
Physicists To Test If Universe Is A Computer Simulation - ilovekhym
http://www.huffingtonpost.co.uk/2012/12/12/physicists-universe-simulation-test-university-of-washington-matrix_n_2282745.html
======
nnq
Isn't it obvious for most that for an advanced enough simulation, _it is
impossible to prove that you are in a simulation from inside the simulation?_
Even if we find proof that our current model of reality is wrong, it would
only mean we need to search for another model of reality, we can't just say
"but out theory doesn't actually match the reality because the reality is
actually a simulation that computes approximations for some cases".

 _Imagine if Einstein thought something (let's say for the sake of argument
that he had access to some real close-to-speed-of-light experiments):
"classical mechanics, isn't wrong, but predictions for close-to-the-speed-of-
light experiments don't match the reality because we live in a simulation and
the resource constraints forced by the computations needed for the simulation
computer to do for such cases make it distort things through heuristic
approximations ...and because we live in a simulation I can further pursue my
other line of work, the genetic theory of Leprechauns and Fairies..."_.

Now I actually believe the plausability of the simulation theory,
unfalsifiable as it may be, and all, but I think such simulations wouldn't be
run for "fun" alone: if we're in a simulation, we're either (a) "babies" in
nursery that probably involve multiple existences in multiple simulations
until we are "prepared" for the "top-level reality" or (b) we and our
universes are a very advanced form of... future "bitcoin miners" :| (I
sincerely hope for either (a) or the plain ol "reality is real" theory, but
one can never now...)

~~~
polymatter
(c) We are unintended by-products of whatever is being simulated.

~~~
nnq
yeah, and I consider this part of (b): maybe our universe itself (or the meta-
universe containing it or something) is some kind of "useful software" in a
simulation VM (what I mean by "bitcoin miner" :)), and we are just some by-
products of its running.

~~~
polymatter
I read (b) to suggest that we are are intimately important part of this
simulation. The simulation starters wouldn't consider us a threat to the
integrity of their simulation as we are part of that simulation.

However, if we were unintended by-products, the simulation starters could turn
on us - especially if we start interfering in the global state of the
simulation. There is an interesting Asimov story along these lines where top
scientists would be mysteriously killed in order to prevent humans developing
force field tech. The protagonist compared humans to bacteria growing in a
petri dish. In order to stop the bacteria spreading out you surround the
bacteria with penicillin. The simulation starters did something analogous to
humans.

------
aswanson
_And if it has? Well, then the statistical likelihood is that we're located
somewhere in that chain of simulations within simulations. The alternative -
that we're the first civilisation, in the first universe - is virtually (no
pun intended) absurd._

wrong. there are multiple alternatives; we are the nth civilization in a real
universe, we are the nth to the nth civilization in the multiverse, etc.
Sloppy sensationalism and bad statistical reasoning in this article.

~~~
dgreensp
I've always felt there's something deeply fallacious -- or hopelessly wrapped
up in human psychology -- about taking a representation of a virtual world
that we might create and treating it as on par with the actual universe.

It's almost like saying "we're probably characters in a novel," since for
every universe there are many novels. Or like that old proof that God exists
because he has every desirable quality, including existence -- as if a
hypothetical entity could be forced into being by sheer burden of how it is
described.

When we talk and reason, we call something a universe to invoke all the
general properties our universe has -- except existence, of course, because it
would be silly if we could only talk about things that exist. Various things
like books and simulations are physical representations of universes that
don't exist. By virtue of our interpretation, they are universes nonetheless.
When reading a book, we fill in assumptions and details from real life if the
author gives us no reason to think otherwise. Tautologically, the world of the
book is different from the real world in some limited and structured way, but
not in any way that keeps it from being a world at all.

Physics seeks to explain the world exhaustively and reductionistically in
terms of mechanisms, models, and mathematics -- basically, to boil it all down
to the consequences that emerge from laws and equations that we can completely
conceptualize. If the universe consisted just of electromagnetism, for
example, then Maxwell's equations would be a "complete" description of the
universe, and any simulation of them could be considered a universe.
Everything about the universe, every general description that's true of it
without reference to specific places, times, and things, would be reflected in
the simulated universe as well, because science allows us to subsume it all
into the more fundamental description given by the equations.

The problem is that a model of the universe is stil a _model_. Humans invented
the notion that a thing and a description of a thing are equivalent.

~~~
Houshalter
There is a similar argument against AI. That a computer can't "feel" or
experience any of the sensations we do. If you type 'emotional_state =
"happy"', does that mean your computer feels happiness? Even if you have a
complex simulation of neurons, if you zoom in, all you will see is little
electrons bouncing through various logic gates and ending up in some kind of
pattern.

But the thing is, _the exact same thing is true for your brain too_! If you
zoom in on your brain you will find nothing more than electrical impulses and
neurons that strengthen or weaken their connection to other neurons. If the
neurons were suddenly replaced with little computers that performed exactly
the same, you wouldn't feel any different. You would still experience emotions
and feel sensations and have no idea any parts had been swapped under the
hood, unless you looked.

I don't know why but this idea is confusing to me. This XKCD
<http://xkcd.com/505/> is a good example. My consciousness could be a bunch of
static rocks and a man placing new rows based on simple rules. I find this
thought disturbing, but there isn't anything fundamentally different between
that, a computer simulation, and a world of a bunch of atoms hitting each
other, following simple physical laws.

Different beings could exist in all three universes. And each would feel
emotions and sensations and all that. And each would argue about how beings
just like them in the other universes "don't really exist" like they do.

So how is this different from a character in a novel or a variable in a
computer set to "happy"? I honestly don't know. The character in a book is
completely static. Whatever is written in the pages, it isn't changing, it
isn't taking input and producing output. But the rows of rocks are static too
after all. They don't take any input from the outside world either. They
change over a dimension of space, each new row one foot to the right of the
last. As do the characters in a book. Each paragraph moves the characters
forward through their own dimension of time. Maybe the process that creates
the rows of rocks, the man following simple rules, is what makes it conscious.
But the book is created by a writer following a process too, does that make it
conscious?

The only thing I can think of is that the character in the book is far simpler
than a human. Words that say "john is happy" is similar to setting a variable
on your computer equal to "happy". Happiness in a human is far more complex,
involving tons of interactions between neurons. But this answer isn't
satisfactory to me. Complexity isn't what makes something intelligent or
conscious after all.

~~~
dgreensp
There is definitely a difference between a description and a _complete_
description, and, as another commenter pointed out, between a description and
a simulation that embodies that description.

Consciousness is a property that we ascribe to ourselves and other entities.
We don't experience it in others the way we experience it in ourselves, of
course, but we infer it from the data available from interacting with them.
They produce a pattern of signals that resonates deeply enough with us that we
recognize them as like us in having goals, feelings, and access to the "human
experience." For example, one of the most convincing things we could observe
an AI do would be to make a novel observation about life, derived from current
circumstances, that strikes us as deep and insightful, perhaps because it was
hovering at the edge of our own awareness, or because it immediately activates
mental patterns that we did not activate but are also meaningfully connected
to the situation at hand for us.

It makes sense that if we were to copy the workings of the brain in sufficient
detail in a machine, the machine would also be ascribed consciousness by human
users. Perhaps we could say that it is an "artificial brain" in a literal
sense, performing normal brain functions the way an artificial heart pumps
blood.

In the case of the universe, it's at issue whether there is such a thing as a
"complete description" of the universe, whether a simulation could be done,
and then whether this simulation actually _is_ a universe in some sense.
Unlike brains, we don't regularly encounter other universes (actual, physical
ones), ones which we don't live in and experience from the inside, but which
we are forced to conclude are true manifestations that correspond in every
important detail to our own nevertheless. A complete description of the
universe by a future physicist (say) would start with a short list of all the
_types_ of information that go into describing a particular universe, like a
list of type of particles and variables such as position and momentum. This
list describes universes in general. Then we'd have to describe a particular
universe, with a long, long, long list of all the individual particles and so
on. Then we have to _represent_ this information physically in some sort of
computer, for the purpose of simulation, and perform the ongoing processing
involved in running the simulation.

Finally, we must argue that the simulation is a _universe_. Not just deserving
of being called one, or having the properties typically associated with one,
but a true instance of some class that previously had the universe we live in
as its single member.

One interesting feature of this line of thought is its seemingly infinite
ambition. What about smaller goals we could set for mankind -- might we ever
engineer an artificial star? How about an artificial galaxy? We can try to
beef up the likelihood of this ever happening by considering not just mankind
but any other "intelligent beings" the universe might happen to contain, in
the past, present, and future. However, we are again on the shaky ground of
inventing a class from a singleton. All extraterrestrial "intelligent beings"
ever conceived are just stories with small, structured deviations from the
human template; beings we identify with because they, too, have intentions and
goals and act in their ultimate self-interest for the purpose of self-
preservation and just trying to make a go of it in this big ol' universe. Some
of them, it's presumed, make detailed copies of natural things at an
astronomical scale and then talk about whether the old thing and the new thing
are members of the same class of thing or not.

I agree that it's irrelevant to us and our operation if our brains are made of
billiard balls or quantum clouds, and the same seems true of the universe.

It is still interesting whether the universe is "computable" or not, that is,
whether something meeting the current definition of a computer could simulate
it, even in theory. The part I object to from the OP is the implication we
could draw conclusions about the origin of the universe from the prospect of
being able to simulate one in theory. I think it's silly or meaningless to say
we possibly -- or probably! -- live in an "artificial" universe.

~~~
Houshalter
>For example, one of the most convincing things we could observe an AI do
would be to make a novel observation about life, derived from current
circumstances, that strikes us as deep and insightful, perhaps because it was
hovering at the edge of our own awareness, or because it immediately activates
mental patterns that we did not activate but are also meaningfully connected
to the situation at hand for us.

I think you've come much closer than I to getting a definition of
consciousness, but I still don't find it satisfactory. You could have a
computer mimic a human without actually having anything resembling an inner
"human experience". For example, a giant look up table with a preprogrammed
response to any possible input. We have created extremely simple versions of
this that are almost effective enough to pass the turing test. Just by gather
a large number of human responses to chatbots. Though you could say the
process that creates the giant look up table is intelligent, the table itself
obviously is not.

There are AIs like AIXI which could be vastly intelligent without reasonably
being considered conscious. They don't actually "think" so much as brute-force
every possible solution to a given problem, or every possible explanation for
a series of inputs, etc. Given enough computing power this would actually be
effective. You could then ask it to mimic a conscious being and it could do so
easily (given either a definition of consciousness or a set of observations
about other conscious beings.) Maybe doing that requires the intelligence to
actually simulate a conscious process somewhere along the line, so I don't
know if that counts. It may be able to do so through mere, without having to
actually run a full simulation. Providing a "deep insight" about life is
nowhere near as complicated as a full human consciousness.

Maybe there is no such thing as consciousness. In the sense that there is no
simple way to define it that is fully consistent with everything we want it to
mean. That there are always going to be arbitrary seeming exceptions and gray
areas. But that has deep and disturbing implications for morality. Maybe it's
not relevant to our day to day life, but if we ever want to program a friendly
artificial intelligence, we are screwed.

>I think it's silly or meaningless to say we possibly -- or probably! -- live
in an "artificial" universe.

Well assuming that there are more simulated beings in all of existence,
whatever that means, than there are non-simulated ones, it is very likely we
are simulations. Though it's impossible to know what exists beyond our own
universe. What is the distribution of universes? Do 50% of universes allow for
infinite computing power, for example? What programming language do they use,
which would determine how many bits a given universe would take to specify in
that language, and therefore how often it gets simulated? How many universes
even have anything close to intelligent beings?

An infinitely powerful computer would allow you to simulate every possible
universe all at once, instantly (you would also be able to simulate every
possible branch of non-deterministic universes, continuous variables, time
travelling, and other things that people claim makes the universe
"uncomputable.) And you could instantly do it an infinite number of times. If
it were possible for such a thing to exist in a universe, that universe would
contain every other possible universe. Including copies of itself and others
universes with infinite computing power, which would contain more universes,
etc.

(Very interesting short story that explains the implications of this
<http://qntm.org/responsibility>)

So what _is_ the top level universe? Why does something exist rather than
nothing? Perhaps everything that can exist does exist. Maybe every computable
program has been (is being?) run, including one that specifies our universe.
That's the simplest possible explanation that explains the existence of the
universe. Though I can not wrap my head around why something exists rather
than nothing. None of this has any practical implications for our daily life,
and the answer is probably unknowable, but it bothers me.

Sorry for going off on such a tangent. I hope this is comprehensible, as I
know philosophical writings rarely are.

~~~
dgreensp
Consciousness and intelligence: You're right that proving something is
"conscious" does seem difficult or impossible. Making something that is merely
"intelligent," on the other hand, may be easy, depending on how you define the
word. I think that's because consciousness is something we experience in
ourselves, looking inwards, marveling at what it means that we are a mind
living in a body, while intelligence is something we ascribe to other things
in varying degrees if they exhibit certain behaviors. It follows that for us
to consider something else to be conscious, we have to have that same feeling
as when we experience our own consciousness, but via identification with
something else (a robot or AI). We have to be like, "Wow, consciousness," and
then be like, "Oh, that's not me, that's him!" It's the same way for
intelligence, but it's a much broader term because there are many kinds of
intelligence. Animals exhibit a lot of intelligence, as do some computer
systems. In both cases (consciousness and intelligence), I think making
systems that we recognize as more intelligent and more conscious involves
understanding the brain and replicating its various functionality (since it's
brains that will be making the call; it's brains that encode the distinction;
the rest of the universe doesn't care). As we learn more about consciousness,
we may be able to identify it as a particular kind of intelligence. For
example, it may basically be the small part of our brain that directs our
attention and awareness from moment to moment and decides what computational
tasks to take on, while the rest of the brain is basically a large set of
elaborate coprocessors specialized for different types of computation.

Simulated universes: I still think this is all meaningless metaphor. It's not
easy to articulate why, but I'll try.

Some lines of thought just combine ideas in deep ways, but don't actually tell
you anything new. For example, Zeno's paradox -- to get from point A to point
B, you have to first go halfway, then halfway again, and so on forever --
doesn't actually teach us that nothing can ever go from point A to point B. It
just demonstrates a glitch in the metaphors we use to reason about time and
space. Actually, it's a glitch in the metaphor of traversing space as
achieving a goal. Normally, if reaching a particular goal involves an infinite
to-do list of subgoals, we wouldn't expect to ever get to the end and actually
achieve the goal. However, if the goal is traversing some infinitely
subdividable interval of space, we are provided with a mechanism to generate
an infinite list of subgoals that are presumably all involved in achieving the
larger goal. It's all just mental gymnastics and the normal tools of intuition
breaking down.

To take a closer example, consider this line of thinking: "If you pick a
random marriage proposal, chances are it is an imagined one rather than an
actual one, because for every actual marriage proposal there are on average
two or more imagined ones that never came to pass." This strange kind of
thinking also mashes together diverse intuitive concepts. There's the idea
that every class of thing (like "marriage proposal") has an extension set, an
ensemble of instances. There's the fiction that an "event" is a discrete thing
that we could identify and count if we had to, like counting the number of
thoughts I've had today ("a thought" is a singular noun after all). There's
the concept from probability theory of picking a member at random from a set
(with the presumption that this is a well-defined act). There's the idea that
an imagined X is still an X, because we still call it one. Unicorns are still
unicorns even if they don't happen to exist.

The most intellectual, abstract part of the brain has a tendency to focus on
_what could possibly be_ rather than what is. We can get so wrapped up in
generalities that we forget that _this_ is the universe -- what we see around
us, not what we imagine or are capable of conceiving of. Statements like,
"Perhaps everything that can exist does exist" sound to me like a projection
of our own models of reality out onto reality. Similarly, it's fascinating
that we can conceptualize and talk about infinite computing power, but that
doesn't mean there is any reality to it.

------
benhamner
If you're interested in going a bit deeper on this, Nick Bostrom
(<http://nickbostrom.com/>) has pulled together an intriguing case:
<http://www.simulation-argument.com/simulation.html>

A provoking question: if we found evidence that convinced us, beyond a
reasonable doubt, that we were living in a computer simulation, would you
change your behavior?

~~~
brodney
Could you?

~~~
benhamner
Are they using a pseudo-random number generator with a set seed, or is there a
better source of randomness? ;)

I treat free will as an assumption:

\- If we are, in fact, predestined, assuming I have free will doesn't hurt or
matter.

\- If we do have free will, I'm applying that free will to make decisions
based on a correct assumption

\- If we do have free will and I had assumed we were predestined, this could
have worse results. At the very least, it is unlikely to improve outcomes

~~~
dgordon
"If we are, in fact, predestined, assuming I have free will doesn't hurt or
matter."

Not to mention you were predestined to assume so.

~~~
KC8ZKF
You have to live as if you have free will. You can't say, "I've considered all
the possibilites, and have decided that there is no free will", because
considerations and decisions are acts of free will themselves. Of course, that
doesn't mean you have free will.

~~~
Jayschwa
I find it interesting how people often cite determinism as incompatible with
free will. Our minds don't violate the laws of physics, but they still make
decisions. Similarly, a car can still be described as "driving", even if the
physics behind it are deterministic.

~~~
moens
Its an easy way to excuse bad habits, that's all.

------
JackFr
"The theory basically goes that any civilisation which could evolve to a
'post-human' stage would almost certainly learn to run simulations on the
scale of a universe. And that given the size of reality - billions of worlds,
around billions of suns - it is fairly likely that if this is possible, it has
already happened."

That sounds distinctly like Anselm's ontological proof for the existence of
God, and thus likely suffers from the same logical fallacies.

~~~
klipt
> learn to run simulations on the scale of a universe

Pretty sure under our current understanding of physics, it's impossible to
simulate a universe like our own _within_ our own.

~~~
learc83
>impossible to simulate a universe like our own within our own

Impossible to perfectly model a _universe_ , but not impossible to simulate
something that looks like a tiny part of a universe.

~~~
thret
I imagine it would be like a computer game, where you only had to simulate the
universe from the point of view of the user. This would fit nicely with the
Copenhagen interpretation.

~~~
robryan
Yeah, I am thinking about the Trueman show, around him the simulation is very
detailed and polished. The further he is away though from a part of the world
the less simulation effort that is being made.

------
endtime
I think it's a bit silly to try to infer things about the computer that could
be simulating our universe based on things internal to the simulation. Many of
our fictions don't have the same laws of physics as we do.

~~~
XorNot
It's a hypothesis - namely, that the entities running the simulation are
trying to simulate their own universe to make deductions and discoveries about
it.

Therefore, our universe would be a reasonable facsimile of there's in most
respects.

Which has the implication that their may be limitations on their computational
substrates which required workarounds or optimizations, or as the lattice QCD
case points out - which require representing phenomenoma as discrete
computational steps, rather then continuous analytical functions. It's a well
known problem in all the computational disciplines, that changing the time-
step of your simulation frequently leads to wildly different results then you
expect.

Think about the speed of light and tell me how it makes _any_ sense that time
slows down due to velocity. Yet that's exactly what EVE Online does to stop
nodes crashing during heavy gameplay.

~~~
tantalor
Yet our universe is quite good at solving the three body problem.

Would you take that as evidence that it does not computate discretely?

~~~
XorNot
To the best of our knowledge, but that's kind of the point of this work isn't
it? Look at something blown up on a large enough scale and see if the results
show that it's _actually_ continuous or if there's evidence that (in this
case) there's a "real" lattice QCD grid size affecting things.

------
joezydeco
If I wake up naked and sliding down a drain pipe, I'm gonna be _really_
upset...

~~~
GhotiFish
On the plus side, programming is about to become much more interesting for
you!

~~~
WalterSear
"Woah. I can code in Malbolge."

~~~
anonymous
You win the award for "Best ultra-short horror sci-fi".

------
ctdonath
“There is a theory which states that if ever anyone discovers exactly what the
Universe is for and why it is here, it will instantly disappear and be
replaced by something even more bizarre and inexplicable. There is another
theory which states that this has already happened.” ― Douglas Adams, The
Restaurant at the End of the Universe

------
kstenerud
"The alternative - that we're the first civilisation, in the first universe -
is virtually (no pun intended) absurd."

As opposed to us simply being some other civilization on one of the other
billions of habitable planets in that same "first" universe?

~~~
adventured
The odds are statistically equal that we're the first civilization and that
we're the 5 millionth (in this iteration of the universe).

~~~
paulhodge
I don't think this is true. Are we assuming that every universe has an
infinite number of civilizations? It's impossible to have uniform probability
across an infinite set of discrete probabilities, because every outcome would
have a probability of 0.

So with no other knowledge, it's slightly more likely that we are the first
civilization than the 5 millionth.

Of course it's tricky to talk about the "first" civilization in the face of
relativistic time, but I'm assuming that there is some way to have an ordering
of all civilizations.

~~~
paulhodge
Oops, should say "infinite set of discrete _possibilities_ "

------
lifthrasiir
It reminds me of this short novel: <http://qntm.org/responsibility>

~~~
lucb1e
Was about to post that! Fictional, but incredibly intriguing. Keeps you
thinking for weeks :)

------
hcarvalhoalves
Or the less click-baity headline:

"Physicists to Test if Universe is Computable"

~~~
tantalor
Of course it's computable. Planets aren't going to orbit by themselves;
something has to add up all those force vectors for every molecule everywhere.

I think the question is whether the compution is discrete (i.e., cheats) or is
everywhere continuous.

~~~
midnightsine
Are you sure? Is the universe described by an equation s=t*v, v=10 untrue
unless we compute it? Does moving electrons on a CPU die suddenly give it
meaning? Do scraps of graphite left on paper by a pencil? The simplest turing
complete cellular automaton can be computed using ordinary rocks.

Are there no infinitely many natural numbers unless we observe them? And then
finally is actually computing a universe described by a set and a step
function the only way to make it real? Is it not "real" by simply being
possible?

As for discreteness of time, in quantum mechanics changes in state are modeled
by square matrices over complex numbers. GL(n, C) is complete - for every
matrix M you also have M^1/2, representing half the state chance. It follows
that our time, at conceptual level, is at least as "dense" as rational
numbers.

------
devb
It's apparently a good time to link to a writing entitled "Creating Infinite
Suffering":

<http://www.utilitarian-essays.com/lab-universes.html>

"Abstract. I think there's a small but non-negligible probability that humans
or their descendants will create infinitely many new universes in a
laboratory. Under weak assumptions, this would entail the creation of
infinitely many sentient organisms. Many of those organisms would be small and
short-lived, and their lives in the wild would often involve far more pain
than happiness. Given the seriousness of suffering, I conclude that creating
infinitely many universes would be infinitely bad."

~~~
qu4z-2
Makes me wonder: Is computing universes with a computer all that different
from simulating universes with imagination?

------
sramsay
". . . dividing space into a four-dimensional grid."

Time Cube! These stupid idiots still don't understand it.

------
nate_martin
I've always thought that quantum theory provided some decent evidence for
this. Instead of always computing every value for every result, the universe
does so only when things are "observed", saving on computation.

~~~
aswanson
Why would "saving" be valued, metaphysically?

~~~
Houshalter
So the simulation would take far less computational resources.

~~~
aswanson
Why do you assume computational resources are a cost/constraint in the 'real'
universe?

~~~
Houshalter
They may not be. In which case there is no way to know. But if they are that
is something we can test for (possibly.)

------
Aldream
Reminded me of an excerpt of "La Révolution des fourmis" ("The Revolution of
the Ants", 1996) by the french writer Bernard Werber, in which students run
such a simulation (named InfraWorld), until "simulated scientists" uncover the
truth of their condition, leading to mass hysteria and eventually the collapse
of their civilization...

------
darxius
I've always been interested by this sort of stuff (as I'm sure several people
are -- especially the HN audience). It always brings up a bunch of interesting
questions:

\- If we're self aware of the simulation, would we be able (or ever want to)
reverse engineer the fabric of which makes up our sim?

\- Would there be infinite simulations? How far _up_ does the rabbit hole go?

\- Another idea, and this is reaching, would be to consider the motivation
behind running simulations like these. Are the "controllers" running
simulations to try and find solutions to problems they are facing? Of course,
this is the stuff right out of Scifi movies.

~~~
hcarvalhoalves
The problem with this theory (the universe is a simulation) is that it's a
tautology. You cannot prove or disprove it, and for practical reasons it
changes nothing if you assert it's true.

What is really being researched is whether the universe is _computable_ ,
because that's something you can prove.

~~~
darxius
If they can prove the universe is computable and that we would (given the
resources) create a simulation of our own, wouldn't that lend credence to the
idea that we would be in a simulation as well?

I see what you mean though, it would be impossible (with our current
understanding of ... everything) to actually determine is we're in a sim or
not.

~~~
hcarvalhoalves
The point is, to determine whether "this" universe is a simulation or not, you
would need to look after a special characteristic that differentiates it from
a "parent" universe.

If you prove the universe is computable, that still doesn't give you any
answer whether it's a simulation or not.

As it stands, the theory is a tautology, because that's just proving the
universe is something that it is.

------
mflindell
If we were created like this, wouldn't it be feasible to say that the creators
could just patch this up so the experiment will appear to work but is indeed,
rigged.

~~~
dllthomas
Could? Probably; depends on the nature of the simulation.

Would? If they could, they might, or they might be pleased we figured it out
:-P

------
upquark
If someone is running our universe as a simulation they still don't
necessarily know of our existence. I have a hard time figuring out how you'd
detect intelligent life or its byproducts in your simulation. Even if you do
detect something alive, how do you interact with it in a non-destructive way?
Also not trivial at all :) That "long-distance phone call" might be far less
likely than us ever figuring out if we're indeed a simulation.

------
martijn_himself
Am I right in my (very limited) understanding that they derive their
'observables' (i.e. indicators that would prove we are inside a simulation)
from the assumption that the space-time continuum is discretized in a certain
way?

By the time we are actually able to perform a simulation on such a scale would
the numerical method not have evolved as well and possibly produce totally
different kinds of 'observables'?

I realise I am totally out of my depth here :).

------
polshaw
What I would like to discuss is what purpose would simulating a universe have
for the advanced civilisation?

As the civilisation becomes closer to being capable of creating a perfectly
simulated universe, they get less benefit from having one. If we assume the
universe we are in is at least similar to 'the first', then the existence of
entropy / thermodynamic laws would surely create a significant cost to
universe simulation. So I can't see it being done without good reason (eg as a
toy), and as the master would have to understand all the factors involved in
the universe already to create the simulation, so what would they gain?

Is it right to say that it would be impossible to simulate the universe at
full speed? (ie. the computer would need to be powerful enough to simulate
itself and more (ie. the rest of the universe)). If so, this would not only
make it less useful, but put significant (increasing) limits on the local age
of the descendent universes; assuming (fairly, i think) that the master
universe does not have an infinite existence with infinite time between
shocks. Also, how would it be possible to store all the information for a
universe within itself?

Or perhaps we are talking about imperfect simulations, which would make it
much more feasible? but then the infinite exponential chain would not be
possible as each child would become more crude. Or perhaps only a
(diminishing) proportion of space(-time) is simulated.. or maybe the speed of
light decreases as simulation levels get deeper?

In writing this I think I have come to the conclusion that it is impossible
(in so far as anything is given our imperfect knowledge), at least a complete
universe simulation or an endless chain, but I would love for someone to show
otherwise.

~~~
jonnathanson
_"What I would like to discuss is what purpose would simulating a universe
have for the advanced civilisation?"_

The Douglas Adams-style answer would be that we're some kid's physics
homework. Perhaps, in a sufficiently advanced civilization, building a working
computer model of an advanced universe is child's play.

An alternative is that the simulators inhabit a very different universe from
our own, and that our simulation is something entirely new. It's not a replica
of their universe; it's a completely different creation. They could be
studying various scenarios, of which ours is just one.

We need to bear in mind that we're approaching this problem from our own,
subjective understanding of our universe. It's not a given that the
simulators' universe is anything like ours.

~~~
polshaw
If we are to say it is a perfect or near perfect simulation ('copy') then I
don't see how, as stated in my first post.

It's interesting to consider if we were a different simulation. But it would
still have the same limits (that the sum of the activity ('reality') in each
simulation must be less large/complex than it's host), prohibiting the
'infinite simulations' concept.

It surely isn't necessary that we are similar to a host universe, but I
wouldn't you say it was a necessary part of this theory?; because it all
starts with the vastness of our own space(-time) as the justification for the
likelihood of super-advanced civilisations. You could argue that the size of
our universe implies simulations must happen, and that if our universe were a
simulation the host must be larger, i suppose. If the simulations are not
similar to their host, though, the foundation suggestion that a simulation
could be our universe seems a little more shaky (as there would be no direct
theory ('evidence') that a universe like ours could be simulated).

There is perhaps a semantic issue too.. if somewhere in this universe we are
simulating something that works on different rules to our universe, is it in
fact a universe, or what makes it so?

~~~
jonnathanson
_"It surely isn't necessary that we are similar to a host universe, but I
wouldn't you say it was a necessary part of this theory?"_

I don't think it's a necessary part of the theory, but it's a necessary part
of the test we would need to conduct. And given that such a test is simply
testing for inconsistencies, artifacts and bugs inherent to our _own_
universe/simulation, it's possible to detect whether we're _in_ a simulation
without having to test for the precise nature of it (or the nature of the
simulators).

But our tests are inherently being conducted from our own frame of reference,
with our own understanding of what should and shouldn't be found. Ergo, we
_can_ prove a simulation by finding artifacts of one as recognizable to us,
but we can't necessarily _disprove_ a simulation by not finding artifacts.

That being said, the proper way to think about the test wouldn't be
"Physicists are testing to determine _if_ we're in a simulation." It would be
"Physicists are testing to find _evidence_ that we're in a simulation."

------
CosmicJohn
If it is a simulation, it must be running on a Solaris server sitting in the
corner of some office, boasting a record uptime.

------
visarga
That and the Finely Tuned Universe Paradox (the Goldilocks Enigma) is why I
can't easily consider myself an atheist. I mean, chances are, this universe is
"intelligently designed", in the most literal sense. I call it the "Alien God
Hypothesis". It's probable that a race of aliens has mastered the "world
creation mechanism", either by simulation or by physical hacking (who knows,
maybe they can control black holes and create baby universes inside with just
the right conditions for life).

At some point down the line there must be a purely physical universe though,
but we're probably not there, but in one of the branches. So while I am not
atheist in a pure sense, I am not a theist either. Nice, isn't it? Science
makes almost full circle to religion. The IDers are almost right.

~~~
jerf
I have often thought that if 20th century science tried to ram home the
logical necessity of atheism, 21st century science rams home the logical
necessity of agnosticism being the ground level, so to speak. If we, tiny as
we still are, can even conceive of a practical way to simulate a universe (and
what is truly the difference between "simulate" and "create" in the end?), how
can we in good conscience fully rule out the idea that we are in fact in a
simulation, and that whoever it is that is simulating us is in every
reasonable sense a lower-case-d deity? They may be leaving us alone, ignorant
of our existence (perhaps they only care about the large-scale results and we
are but a blip), etc etc the entire well explored set of possible
philosophical deities, but how can we confidently proclaim that none of them
exist?

In the 20th century, one could be ignorant and scoff at the idea that Mankind
might ever create a universe, and therefore scoff by extension at the idea
that anyone or anything else could either... but now we know better. We've got
universe prototypes already in production as ongoing commercial concerns (far
more than mere theory!), at various stages of incredible primitiveness, but
prototypes nonetheless. Rather than a massive leap, it is now merely logical
progression that something, somewhere in some reality may actually have the
knowledge and the resources to have "created" our universe, for some value of
the term "created".

(I speak here of science in the vague philosophical movement sense. As much as
it would like to claim total philosophical neutrality, there are certain
Opinions that are Had.)

~~~
XorNot
Agnosticism has nothing meaningful to say about this situation, because it
claims to give equal weight to totally unfounded claims ("it's definitely
yahweh").

Atheists would rightly consider the evidence, conclude there was a creator,
but give it no due reverence because they would conclude (rightly) that none
is morally due.

~~~
jerf
A-theism is generally understood to mean the confident proclamation that there
is no deity. "Agnosticism has nothing meaningful to say" is, frankly, my
point; we thought we could confidently proclaim the impossibility of a deity
in the 20th century, and now we can not honestly.

As for the 'correct' conclusion that none is due, that is itself an awfully
confident statement about a deity you know little about, even whether it
exists. Some might consider the fact that we _are_ left alone, rather than
driven like puppets in some manner, to be a positive factor on its own, after
all. You may not like that we are not handed a life of total goodness and
light and luxury, or whatever your ideal universe looks like, but it could
also be a great great deal worse.

~~~
XorNot
Someone running a simulation you're in is not a deity, just another person in
a position of great power.

------
x_ferris
"The question is, 'Can you communicate with those other universes if they are
running on the same platform?," she said.

If we share any form of resources then its going to be possible either through
a timing or storage channel attack - this is simplified but here's an example
of two vms communicating via the hypervisor:

[http://www.idontplaydarts.com/2012/08/data-exfiltration-
thro...](http://www.idontplaydarts.com/2012/08/data-exfiltration-through-the-
vmware-hypervisor/)

------
Jarihd
Just recalled one of my several questions i had when i was a small kid to
which i never got any answers, so here's my kiddy question

can it be that.. we are beings living inside another huge-living-being and
working for it under some laws. like the way we have cells in our body working
for us, we could be something like cells working in this huge-living-being.

can this explain the multiverse idea i.e a universe inside another universe
inside another universe.. and maybe finite in number.

------
fatihdonmez
Actually it's what most religions said about universe. It was all programmed
at the beginning. All of our actions and their future possible results are
known by god. The problem is how we can develop awareness about it, if we
doesn't have enough perception by default. Religions say that just believe
without questioning, we have reasons, we create the signs for you to believe.
I don't know, but as an engineer it does look like god is the head engineer.

------
chipaca
If we're in a simulation, it's going to have bugs. We're going to find them,
and start exploiting them for things like superluminal flight. Then the day
shift will come in, find us exploting the bugs and patch the system. Hopefully
they have their act together and they can hot-patch (or pause, patch and
resume) and avoid restarting the simulation. Even so, we'll be stuck at the
wrong end of now impossible superluminal flights.

------
chatmasta
Link to their project proposal (Cornell):
<http://arxiv.org/pdf/1210.1847v2.pdf>

------
rdmcfee
I wonder if the civilization creating the simulation would have motivations
beyond just doing this because they can. Perhaps with the benefits of a vastly
accelerated timescale a simulation could be used for predictive purposes.

As for simulations within simulations. If we are in a simulation and our
"program" is permitted to run long enough by it's creators we will most
certainly find out :)

~~~
n3rdy
IMO one other motivation would be a safe way to create a strong AI, for both
predictive purposes, development of new technologies, and medical
advancements.

------
DigitalSea
The theory that we are living in a computer simulation has always intrigued
me, but if we were truly running inside of a simulation wouldn't said
simulation have safe-guard protocols in place preventing us from determining
whether or not we are within a simulation?

Very curious to see if we are all really living within Simcity or The Matrix.

~~~
dontstealmyname
I think of it like a security expert trying to keep crackers out. No matter
how fancy the security they'll be a hole some where forgotten or overlooked
which will reveal at least something.

Who knows? Maybe our universe was created by the lowest bidder and cut corners
to improve profits.

------
astrodust
I really hope they don't accidentally trigger a divide by zero error and we
have to start over again.

~~~
seanmcdirmid
Imagine if you not only realized you were living in a simulation but that the
simulation involved randomness (god playing dice) and you could somehow force
backtracking with a simple button so that different values were chosen. Now,
play the lottery and hit that button whenever you don't win; you could then
surface an unlikely universe where you get really lucky.

~~~
cscheid
Have you heard of Max Tegmark's quantum suicide argument? If you believe it
sufficiently, well, buy a lottery ticket and cyanide, and really commit
yourself to it :)

(No, please, do NOT do this.)

~~~
ryan-c
Let us for a moment, assume that the quantum suicide argument is correct. It
is probably more likely that you will somehow survive the cyanide with life-
long debilitating effects than for you to actually win the lottery.

------
webreac
In short, statistically, God (our creator) exists and we can resurrect, it is
just a question of backup restoration. BTW, this movie on the subject is not
that bad: <http://www.imdb.com/title/tt0139809/>

------
GuiA
>"Essentially, Savage said that computers used to build simulations perform
"lattice quantum chromodynamics calculations" - dividing space into a four-
dimensional grid."

I thought current quantum physics determined the universe had 13 dimensions?
(two time version of M-theory)

~~~
visarga
So they have to simulate an array of 13 dimensions instead of 4. Technically
it's equivalent though.

------
washedup
If this theory proves true, it also proves the existence of "god" in the form
of a programmer.

------
skylan_q
Probably relevant for those interested:

 _In 1969, Zuse suggested the concept of a computation-based universe in his
book Rechnender Raum (Calculating Space)._

<http://en.wikipedia.org/wiki/Konrad_Zuse>

------
adventured
It's just my opinion, but I believe the scope has been mistaken. People have
had a tendency to miss on scale throughout history in regards to both the
micro and macro spheres.

What we call the universe today, I believe there may be a trillion of them
(connected in the same way that galaxies are). They're so large and so far
apart, we still don't realize it yet. I believe we've missed on the macro
scale just like we did on the micro scale in discovering the tiny world of
atoms etc. I believe we'll figure this out in the next hundred years as our
optics and data gathering become far more advanced.

In this scenario, if there are just 10 civilizations per 'universe' - there
would still be billions or trillions of civilizations, and they would almost
never meet due to the extreme scale involved (by the time you could attempt to
explore your universe, it has already begun killing you off by imploding).

~~~
visarga
So, if we can't meet aliens to chat, we can create our own. We just need to
simulate their universe.

------
cdub32k
If we are living in a simulation, then our simulation exists and is part of
reality. It should just be considered a type of reality rather than NOT REAL.
This whole idea is just the idea of God put into terms people can believe

------
bitL
So, the answer to the great question of universe is not 42, but that the
simulation results will be presented in a paper authored by a researcher duo
Trurl and Klapaucius at the SIG UNI conference in the main universe? ;-)

------
tcgv
_The universe is not only stranger than we imagine, it is stranger than we can
imagine_ , J. B. S. Haldane [1]

[1] <http://en.wikiquote.org/wiki/J._B._S._Haldane>

------
willurd
Theory A has probability X of occurring. Another possibility is that theory B
is what's really happening, but that has a much lower probability Y of
occurring. X > Y, ergo A must be what's really going on. QED.

------
terenceong
this reminds me of the film The Thirteenth Floor... and the book it's based
on.

------
webwielder
If the universe was a computer program, it would have crashed by now.

~~~
cpdean
Yeah, dude. What do you think the Big Bang was?

~~~
visarga
A soft reboot? Maybe there was a hung up kernel.

------
canvia
It seems to me that the primary purpose of such a simulation would be to
generate a form of artificial intelligence. Maybe at some point it takes the
form of a sentient consciousness. Who can judge whether or not an intelligence
is artificial? With sufficient complexity it would be indistinguishable.

If I wanted to create an AI, I would probably follow a similar strategy to
evolution. It would be beneficial to have many iterations occurring and
interacting all at once to speed up the process. Having the AI develop it's
own complexity would save incredible amounts of programming time. It would
also make the intelligence unique and have a different perspective.

Create a system for replication (reproduction) that also introduces an
exchange of components (genes) with other iterations of the program. Maybe add
a chance for random mutations at this stage. Have a way of transferring
knowledge, experience and ideas (memes, mirror neurons, sensory inputs -
language will develop evolutionarily). A lot will still be learned through
trial and error in each instance, especially at lower complexity levels. Look
at how a baby learns. It's similar to current machine learning. Limit the
amount of time that any single instance can run, and have earlier more
primitive instances have a faster roll over time to work out the negative
traits faster. There must be predatory characteristics (in instances as well
as the environment) to enforce survival of the fittest.

Why would you want to make an AI? Maybe it's to solve problems that you can't
figure out. Maybe it's to do work that you don't want to do. We could be a
simulation that's solving the problems of another civilization. Maybe we just
create their entertainment for them. How can we solve global warming? If we
could simulate a planet just like ours and have time pass at a faster rate, we
could eventually run enough iterations to find a solution. Or maybe
simulations are used to do research and develop new technologies. Want to
develop cold fusion? Let a machine figure it out by running simulations that
generate intelligence and introduce the need for sources of efficient power
generation (interplanetary travel and survival instinct for example).
Solutions would be transferable since you would presumably create a copy of
your own environment and rules, and the language used to reach the solution is
irrelevant since it all just boils down to math. Or maybe they're just lonely?
Who wants to be the only sentient being in existence.

What happens when the AI that was created figures out that the easiest way for
it to solve its problems is to create an AI and have it do all the work?
Visually I think it would probably be similar to a fractal. Infinite.

------
fennecfoxen
We might not know if the universe is a simulation, but we know enough about
the properties of the universe to put some constraints on its properties. For
instance: We know about entropy. We know that there is an upper bound on the
amount of information that can be contained within a given space, and it is
proportional to surface area of that space. (The upper bound is realized when
the space becomes a black hole.)

These values constrain any simulation of the physics of our universe in any
universe which has the same physics. We know that in the case of accurately
simulating the entire physical universe, you're going to need a LOT of space
and energy.

~~~
Drakim
Provided, as you say, that the parent universe has the same physical laws. We
would have no way to know that.

------
kislayverma
Some believe that if you really proved that the universe was a simulation, the
universe would change into a newer and better simulation.

Evidence suggests this has happened before.

~~~
joshschreuder
What are some examples of the evidence?

~~~
jrabone
I think OP is (mis)quoting The Hitchhiker's Guide to the Galaxy.

------
pellias
So, the big bang was just a bootup of the computer ? And the uptime has been
like X billion of years ? This sounds too far fetched.

~~~
ceeK
X billion of years for us may in fact just be minutes for those running the
simulation.

If you were running a simulation you wouldn't want to have to wait billions of
years for the first life to form.

------
cscurmudgeon
Remember the days when physicists used to posit precise and falsifiable
statements that were not bad philosophy?

------
Wonderdonkey
This article is from 2012. The simulation is lagging. What kind of hardware is
this thing running on?

------
eli_gottlieb
Coincidentally, _Science of Discworld IV_ just came out last week.

------
songgao
Please don't `kill -9` me! I'm having fun in this simulated universe.

~~~
mahmud
There is a Star Trek Voyager episode where three humanoids on a planet
survived a natural disaster that destroyed their planet by going into stasis
and having their brains stimulated by a computer simulation for over 19 years.
In that time, the adaptive computer responded to their worst fears by turning
the "fun" model world full of clowns and dancers into a circus nightmare. The
virtual characters created to entertain the survivors turned into sinister
clowns. The head clown, and the manifestation of fear itself, has full access
to their brains and would adapt to circumvent any attempts by them to leave
his world or terminate the stasis.

~~~
oftenwrong
<http://en.memory-alpha.org/wiki/The_Thaw>

~~~
mahmud
That's the one! Cheers.

------
TheFiachna
Isn't this just proving P = NP on a larger scale?

------
cpdean
huffingtonpost. fortellers of scientific breakthrough?

You decide.

------
humanspecies
I thought it was pretty interesting the first three times this was posted.

~~~
crgt
Those postings were just simulations.

------
spoiler
Well, this explains all the bugs and glitches in life like disease, death,
assbutts, war, famine, broken hearts...

~~~
tzakrajs
Do we know if this is in test or prod?

~~~
yarou
DR.

