Physicists To Test If Universe Is A Computer Simulation (link)

post by D_Alex · 2013-04-17T02:23:23.804Z · score: 4 (11 votes) · LW · GW · Legacy · 50 comments

If it is... I hope they do not crash the system with the test.

http://www.huffingtonpost.co.uk/2012/12/12/physicists-universe-simulation-test-university-of-washington-matrix_n_2282745.html

Be sure to check out the actual reseach papers linked in the article! I would have linked to them directly, but the article is full of follow-on links of considerable interest.

 

50 comments

Comments sorted by top scores.

comment by jimrandomh · 2013-04-17T03:01:26.412Z · score: 31 (31 votes) · LW(p) · GW(p)

This is testing for discretization of space. Which would be a very interesting fact about the universe, but somewhat orthogonal to whether it's a simulation; a root-level universe could still be discretized, and a simulated universe could be continuous or discretized more finely than any instrument can detect.

comment by wedrifid · 2013-04-17T10:48:26.175Z · score: 20 (20 votes) · LW(p) · GW(p)

This is testing for discretization of space.

Really? Wow. That's FAR more interesting than the actual subject title.

comment by DaFranker · 2013-04-17T16:24:48.407Z · score: 3 (3 votes) · LW(p) · GW(p)

I'm quite partial to the idea that this was actually the whole point of the experiment, and they just spun it as "Let's see if we're in the Matrix!" to get more public attention (and easier grant monies).

comment by [deleted] · 2013-04-17T19:03:11.738Z · score: 1 (1 votes) · LW(p) · GW(p)

If you're interested in that kind of stuff, see this.

comment by wedrifid · 2013-04-18T03:06:59.838Z · score: 1 (1 votes) · LW(p) · GW(p)

If you're interested in that kind of stuff, see this.

Thanks for the link. I like seeing empiricism used to actively narrow the search space for quantum gravity theory candidates.

comment by [deleted] · 2013-04-17T19:04:59.778Z · score: 3 (3 votes) · LW(p) · GW(p)

IIRC, they tested for a specific kind of space discretization that, if it wasn't for the SH, wouldn't be particularly easy to locate in hypothesis-space. (Actually, it wouldn't be terribly easy to locate in hypothesis-space even given the SH, if I understand this correctly.)

comment by jake987722 · 2013-04-17T04:50:54.693Z · score: 3 (3 votes) · LW(p) · GW(p)

These are good points. Do you think that if the researchers did find the sort of discretization that they are hypothesizing, that this would represent at least some weak evidence in favor of the simulation hypothesis, or do you think it's completely uninformative with respect to the simulation hypothesis?

comment by CarlShulman · 2013-04-17T06:58:17.009Z · score: 5 (5 votes) · LW(p) · GW(p)

I'd say it would be very weak to negligible evidence in favor.

comment by Decius · 2013-04-19T04:15:45.393Z · score: 0 (0 votes) · LW(p) · GW(p)

I think that the simulation hypothesis does not permit any evidence for or against that does not violate the laws of physics. There's no way to distinguish between being in a real universe, a discrete simulation of a continuous universe, a discrete simulation of a discrete universe, or a continuous simulation of either a discrete or continuous universe with limited measuring tools.

If the laws of physics starting changing in dramatically interesting ways, I might see that as evidence of simulation... and now I need to reevaluate the evidence about cold fusion in that light...

comment by Jayson_Virissimo · 2013-04-17T02:34:58.141Z · score: 10 (10 votes) · LW(p) · GW(p)

The original research this article is based on was mentioned on Less Wrong last year.

comment by Luke_A_Somers · 2013-04-17T12:39:56.654Z · score: 8 (8 votes) · LW(p) · GW(p)

An article inked from the linked article quotes another article as saying,

"the problem with all simulations is that the laws of physics, which appear continuous, have to be superimposed onto a discrete three dimensional lattice which advances in steps of time"

This is false. It may be the assumption of this approach, but it's not so. I've worked with non-time-stepped simulations and adaptively-time-stepped simulations. I've also worked with non-lattice, non-3D simulations.

Of course the original article comes out and says it, but it bugs me that this explicit assumption ended up cast as a conclusion.

comment by Decius · 2013-04-19T04:09:13.136Z · score: 0 (0 votes) · LW(p) · GW(p)

Surely one can simply manipulate the four-(or eleven)-dimensional equations directly, rather than trying to make a measurement of a continuous object with a tool that only measures discrete states?

comment by Luke_A_Somers · 2013-04-19T12:34:10.057Z · score: 0 (0 votes) · LW(p) · GW(p)

If you do that, it's analytical physics, not simulation. Unless you're just collapsing the wavefunction when you notice large entanglements, or something.

comment by Decius · 2013-04-20T01:26:39.071Z · score: 0 (0 votes) · LW(p) · GW(p)

It's the difference between plotting a countably infinite number of points and drawing a line.

comment by gryffinp · 2013-04-17T05:43:13.000Z · score: 7 (9 votes) · LW(p) · GW(p)

You know, I was musing on the "Universe as Matrix" idea a while back, and I came to some interesting conclusions.

I realized first that, given sufficiently attentive creator(s), any attempt to prove that the Universe was a simulation must inevitably fail. Because if if such a proof were found, the proverbial Dark Lords could simply pause the sim, patch out the error that revealed the discrepancy, and roll back to before it was revealed. Similarly, proof that we weren't in a Matrix should be equally impossible, since any evidence that proved the impossibility could simply be falsified by the system to maintain the illusion.

At this point my train of thought went on to a different track: if we did know that we were living in a simulated universe, what should we do about it? After some pondering, I concluded that we would have spent all of our existence living in the sim anyway, so I wouldn't see much need for massive upheavals of human life. And if the Dark Lords were indeed trying to enforce a "realistic" simulation, then attempting to communicate with them would be fruitless, since they would not respond. But...

For whatever reason, the creators would have created this universe. It seems to me that if you were going to create a universal simulation, you would do it because you wanted to see what would happen inside. And we humans have a rather strong attachment to existing, so we should try to continue that state of affairs as far as possible. Therefore, in this scenario, every human being would have a solemn duty to make the world as interesting as possible.

It was at that moment that I realized that I had created a religion.

comment by CarlShulman · 2013-04-17T06:57:41.049Z · score: 6 (6 votes) · LW(p) · GW(p)

Robin Hanson has written on this topic.

comment by gryffinp · 2013-04-17T12:42:32.545Z · score: 1 (1 votes) · LW(p) · GW(p)

Huh. I'm certain that I hadn't read this before.

Obviously he gave it a little more thought than my own shower-musings received.

comment by Luke_A_Somers · 2013-04-17T12:33:50.029Z · score: 4 (4 votes) · LW(p) · GW(p)

You're assuming that the Dark Lords are aware of our existence and care.

Given the fraction of the universe that we occupy, I'm not betting on it.

comment by Locaha · 2013-04-19T08:38:16.720Z · score: 0 (0 votes) · LW(p) · GW(p)

What, can't they search for local reversals of entropy?

comment by Locaha · 2013-04-19T08:35:55.563Z · score: 2 (2 votes) · LW(p) · GW(p)

Interesting as in "interesting times"?

I think the Dark Lord already designed us to be interest maximizers. They probably lead dull lives, the poor things...

comment by Lukas_Gloor · 2013-04-17T20:54:41.153Z · score: 2 (2 votes) · LW(p) · GW(p)

Therefore, in this scenario, every human being would have a solemn duty to make the world as interesting as possible.

Great post but this is where you lost me. I have a hard time prioritzing "interesting" over reducing suffering, and I find it repugnant that some beings created a universe where quintillions of sentient creatures have been suffering and dying for half a billion years on this planet alone. OK, maybe the creators had the decency to "shortcut" all the suffering so it wasn't actually experienced, that's the upside of the thought.

Hmm, that makes for a good religion too, you only remember the suffering, but during the actual moments you were zombified, you're misremembering!

comment by Decius · 2013-04-19T04:06:44.532Z · score: 1 (1 votes) · LW(p) · GW(p)

My trouble was in figuring out what "interesting" means to the beings which can model a universe.

comment by Decius · 2013-04-19T04:18:26.055Z · score: 0 (0 votes) · LW(p) · GW(p)

I find it repugnant that some beings created a universe where quintillions of sentient creatures have been suffering and dying for half a billion years on this planet alone.

Meanwhile, they find something utterly alien about solar fusion repugnant yet utterly fascinating.

comment by Lukas_Gloor · 2013-04-19T07:30:03.861Z · score: 1 (1 votes) · LW(p) · GW(p)

Yes, in which case their evaluation doesn't correspond to any first-person-evaluations other than their own (because solar fusion likely doesn't have any of that), whereas my evaluation reflects all the first-person-perspectives out there. I'm being altruistic, they aren't. Sure, they might not care about that, and indeed, if the creators themselves aren't capable of suffering, they might not even realize they're being a**holes, but otherwise they'd obviously be total jerks in a very objective sense -- for whatever that's worth.

comment by Decius · 2013-04-20T01:28:32.744Z · score: -1 (1 votes) · LW(p) · GW(p)

What if they have first-person perspectives which are objectively comparable to us in the same way that we are comparable to solar fusion?

What are the necessary and sufficient conditions to be "total jerks" in any objective sense?

comment by Lukas_Gloor · 2013-04-20T06:33:19.805Z · score: 1 (1 votes) · LW(p) · GW(p)

Then, if I understand the question correcly, the creators would be being partially altruistic, which we'd mistake for being non-altruistic because we don't understand that solar fusions can suffer.

"Not taking other-regarding reasons for actions seriously" makes you a total jerk. "Others" are beings with a first-person perspective, the only type of entities for which things can go well or not well in a sense that is more than just metaphorical. You could say that it is "bad for a rock" if the rock is split into parts, but there isn't anything there to mind the splitting so at best you're saying that you find it bad if rocks are split.

The above view fits into LW-metaethics the following way: No matter their "terminal values", everyone can try to answer which action-guiding set of principles best reflects what is good or bad for others. So once you specify what the goalpost of ethics in this sense is, everyone can play the game. Some agents will however state that they don't care about ethics if defined like that, which implies that their "terminal value" doesn't include altruism (or at least that they think it doesn't, which may sometimes happen if people are too quick to declare things their "terminal value" -- it's kind of a self-fulfilling prophecy if you think about it).

comment by Decius · 2013-04-21T03:34:05.198Z · score: 0 (0 votes) · LW(p) · GW(p)

Would it be immoral to fully simulate a single human with brain cancer if there was an expected return of saving more than one actual human with brain cancer? What if there was an expectation of saving less than one actual human? (Say, a one-in-X chance of saving fewer than X patients) What if there was no chance of saving an actual patient at all as a result of the simulation? Assume that simulating the human and cancer well enough requires that the simulated human simulate saying that he is self-aware, among other things.

comment by TheOtherDave · 2013-04-21T06:52:38.904Z · score: 2 (2 votes) · LW(p) · GW(p)

I've never quite understood, in cases like this, how "fully simulate a single human with brain cancer" and "create a single human with brain cancer" are supposed to differ from one another. Because boy do my intuitions about the situation change when I change the verb.

comment by gryffinp · 2013-04-17T22:51:25.427Z · score: 0 (0 votes) · LW(p) · GW(p)

I find it repugnant that some beings created a universe where quintillions of sentient creatures have been suffering and dying for half a billion years on this planet alone.

Isn't that an inevitable conclusion of the basic "the universe is a simulation" premise?

comment by NancyLebovitz · 2013-04-17T14:48:53.843Z · score: 2 (2 votes) · LW(p) · GW(p)

I'm a different sort of Dark Lord, I suppose-- if my sims found out they were living in a simulation, I'd be fascinated to see what they'd do next.

comment by Locaha · 2013-04-19T08:37:13.301Z · score: 0 (0 votes) · LW(p) · GW(p)

wrong post.

comment by Nornagest · 2013-04-17T21:47:09.064Z · score: 1 (1 votes) · LW(p) · GW(p)

It seems to me that if you were going to create a universal simulation, you would do it because you wanted to see what would happen inside. And we humans have a rather strong attachment to existing, so we should try to continue that state of affairs as far as possible. Therefore, in this scenario, every human being would have a solemn duty to make the world as interesting as possible.

That seems to share some ideas with Neal Stephenson's fictional religion of Kelx, as described in Anathem.

comment by gryffinp · 2013-04-17T22:36:43.958Z · score: 0 (0 votes) · LW(p) · GW(p)

Ah. This one, I've read.

Thank you by the way, I had actually remembered about that as I was typing this up (In a sort of "Speaking of Religions with unusual premises..." way), but forgotten what it was called and who came up with it. I had speculated that it might have been from a Heinlein novel, since the half-remembered premise of "lone protagonist is saved from arctic peril and then gets to listen to someone politely explain their philosophy" sounded vaguely Heinleinish.

comment by NancyLebovitz · 2013-04-19T17:10:57.613Z · score: 0 (0 votes) · LW(p) · GW(p)

Therefore, in this scenario, every human being would have a solemn duty to make the world as interesting as possible.

If you look at the number of different sorts of stories created by humans, who are probably less complex than whoever made our universe, I think it's fair to say we have no idea what counts as interesting to them.

comment by Kawoomba · 2013-04-17T09:55:42.436Z · score: 2 (2 votes) · LW(p) · GW(p)

Have you ever half-jokingly said "Computer, exit", when you were all by yourself?

[pollid:454]

comment by [deleted] · 2013-04-17T11:35:24.943Z · score: 3 (3 votes) · LW(p) · GW(p)

http://xkcd.com/525/

comment by TitaniumDragon · 2013-04-20T20:14:36.901Z · score: 2 (2 votes) · LW(p) · GW(p)

There's a Freefall comic where the captain says to end all virtual reality simulations and someone else covers his eyes, making him scream. Can't find it offhand though.

comment by [deleted] · 2013-04-17T11:31:17.076Z · score: 0 (0 votes) · LW(p) · GW(p)

Previously mentioned here.

comment by TitaniumDragon · 2013-04-17T09:28:03.599Z · score: 0 (4 votes) · LW(p) · GW(p)

It is extremely unlikely that the Universe is a simulation for a wide variety of reasons, foremost amongst them being expense. The level of simulation present in the Universe is sufficiently high that the only purpose of it would BE simulation, meaning that our physical laws would necessarily be quite close to the laws of whatever universe overlies us. However, this implies that building an Earth simulator with the level of fine-grained reality present here would be insanely expensive.

Ergo, it is highly unlikely that we are in a simulation because the amount of matter-energy necessary to generate said simulation is far in excess of any possible benefit for doing so.

comment by Tenoke · 2013-04-17T12:07:22.241Z · score: 8 (8 votes) · LW(p) · GW(p)

[1] The level of simulation present in the Universe is sufficiently high that the only purpose of it would BE simulation, meaning that [2] our physical laws would necessarily be quite close to the laws of whatever universe overlies us.

[2] does not follow from [1]. The REAL real world might be sufficiently more complex than ours and it can be running thousand of simulations for a variety of reasons. I'm really not sure why you think that our level of simulation or physical laws are as complex as it gets but this is not a valid argument.

For a quick example of what I mean I would like you to think about us full-on simulating a 2 dimnesions(+time) environment.

comment by smk · 2013-04-23T07:45:46.193Z · score: 0 (0 votes) · LW(p) · GW(p)

In the absence of other evidence, could you not use some sort of complexity measure to estimate that, if our universe is being simulated, the simulating universe is more likely to have simpler laws than more complex ones? (And maybe even that having no simulating universe--meaning our universe is not a simulation--is even simpler, and therefore more likely?) But I have no idea what the actual difference in probabilities would be, if you could.

comment by PrawnOfFate · 2013-04-17T09:34:07.729Z · score: 4 (4 votes) · LW(p) · GW(p)

It is extremely unlikely that the Universe is a simulation for a wide variety of reasons, foremost amongst them being expense

Unless our simulator are fooling us about the expense of computational power.

comment by TitaniumDragon · 2013-04-17T09:38:11.690Z · score: 2 (2 votes) · LW(p) · GW(p)

If the Flying Spaghetti Monster is running the simulation, it is non-falsifiable, but also not worth considering because he can just stick his noodley appendage in and undo any results he doesn't like anyway retroactively. Its not like we would know the difference.

For us to break the fourth wall, either our creators would have to desire it or be pretty bad at running simulations.

comment by PrawnOfFate · 2013-04-17T10:06:33.059Z · score: 3 (5 votes) · LW(p) · GW(p)

..like the ones in The Matri, who allowed its denizens to evolve to knowledge of virtual reality, rather than keeping them at a medieval level, or using the bio-energy of sheep...

But I am more interested in the epistemic mistake people keep making. People keep assuming that it is possible for simulatees to know what is going on outside the simulation (or, equivalently, that basic laws must be same).

comment by John_D · 2013-04-18T04:03:43.723Z · score: 1 (1 votes) · LW(p) · GW(p)

"For us to break the fourth wall, either our creators would have to desire it or be pretty bad at running simulations."

There is also the possibility that, assuming we live in a simulation, the creators simply do not care or mind whether they are discovered or not. This would also leave open the possibility of breaking the fourth wall.

comment by roystgnr · 2013-04-17T18:12:51.889Z · score: 0 (0 votes) · LW(p) · GW(p)

Deliberate "fooling" may not even be required. Are Redstone Computers colossal and slow because Notch was trying to deceive some Minecraft denizens? It seems to simply be a necessary fact of "emulation" that any computer built out of physics X is going to be no faster than the computer required to simulate physics X.

comment by Decius · 2013-04-19T04:03:03.861Z · score: 1 (5 votes) · LW(p) · GW(p)

How could you possibly know what kinds of things are expensive in a universe that can simulate ours?

comment by TitaniumDragon · 2013-04-20T22:22:24.576Z · score: 3 (3 votes) · LW(p) · GW(p)

What matters is not knowledge but probability. Is it likely that something as complicated as our Universe would be simulated?

Is it likely that they would simulate something with vastly different rules than their own universe with such a high level of complexity?

It is possible that the Universe is a simulation, but it is highly improbable due to the difficulty and complexity inherent to doing so. Creating something of this level of complexity for non-simulation purposes is unlikely.

It is of course impossible to disprove it absolutely, but it doesn't really matter. You cannot disprove the FSM or a sufficiently dedicated staff making you believe that reality is real when they're actually setting it up around you, but it really doesn't matter because it is non-falsifiable.

If there is no reason to believe in something, then it is incorrect to believe in it, even if it happens to be true.

comment by Decius · 2013-04-21T02:49:06.472Z · score: 1 (3 votes) · LW(p) · GW(p)

Reference Dwarf Fortress.