This page examines the theory that our universe is in fact a simulated universe which is running on a
massively powerful computer programmed by some advanced civilisation. Though the world feels "real" to us, we might be merely logic states in an advanced computer. As improbable as this might sound, the
theory has gained a lot of attention recently due to a similar idea in the film The Matrix, and the idea is even attracting the attention of several physicists.
unlikely description of our reality:
1) The "Brain-in-a-Vat" Scenario
The idea that we might be living in a simulated world is so fascinating because it is impossible to disprove the theory that we are living in a simulated universe. In order to see how difficult it is to disprove, consider the Brain-in-a-Vat Argument. The Brain-in-a-Vat Argument considers the situation whereby a person's brain has been removed from their body and is floating in a life-sustaining fluid. The brain is connected by wires to a computer which provides the brain with exactly the same impulses as the brain would normally receive, the computer effectively creating a "virtual reality". The person with the disembodied brain would continue to have perfectly normal conscious experiences without these being related to objects or events in the real world. It would be impossible for the person to discover the reality of their simulated world.
coma in a vat while the aliens' computer fed him false sensory information (fortunately for Keanu Reeves, the aliens did not remove his brain!). The simulated world created inside Reeves's head was called the Matrix, and for Reeves it was indistinguishable from normal reality.
While it might certainly be the case that the reality I feel is just a "dream state" and I am actually a
brain-in-a-vat, I feel that would be very unlikely. I can think of no reason why a "Grand Simulator" would
behave in that way. This is because the only person able to experience the excitement of the elaborate
virtual reality world would be the person whose brain is in the vat: the simulator would not experience
anything. So why bother to go to all the trouble of inputting an elaborate virtual reality world into the head of some poor unknowing person? What could possibly be your motive?
In the movie The Matrix the motive of the simulators was explained by claiming that the humans in the vat were being used as batteries (to power the aliens' machines). But if that was the case, why did the aliens need to go to all that trouble of creating that virtual reality world in the heads of their human captives?
Couldn't the aliens simply just have kept their human captives in a drug-induced coma while extracting the energy from them? Why bother with creating the Matrix world?
2) The "Universe-in-a-Computer" Scenario
However, there is another model of our world as a computer simulation which does not require the
confinement of some poor soul floating in a vat. Instead, the possible type of computer-simulated universe which will be suggested here is one in which our entire universe is contained within the computer of an advanced simulation (i.e., there is no need for our universe to have its own "Keanu Reeves" floating in a vat somewhere). In this case, the "particles" of our universe would be represented by "bits" inside the alien computer. This is now a similar scenario to the computer game The Sims in which all the simulated characters and the entire simulated world is contained within the simulating computer.
contained within the simulating computer (i.e., no need for an equivalent of Keanu Reeves's character).
This scenario is similar to the computer game The Sims.
The motivation of the simulators in creating this simulated world is now much clearer: the world could be viewed and experienced on the computer for entertainment purposes, just as we currently enjoying playing so-called God games such as The Sims.
David Deutsch finds the simulated universe hypothesis highly distasteful: "It entails giving up on
explanation in science. It is in the very nature of computational universality that if we and our world were composed of software, we should have no means of understanding the real physics - the physics
underlying the hardware of the Great Simulator itself. Of course, no one can prove that we are not
software. Like all [many] conspiracy theories, this one is untestable. But if we are to adopt the methodology of believing such theories, we may as well save ourselves the trouble of all that algebra and all those experiments, and go back to explaining the world in terms of the sex lives of Greek gods." (quote taken from David Deutsch's paper It from Qubit). And many scientists have criticised the idea on that very basis that if it is untestable (unfalsifiable): if a theory can never be proved wrong then it should not be regarded as scientific. However, Brian Whitworth in his paper The Physical World as a Virtual Reality makes the point that the existing orthodox view of the physics establishment is equally unfalsifiable: "The theory that the world is is an objective reality is just as unprovable as the theory that it is a virtual reality. It is inconsistent to dismiss a new theory because it is unprovable when the accepted theory is in exactly the same boat."
To sum up, the simple truth is that if our universe was a computer simulation is some strange alien
computer, we would never be able to detect it or prove that that was the case. We would never be able to tell.
The General Uncertainty Principle
So if we were living in a simulated universe we would never be able to detect it - there would always be an uncertainty as to whether our universe was real or not. A fundamental uncertainty. But does the
uncertainty go deeper?
Let us imagine the universe of the "Grand Simulator", the universe which contains the computer which is simulating our universe. Would the Grand Simulator know if HIS universe was being simulated or not? The answer is clearly no. No matter how far you travel down the "simulation tree" you can never know if you have reached ultimate reality - there will always exist that uncertainty. Uncertainty seem to be fundamental, and any form of certainty is revealed as being just an illusion: you can never be certain of anything, the only certainty is uncertainty.
David Deutsch appeared well-aware of the drastic implication for science when he said: "From the point of view of science it's a catastrophic idea, the purpose of science is to understand reality. If we're living in a virtual reality we are forever barred from understanding nature." Well, maybe Deutsch is being too pessimistic. Maybe we just have to accept uncertainty as being part of science, and it is certainty which is just an illusion. As science and mathematics digs ever deeper, it is starting to reveal this uncertainty in principles such as Gödel's Theorem, and the Heisenberg Uncertainty Principle from quantum mechanics. Physics has been able to incorporate the uncertainty of the Heisenberg Uncertainty Principle and made it part of science, not something to be feared.
The Simulation Argument
The Simulation Argument presented by Oxford University philosopher Nick Bostrom is ambitious in that it that it does not stop by merely suggesting that we might be living in a simulated universe, it argues that we probably are living in a simulated universe! The argument uses evidence gathered from the world around us (about the rapid growth of our computer technology) and solid scientific reasoning to show that a rational scientific person has to take seriously the possibility that we are already living in a computer simulation.
The basic principle behind this theory is that the human civilisation will one day have access to sufficient computing power capable of running simulations of their ancestors (us!). Maybe in a few thousand years in the future we might actually make a re-appearance (as Sims) in those advanced simulations. That doesn't sound too far-fetched, does it? But what if it is the case that human civilisation has, in fact, already reached that advanced state and is already running those simulations? That would mean we are living in a simulated world right now!
In fact, the future human race could easily create simulations containing astronomical numbers of
simulated beings (this has the ring of truth to it: when you run The Sims there's only one of you, but the
program contains thousands of Sims). There is therefore a possibility that the number of conscious,
simulated humans will one day become very much larger than the number of real humans.
The Simulation Argument then goes one step further by stating that with the number of simulated humans inevitably outnumbering real humans, the computer simulation scenario is actually the most probable situation (unless you think the human race is going to become extinct pretty soon, or we're going to get bored with The Sims and start playing Tetris again - both of which seem quite unlikely).
To sum up, the Simulation Argument is a rigorously-presented argument which means that a rational,
scientific person considering the extraordinary recent increase in computing power available to us, now
has to treat seriously the possibility that we are already living in computer simulation.
On the page entitled Is the Universe a Computer? we imagined how the universe could be created by a
million monkeys randomly typing into a typewriter for ten hours a day. We concluded that the probability of a monkey typing the information which defines the universe would be infinitely small. However, if the same monkeys type onto a computer instead then there would be a much higher probability that one monkey might type the short computer program which could produce our universe (a short computer program can generate tremendously complex structures, such as intricate fractals). A monkey typing into a laptop computer might write a (very) simple computer program which could produce something highly-complex.
However, if we now entertain the possibility that the universe could be generated by some intelligent entity (some "Grand Computer Programmer") then we find we can interpret this result differently. We had previously assumed that the short program which produced the universe was generated by a random
process (a monkey). However, we can now consider an alternative scenario that the program is short
because a simple, short program would be easier for our Grand Programmer to write, and would be a
more compact and elegant solution for producing a complex universe. A short, elegant program would be
the result of good software design.
John Barrow describes this well in his book "Impossibility": "Just as the most expert computer programmer is the one who can write the shortest program to effect a particular task, so we might expect the Architect of the ultimate program that we call the laws of nature to be elegantly economical on logic and raw materials. It is a common tendency to think that it would be a hallmark of the universe's profundity if it were unfathomably complicated, but this is a strange prejudice. This view is motivated by the idea that the Creator needs to be superhuman - and what better way to assert that superiority than by incomprehensibility? But why should that be so? Anyone can explain how to assemble a model aircraft in 500 pages of instructions; it is not so easy to do it in 10 lines. Profound simplicity is far more impressive than profound complexity."
The Big Brother Universe
But do we have any evidence that we are living in a computer simulation? Is it just a coincidence that our current popular pastimes - such as watching reality shows like Big Brother and playing God games such as The Sims or the latest astonishing game called Spore - are aimed at producing environments identical to the one in which we find ourselves? Why should that be? It doesn't have to be that way. We love to watch these participants carry out their (often boring!) daily activities, contained within a carefully controlled, closed environment. There's no reason why these forms of entertainment should be so popular, but the fact of their popularity and their increasing sophistication does seem to provide circumstantial evidence that maybe 500 to 1,000 years from now we would ourselves be interested in creating simulations of the environment we now inhabit. And that, in turn, might be viewed as providing evidence-of-a-kind that we are, indeed, already participants that ultimate game of Big Brother.
entertaining and praiseworthy" (see here) - surprisingly similar to the tactics likely to avoid eviction from the Big Brother house!
Here are some insights about the Big Brother environment:
If our universe is a simulation, then the Big Brother house would be a simulation within a simulation. On eviction from the house, the contestant returns to the higher-level simulation. Similarly, if you were woken (evicted) from a particularly vivid dream you would return to the higher-level reality. By analogy, if our universe really is a simulation then maybe when we are evicted (die) we move to the higher-level reality - maybe this could give some solace to those who believe in some form of existence after death! Contestants on the show frequently behave unnaturally, aware that they are being watched. In physics
we know you cannot make an observation without distorting the experiment. The only way to avoid this
would be if the contestants were unaware they were being observed (in a recent reality show, Space
Cadets, the participants were completely unaware they were on a show). This would provide an
explanation for why we would not be informed if we inhabited a simulation.
to increase the entertainment value. If our universe is simulated then maybe that would provide an
explanation for natural disasters and other challenges - they're designed to increase the entertainment
value for those viewing the simulation.
Maybe we should modify Edward R. Harrison's "natural selection" universe theory in which only universes conducive to intelligent life would predominate. Instead we should say that only those universes which support intelligent life which is interested in creating Big Brother-style simulations would predominate. Wouldn't it be ironic if now by taking a look at ourselves, and our own behaviour, we may indeed - as Stephen Hawking famously said - finally get to "know the mind of God"?