Could we be living in a computer simulation of some sort?  In priciple physics will never be able to directly test this.  It is an appealing idea, mentioned by everyone from scientist to pop culture figures.  It appeals as this would naturally explain certain foundational mysteries of science.  Such as the fact that we can write mathematical laws that predict precisely what will occur in nature.  Can this question even be interrogated scientifically?  Is the question “Are we living in a simulation?” a matter for science or belief? The key difference between evidence-based science and faith-based belief is that in principle scientific questions can be answered by an experiment done in the real world.  Upon review of the types of simulation that are hypothetically possible I will pose the only scientifically valid version of this question as well as a test to find the answer.

There are a few different possibilities for our existence being a simulation I will focus on two. 

An ancestor simulation is the idea that with computers becoming steadily more and more powerful over time, there is a chance that our current year is not the actual physical year.  That we are instead a simulation ran for the benefit of some future generation.  The reason could be for research, or for entertainment.  A simulation of what the ancestors were like by future humans interested in our time period.  There are people who might like to be able to do such a thing.  People who reenact past times.  This is certainly something that would appeal to at least some people.  Consider deep nostalgia in which a photograph, painting, or even an image of a statue is animated using deep learning AI.

 

 

Quite a few people have an interest in this sort of thing.  Given enough time a future version of our species could hypothetically simulate any past point in time.  

An advanced alien simulation is another possibility.  There are a few ways this could come about.  An advanced non-human civilization runs a simulation of a large section of the universe.  The reason being to make very precise and detailed forecast of various astrophysical or cosmological phenomena.  This civilization need not inhabit a universe much like ours at all.  For example, if there are physical dimensions beyond the 4 that comprise our universe.  Say a 5-dimensional universe containing a computer running a simulation of our 4D universe.  Like how we run video games which simulate a 3D universe of which we view a 2D projection.

Bostrom’s criteria.

The key criteria due to Nick Bostrom essentially is that given enough time a civilization would be able to simulate conscious beings at a great enough fidelity that such beings would not know they are in a simulation. (1)

Looking at Bostrom’s criteria can we test any of them and therefore treat this scientifically?  The question is in principle can conscious beings be simulated?   Can the simulation be good enough to fool the conscious beings that exist in it?

The way to test it would be to try and create exactly this kind of simulation. 

In fact, we do try to create exactly that kind of simulation to an extent.  Open world video games such as “Grand Theft Auto”, GTA Online do precisely this.  Every human player in a “room” explores this open world filled with beings called NPC’s, non-player characters.  Often the human players all see and interact with the same NPCs on a mission, or just in the same general area of the map.  The NPC’s will react to what occurs to save their lives.  They will run for their lives or pull out a gun and attack or defend themselves.  In some ways they behave like real people who are reacting on a sort of auto pilot or instinct.  Parts of this open world simulation that no human player is interacting with will be simulated at a low resolution.  Just enough detail to convince human players that the area they occupy is real. 

The question then is at what point would the NPCs in a game like Grand Theft Auto be considered conscious?  Clearly, they are not now their reactions are scripted.  At the same time, many actions of real (?) human beings and animals are instinctive, automatic, and almost algorithmic. 

If we reach a point at which we can simulate an undisputedly conscious being then it will show that in principle we could be in a simulation.

The problem is testing our universe itself to see if we are the simulator or the simulated. 

Sabine Hossenfelder’s Objection(s)

Hossenfelder’s Objection, simulating the laws of physics would be impossible.  (2)

Let me pose the question as follows.

Could we be living in a simulation of a 4D universe running on a computing device that exist in a higher dimensional universe? One way to test this would be to look for proof of one or more extra dimensions.  This is not crazy.  This is something we have done and will do again in the form of M Theory and particle physics.   The issue that would arise is how could we know these new natural laws are those of some much greater reality than the one we perceive?  There would be no way.   

This may be harder to address than consciousness.  There would have to be some way that we could test if the laws of nature we have are the true laws of nature, and not some more fundamental underlying laws.  The problem that would arise from any such test is that any more fundamental laws we found, would simply become the “laws of nature”.  Which we would then want to test and see if there are some even more fundamental laws of nature.  Which is what we do anyway. That is just being a physicist!

Since we would not be able to answer this question with science Hossenfelder is correct.  This universe being a simulation is not something we could answer any more than whether God is real.

Science is not the source of all truth.

  It is possible that the universe is a simulation.  It is possible that our natural universe is the creation of a higher being or beings.  It is possible we exist due to a random fluctuation in various quantum fields.  The simulation hypothesis is an attempt to answer what I call "Why questions".  "Why are the laws of nature what they are?". 

Real science , at least real physics, is in my opinion how questions.  "How can we simulate a universe?"  or "Can we simulate a universe even in principle?".   This comptuer scientists can work on and will work on.  Perhaps 1000 years from now Grand Theft Auto 6 will come out and have simulations so real that can give the people playing it PTSD. (4)

References:
  1) Bostrom, Nick (2003). "Are You Living in a Computer Simulation?". Philosophical Quarterly. 53 (211): 243–255. doi:10.1111/1467-9213.00309.

2) Hossenfelder, Sabine (2012), “The Simulation Hypothesis is Pseudoscience”  https://youtu.be/HCSqogSPU_Q

3.) Purslow Matt, “Rockstar Developers Patent New NPC Tech, Potentially for GTA 6; A whole new world of smart drivers?” IGN Jan 2021

 4.) Elliott, Luther  "More than Just a Game? Combat-Themed Gaming Among Recent Veterans with Posttraumatic Stress Disorder"  Games Health J. 2015 Aug 1; 4(4): 271–277.
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