Are we living in a computer simulation?

What is real? It's a question that has puzzled and amused countless people. As human beings, we're capable of directly perceiving only a fraction of what surrounds us. From a personal point of view, reality seems pretty limited. Is the Internet real? Am I real? Are you?

Many philosophers have put forth the notion of reality being an illusion. One recent version of this theory made the news in 2003. That's when Nick Bostrom, a philosopher at the University of Oxford, put forth an interesting question. What if our reality is actually a computer world that exists in some other reality? At first, you might scoff at the suggestion. But Bostrom's argument is fascinating.

First, Bostrom says, assume that we will reach a point technologically in which we can create a simulated version of a universe -- perhaps even a copy of our own. This could be the singularity, when humans use our understanding of technology and biology to become transhuman. Bostrom argues that if we can create a universe simulation, we almost certainly will do so. Further, we would probably create as many simulations as we could in order to learn more about our own universe, among other reasons.

Next, we assume that the virtual inhabitants of the simulated universe possess characteristics similar to our own, including consciousness, but are unaware that they're in a simulation. Bostrom states that if this is technologically possible, then it's virtually impossible that we aren't living in a computer simulation already.

That's because we can't assume that some other version of intelligent beings -- human or otherwise -- hasn't already hit that technological landmark and created a simulation in which we are now living. Everything we can observe and test would exist within the realm of the simulation, giving us no clue that our reality is in fact just a bunch of ones and zeroes.

Even more mind boggling is the possibility that our universe could be a simulation within another simulation and that we, in turn, could create our own simulations. It becomes a dizzying series of universe nesting dolls, each one contained within another universe.

Bostrom says this doesn't mean that we're definitely living in a computer simulation. The truth might be that it's impossible for us to reach a point in which we can simulate a universe to that extent. That could be due to technological limitations, or it might mean that humans could go extinct before ever reaching the level of sophistication required to simulate a universe on that scale. It's not exactly a happy picture.

As far as philosophical arguments go, this one is a doozy. But why stop there? Three physicists suggest there may be a way to detect whether our universe is really an advanced video game.

Please Wait, Universe Loading

Silas R. Beane, Zohreh Davoudi and Martin J. Savage found the notion of the universe as a computer simulation to be fascinating. They began to think about how it might be possible to determine if our own universe is a numerical simulation. It all begins with lattice gauge theory and quantum chromodynamics (QCD).

We know of four fundamental forces in our universe: strong nuclear force, electromagnetism, weak nuclear force and gravity. Lattice gauge theory and QCD focus on the strong nuclear force, which is the force that holds subatomic particles together. It's the strongest of the four fundamental forces but also has the shortest range.

Quantum chromodynamics is a theory that explains the fundamental nature of the strong force in four space-time dimensions. Using high-performance computing (HPC), it's possible for researchers to simulate an incredibly small universe in an effort to study QCD. It's on the femto scale, which is even smaller than the nano scale. A nanometer is one-billionth of a meter -- a femtometer is one-quadrillionth, or 10^-15 meters.

Within this simulation, researchers use a lattice structure to represent the space-time continuum. If we were to somehow shrink down small enough to be inside this universe, we might be able to detect that it's a construct by observing how certain energies interact with the lattice.

In our universe, that energy could be cosmic rays. If scientists could observe cosmic rays behaving as if there is a lattice around our own universe, it would suggest that we are actually inside a computer simulation that uses the same techniques as lattice gauge theory.

We would have to develop technology sufficiently sophisticated and powerful enough to detect these cosmic rays and measure their behaviors to notice a lattice structure. This approach also assumes a few other constraints:

The entities that designed the simulation followed a practice similar to what researchers are doing with QCD experiments.
The entities had limited resources with which to work, meaning our universe would also be finite.
The universe's designers are not actively preventing us from discovering that we're in a simulation.

If your mind isn't spinning already, let's move on to think about what living within a computer simulation would actually mean.

So Now What?

Let's get this out of the way first: The simulation argument doesn't prove that we're living in a computer simulation. The argument is built atop assumptions. If one or more of those assumptions proves to be false, the argument is invalid.

Beyond that, the argument is unfalsifiable. A falsifiable theory is one that can be disproven in an experiment or observation. Science and the scientific method depend upon falsifiability. If there are no criteria under which a theory could be disproven, it's unfalsifiable and unscientific. For example, if I claimed that you're always being followed by a 2-foot-tall (0.6-meter-tall) mouse that's invisible, impossible to touch and makes no noise, that's unfalsifiable. There's no way to disprove my statement, which removes it from the realm of science.

The simulation argument falls into this category -- if we were to use the test method suggested by the three physicists, a negative result wouldn't necessarily mean we could state with authority that we aren't in a simulation. Perhaps the simulation would prevent us from discovering the truth. That's why the argument is philosophical rather than scientific. But for argument's sake, what would it mean to us if our universe were just a simulation?

If we never have any way of knowing, there's no reason anything would change. From our perspective, the universe would be as it always has been. But imagine that we find a way to prove beyond any doubt that we're inside a computer simulation.

The religious implications would be dramatic. We would have proof that there is some sort of creator. That creator may or may not resemble our religious icons. Any announcement that our universe is just a simulation would likely encounter skepticism and denial across a broad spectrum of people. The cultural and social implications are enormous.

From a practical, day-to-day perspective, things might not change that much. Even if everything we know and can know is a simulation, we still exist within that universe. We still eat, breathe, live and die. The conditions around us don't change whether we're in reality or some other reality's virtual world.

That could shift if we found some way to interact with the beings that created the simulation. It could mean that our world is similar to the one in the movie "The Matrix" -- by changing some code, we could end up drastically changing ourselves or our environment. Or it might mean they get bored with their simulation and shut the whole thing off.

Ultimately, there's no way for us to know right now if our universe is a simulation or not. But it sure makes you think, doesn't it?

Lots More Information

Author's Note

I first became interested in this concept back when I took a philosophy course in college. It seemed like an interesting -- though unanswerable -- question: Is reality an illusion? We know that there are things we can't perceive going on all around us and that our brains influence our perception of events. But how far down does that subjective experience go? Then, in 2012, the computer simulation story popped back up as physicists suggested a possible test that could indicate we're all just computer data. I'm pretty sure that at the end of the day I don't really want to know.

Sources

Beane, Silar R. et al. "Constraints on the Universe as a Numerical Simulation." Cornell University Library. Nov. 9, 2012. (Dec. 1, 2012) http://arxiv.org/pdf/1210.1847v2.pdf
Bostrom, Nick. "Are You Living In A Computer Simulation?" Philosophical Quarterly, Vol. 53, No. 211, pp. 243-255.
Dillow, Clay. "How Do We Know We're Not Living Inside A Massive Computer Simulation?" PopSci. Oct. 11, 2012. (Dec. 1, 2012) http://www.popsci.com/technology/article/2012-10/how-do-we-know-were-not-living-inside-massive-computer-simulation
RationalWiki. "Simulation argument." Sept. 4, 2012. (Dec. 1, 2012) http://rationalwiki.org/wiki/Simulation_argument
Scholarpedia. "Lattice gauge theories." March 29, 2012. (Dec. 1, 2012) http://www.scholarpedia.org/article/Lattice_gauge_theories
Smoot Group. "The Strong Nuclear Force." (. 1, 2012) http://aether.lbl.gov/elements/stellar/strong/strong.html