Does God play dice with the universe?

[jack]

It only recently occurred to me that people who objected to the non-deterministic nature of quantum mechanics were *right* if you think many-worlds interpretation is correct.

It's like, since Newton, physicists had a tacit assumption:

#1. The laws of physics are deterministic.

But then we discovered lots of evidence for QM that we couldn't ignore, and many people adopted a different assumption:

#2. The evidence for QM

And these seemed contradictory, so people who had #1 were (rightly) suspicious of #2, but people who accepted #2 felt they had no choice but to reject #1.

But was also assuming without even realising:

#3: there is only one universe, not a giant number of parallel universes

And it turns out that if you drop #3, you can keep #1 and #2.

Now, I don't think that's sufficient reason by itself to assume MWI. There are lots of other paradoxes that disappear (if QM works the way we think it does, though many physicists still think that is premature). But it's interesting that we might have to drop #1 one day, but not yet.

And I knew all that _in theory_, but I'd not actually stopped to think about Einstein's "god plays dice" quip since I learned slightly more about MWI.

Comments

[ptc24]

I think Bohmian mechanics (and other global hidden variables interpretations?) lets you assume #1 and #2 and #3 - it has problems of its own though. I still haven't got my head around superdeterminism and whether it's an issue, for one.

That said, with hidden variables, you might imagine a deistic god who played dice once but who has now put the dice back in the box in order to sit back and observe the consequences.

While we're on QM, I was reading Wikipedia, and came across the wonderful German phrase Kopenhagener Geist der Quantentheorie - Geist here is presumably as in Zeitgeist.

ObChemist: "Electron density is the square of the wavefunction. 'nuff said... for chemistry, at least."

[gerald_duck]

a deistic god who played dice once

Following the rabbit down the hole, my feeling is that once one recognises a deity that is omniscient and omnipotent, for that to make any kind of sense that deity also has to exist outside of, or transcend, time and space: though in casual terms one might talk of the deity having foretold the future, it might make more sense to say that the deity is not constrained by any notion of "the present".

If so, and if that deity is a dice-roller, the question of when the dice were/are/will be rolled becomes meaningless.

[ptc24]

I have this little phrase "causal sequence"[1] for times like this; I've never really field-tested it in argument, so I don't know if the "yes, you can have the word 'time', you're welcome to it, I'll use some other term to talk about what's important here" gambit falls flat on it's face or not.

[1] Possibly for special relativity a "causal DAG" would work. General relativity in principle allows closed timelike curves which if they existed would seem to put a damper on the notion of causality, although lots of physicists seem to think that you're not going to get them due to some physics we haven't discovered yet. Maybe a working quantum gravity theory would have a really screwy theory of causality.

[jack]

a "causal DAG"

I like this description.

Although IIRC the equations work just as well whether there are cycles or not, as long as it's locally directed, we just don't know if that has actually happened, or what it would be like to live in...

[ptc24]

CTCs: I think part of the reason I want a "causal sequence/DAG" is that closed timelike curves lead you to think "why that curve and not some other?". The equations can work, but with CTCs you potentially - or possibly even necessarily - have a bad case of the creation-of-information paradox.

I think my idea of a "causal sequence" is overloaded. One use for it is in the "entropy's arrow" thought experiment; imagine a low-entropy state at some point in time, and higher-entropy states either side. You could make a case for the causal sequence to be radiating outward from that low entropy point in both time directions. However ISTR that at least some ideas of the Big Bang[1] have the idea of a point in curved spacetime where all directions are into the future, a sort of North Pole of time... but then you could use the "causal sequence" gambit to ask what was causally prior to that.

As I say, it's not an idea I'm committed to, it's one I need to... stop thinking about and start discussing.

[1] Someone suggested a better term would be Everywhere stretch - warning! YouTube!

[jack]

As I say, it's not an idea I'm committed to, it's one I need to... stop thinking about and start discussing.

Yeah, but I agree it seems promising: I don't know exactly how the different sorts of casual sequence relate, my idea is slightly different, but it sounds right that they're related but different...

closed timelike curves lead you to think "why that curve and not some other?"

Yes... this is indeed the problem. But I'm not sure if it's a worse problem than "why the universe is the way it is" anyway, or just one we're less used to discussing. After all, we don't have a good answer for "why there should be one contiguous timeline with no loops" other than "that's what we're used to".

(If either case is 'caused' by something in which the universe's timeline is embedded, that could obviously determine either, but we have no good way of knowing anything about it)

you could use the "causal sequence" gambit to ask what was causally prior to that.

Yeah, that's a good description. People's intuition says there must be something temporally prior to the big bang, and it seems we actually have no good evidence for that (or even any idea what it would mean). But they're right that something must be casually prior, in your description.

[jack]

If you imagine deity high on the omni-X scales, I think this is an obviously sensible interpretation. It's like "God's writing a novel in which we are the characters", or "God's dreaming and we are the players" or "God's playing a computer game"...

It makes several things about how people often view God make more sense, though I think it opens many other cans of worms in the process by contradicting other things people would like in the concept of "God".

the question of when the dice were/are/will be rolled becomes meaningless.

Well, it's not at a point in our timeline, but if it's fixed by a God to whom our timeline is a is unrolled like a film strip, etc, then from our perspective, it's fixed from the beginning of the universe, with all the benefits and contradictions that entails.

[ptc24]

Omni-X: I've heard of an interpretation of "omnipotent" that's reasonably low on the omni-X scale - I've heard someone say "an omnipotent god can do anything that can be done by power" - their words, or close enough. This lets tau stay stubbornly approximate to 6.28, while still leaving room for miracles etc., and I think it might just constrain God into keeping the universe consistent - no retcons, vaugeness, detail made up when needed, or other novel-writer stuff. That said, maybe you could conceive of a God who has the power to do the novel-writer stuff but who won't, possibly for ethical reasons (something to do with the Categorical Imperative, perhaps).

If you have an unconstrained novel-writer God, then you don't need to worry about unifying QM and general relativity, or indeed the compatibility of any theory with any other theory. Postmodernists would love it!

(Incidentally, why are there theists who have trouble believing in miracles?)

[jack]

"an omnipotent god can do anything that can be done by power"

Yeah, that's a good description.

I've also heard the other end of the scale: assuming any sentence starting "God can" is automatically true, even if it's so incoherent it doesn't really have a meaning attached.

I've heard a variety of ideas expressed: AFAICT there's no universally shared understanding that one is what's meant.

If you have an unconstrained novel-writer God, then you don't need to worry about unifying QM and general relativity

God certainly could rewrite the laws of physics from moment to moment. Or even just make them up as He/She went along, with no underlying physical theory at all, as almost all novelist do a little bit or a lot.

If He/She did, there would be no way to tell: a character in a retcon feels like the retcon was true all along.

But insofar as we can trust the history we're aware of, it generally seems suggestive that the more we learn about the universe, the more it looks like it's based on emergent behaviours of some underlying equations, and the less it looks like it's based on what "sounds plausible" to a personality. (I agree the opposite would be good evidence we might be in a simulation or a universe created by a personality.)

So it seems like, God or not, the best assumption is that the universe does run on rules. If I believed in this sort of God, I guess I'd imagine them running a simulation, not liking it, rewinding a bit and putting in a flood, not liking it, rewinding it a bit, putting in a self-insert character in galilee, etc... :)

[ptc24]

The making-it-up as They go along: the main thing I'm thinking of is the difficulty of unifying QM and general relativity in a satisfactory manner. A novelist God could be imagined thinking, "Hmmm, do I need QM or GR for this detail?" although if They need to pause then they're failing at a certain sort of perfection. I have a standard idea of telescopic observation of Mercury - you need GR to explain where it is and QM to explain why the rocks on the surface have the properties they have. My standard gambit is to boggle at how any bit of rock is meant to "know" whether it's meant to be behaving according to QM or GR right now; with a novelist god... that's not a problem.

Rewinding: I think this one of those cases where those ethics I alluded to come in; there's something icky about those rewinds. That said, I'm not sure it's any worse than floods. I should write my thoughts up some time.

[jack]

I don't know any of those theories at all, so I can't make an informed judgement :(

But if they still involve dropping #4 locality to retain #3, I'm cautiously pessimistic...

[gerald_duck]

Are you aware of the concept of quantum immortality? I find it intriguing. Probably even more so than Schrodinger's Cat.

Whereas Schrodinger attempted to provide an obviously absurd interpretation of quantum physics and was (as I understand it) surprised people accepted it at face value, it's much harder to accept any theory that implies quantum immortality.

Personally, on an unreasoned, emotive level, my instinct is that sooner or later people will start modelling QM as chaotic rather than fundamentally unknowable. That would square #1 with #2 in a more satisfactory way than MWI.

[jack]

my instinct is that sooner or later people will start modelling QM as chaotic rather than fundamentally unknowable. That would square #1 with #2 in a more satisfactory way than MWI.

Hm. I agree that whenever anything looks random, "it's actually a chaotic system based on deterministic rules" is almost always the right guess.

But from a point of view of QM, that sounds exactly like the reasoning which led people to http://en.wikipedia.org/wiki/Hidden_variable_theory. That is, "if it LOOKS random, it may be determined by something we can't see". And this is one possible source for those "things we can't see".

But I understood that http://en.wikipedia.org/wiki/Bell's_theorem#Importance_of_the_theorem said that you couldn't have hidden variables of any sort set up in advance that explain the apparent "action at a distance" of QM. That's either:

* explained by both possibilities happening in different "worlds" (ie. waveform evolves into multiple non-interacting parts which all evolve normally)
* or the hidden information travels faster than light (which is an assumption we really think we're wrong to drop),
* or we ignore the physical reality and resort to the copenhagen interpretation
* or there's some resolution to the apparent contradiction we haven't thought of, by dropping some further assumption we've not considered...?

If that dichotomy is true, MWI seems by far the best get-out, since the problem is "surely that can't possibly be true, it's too ridiculous" which has previously shown to be a bad guide to physical reality, and everything else has worse problems. But have I misinterpreted the problems of hidden variable theory? Or do they not apply to a chaotic system for some reason I don't understand?

[jack]

Are you aware of the concept of quantum immortality? I find it intriguing.

I've read about it, but don't have any good answers. My instinct is that the problem comes in our understanding of "how to translate physical reality to the subjective experience of being a conscious brain in that reality" not in our understanding of the underlying physical reality, but I'm not sure.

Eg. I think I've seen similar thought experiments that could happen in a purely classical world, which if true says this is a philosophical problem we need to understand, but QM just makes more common, isn't conceptually related to. But I'm not sure.