Could we be living in a simulation?
I think that is related first of all to the question of what we mean by a simulation.
If the question is, “Could we be living inside of a computer program?”
then my answer would be: of course, yes.
Because the only thing that we get with some certainty from the outside world is information.
And the only thing that we find with certainty in this information is regularity.
And for a system to produce regularity in information (that is, discernible differences
that change in a way that is somewhat not random and somewhat predictable), for this
it needs to compute.
So it’s necessary and sufficient for the universe—whatever else it does—that it
computes.
And we cannot really know what else it does.
So in my view it’s necessary and sufficient that the universe is some kind of computer
in a pretty literal sense by the way we define computers and computer science.
It doesn’t mean that we know what kind of computational class this system is in, and
there is I think a lot of contest and ideas in physics what kind of computational class
the universe really is and what capabilities it has.
What can compute and what cannot compute.
But still it’s computational in some sense.
The question of whether we are living in a simulation is more related to something more
narrow, that is: this computer program that you’re living in intentionally created,
or is it just a natural occurrence?
And of course we cannot really know this because no feature in the world points at this thing
being a simulation in this sense.
I don’t see anything that would convince me that you are in a simulation.
But if it is one, I don’t think it’s for our benefit.
I don’t think that all these galaxies and stars and all the intricate elementary particle
structures that we can observe in some sense—they are not necessary for our experience as primates
on the planetary surface.
It would be needed to be painted on the telescopes and microscopes by the simulator.
So I don’t think that these are smokes and mirrors when we look into the sky and we see
these bazillions of galaxies.
I do think that if this is a simulation then there would be an important feature of the
simulation, which means the simulation is not there to create us.
The simulation is probably there to explore some aspects of hypothetical physics, and
we are just a random side effect or an artifact of the fact that evolution is possible in
this universe, so we could emerge in it.
I think it’s very unlikely that we are in a simulation, because if I would build a simulation
of the universe I would make the computer that it runs on “irreversible”.
What that means is that the operations that happen in that universe can delete bits.
It means that a state that you observe in the universe can have multiple possible states
that it comes from.
And if you look at what we know empirically in physics, that doesn’t seem to be the
case.
Our universe seems to be reversible.
And this means we cannot really delete bits.
If you cannot delete bits it means that everything that we like is irreversible.
You stabilize your body temperature, you forget yesterday’s body temperature in your body.
It means that you have to delete bits in some sense.
All those things that we are interested in life—planets, stars, computers, organisms,
minds—are irreversible in some sense.
They all need to delete bits to keep their structures stable against the onslaught of
the substrate, which has its different logic and its different direction that it wants
to go into.
So in some sense you get waste bits.
You need to throw these bits out of your system, and this is what observers perceive as increasing
entropy, these waste bits.
And if you would be living in a simulation like Minecraft, in Minecraft you can build
perpetual mobiles [perpetual motion machines].
That’s because you don’t have entropies in Minecraft.
Minecraft can delete bits.
It can forget its previous state.
This universe apparently cannot.
So the reason why we cannot have nice things in this universe, why we cannot have perpetual
mobiles, the entropy is always accumulating and is always going to get us in the end.
Maybe we’ll always have to die as living beings.
But that’s why life is always temporary.
Every self-stabilizing system will only have finite lifespan in this universe.
That would not be a feature I would put into a simulation.
So there is this argument that, for instance, Elon Musk made, that we can build game consoles
that create virtual worlds that look a lot like simulations to us of this universe.
They can be so realistic that we cannot really distinguish them.
And this argument is made that every civilization that has sufficient technical capabilities
is going to build many of these game consoles, so the probability that when you look around
and you find yourself in a pretty realistic looking world that you’re actually in a
simulation is much higher than the probability that you are in based reality.
But I think what this doesn’t take into account is the level of detail that you’re
going to achieve in such a simulation.
It seems that our universe has an amazing amount of detail and to get this amount of
detail in a subset of this computer, it’s very hard because if you build a computer
here on this planet it means you cannot simulate a big universe in it.
You can only simulate very, very, very small slow universe in it.
So every universe that you step into, another universe is going to have many orders of less
detail.
So I think if you find yourself in a very detailed universe that has many, many galaxies
and much more detail than you need to have intelligent life and civilizations in it and
so on, it’s unlikely going to be a simulated universe created by a civilization.
It’s more likely that it’s base reality.