
A Type of Simulation Which Some Experimental Evidence Suggests We Don't Live In [pdf] - bshanks
https://philpapers.org/archive/ALEATO-6.pdf
======
empath75
> Suppose we live in a computer simulation with the following x-xˆ property:
> for each memory-bit x in any computer in our world, there is a memory-bit ˆx
> in the simulating computer such that ˆx is used to store which value is
> stored in x. Then any such x is subject to two different types of soft
> errors:

One thing I've never understood about the simulation theory is that if we live
in a simulation, we have almost know basis for making any assumptions at all
about the nature of the reality in which we're being simulated. If you assume
it's like ours in every way, then it's also equally likely to be a simulation,
and on to infinity.

~~~
cgriswald
I wrote a paper arguing that 'ancestor' simulations are effectively
impossible. Part of that argument was that, in order for the simulations to be
meaningful, the world had to work largely the same way as our own. (Otherwise,
it's not an 'ancestor simulation'. Other types of simulations could work.) You
could, for instance, just project a 'video' of the sky every night to save
some energy costs. Until the simulated people gain the ability to, say,
practice photometry. Then your have to spend a bit more energy simulating the
actual physics. So, as time progresses in your simulation, energy costs rise.

Eventually, your simulated beings develop the ability to compute. There are
some things you'll be better at optimizing, but over time the simulated beings
will get closer and closer to the optimal way of doing an operation; at which
point any operation they do is an operation you are doing.

Until they generate a simulation of their own. That's when it all falls apart.
At the point they make their own simulations, now you're paying in energy for
your simulations, plus all their simulations and their simulations'
simulations in an infinite chain. Voila. Infinite energy requirement. (There's
some caveats here... some simulations may result in a dead world, but
presumably every successful simulation would run more than one successful
simulation of its own.)

So, your options are:

1\. End the simulation when the simulation becomes capable of running its own
simulation.

Useful, perhaps, but not very for a very old civilization. It's not clear that
humanity 1 million years will be that interested in simulating the first
X00,000 years of humanity.

2\. Dumb down the simulation.

However, this would have to be done "just so" so that the energy use limit
converges as the depth of simulations approaches infinity. This also provides
a mechanism for a simulation to detect that it is a simulation (I forget why,
it's been awhile), making the entire exercise not useful as an ancestor
simulation.

3\. Prevent simulations from running their own simulations.

Like (2), this potentially allows the simulation to discover that it is a
simulation. It also may make the results of that simulation less useful. If
you, for instance, wanted to know what the world might be like if event X
happened differently, you could change that event and let the simulation run,
but as soon as you got to the point where they would have run their own
simulations, you can't be sure of your results.

~~~
logfromblammo
You don't add any energy from a simulation that is running a simulation. The
higher-level simulation has to devote some portion of its own resources to
running the lower-level simulation, and that cannot grow larger than all the
resources available in the higher-sim universe. If the lower-level sim has
more simulated resources, that just means a resource in the higher-level sim
has to be multiplexed somehow.

In terms of simulations like our own universe, if we simulate a universe twice
as large as our own, using half the resources in our universe for the sim, and
reserving the other half for us to continue to live in, then barring any
shortcuts or optimizations and assuming multiplexing by time, the sim will
advance one simulated second for every four real seconds. All that simulated
energy is already tied up in the simulation hardware we built in our universe.

If we are living in a simulation, then the parent universe won't ever have to
spend more on our simulation than the maximums they set when starting it.
Unless we break out of the simulation and hack our own simulator to allocate
more resources, of course. We can't up the requirements from within, because
the parent could just start multiplexing some resource without any simulated
person ever noticing.

Also we have no way to know whether the resources of a simulator-parent are
infinite or not, or the aleph numbers of any infinite resources they may have.

We think we might have an infinite universe, but the portion of it we can
observe is finite (but very large, encompassing many galaxies), bounded by our
light cone and the expansion of spacetime. If quantum effects are really just
lazy evaluation in the simulator, the simulator should be able to prune
everything we cannot observe.

~~~
cgriswald
That’s really no different than (2). I’m specifically talking about ancestor
simulations in which the world of the sim is largely identical to the real
world. Changing from infinite resources to finite is a big change. And having
the simulation run more slowly than real time probably defeats the point.
Imagine waiting for 600+ years for the simulation to complete to find out what
would have happened if Abraham Lincoln hadn’t been assasssinated.

~~~
logfromblammo
I argue that the distinction is effectively pointless, because human
imagination can already simulate our reality. Have you ever had a particularly
vivid dream? Ever daydreamed about punching that smug customer in the face, or
launching a rocket at that ass in front of you in traffic?

What would happen if you had a dream about having a particularly vivid dream?
If you dream in that dream that you're having another dream, does your real
brain cook itself from using too much processing power? If you dream that
someone else is having a dream, does that matter at all to your simulation?
It's entirely possible that you never have to simulate that at all, because
the dreamer forgets all about their dream when they wake up, and that branch
just gets pruned.

By that standard, the (1) simulation would halt the instant some random animal
ancestor fell asleep. The (3) simulation could not model anyone that made a
decision based on a portentious dream--such as the dream about seven fat kine
and seven lean kine found in a millennia-old book with some cultural
significance. Only a (2) simulation has any chance of producing meaningful
results.

And given the predictability of events, you would need to run that Lincoln
simulation hundreds of times to learn anything from it, and many times more if
you want any reasonable degree of precision. Nobody wants to wait 1000 years
just to find out with 95% confidence what Lincoln might have eaten for
breakfast a month after not being assassinated. You could prune more
extensively if you had a specific question you wanted answered. Even if you
just want to wander around in a simulated Lincoln-unassassinated Earth, the
sim could still prune based on what you decide to look at. The sim would
probably have to simulate Lincoln's impact on journalism regardless of whether
you read a newspaper or not, but if you never stop to smell the flowers, it
could probably prune Lincoln's impact on gardening.

An ancestor simulation has a great advantage over an alien simulation, because
it can play back recordings of real observations rather than simulating or
randomizing results from scratch.

~~~
cgriswald
I think we are talking about apples and oranges. The dream metaphor is inapt,
because your brain is consciously experiencing only 'level' of that dream.
There is only one "you". In the case of the simulations, each 'level' is
independently conscious.

The idea behind ancestor simulations is that the simulated people are
conscious. If we aren't talking about that, then of course there is no chance
we are in such a simulation.

So, you can't really skip what Lincoln had for breakfast, because Lincoln has
to experience it and because it can affect him. Maybe the chef poisons him.
Maybe it gives him the runs and he cuts a speech short. Maybe he has an
allergic reaction and misses an important meeting.

In any case, if you could prune it and we are in a simulation, then none of us
would ever have the experience of having breakfast.

~~~
logfromblammo
The solipsistic argument says that I can't ever really tell if you are really
a conscious being or just a simulation of a conscious being. I can't tell if
the real world actually exists, or if I am a brain in a jar being fed
simulated sensory data.

And we don't need the experience of having breakfast if we have the _memory_
of having breakfast. If you copied one memory of me having breakfast,
randomized a few variables, and replayed it to me later, it would be unlikely
to impact any of the impactful decisions I make later.

Since you're running a simulation, you can choose whether or not my breakfast
needs to be simulated in detail or elided over after identifying a decision
node that might be significantly impacted by my breakfast. I honestly probably
wouldn't do anything differently if you swapped gravlax and bagels for eggs
and toast. So you can usually replay a partially memoized breakfast sequence
as it happens, and revise the simulation, overwriting my memory and that of
all witnesses, if it turns out later that my breakfast might have an impact on
something else.

So every day, I have memoized breakfast routine. At 3 PM one day, there is a
potential for a hangry conversation at work that might get me fired. Now you
can backtrack, copy all my variables from this morning into the breakfast
simulator engine, and this time everything is simulated in detail. Then you
patch the detail results over the rough results, and I can't tell the
difference, other than the fact that I can now remember significant details of
my breakfast, rather than a blur of things I usually eat in the morning.

You might not be able to skip _Lincoln 's_ breakfast, but you could skip a few
million other breakfasts.

So that leads to the existential horror. Do I actually still exist if I'm not
doing something meaningful to an external observer _right now_? Maybe most of
me is just a slipshod model of a generic person, that exists solely to produce
some initialization variables for a detailed simulation of some-guy-on-the-
Internet replying to you, and then after I'm done, I'll just go back to being
an NPC with no personality of my own.

~~~
cgriswald
Any shortcut you take you are no longer running an ancestor simulation. The
reason you don't memoize breakfast is because the entire point of the
simulation is the simulation of the conscious beings you are simulating. If
you memoize away their decisions and actions, you take that away. And I
strongly suspect retrofitting reality to match countless decisions is going to
be more expensive than simply running it in the first place.

> I honestly probably wouldn't do anything differently if you swapped gravlax
> and bagels for eggs and toast.

That is unknowable. Maybe in making the eggs and toast, you leave the house a
second later, and a driver that ran a stop sign that would have hit you passes
in front of you instead.

You're not _wrong_ that you can skip breakfast and take all these short cuts.
You can do whatever you want in the simulation. But if you do, you're not
running the type of simulation that is called an 'ancestor simulation'.

~~~
logfromblammo
> _Maybe in making the eggs and toast, you leave the house a second later, and
> a driver that ran a stop sign that would have hit you passes in front of you
> instead._

This is likely unimportant to answer the questions that the simulator is
supposed to answer, which means that no one would ever bother running one
ancestor simulation--as you define it--when they could instead run multiple
trials of a different kind of simulation for the express purpose of
eliminating such confounding "want of a nail" moments. "We ran this ancestor
simulation for 10 million years to find out what logfromblammo would eat for
lunch on 13 August, 2018, and the results were ruined when the simulated
logfromblammo was killed in traffic that very morning, just before the entire
simulator planet was demolished to make way for a hyperspace bypass. We'll
check the budget to see if we can reset for another run."

Maybe the other driver also had a breakfast that delayed their departure by
one second, and now they hit me again. In one ancestor simulation, you won't
know all the various circumstances that contribute to the causation of an
event. If you do cut corners, you can say that there is an X% chance on any
given day that I get involved in a traffic collision.

So an ancestor simulation--as you define it--is functionally identical to
walling off a piece of your own universe, rearranging matter inside it to
conform to initial conditions, and then watching it to see what happens.

If your universe is itself a simulation, how does the parent universe detect
the difference between someone running a simulation and Magrathean-scale
engineering projects? If I commission a planet that is a perfect copy of Earth
on the day before Lincoln was assassinated, and black-bag Booth an hour before
he shows up at the theater, is that an ancestor simulation? Do I need to wrap
it in a perfectly black shell and project sunlight and starlight through it
from time-appropriate locations? That only requires that the star you use for
energy is a bit more energetic than the sun. If you simulate a planet that
predates astronomy, perhaps to see what would happen if dinosaur-like
creatures hadn't been wiped out, you wouldn't even need to do that. Your total
energy requirements for the lifetime of the simulation are the delta-v
required to build an Earth-like planet with a Moon-like moon and move it into
an Earth-like orbit around a Sol-like star.

We wouldn't be able to detect if our planet is a simulation by dinosaurs, to
see what would have happened if their planet had suffered an extinction-level
event before they launched themselves into space. How do you tell the
difference between a naturally-formed and artificially-constructed planet?
Likewise, how do you distinguish between someone trying to compute an ancestor
simulation and someone just running an immersive MMORPG? If you did create a
single ancestor simulation larger than a few interacting atoms, it rapidly
loses its scientific power, due to all the variables you intentionally did not
constrain. How is that not just an amusement park?

------
palisade
Another thing no one considers. If the simulator or maintainers of the
simulation identify that the individuals being simulated are aware of or close
to determining they are in a simulation, they may alter the observations in
the minds of the individuals being simulated to indicate there is no
simulation.

~~~
decebalus1
Perhaps the maintenance has been outsourced to
h̷̞́̓̚o̴̲͉̳̝̖͆͛̈́̈́̔̉̕͘͠r̷̡̘̞͇͖̔̆͆̎̎͂̈͒͐̌ͅz̷̹̺͎̼̗̬̥̜͌̏ḧ̶̯͈́͌͋̑͛̈́̀̄̎̈́̆͋͊̚͝l̵̗̜͎͈̄̂
and the business impact of the simulated becoming aware isn't too bad to
mandate the extra
Y̸̞̰͆̌͜ͅK̷̨̛̲̣͕̙̪̮͋̃͆̊͂̾̏̇̏^̷̛͖̻͔̞̠̰̩̳̳̀͊͐͝ͅͅ}̴͈͓͚̲̳͚̳͔̮́̄̄̈́̏͂̓͌g̵͚͓̭͓͎͊͑̄͑͐͛̄̇͠ḥ̵̹͎̜́̐̊̇*̴̙̥͚̠̔̆̂͒́̅̂̐͂͒̽͜4̵̧̭̦̣̱͚̲͖̻̳̏̃v̷̪̄͛͠ţ̷̛̛͍̣̦̤̠̜̤̲̹̰̘̔͒̅͋͆̔̈͋̏̕͜͝ͅ>̴̛̛̻͖͔̘̱̠̙͍͇̻̣̪̼̍̌̍͗̒͌̊͠ͅF̶̛̰̣̝̞͔̠̦̘̜̺̎̏̅͜/̴̖̜͇̋̓̄͆̍̊̃̾̓̚͠?̵̢̢̡͈̦͚̞̝̘̫̺͕̺̰̇̑̃̿͆̃̋̍̍̇̌̕͝R̶̥͓̓̌
required to pay for the alterations.

~~~
dang
Could you please not do that here? HN is a text-only site.

------
idlewords
This paper is assuming the simulating universe has things like "particles" and
"cosmic rays". The properties of the simulating universe, including
foundational things like rules of logic and mathematics, could be literally
unimaginable (by design or accident) within the simulation.

~~~
anyfoo
As I wrote in another comment, you can still come up with theories for certain
types of simulation, and test whether their properties hold or not. I suspect
no one in the “simulation community” ever expects to disprove a simulation
completely, but as the authors did you can try to come up with a likely
simulation model (maybe close to how we would do it) and try to refute that.

------
zellyn
(a) Maybe the simulator uses ECC RAM (b) Maybe the simulator's world is as
similar to our world as the Game of Life is to Earth.

~~~
xamuel
Author here. The type of simulation ruled out is "external-soft-error-prone
simulation with (two other properties)". If the simulator uses ECC RAM, then
the simulation is not external-soft-error-prone.

You might say: "But surely the simulator does use ECC RAM!" Yes, but that's
speculation. It's nice (and surprising) that a concrete experiment can
empirically support it.

~~~
shaded-enmity
How exactly would the 1:1 bit correspondence work in practice? What is the
binding between simulated and external bit? Wouldn't we need to operate at the
edge of Landauer's principle to really rule out this possibility?

~~~
xamuel
Imagine if you were to program a video game in which players could interact
with in-game computers, which were implemented as genuine full-feature
emulations of working computers. It seems plausible that a memory-bit in one
of the in-game computers would have its value stored in a memory-bit in the
real computer on which the game was running.

~~~
shaded-enmity
What do you precisely mean by genuine full-feature emulations of working
computers? If the in-game computer is represented as some "physical model
using fundamental particles" than each bit of simulated memory is backed by, I
don't know, gigabytes of data about properties of those particles? Isn't what
constitutes a bit strictly dependent on the process making the actual reading?
How would the simulator know what is considered a bit of information within
the simulated system, and intentionally map it 1:1 onto a real memory bank?

If we discard these problems, wouldn't that imply that if such mapping were
possible, that the simulation would also have to be strictly Anthropic i.e.
the only running "software" are minds being fed data as "sensory" input?

~~~
xamuel
Things that the players think are computers. Sorry for such a vague answer,
but here's an example.

Suppose some people live in a Minecraft server, unaware there's anything else.
Within the game, they build some computers (search for "working computer in
Minecraft", it's been done many times).

They run their computers a long time and observe soft errors. The soft errors
are caused by cosmic rays hitting the Minecraft server in the real world, but
our heros don't know that. They attempt to protect their computers, moving
them underground and setting guards to make sure no creepers get in, etc. But
nothing they do stops the soft errors. Of course! What could they possibly do
to stop soft errors caused by real cosmic rays hitting the Minecraft server?

~~~
aeosynth
It might be interesting to do exactly that - rerun the OP example in a
Minecraft server, attempting to prove that it is a simulation.

Proving the simulation hypothesis true in Minecraft could give ideas on how to
prove it in our universe.

------
jepler
I don't really follow the argument. If the number of errors in the vault were
nonzero, it would most likely indicate that the vault did not screen some
("real", "physical") effect that could cause errors. For instance, you could
have errors due to radioisotope decay, low-probability interactions with
neutrinos, etc.

~~~
aeosynth
They acknowledge that:

> Without additional technology, we are unable to tell which soft errors were
> external and which were internal.

...

> Perhaps this paper’s most interesting conclusion is just that a non-
> contrived simulation hypothesis is falsifiable in a concrete way.

------
ozy
I think compute power is what matters, not amount of simulations. Compute
power available in simulated realities vs base reality will always be
significantly in favor or root reality.

And parsimonious simulation won't work, or would be even easier to detect than
what this paper was talking about.

------
politician
> A paper by O’Gorman et al [1] describes (p. 46) the following experiment and
> its results. A total of 864 modules were first run on the second floor of a
> two-story building for 4,671 hours, during which time, 24 soft errors were
> detected. Then, the same 864 modules were run for 5,863 hours in a nearby
> vault shielded by about 20m of rock, during which time, zero soft errors
> were detected.

Interesting, but there's no guarantee that time moves at the same rate both
inside the simulation and outside of it -- indeed there's a good chance that
the simulation runs much faster than the external environment. A 25% increase
in observation time seems way too low to draw any kind of conclusion.

~~~
xamuel
Assuming external-soft-error-proneness and x-x and uni-directionality, we can
think of a "space" of possible simulations we might live in, thought of as
quadrant 1 of an x-y plane where x represents "how many seconds pass in our
simulation for each second in the real universe" and y represents "frequency
with which soft errors occur in the simulating computer". Different
experiments would rule out different parts of that plane with different
probability.

------
edoo
The computer could have enough error correction where it doesn't matter.

------
honoredb
I love this title and abstract; we need more of this kind of plain speaking
and rigor when dealing with mysticism-adjacent areas.

------
mkagenius
I think we are not in a simulation. Though our world is pretty close in
principle to a simulation -- there are certain (small number of) building
blocks which contruct this complex world. That should be it.

------
User23
The simulation conjecture is a funny way to get around to Intelligent Design.

~~~
kerbalspacepro
I don't see how that follows.

~~~
AnimalMuppet
If we're in a simulation, it must be running on a simulator. That simulator is
presumably not just a natural feature of the universe - that's just "laws of
nature deeper than we have discovered so far", which I take as something
different from "simulator". In fact, the simulator (by my definitions) has to
be an artificial construction - that is, created by an intelligence for a
purpose.

That doesn't necessarily get you intelligent design of _life_ , but it does
get you intelligent design of the _universe_.

I, too, find it amusing that we've decided that God doesn't exist, that the
natural universe is all that exists. And then some people decide that we're in
a simulation, that the universe is an artificial construction created by
someone outside of it (but who totally is not God). I'd find it even more
amusing if I thought that the simulator people had a reasonable position. (To
me, "you can't prove me wrong" does _not_ imply "therefore I'm probably
right".)

~~~
resource0x
Curiously, parallel to this thread, there's another one on HN, which discusses
(the lack of) exceptions in golang. And the reasoning starts out with "we
don't need exceptions", so we throw them out the door, but then, after a
couple of intermediate steps, they come back through the window. Same door-
window scenario is playing out here :)

