and things that formally have been discussed in the realm of religion,” Gates suggested. “The reason is quite simple: If we’re programs in the computer, then as long as I have a computer that’s not damaged, I can always re-run the program.”
And if someone somewhere created our simulation, would that make this entity God? “We in this universe can create simulated worlds and there’s nothing remotely spooky about that,” Chalmers said. “Our creator isn’t especially spooky, it’s just some teenage hacker in the next universe up.” Turn the tables, and we are essentially gods over our own computer creations. “We don’t think of ourselves as deities when we program Mario, even though we have power over how high Mario jumps,” Tyson said. “There’s no reason to think they’re all-powerful just because they control everything we do.” And a simulated universe introduces another disturbing possibility. “What happens,” Tyson said, “if there’s a bug that crashes the entire program?”
Simulated reality is the hypothesis that reality could be simulated—for example by quantum computer simulation—to a degree indistinguishable from "true" reality. It could contain conscious minds which may or may not be fully aware that they are living inside a simulation. This is quite different from the current, technologically achievable concept of virtual reality. Virtual reality is easily distinguished from the experience of actuality; participants are never in doubt about the nature of what they experience. Simulated reality, by contrast, would be hard or impossible to separate from "true" reality. There has been much debate over this topic, ranging from philosophical discourse to practical applications in computing.
The dream argument is the postulation that the act of dreaming provides preliminary evidence that the senses we trust to distinguish reality from illusion should not be fully trusted, and therefore, any state that is dependent on our senses should at the very least be carefully examined and rigorously tested to determine whether it is in fact reality.
The Avataṃsaka Sūtra (Sanskrit; alternatively, the Mahāvaipulya Buddhāvataṃsaka Sūtra) is one of the most influential Mahayana sutras of East Asian Buddhism. The title is rendered in English as Flower Garland Sutra, Flower Adornment Sutra, or Flower Ornament Scripture. It has been called by the translator Thomas Cleary "the most grandiose, the most comprehensive, and the most beautifully arrayed of the Buddhist scriptures."
The Avataṃsaka Sūtra describes a cosmos of infinite realms upon realms, mutually containing one another. This sutra was especially influential in East Asian Buddhism. The vision expressed in this work was the foundation for the creation of the Huayan school of Chinese Buddhism, which was characterized by a philosophy of interpenetration. The Huayan school is known as Hwaeom in Korea and Kegon in Japan. The sutra is also influential in Chan Buddhism.
The sutra, among the longest in the Buddhist canon, is a compilation of disparate texts on various topics such as the Bodhisattva path, the interpenetration of phenomena (dharmas), the visionary powers of meditation and the equality of things in emptiness. According to Paul Demiéville, the collection is "characterized by overflowing visionary images, which multiply everything to infinity, by a type of monadology that teaches the interpenetration of the one whole and the particularized many, of spirit and matter" and by "the notion of a gradual progress towards liberation through successive stages and an obsessive preference for images of light and radiance." Likewise, Alan Fox has described the sutra's worldview as "fractal", "holographic" and "psychedelic".
The East Asian view of the text is that it expresses the universe as seen by a Buddha (the Dharmadhatu), who sees all phenomena as empty and thus infinitely interpenetrating, from the point of view of enlightenment. This interpenetration is described in the Avatamsaka as the perception "that the fields full of assemblies, the beings and aeons which are as many as all the dust particles, are all present in every particle of dust." Thus, a Buddhas view of reality is also said to be "inconceivable; no sentient being can fathom it". Paul Williams notes that the sutra speaks of both Yogacara and Madhyamaka doctrines, stating that all things are empty of inherent existence and also of a "pure untainted awareness or consciousness (amalacitta) as the ground of all phenomena".The Avatamsaka sutra also highlights the visionary and mystical power of attaining the spiritual wisdom which sees the nature of the world:
Endless action arises from the mind; from action arises the multifarious world. Having understood that the world's true nature is mind, you display bodies of your own in harmony with the world. Having realized that this world is like a dream, and that all Buddhas are like mere reflections, that all principles [dharma] are like an echo, you move unimpeded in the world (Trans in Gomez, 1967: lxxxi)As a result of their meditative power, Buddhas have the magical ability to create and manifest infinite forms, and they do this in many skillful ways out of great compassion for all beings.
The point of these teachings is to lead all beings through the ten bodhisattva levels to the goal of Buddhahood (which is done for sake of all other beings). These stages of spiritual attainment are also widely discussed in various parts of the sutra (book 15, book 26). The sutra also includes numerous Buddhas and their Buddhalands which are said to be infinite, representing a vast cosmic view of reality, though it centers on a most important figure, the Buddha Vairocana (great radiance). Vairocana is a cosmic being who is the source of light and enlightenment of the 'Lotus universe', who is said to contain all world systems. According to Paul Williams, the Buddha "is said or implied at various places in this vast and heterogeneous sutra to be the universe itself, to be the same as ‘absence of intrinsic existence’ or emptiness, and to be the Buddha’s all-pervading omniscient awareness." The very body of Vairocana is also seen as a reflection of the whole universe:
- In all atoms of all lands
- Buddha enters, each and every one,
- Producing miracle displays for sentient beings:
- Such is the way of Vairocana....
- The techniques of the Buddhas are inconceivable,
- All appearing in accord with beings’ minds....
- In each atom the Buddhas of all times
- Appear, according to inclinations;
- While their essential nature neither comes nor goes,
- By their vow power they pervade the worlds.(Cleary 1984–7: I, Bk 4)
The body of [Vairocana] Buddha is inconceivable. In his body are all sorts of lands of sentient beings. Even in a single pore are countless vast oceans.Also, for the Avatamsaka, the historical Buddha Sakyamuni is simply a magical emanation of the cosmic Buddha Vairocana.
The simulation hypothesis proposes that all of reality, including the earth and the universe, is in fact an artificial simulation, most likely a computer simulation. Some versions rely on the development of a simulated reality, a proposed technology that would seem realistic enough to convince its inhabitants. The hypothesis has been a central plot device of many science fiction stories and films.
Many works of science fiction as well as some forecasts by serious technologists and futurologists predict that enormous amounts of computing power will be available in the future. Let us suppose for a moment that these predictions are correct. One thing that later generations might do with their super-powerful computers is run detailed simulations of their forebears or of people like their forebears. Because their computers would be so powerful, they could run a great many such simulations. Suppose that these simulated people are conscious (as they would be if the simulations were sufficiently fine-grained and if a certain quite widely accepted position in the philosophy of mind is correct). Then it could be the case that the vast majority of minds like ours do not belong to the original race but rather to people simulated by the advanced descendants of an original race. It is then possible to argue that, if this were the case, we would be rational to think that we are likely among the simulated minds rather than among the original biological ones. Therefore, if we don't think that we are currently living in a computer simulation, we are not entitled to believe that we will have descendants who will run lots of such simulations of their forebears.
— Nick Bostrom, Are you living in a computer simulation?, 2003
Ancestor simulation
In 2003, philosopher Nick Bostrom proposed a trilemma that he called "the simulation argument". Despite the name, Bostrom's "simulation argument" does not directly argue that we live in a simulation; instead, Bostrom's trilemma argues that one of three unlikely-seeming propositions is almost certainly true:
- "The fraction of human-level civilizations that reach a posthuman stage (that is, one capable of running high-fidelity ancestor simulations) is very close to zero", or
- "The fraction of posthuman civilizations that are interested in running ancestor-simulations is very close to zero", or
- "The fraction of all people with our kind of experiences that are living in a simulation is very close to one"
Bostrom goes on to use a type of anthropic reasoning to claim that, if the third proposition is the one of those three that is true, and almost all people with our kind of experiences live in simulations, then we are almost certainly living in a simulation.
Bostrom claims his argument goes beyond the classical ancient "skeptical hypothesis", claiming that "...we have interesting empirical reasons to believe that a certain disjunctive claim about the world is true", the third of the three disjunctive propositions being that we are almost certainly living in a simulation. Thus, Bostrom, and writers in agreement with Bostrom such as David Chalmers, argue there might be empirical reasons for the "simulation hypothesis", and that therefore the simulation hypothesis is not a skeptical hypothesis but rather a "metaphysical hypothesis". Bostrom states he personally sees no strong argument for which of the three trilemma propositions is the true one: "If (1) is true, then we will almost certainly go extinct before reaching posthumanity. If (2) is true, then there must be a strong convergence among the courses of advanced civilizations so that virtually none contains any relatively wealthy individuals who desire to run ancestor-simulations and are free to do so. If (3) is true, then we almost certainly live in a simulation. In the dark forest of our current ignorance, it seems sensible to apportion one's credence roughly evenly between (1), (2), and (3)... I note that people who hear about the simulation argument often react by saying, 'Yes, I accept the argument, and it is obvious that it is possibility #n that obtains.' But different people pick a different n. Some think it obvious that (1) is true, others that (2) is true, yet others that (3) is true."
As a corollary to the trilemma, Bostrom states that "Unless we are now living in a simulation, our descendants will almost certainly never run an ancestor-simulation."
7. Kerbal Space Program
This one simulates a fictional universe, but it's widely hailed as a great educational game about astrophysics.
Construct viable spacecraft that can overcome the effects of gravity and fuel consumption to get your little Kerbals into orbit. Sound easy? It's not.
The position, size and quantity of components you add to your ship will determine whether it reaches the stratosphere or explodes on the scaffold. Timed rocket booster sequences and jettisoning depleted fuel cells are critical to success. Oh, and you'll need to install a parachute to the capsule if you want your Kerbals to survive re-entry.
The game is still in the works, but improving and expanding all the time. Buy the in-dev version for $18, or try the older demo for free.
8. http://www.illustris-project.org/
9. http://stars.chromeexperiments.com/
