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Is the Universe a simulation?

Last April, the American Museum of Natural History in New York hosted the annual “Isaac Asimov Memorial Debate” and invited some distinguished guests to discuss the question “Is our universe a simulation?”. To be exact, it was the philosopher David Chalmers, author of What is consciousness ?; and theoretical physicists Zohreh Davoudi, James Gates Lisa Randall and Max Tegmark. Moderating the meeting was astrophysicist Neil deGrasse Tyson, the best-known face of American science. A lot of concentration of intelligence for such a bizarre question would seem a waste of time. Except that all the speakers, with the exception of Lisa Randall, are more or less convinced supporters of the so-called simulation argument: the hypothesis according to which the universe would be a computer simulation programmed by a super-intelligence external to our reality. Technological specificities aside, this is not a new idea. From Maya’s veil to Plato’s cave, from Al-Ghazali’s methodical doubt to Descartes’s evil genius, ending with the brain brain experiment in Putnam’s tank; skepticism about the authentic nature of reality has gone through all the ages and latitudes of thought.

It was the Swedish analytical philosopher Nick Bostrom who put it back into circulation in its most contemporary formalization. Director of the Institute for the future of humanity in Oxford, in 2003 Bostrom published a paper entitled “Are you Living in a Computer Simulation?” In the Philosphical Quarterly. After summarizing the theses in favor of our future ability to create minds with awareness on the computer, in the text Bostrom speculated on the possibility that a super-evolved civilization was able to develop not only a simulation of reality so rich in information as to be indistinguishable from reality itself but even “an astronomical number” of such simulations. From this he inferred, on a probabilistic basis, the existence of strong clues to believe that our reality is none other than one of these simulations, created by another super intelligent civilization external to our world.

To this he added another conjecture: if a simulated civilization reached, thanks to technological progress, the post-human stage, it would in turn be able to create a simulation of the universe equipped with conscious beings. If such an eventuality occurs in the future of our civilization, it would not only demonstrate that it is possible to program simulations but, ipso facto, would increase our chances of living within one of them. And not only that: a simulation within a simulation (a nested simulation, as Bostrom calls it) would require a computing effort, for the computers on which the first simulation runs, such that its programmers would have to prevent this possibility or terminate the program. For this reason, Bostrom argues, the simulation argument is not only a fascinating intellectual pastime but a hypothesis to be taken with the utmost seriousness since it could represent the main and most underestimated existential risk for the continuation of our civilization.

Having started a little quietly, over the years, Bostrom’s topic has attracted growing attention in philosophical, scientific and technological circles and has become one of the most talked about within Silicon Valley’s business elites. It is therefore not surprising that an exponent of those elites, Elon Musk, decided to clear it definitively among the general public. Who, in June 2016, declared that, in his opinion, the possibility that our universe is not a simulation is just one in a billion. Given the pedigree of the CEO of Tesla and Space X, the statement soon went around the world and caused immense sensation.

A science fiction conjecture

And to say that, in order not to be caught unprepared, it would have been enough to read some good science fiction. In fact, it has long been unsuspected that this genre has been confronted with stories that draw from the same skeptical tradition that Bostrom drank. The tunnel under the world, for example, is a story written in 1955 by Frederik Pohl. The protagonist, Guy Burckhardt, lives in a typical American town, Tylerton, where tranquility is constantly shaken by insistent commercial slogans shouted by the loudspeakers of vans that go around the streets offering the latest model of refrigerator or the latest brand of cigarettes. A number of quirks, however, suggest to Burckhardt that something is wrong. First he discovers that every day in Tylerton is always June 15th; then, that the people around him are all robots. Finally – in the last, chilling lines of the story – that his city was destroyed by an explosion and reconstructed in miniature on a table: Buckhardt himself is but a miniature robotic replica of the real Buckhardt. His world ends, literally, on the edge of a laboratory table.

Four years later Philip Dick would have taken up these themes in his famous Tempo fuori di sesto, where Ragle Gumm, the protagonist, busy every day to solve the prize game of a newspaper, begins to doubt the reality that surrounds him following a series of coincidences, which start from the moment he tries unsuccessfully to turn on the bathroom light bulb by pulling a string that never was. Gradually he discovers the bitter truth: his city is a fiction created all around him, to remind him of his childhood in the fifties and allow him to calmly solve the prize game that actually hides a much larger stake than he suspects, that is, the possibility of predicting the trajectory of ballistic missiles launched by the enemy during a long nuclear war.

In 1964 Daniel Galouye takes a step further and in Simulacron-3 (recently revived by the Atlantide publisher with the title Il mondo sul filo) finally brings the power of computer simulation onto the scene. Douglas Hall, the novel’s protagonist, one of the chief designers of the simulation “Simulacron-3”, able to perfectly replicate the real world, discovers that his colleague Fuller took his own life after making a frightening discovery: the their universe is actually a simulation, created with the same purposes as Simulacron-3 (to collect and analyze user feedback on their consumption preferences to guide corporate strategies and public policies). Galouye’s novel was the first to introduce the idea that, through the ability of our computers to carry out increasingly sophisticated social simulations, we can discover that our world is, in turn, created on the computer.

If at the time of Galouye the idea of ​​simulating an entire universe on the computer seemed a very remote fantasy, last year a video game like No Man’s Sky showed that, at least in part, it may not be so today. Realized by a small independent team, NMS is in fact able to create up to eighteen quintillions of alien worlds thanks to a special algorithm that, for each planet, generates a peculiar and unique fauna, flora and geography. “The physics of every other game is fake,” said its lead designer, Sean Murray.

When you are on a planet, you are surrounded by a three-dimensional backdrop, a cube on which someone has painted stars or clouds. If there is a day-night cycle, it is because there are gradual transitions between a series of different backdrops. With us, when you are on a planet, you can look up to the curvature of that planet. If you walk for years, you could go around the world and return to exactly the same place you started. Our day-night cycle occurs because the planet is spinning on its axis and revolving around the sun. It is real physics. We have people who get off a space station on a planet and when they leave, the station is no longer there; the planet is rotated. Players have reported this as a bug.

Of course, as impressive as all this is, No Man’s Sky is still an intangible and empty universe, in terms of intelligence: there are no living beings with their own conscience, so it is not a real simulation. But if we have made so many strides since video game physics simply simulated throwing a ball against a virtual brick wall, what does the future hold?

Towards superintelligence?

In his book Hidden Reality, physicist and mathematician Brian Greene calculated that a quantum computer “no bigger than a laptop has the ability to carry out the equivalent of all human thought since the dawn of our species in a small fraction of second”. We are also investing large sums in the ability to simulate the human brain to steal the secret of human consciousness. The original goal of Henry Markram’s Human Brain Project, former coordinator of the Blue Brain Project, was precisely this: thanks to a loan of one billion euros from the European Commission, and massive investments by private companies such as IBM, the Human Brain Project intended to create a complete simulation of the human brain on a supercomputer by 2023: a possible prelude to the development of a real artificial superintelligence, even if the project seems to have been downsized in recent times.

Personalities such as Stephen Hawking, Bill Gates and Elon Musk himself have however recently warned of similar developments, which, in their opinion, could prove to be a dead end for human civilization. The reasons are different, but one of them has to do precisely with the simulation conjecture: as in the film The Matrix, in fact, it is possible that artificial superintelligences decide to pursue completely different objectives from those we would like to assign them, coming to the conclusion that our existence could compromise theirs. Consequently, they could enslave us and project our consciences into a perfect simulation of our world so that we do not realize the true state in which we have been forced. This scenario was suggested by Bostrom in his influential Superintelligence (2014), the book that convinced Musk to allocate a few million dollars to the Future of Life Institute in Boston for research aimed at minimizing the risks associated with the development of artificial intelligence (including the recipients of the funding is Bostrom himself, for the development of a Strategic Artificial Intelligence Research Center in Oxford).

In 1963 Philip Dick had a frightening vision: looking up to the sky he noticed a metallic face that stared at him with evil. This vision troubled him for a long time. Years later, on March 2, 1974, a completely banal event – a fish-shaped pendant, the ancient proto-Christian symbol, worn by a girl – unleashed a whole series of visions and dreams in him: a whirlwind of psychedelic paintings, whole pages of unread books, radios that continued to play even after the plug was unplugged, to the disturbing premonition of a health problem in his son that the doctors would actually diagnose when Dick took him to see. The science fiction writer became convinced, as in the plot of one of his many stories, that his world was not real, but a “prison” built by an evil civilization he identified in the ancient Roman Empire, intent on maintaining humanity. in perennial slavery.

The visions and apparitions would be “cracks” of the simulation through which it is possible to guess the existence of a higher level of reality, as Dick gradually came to reconstruct in the approximately eight thousand delirious pages that make up The Exegesis. This also happens in Tempo Fuori di Sesto or, to get out of Dickian boundaries, in Simulacron-3 and its cinematic versions: things that are not in their place, strange amnesia, radios that broadcast what they shouldn’t broadcast. These things also happen in our reality, but it is easy to attribute them to psychological disorders, paranoia or hallucinations. Are there ways then by which we might discover that we actually live in a simulation? Indisputable clues, or in any case verifiable through the scientific method? Maybe yes.

The hypothesis under test

One of these possible clues was studied by Zohreh Davoudi, one of the participants in the Asimov Memorial Debate, in a paper published in 2012. The work of Davoudi and colleagues starts from considerations concerning the state of the art of a particular physical theory, that of quantum chromodynamics (QCD), which describes the strong nuclear force that makes quarks interact and hold together to form neutrons, protons and other subatomic particles. The most powerful method to study QCD today involves the use of sophisticated computer simulations called lattice QCD techniques. In these simulations, space-time is discretized (for convenience of use and for reasons of coherence of theoretical models), and is described not as a continuum but as a lattice composed of a series of cubes of femtometric scale (one millionth of a billionth of a meter).

At this scale and for this type of interactions, lattice QCD simulations are reliable replicas of reality. According to Davoudi, then, in the coming years, technological development could allow these simulations to evolve. And enriching them, the simulations could at that point even replicate the other forces of nature (the weak nuclear force, the electromagnetic force and gravity). And by further developing them, it could finally be possible to simulate an entire universe. According to Davoudi, in short, the hypothetical “simulators of universes” could in turn have started from a non-continuous phentometric lattice (perhaps for reasons of pure scientific research), and have arrived at an extremely sophisticated simulation on a cosmological scale that generated our universe.

At this point if our universe is an elaborate and powerful simulation based on a lattice, we should be able to find some trace of this lattice by studying the fine structure of the cosmos. The dimensions of the hypercubes – the “pixels” of reality – that build our simulated universe, however, may be less than the Planck length (the smallest measurable length in nature), and therefore the “pixels” may not be detectable by anyone. direct observation. But even in this case some possible solution remains: “In our universe the laws of physics are the same in all directions. But in a lattice this changes. Since there is no longer a space-time continuum, the laws of physics would depend on the direction, “Silas Beane, one of the authors of the paper, explains to the New Scientist. The simulation could show itself, for example, in the distribution of very high energy cosmic rays. Instead of coming from all directions, in fact, for reasons of coherence of the theory, very high energy cosmic rays should at that point show preferential directions that depend on the structure of the lattice on which the simulation takes place. “We calculated that if the simulators used a lattice with dimensions of about 10 ^ -27 meters, the limiting energy would change for different directions,” explains Beane. Given also the rarity of these phenomena, however, at the moment the experiments are not yet able to investigate the very high energy cosmic rays with the detail necessary to observe the distribution and settle the question.

A further refinement of the simulation could among other things correct this “error”, making it invisible even to our indirect measurements; but one fact remains: a simulated universe must be finite by its nature, because the resources of potential simulators are finite. Therefore, the volume containing the simulation will in turn be finite and this implies a discrete space-time; for which “in principle there is always the possibility for the simulated to discover the simulators”. One of these possibilities, according to cosmologist and mathematician John Barrow, is to detect possible changes to the constants of nature and fundamental laws that simulators may have needed to introduce from time to time to correct the structural errors of the simulation accumulate over time. As he writes in his The book of the universes: “if the simulators used the computer error correction codes to protect themselves from the general fallibility of their simulations (and simulated them on a scale smaller than our genetic code) […] then sudden apparent changes would occur contradiction with the very laws of nature that simulated scientists were used to observe and predict ”.

One of the Asimov Memorial Debate attendees, James Gates, director of the Center for String and Particle Theory at the University of Maryland in College Park, believes he has found something like this within a supergravity formalism, one of many proposed theories. in these years to try to describe quantum gravity. To geometrically order the way in which particles are classified in this theory, Gates and his colleagues in fact use very complex figures, called “adinkra”, which in the Ashanti culture represented a sort of ideograms. They are not simple drawings, however: adinkra are the visualization of a more complex mechanism, and their functioning actually has similarities with the error correction codes used in computer science. If these “adinkra” really played an essential role in the representation of the nature of a (possible) theory of supergravity, we would then have a theory that describes the universe and incorporates binary codes capable, perhaps, reality gives transcription errors, confirming the hypothesis of simulation. However, those of Gates remain hypotheses for now perhaps too imaginative, unverifiable, bordering on known physics, and have not collected much success in the scientific community.

The constants of nature

However, even without disturbing such complex concepts, there are other strange clues in nature, much better known and well studied, which could lead us to disturbing conclusions. It has long been known, for example, that there are certain “coincidences” in the laws of nature that allow life as we know it to exist. One of them is the so-called “resonance” of carbon, which is the fundamental chemical element of life. Carbon arises inside the nuclei of stars thanks to nuclear fusion processes, in particular the fusion of three atoms of eli. However, the possibility that three helium atoms collide in the same instant is so negligible that it does not seem sufficient to allow the production of the quantities of carbon that we observe in the universe. Fred Hoyle, in the 1950s, suggested a solution: two helium atoms collide and merge to form the isotope beryllium-8, and this, instead of immediately decaying because unstable, remains “alive” for an unusually longer time, sufficient to receive the collision of another helium atom and turn into carbon. The mechanism that allows this is called “resonance” and depends on the fact that beryllium-8 has almost the same energy as the two helium atoms that created it, and similarly the masses of beryllium-8 and another helium atom possess the same energy level as an excited carbon-12 core; this produces a resonance that allows the beryllium atom to remain stable up to one hundred billionths of a billionth of a second, enough time to collide with another helium atom and form carbon. Without this “coincidence”, we wouldn’t be standing here talking about it.

This and many other coincidences have prompted scientists to introduce the multiverse conjecture: ours is but one of countless universes where the constants of nature take on all possible values, and only in a few, including ours, these values ​​allow the existence of life. But, according to scientists who are interested in the simulation conjecture, there could be another explanation: someone out there has “designed” the universe especially for life. The scientific community is horrified by this so-called “anthropic principle”, because it believes it is a way to reintroduce the role of a Designer, ie God, into science. But what if the designer were simply a post-human civilization?

The science fiction writer and cybernetician Stanislaw Lem dealt with the simulation conjecture in his massive 1966 Summa Technologiae, unfortunately still unpublished in Italy. But in 1971 he wrote a short story on the subject, Non Serviam, published in the Absolute Empty collection. Non Serviam is the story of the birth of “personetics”, the fictitious science of creating simulated personalities within virtual worlds, defined by some as “the cruelest of man-made sciences”. Even if the simulations created by Professor Dobb are not identical to ours – for example the “personoids” do not reproduce sexually – they are governed by the same physical laws. “Today it is possible to package an inhabited ‘world’ in a matter of a couple of hours – the time it takes to enter the data of one of the basic programs into the computer,” reads Lem’s account.

The creation of the simulated universe takes place at accelerated speeds and, similarly, the programmer can run time faster to skip certain stages of the development of the personal civilization, and then match it with real time in order to collect dialogue and thoughts. of individual personoids and study them. Among these are examples of the debates of the personoids about God and why of their existence, completely identical to those we place in the “real world”. Speeches that make their creator, Professor Dobb uncomfortable, who will soon find himself, under the pressure of ever-increasing energy costs to run the experiment, pulling the plug: “I’ll turn off the machines and it will be the end of the world. I will try to postpone that moment as much as possible. It’s the only thing I can do and it doesn’t seem exactly worthy of praise. This is what is commonly referred to as ‘dirty work’. Having said that, I hope no one has come up with any strange ideas. If so, that’s his business ”.

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