Two years ago, I wrote a post about the work of Nick Bostrom (of Oxford University) and David Kipping (of Columbia University) regarding the unsettling possibility that we -- and by "we," I mean the entire observable universe -- might be a giant computer simulation.
There are a lot of other scientists who take this possibility seriously. In fact, back in 2016 there was a fascinating panel discussion (well worth watching in its entirety), moderated by astrophysicist Neil deGrasse Tyson, considering the question. Interestingly, Tyson -- who I consider to be a skeptic's skeptic -- was himself very accepting of the claim, and said at the end that if hard evidence is ever found that we are living in a simulation, he'll "be the only one in the room who's not surprised."
Other participants brought up some mind-boggling points. The brilliant Swedish-American cosmologist Max Tegmark, of MIT, asked the question of why the fundamental rules of physics are mathematical. He went on to point out that if you were a character inside a computer game (even a simple one), and you started to analyze the behavior of things in the game from within the game -- i.e., to do science -- you'd see the same thing. Okay, in our universe the math is more complicated than the rules governing a computer game, but when you get down to the most basic levels, it still is just math. "Everything is mathematical," he said. "And if everything is mathematical, then it's programmable."
One of the most interesting approaches came from Zohreh Davoudi, also of MIT. Davoudi is studying high-energy cosmic rays -- orders of magnitude more energetic than anything we can create in the lab -- as a way of probing the universe for what amount to glitches in the simulation. It's analogous to the screen-door effect , a well-known phenomenon in visual displays, where (because there isn't sufficient resolution or computing power to give an infinitely smooth picture) if you zoom in too much, images pixellate. The same thing, Davoudi says, could happen at extremely high energies; since you'd need an infinite amount of information to simulate behavior of particles on those scales, glitchiness in extreme conditions could be a hint we're inside a simulation. "We're looking for evidence of cutting corners to make the simulation run with less demand on memory," she said. "It's one way to test the claim empirically."
The reason this comes up is because of a recent paper by Roman Yampolskiy (of the University of Louisville) called, simply, "How to Hack the Simulation?" Yampolskiy springboards from the arguments of Bostrom, Kipping, and others -- if you accept that it's possible, or even likely, that we're in a simulation, is there a way to hack our way out of it?
The open question, of course, is whether we should. As I recall from The Matrix, the world inside the Matrix was a hell of a lot more pleasant than the apocalyptic hellscape outside it.
Be that as it may, Yampolskiy presents a detailed argument about whether it's even possible to hack ourselves out of a simulation (and answers the question "yes"). Not only does he, like Tegmark, use examples from computer games, but also describes an astonishing experiment I'd never heard of where the connectome (map of neural connections in the brain) of a roundworm, Caenorhabditis elegans, was uploaded into a robot body which then was able to navigate its environment exactly as the real, living worm did. (The more I think about this experiment, the more freaked out I become. Did the robotic worm know it was in a simulated body?)
Evaluating the strength of Yampolskiy's technical arguments is a bit beyond me, but to me where it becomes really interesting is when he gets into concrete suggestions of how we could get a glimpse of the world outside the simulation. One method, he says, is get enormous numbers of people to do something identical and (presumably) easy to simulate, and then simultaneously all doing something different. He writes:
If, say, 100 million of us do nothing (maybe by closing our eyes and meditating and thinking nothing), then the forecasting load-balancing algorithms will pack more and more of us in the same machine. The next step is, then, for all of us to get very active very quickly (doing something that requires intense processing and I/O) all at the same time. This has a chance to overload some machines, making them run short of resources, being unable to meet the computation/communication needed for the simulation. Upon being overloaded, some basic checks will start to be dropped, and the system will be open for exploitation in this period... The system may not be able to perform all those checks in an overloaded state... We can... try to break causality. Maybe by catching a ball before someone throws it to you. Or we can try to attack this by playing with the timing, trying to make things asynchronous.
Of course, the problem here is that it's damn near impossible to get a hundred people to cooperate and follow directions, much less a hundred million.
Another suggestion is to increase the demand on the system by creating our own simulation -- a possibility Bostrom and Kipping considered, that we could be in a near-infinite nesting of universes within universes. Yampolskiy says the problem is computing power; even if we're positing a simulator way smarter than we are, there's a limit, and we might be able to exploit that:
The most obvious strategy would be to try to cause the equivalent of a stack overflow—asking for more space in the active memory of a program than is available—by creating an infinitely, or at least excessively, recursive process. And the way to do that would be to build our own simulated realities, designed so that within those virtual worlds are entities creating their version of a simulated reality, which is in turn doing the same, and so on all the way down the rabbit hole. If all of this worked, the universe as we know it might crash, revealing itself as a mirage just as we winked out of existence.
In which case the triumph of being right would be cancelled out rather spectacularly by the fact that we'd immediately afterward cease to exist.
The whole question is as fascinating as it is unsettling, and Yampolskiy's analysis is at least is a start (along with more technical approaches like Davoudi's cosmic ray experiments) toward putting this on firmer scientific ground. Until we can do that, I tend to agree with theoretical physicist James Sylvester Gates, of the University of Maryland, who criticizes the simulator argument as not being science at all. "The simulator hypothesis is equivalent to God," Gates said. "At its heart, it is a theological argument -- that there's a programmer who lives outside our universe and is controlling things here from out there. The fact is, if the simulator's universe is inaccessible to us, it puts the claim outside the realm of science entirely."
So despite Bostrom and Kipping's mathematical argument and Tyson's statement that he won't be surprised to find evidence, I'm still dubious -- not because I don't think it's possible we're in a simulation, but because I don't believe that it's going to turn out to be testable. I doubt very much that Mario knows he's a two-dimensional image on a computer monitor, for example; even though he actually is, I don't see how he could figure that out from inside the program. (That particular problem was dealt with in brilliant fashion in the Star Trek: The Next Generation episode "Ship in a Bottle" -- where in the end even the brilliant Professor Moriarty never did figure out that he was still trapped on the Holodeck.)
Which seems like good advice whether we're in a simulation or not.
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