Wednesday, November 26, 2008

The Uninterested God

It goes without saying that, in order to create the universe, God must be all-powerful, all-knowing, and basically absolute in every other way we can come up with. I say "it goes without saying" empirically, since over the course of my entire life, I've never seen anybody question it. Well, let's do something novel today. :)

The concept of simulated reality is an interesting one, and was on my mind because of the recent xkcd. A quick rundown for the non-CS majors (and ex-CS majors who never made it to Automata Theory :) in the audience: A cellular automaton (which is what the dude is doing with the rocks) has been proven to be equivalent to a Turing machine, and therefore is capable of any computation that any other Turing-complete machine is capable of. All computers are Turing-complete (well, unless you want to be a jerk about it and say that they're just finite-state machines), meaning that a guy in the desert with infinite rocks can run any program that any computer in the world can.

Now, if you accept even the weakest possible form of the simulation hypothesis - that, were we living in a simulated universe, it would pretty much look like this one - then you have to at least admit the possibility that God is, in fact, standing in a desert pushing rocks around. If we can assume perfect simulation, then there's no way for us to "peek under the covers". Or, to put it another way, if the universe is just a simulation, weoll never find out. An uninterested God is kind of depressing, but empirically, at least, it's indistinguishable from the alternative.

Let's go one step further. What if, a billion or two years ago, our God-of-rocks got bored of pushing the rocks around? After sitting around for a while, he decides to build a machine of some sort to push rocks around for him, because he's not a slacker like me and doesn't just drop projects halfway through. Now, there's no longer anybody at the helm; our universe is running completely on autopilot. Here's the neat bit, though: not only would we not notice the switchover, we wouldn't even be able to tell that a switchover had taken place. Our little machina ex deus has taken the reins without (from our perspective) skipping a beat.

Let's go one step further. Suppose that, instead of placing rocks in rows, our God-of-rocks had laid out a careful pattern of rocks at the top of an infinite hill, and then set them rolling in such a way that, as they bounced off each other, they fulfilled the rules of the cellular automaton. Now, he doesn't even have to build a machine; gravity will keep the universe running in perpetuity. There are a few key questions, though. The first, and easiest: what if the hill isn't actually infinite? What happens to us when the simulation, forgive the pun, crashes? The second: What if there was no God-of-rocks in the first place, and the rocks had just happened to be in a convenient pattern when they fell? Do we still get to exist? The third, and most brainbreaking question: There are some rocks on the other side of the hill, that fall at random. Do they end up creating a universe too? What about falling motes of dust, or flowing water molecules? Hell, since we're talking about cellular automata, what about our own cells? Could we, by our very existence, be creating simulated worlds?

Let's stop there. It's really easy to drive yourself crazy by following that line of reasoning too far.

...well, okay, one more. What makes a "real" universe any more real than a simulated one?


Kiriska said...

I love the concept of a simulated reality. Even before all that Matrix nonsense. The concept of existence, reality, etc, has always been very interesting to me, and I love reading about it and related nonsense on Wikipedia, bwahaha.

(Was that ex-CS major bit aimed at me, I wonder? You know it's funny. I don't really stop associating myself with something even though I've left it. I still use an inclusive pronoun "we" when talking about UT, CS majors, and my high school. But I won't use "we" when talking about Texas, Houston, or the South.

Thinking about this stuff and breaking my brain is fun. But the bottom line? "Reality" is whatever you perceive it to be. There is no difference between a "real" reality and a simulated one if there is no way to tell the difference while you're inside it. If you perceive something to be real, then it really don't matter whether or not it actually is. It goes back to that story about the guy that froze to death in a meat locker that wasn't actually turned on. He thought he was going to freeze to death, so he did. o_o Or something!

Frank Church said...

It's Thanksgiving holiday, and you're making me think - and about God? Argh, I'm happy in my atheism.

So, randomly: that xkcd comic reminded me of the end of Small Gods.

I'm the type of person to take your questions pretty literally...what happens if the universe crashes? Well, you know how according to quantum mechanics, chalk can fly up? or how sperm whales can appear in the air? Perhaps stuff like that would happen, except much more extreme. (My intuition says we would die, and pretty quickly. So if your pencil flies up, watch out.) No God of rocks (I'll call it Deus saxorum, that sounds classier): Sure, I think we'd still exist. Why not?

I guess we're kind of assuming there's something that maps these falling rocks onto us: an isomorphism of...what, exactly? Who created this map? It's not the deus saxorum - he's just this guy, you know.

-So, if that isomorphism is still there, I figure the rocks will create the same universe.

Random rocks - Well, again, we're kinda coming back to the isomorphism. Does it make something coherent out of these random rocks? I don't think I can say much about whatever universe the random rocks create. As for our existence creating a universe - I don't think I'm going to go there. That question just breaks my brain, and I have absolutely no idea how to respond to it anyways.

Your final question: Well, I guess there isn't anything, is there? This universe could be simulated, for all I know. And if so, kudos to the chap running all this: you're doing a pretty good job, except for that time I misplaced that roll of quarters earlier this week. I'd like that back kthx.

So, can I go back to break now? :) If you're curious, I'm staying at Swarthmore over break, because flying back would just be too much of a hassle. I shall be spending break sleeping late, listening to Mahler's 9th symphony over and over, and reading something called The Heart is a Lonely Hunter, which looks pretty good 30 pages in.

Also, this entry (along with the Mumbai bombings) has reminded me of Sacred Games, so I'll ask Ganesh Gaitonde's final question: p-static-ji, do you believe in God?

P. Static said...

kiriska: Well, I needed a category for people that were CS majors, but never took automata >_>

frank church: The mapping comes in because what's happening to the rocks is equivalent (in some abstract theoretical sense) to The Matrix, running on some computer eating Soylent Green. There's no practical difference from inside the simulation.

I'm honestly not sure whether or not I believe in God, or even what it would mean for me to. If God exists, he or she has a lot to answer for. :/

Frank Church said...

(I'm still pretty uncomfortable about the isomorphism, although I agree it's irrelevant to the actions in the simulation.)

...I'm noticing something interesting: although I think it doesn't really make a difference if the universe is Deist or if it's just rocks falling randomly, I refuse to believe it's Deist. I guess that's faith.

Also, you've hit on a question I've always wondered about: what does it mean to believe in God? I could go on for a while about that. Also, there's probably a joke in here about a former Democratic senator from Idaho and his last name. (His son became a minister. Isn't that perfect?)

You are making me want to take up blogging again. How much time must elapse before it doesn't look like I'm shamelessly copying you? :) Enjoy your turkey, or turducken, or whatever it is that you eat.

P. Static said...

And what's wrong with shameless copying? (Or: "This is shameless! This is copying!" "Shame? This is the Internet!") :D

Kiriska said...

The more blogs on the Internet, the more I have to distract myself with; therefore, you should start a blog. Copy all you want. 8D