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The physics of reality
December 3, 2005 6:35 PM   Subscribe

Does God Play Dice?
posted by Gyan (104 comments total)

 
Yup.
posted by MetaMonkey at 6:47 PM on December 3, 2005


I think the refusal to accept that predictions can only apply to populations is pretty caveman.
posted by scarabic at 6:49 PM on December 3, 2005


This is the original quote, from a letter Einstein to Max Born in 1926.

"Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. Quantum theory says a lot, but does not really bring us any closer to the secret of the Old One. I, at any rate, am convinced that He (God) does not throw dice."
posted by nanojath at 6:54 PM on December 3, 2005


"Not only does God definitely play dice, but He sometimes confuses us by throwing them where they can't be seen." -- Stephen Hawking
posted by allen.spaulding at 6:58 PM on December 3, 2005


I'm afraid so. But I wouldn't put it past him to cheat now and again.
posted by Opposite George at 6:59 PM on December 3, 2005


er, Him
Please don't send me to Hell Please don't send me to Hell Please don't send me to Hell Please don't send me to Hell!
posted by Opposite George at 7:00 PM on December 3, 2005


PARCHESSIE... that or Chutes and Ladders
posted by edgeways at 7:00 PM on December 3, 2005


For all your pleading, She just might.
posted by stirfry at 7:02 PM on December 3, 2005


Does God Play Dice?

no. he plays billiards.
posted by quonsar at 7:09 PM on December 3, 2005


Don't tell Rothko. He thinks that science, including physics, sees the universe as deterministic.
posted by Ethereal Bligh at 7:19 PM on December 3, 2005


Yup. And they're loaded.
posted by postmodernmillie at 7:23 PM on December 3, 2005


Everytime I am high or drunk there's some damn physics post on here and I get confused for weeks.

The 80s iTunes music feed isn't helping either.

I contributed absolutely nothing to this post, I guess I will head over to fark now.
posted by evilelvis at 7:28 PM on December 3, 2005


What I'd like to know is, whom does He ask to blow on 'em?
posted by rob511 at 7:28 PM on December 3, 2005


Time to bring back Luke Rhinehart's The Diceman...
posted by growabrain at 7:30 PM on December 3, 2005


God?
posted by Eideteker at 7:33 PM on December 3, 2005


Time to bring back Luke Rhinehart's The Diceman...

Hickory Dickory Dock... Oh nevermind.

Huh.. huh huh... Rob511 said "blow." Huh huh...
posted by Opposite George at 7:34 PM on December 3, 2005


Many Worlds (and equivalent non-collapse) interpretations of QM still leave room for a completely deterministic universe.
posted by justkevin at 7:37 PM on December 3, 2005


Yes, and the bitch CHEATS, too.
posted by ottereroticist at 7:43 PM on December 3, 2005


"A system that requires more than this quantity of information to describe it in detail is so complex that the normal mathematical laws of physics cannot be applied to arbitrary precision without exceeding the information capacity of the universe. Cosmology thus imposes a small but irreducible uncertainty, or fuzziness, in the operation of physical laws."

Ooh, that is tremendously interesting. I've followed complexity theory for a long, long time; but this epistemological physical foundation for a definition of "complexity" is something I've not seen before and has enormous intuitive appeal to me. If nothing else, it's not so damned hand-wavy. My own interest has long been an information theory approach to physics and so you can see why I like this idea so much.

I find it interesting the Einstein was so wrong on QM. He spent a lot of time in his later years trying to poke holes in it and the "EPR paradox" is a famous example. There's a lot of junk popular science built around that thought experiment—how they (Einstein, Podolsky, and Rosen) were wrong about it is very subtle and I think most laypeople don't get it. Anyway, the reason Einstein's resistance to QM is interesting is because he's the father of one great physical theory who was resistant to another. QM in its modern form is a hugely successful theory, just as Relativity is.

On preview: "Many Worlds (and equivalent non-collapse) interpretations of QM still leave room for a completely deterministic universe."

Yes, but that's not what Rothko had in mind. I see the appeal in the many worlds interpretation, but to my mind it's just replacing one mystery with another.
posted by Ethereal Bligh at 7:48 PM on December 3, 2005


I rolled a ten. Is that good?
posted by jenovus at 7:57 PM on December 3, 2005


"God does not play dice with the universe. But if he did, he'd play Don't Pass and take full odds." -- Einstein

"Not only does God play dice with the uinverse, he bets the field. And wins." -- Hawking.
posted by zanni at 7:58 PM on December 3, 2005


Many Worlds (and equivalent non-collapse) interpretations of QM still leave room for a completely deterministic universe.

Moreover, the only thing non-deterministic about the collapse interpretations, that I can tell (IANA physicist), is the collapse of the wave function. And no one has rigorously defined the conditions that cause the collapse to occur.

Non-locality has been shown. Non-deterministic is still... undetermined.
posted by Bort at 8:03 PM on December 3, 2005


MetaFilter: I contributed absolutely nothing to this post, I guess I will head over to fark now.
posted by homunculus at 8:10 PM on December 3, 2005


He always rolls 2d+20. It's just his way.
posted by blue_beetle at 8:15 PM on December 3, 2005


Gauge invariance re-interpreted as information loss between a truly Planck-scale theory and the theory of quantum particles ... that's briliant!

T'Hooft's name is also really fun to pronounce.
posted by growli at 8:18 PM on December 3, 2005


Are space and time discrete?

Duh. The universe is just a big computer simulation. Hasn't he seen "The Matrix?"
posted by ZenMasterThis at 8:35 PM on December 3, 2005


Metafilter: Somehow, by preferencing another users comment with "Metafilter:" I add something to this thread.
posted by allen.spaulding at 8:39 PM on December 3, 2005


Cosmology thus imposes a small but irreducible uncertainty, or fuzziness, in the operation of physical laws.

is he certain about this?
posted by carsonb at 8:49 PM on December 3, 2005


Where's TurtlesAllTheWayDown? They'll settle this question once and for all.
posted by WolfDaddy at 8:58 PM on December 3, 2005


I PUT ON MY ROBES AND WIZARD HAT!
posted by loquacious at 9:06 PM on December 3, 2005


Okay, can we stop with the stupid dice jokes already? Nobody except Ethereal Bligh has even seriously discussed the article. IANA physicist either, but I find the topic fascinating, so if there are any physicists in the house, it would be great to have them elaborate.
posted by blue shadows at 9:12 PM on December 3, 2005


Metafilter: Attempt at droll humor in the form of a pithy jab fails miserably.
posted by notsnot at 9:14 PM on December 3, 2005


"Moreover, the only thing non-deterministic about the collapse interpretations, that I can tell (IANA physicist), is the collapse of the wave function. And no one has rigorously defined the conditions that cause the collapse to occur.

"Non-locality has been shown. Non-deterministic is still... undetermined."


The collapse is hardly a triviality. "Determinism" has more philosophical weight than emprical weight. That is to say, determinism has always been about the ultimate nature of the universe and not some rigorous quality because even under the best of conditions there is experimental error. The eighteenth and nineteenth century determinists were making assumptions about the nature of reality on the basis of their success at reductively and deterministically describing and predicting phenomena that had previously remained opaque. Early atomic theory in chemistry laid a philosophical foundation for a completely mechanistic and deterministic description of reality built around the classical mechanics that had been so widly successful. This was not just a worldview of those scientists investigating this, it was a defining movement of western thought.

In this sense, then, QM radically challenged this view. (And here, too, there is a relationship of the physical theories to a contemporary cultural movement.) The collapse of the waveform is inherent in the development of this physics and non-collapse interpretations are retrofits. We experience the world as if the waveforms are collapsing—and the Copenhagen interpretation describes that experience of the universe quite successfully (but not deterministically). It just doesn't seem to care much for the question of why the waveform collapses. I think Bohr saw that "why" (or even the "how" beyond what is simple obvious) as a meaningless question.

In my non-physicist opinion, the competing ontologies of indeterminism versus determinism within the context of modern physics and popular culture is exemplified by Heisenberg Uncertainty. The dominant lay comprehension of HU is that you can't measure something without affecting it; thus there is a mechanistic limitation on the extent of possible knowledge. I think that some physicists may see HU the same way—probably the experimentalists—but I'm pretty sure most of the theorists see HU as an epistemological principle and not merely a mechanistic principle.

Human intuition is by nature deterministically-oriented. This is true if for no other reason than that it is teologically centered, as well. The mechanistic interpretation of HU is almost immediately intuitively accessible while the epistemological interpretation much more challenging. And thus also are the competing interpretations of QM in the popular mind as well as within physics. The layperson quite strongly wants a deterministic view. Not because they want a world without choice—quite the contrary. The human intuition is that of a universe that is deterministic with the exception of human consciousness and in that regard the many-worlds view is comforting. In it, the physical universe is nicely deterministic while our experience of it can only be described metaphysically.

But I think the mechanistic comprehending of HU is misguided and thus I think, similarly in quality, are the non-collapse views of QM.
posted by Ethereal Bligh at 9:30 PM on December 3, 2005


Sorry, Keith M. Ellis, I'd respond to your trolling but I was out getting drunk with my partner and playing pool. Whereupon we will now be going to bed. Enjoy the rest of your night, Keith.
posted by Rothko at 9:30 PM on December 3, 2005


Quantum mechanics is perplexing, and likely to remain so. The departure from ordinary classical intuition that came with the emergence of quantum mechanics is almost surely irrevocable. An improved future theory, if there is one, will probably only lead us farther afield.

Well, that would explain all of the non-comment comments so far.
posted by spock at 9:31 PM on December 3, 2005


clikkity-clakkity-clakkity-CLACK!
posted by scarabic at 9:32 PM on December 3, 2005


"I'd respond to your trolling..."

Would you perhaps learn the meaning of the word "troll"? Hint: it doesn't mean "someone who disagrees with Alex".
posted by Ethereal Bligh at 9:34 PM on December 3, 2005


blue shadows: :(
posted by jenovus at 9:42 PM on December 3, 2005


Ethereal Bligh : "But I think the mechanistic comprehending of HU is misguided"

Why?
posted by Gyan at 9:47 PM on December 3, 2005


Because implicit in that mechanistic view is the assumption that both qualities do exist simulataneously, we just can't measure both. I think HU says something more fundamental. That's how I learned it (not formally); that's how I strongly intuit it; and that's how I think most particle physicists see it (certainly those I've known). I think this view is validated if you go and look at what the theorists of the era—like Bohr—had to say at that time when physicists cared deeply about the philosophical implications of QM, and which is the context in which the Copenhagen interpretation arose.
posted by Ethereal Bligh at 10:01 PM on December 3, 2005


Would you perhaps learn the meaning of the word "troll"? Hint: it doesn't mean "someone who disagrees with Alex".

Hey jackass. What 'trolling' is is bringing up someone's named randomly in order to bait them.
posted by xmutex at 10:08 PM on December 3, 2005


Your latest comment doesn't add anything new. Why do you think that HU says something more fundamental? Intuition?
posted by Gyan at 10:08 PM on December 3, 2005



posted by spock at 10:10 PM on December 3, 2005


"...Essentially, this is due to the phenomenon we call quantum interference between histories, which is due, in turn, to the way we calculate the quantum measure of a bunch of histories as the square of the sum of the amplitudes of the histories in the bunch. When you add some numbers and then square the result, you do not get the sum of the squares - there are also cross terms, which are the expression of the interference that spoils the interpretation as probabilities." — Fay Dowker

This completely lost me.

The rest of the article is fascinating though, thank you Gyan.

Ethereal Bligh elucidates "I think HU says something more fundamental."

Yes?
posted by Colloquial Collision at 10:22 PM on December 3, 2005


I think this view is validated if you go and look at what the theorists of the era—like Bohr—had to say

"(Heisenberg, 1927, p. 197), where [Heisenberg] discusses the idea that, behind our observational data, there might still exist a hidden reality in which quantum systems have definite values for position and momentum, unaffected by the uncertainty relations" - from here

"Einstein was by no means alone in denying that quantum mechanics precludes determinism. Erwin Schroedinger himself believed his equations to be completely deterministic -- and maintained that view his whole life." - from here
posted by Bort at 10:26 PM on December 3, 2005


"Hey jackass. What 'trolling' is is bringing up someone's named randomly in order to bait them."

Hey, fuckwit. What "trolling" is is either a) the classic meaning: cleverly saying something risible insincerely to provoke a response ("what's the state capitol of Canada?"); or b) contemporary meaning: saying risible things in order to provoke a flamewar.

Let's see: did I bring up his name "randomly"? Nope. It was deliberate and it was in reference to things that he wrote here, in metafilter, just a few days ago on exactly this topic. That's not random. Was it in order to bait him? Nope. I didn't write it with him reading it in mind. And, again, even if I had, it wouldn't be "trolling".
posted by Ethereal Bligh at 10:28 PM on December 3, 2005


EB, I once wrote a song about Heisenberg being a big pussy. All this 'we can't know' bullshit is pure escapism. In my opinion Bohr's model of the atom was and is correct and all the rest of the arguments are just the product of grad students trying for some kind of job security. Quantum mechanics is complete and utter bullshit.

The so called sub-atomic particles are artifacts; they do not exist in the natural world. In the same way that we can use supercolliders to create elements in the periodic table that do not occur in nature on the high side you can 'break' atoms to create dinguses on the low side of the scale.

Vis-a-viz rolling dice; God is... so yes, yes he does.
posted by Mr T at 10:35 PM on December 3, 2005


That page, 3.1, third paragraph:

"On the one hand, Bohr was quite enthusiastic about Heisenberg's ideas which seemed to fit wonderfully with his own thinking. Indeed, in his subsequent work, Bohr always presented the uncertainty relations as the symbolic expression of his complementarity viewpoint. On the other hand, he criticized Heisenberg severely for his suggestion that these relations were due to discontinuous changes occurring during a measurement process. Rather, Bohr argued, their proper derivation should start from the indispensability of both particle and wave concepts. He pointed out that the uncertainties in the experiment did not exclusively arise from the discontinuities but also from the fact that in the experiment we need to take into account both the particle theory and the wave theory. It is not so much the unknown disturbance which renders the momentum of the electron uncertain but rather the fact that the position and the momentum of the electron cannot be simultaneously defined in this experiment."

Also:

"The experimental context, rather than changing or disturbing pre-existing properties of the object, defines what can meaningfully be said about the object."

And especially, quoting Bohr:

"[…] a sentence like "we cannot know both the momentum and the position of an atomic object" raises at once questions as to the physical reality of two such attributes of the object, which can be answered only by referring to the mutual exclusive conditions for an unambiguous use of space-time concepts, on the one hand, and dynamical conservation laws on the other hand. (Bohr, 1948, p. 315; also Bohr 1949, p. 211)
It would in particular not be out of place in this connection to warn against a misunderstanding likely to arise when one tries to express the content of Heisenberg's well-known indeterminacy relation by such a statement as ‘the position and momentum of a particle cannot simultaneously be measured with arbitrary accuracy’. According to such a formulation it would appear as though we had to do with some arbitrary renunciation of the measurement of either the one or the other of two well-defined attributes of the object, which would not preclude the possibility of a future theory taking both attributes into account on the lines of the classical physics. (Bohr 1937, p. 292)"


...and the author writes in his conclusion:

"Indeed, this minimal interpretation leaves open whether it makes sense to attribute precise values of position and momentum to an individual system. Some interpretations of quantum mechanics, e.g. Heisenberg and Bohr, deny this; while others, e.g. the interpretation of de Broglie and Bohm insist that each individual system has a definite position and momentum."
posted by Ethereal Bligh at 10:43 PM on December 3, 2005


Ethereal Bligh: My own interest has long been an information theory approach to physics and so you can see why I like this idea so much.

The discussion of black holes in Rothko's recent question led me to look into the meaning of "information" in the quantum mechanical sense just today... I have been very bothered by the notion of conservation of information that is brought up in conjunction with Hawking's black hole bet, in particular this:
At first, the notion that information, like energy, cannot be destroyed seems like a dubious pronouncement. Tear out a page from a book and drop it into a fire and the information seems to vanish. After all, the second law of thermodynamics says that an orderly system (like a page arrayed with words and numbers) will inevitably become more and more disordered, increasing in entropy, until it eventually becomes a meaningless mess. In principle, however, information doesn't truly disappear. The markings of ink on the page are preserved in the way the flame flickers and the smoke curls, in the ripples of heat radiating through the air and the pattern of the ashes delicately falling to the ground. The practical difficulties of retrieving this subtle data and restoring the original order give the second law its vaunted power. But in theory one could reconstruct every paragraph. The information is supposed to be out there in the universe somewhere.
Rothko's question, and the answers, all suggest that Hawking radiation is random, which doesn't resolve well with the idea that writing on a burned piece of paper can be reconstructed.

Now that I have looked into it a bit more I think I understand the problem. I think information in the quantum mechanical sense isn't actually information at all, more like complexity. I think the entire discussion about the burned paper is a completely false analogy. I wonder where the notion originated, and I kind of doubt that it comes from a physicist at all.

So anyway, while looking into it I came across the wikipedia article Physical Information which led me to a promising but inscrutable article on Fisher Information... Something I will look into more one day I guess. Any good links on the subject would be appreciated.

Finally, it is interesting to take a look at what comes up when you look for Law of Conservation of Information...
posted by Chuckles at 10:52 PM on December 3, 2005


When respectable physicists are reduced to desperate handwaving and speculation about how things actually work, it's clearly time for the real crackpots to come out of the woodwork and contribute. So here's my own personal take on the likely shape of a Theory of Everything:

We won't ever get a perfect one.

The reasoning is as follows: Only what has happened, has happened; only what is happening, is happening; and only what will happen, will happen. This, being tautological, is clearly true.

Therefore, the probability that something other than what actually will happen does happen is always precisely zero. Another way of saying that is that possibilities are illusory, and simply reflect our ignorance about what is actually going to happen.

The laws of physics are a distillation - a compression, if you like - of centuries of patient observation. They describe the shape of reality down to very fine levels of detail, and allow us to make confident predictions about what is going to happen - provided we control the conditions of our observables well enough. If we don't, our experiments/designs/systems get messed up by "outside influences" - that is, things that are too complicated to be practicable to include within the mathematical framework of our prediction models.

One of the fundamental laws of physics is that like causes produce like effects. This is often strengthened in people's minds to "identical causes must produce identical effects". But if you think about that for a while, it will become apparent that you can't have two different experiments with identical conditions; if you did, they'd be the same experiment. Therefore, notions involving identical causes are not very useful, and we're better off sticking with notions about like causes.

Which is why it makes perfect sense to me that quantum mechanics makes only statistical predictions. The objects that QM makes predictions about are not, in fact, observables; they're inferrables. Nobody has ever observed an electron, or a photon, or a proton, or a quark; these are imaginary objects whose properties we think we understand, but in my view this is mainly because we made them up in order to make sense of other things.

And when we're dealing with made-up observables, it shouldn't really shock us that they don't have all the properties we generally associate with things we can observe - like, for example, the property of continuous existence over time.

It strikes me as erroneous to think of an electron as a little bullet-like object that has a trajectory and must therefore logically pass through one slit or the other. I'm perfectly comfortable with electrons that don't retain any of their properties at all - including such seemingly fundamental properties as size and location - between the times we see them interacting with other things, like electron guns and phosphor screens.

I mean, the little bastards are all supposed to be identical. Personally I'm suspicious of that; if there's a bunch of things, and the only way you can tell them apart is that some of them are over here and the others are over there, I'm more inclined to view them as more process- or effect-like than object-like.

The business with the collapse of the wave function and the quantum/classical dichotomy strikes me as a bit of a non-starter, as paradoxes go. The wave function collapses when we collapse it in order to fit a prediction to our observables. The wave function is not an object within our experiment; it's part of our predictive model about the experiment, and as long as we play by the rules we can collapse it whenever it's useful to do so. The boundary between quantum and classical worlds is fuzzy and situation-dependent, and occurs where the errors caused by applying classical models to our observables cause less trouble than the impracticability of actually applying the requisite insanely complicated wave function.

The whole many-worlds thing strikes me as another fable written by people who have lost the ability to distinguish the map from the territory; people who can say things like "Under all conceivable circumstances, the laws of nature should dictate how the universe evolves" with apparent conviction. ISTM that the laws of nature dictate precisely squat, and that the fact that we can't always tell exactly what nature is about to do next is nothing to get too upset about.

So I like Davies's point about maximum computable complexity; it fits nicely with my prejudices. ISTM that there is always going to be some level of system complexity at which it's faster to see what a system actually does than it is to predict its behavior in advance, and that this fact puts an upper bound on how good a Theory of Everything can possibly be.

I also agree with his intuitions about quantum computing. I suspect that despite the hype, quantum computers will be never be significantly more useful for cracking NP-complete problems than fast conventional machines - there will be an upper bound on what's computable with a given amount of time and energy regardless of how it's done, and the more capacity you build into a quantum computer, the less reliable it will become; at some point, you'll need to check your results with a slow old von Neumann machine in order to have confidence that they're right.

OK, now it's time for some serious handwaving.

Flabdablet's Chemically Augmented Picture of Everything goes like this: everything does everything all at once, all the time. Most of that just cancels itself out pretty damn quick; the only bits of it that we can observe are the massively improbable regions of self-consistency. In other words, most of the universe is busy shooting its own grandfather at all conceivable scales, and everything we can observe is just the stuff that's fortunate enough to be staying out of the lines of fire. If you have the chops to work up something mathematically rigorous with only this as the starting assumption, there's clearly a Nobel in it for you and you're welcome to it.

't Hooft is indeed fun to say. I never expected a respectable physicist to be named for the sound of a stoner collapsing into a beanbag.
posted by flabdablet at 11:01 PM on December 3, 2005


I went to look for the song but alas I think it resides on a dead hard drive in my closet. While looking for it I did find this; just for you EB:

I sure don't have a will of my own
if I did I would make a run for my home
but now all I do is drift and pray
that some day the wind will blow my way

(chorus)
someday
I'll fly
I'll fly
I'll drift on away

You know I have to go wherever the wind blows
but I'll probably drift down to New Mexico
I just hope I don't land in a pueblo
cuz you know those indians don't like the gringos

chorus

Taos is pretty nice and Santa Fe is OK
It's a great place to visit on a sunny Winter day
it's just I want to be where I want'a go
and right now that sure ain't New Mexico

chorus

-me 1998
posted by Mr T at 11:09 PM on December 3, 2005


Chuckles: I bought Frieden's book, Physics from Fisher Information, because I thought it sounded interesting; I have yet to get anything useful from it because I don't have the requisite mathematical background. If you do, and you want it, I'll send it to you for the cost of postage.
posted by flabdablet at 11:12 PM on December 3, 2005


When respectable physicists are reduced to desperate handwaving and speculation about how things actually work, it's clearly time for the real crackpots to come out of the woodwork and contribute.

Comedy Gold. I salute you!

*drops pants*

*faints*
posted by Mr T at 11:25 PM on December 3, 2005


Thanks flabdablet, I would love to give it a try!

I can't be sure weather I have the required background to be honest, I have studied lots of information theory through engineering, but I didn't find the article I linked particularly understandable... That might just be laziness of the moment, it requires more intense attention than I am giving it, and the book must be more thorough. Anyway, my email is in my profile. Thanks again!
posted by Chuckles at 11:37 PM on December 3, 2005


Sorry, Keith. I think Alex can be pretty strident and annoying and all that, but it was pretty juvenile of you to take a swipe at him before he even posted in this thread. Even if your behavior doesn't meet the dictionary definition of "trolling," it's still awfully rich of you to feign that much indignation at being called on it.

I'll give you the benefit of the doubt and assume you've had half as much to drink as I have tonight. Sweet dreams, hot stuff.
posted by joe lisboa at 11:50 PM on December 3, 2005


From the page Chuckles linked to:
Current astronomical data suggests that the universe is "open", i.e. there is insufficient gravitational pull inward to overcome the outward motion of the outermost galaxies. Most (but not all) galaxies show red-shifted spectra and hence an ever-outward motion. If these trends continue indefinitely the universe will ultimately "die", all particles infinitely spaced apart and at temperature zero. Moreover, there is no apparent mechanism available for reversing the expansion trend. So-called "dark energy" is thought to be its cause, but no one knows the nature of this energy. Still, an open universe would violate many basic concepts of theoretical astronomy. Hence, observation and theory disagree on this effect. Many theoreticians (e.g., [13]) feel that there must be a mechanism for reversing the expansion. We agree with them, based upon the following indirect, but knowledge-based, reasoning as in [1] and [10].

An unbounded expansion of the universe would rule out cyclical repetition of its states, causing the current state of the universe to exist but once. This would confer a "special" status upon the current state. However, since Copernicus, astronomy has regarded any current state as "typical" and not special (the "Copernican principle"). Also, occurring but once, the state would be extremely rare, so rare as to have vanishing probability of occurrence. How could we then exist?

Given these contradictions, the universe must eventually reverse its expansion and collapse, subsequently expanding and contracting endlessly. How can this transpire?

The success of the EPI approach in constructing physics suggests that natural law really is knowledge-based. Therefore, man - the ultimate seeker and amasser of knowledge - must have a key role to play in the evolution of the universe. That is, knowledge really is power, and hence knowledge must eventually give rise to an effective force.
Paraphrase: Observation and theory disagree. But theory must ultimately be correct; therefore I have a simply enormous willy!

It breaks my heart to see a boy that young go bad.
posted by flabdablet at 11:57 PM on December 3, 2005


Heh, I didn't read that part, it certainly is disheartening. But then look at his use of highlights...
posted by Chuckles at 12:10 AM on December 4, 2005


It's totally Web 2.0!
posted by Chuckles at 12:11 AM on December 4, 2005


Ooh, that is tremendously interesting. I've followed complexity theory for a long, long time; but this epistemological physical foundation for a definition of "complexity" is something I've not seen before and has enormous intuitive appeal to me.

Really? I've heard people say stuff like "This crypto cannot be broken before the universe expires" for a while.
posted by delmoi at 12:42 AM on December 4, 2005


Okay, can we stop with the stupid dice jokes already? Nobody except Ethereal Bligh has even seriously discussed the article. IANA physicist either, but I find the topic fascinating, so if there are any physicists in the house, it would be great to have them elaborate.

Well, given how few people in the world actualy understand QM what do you expect?

Then there are all the people who run not smart enough to understand that they don't understand it...
posted by delmoi at 12:45 AM on December 4, 2005


Quanta le gusta?
posted by longsleeves at 1:27 AM on December 4, 2005


God is dice.
posted by provolot at 3:01 AM on December 4, 2005


Actually, provolot, God is Dios.
posted by graventy at 3:34 AM on December 4, 2005


For something more about information as an active ingredient in physics you might want check this out, I apologize for not being able to turn it into an actual link.

http://www.rialian.com/rnboyd/quantum&beyond.htm
posted by donfactor at 6:11 AM on December 4, 2005


...and the author writes in his conclusion:

"Indeed, this minimal interpretation leaves open whether it makes sense to attribute precise values of position and momentum to an individual system. Some interpretations of quantum mechanics, e.g. Heisenberg and Bohr, deny this; while others, e.g. the interpretation of de Broglie and Bohm insist that each individual system has a definite position and momentum."


So, in summary, even the originators of QM did not agree about some of the implication of the theory. Such as if a particle has both a precise position and momentum, or whether the universe is deterministic.

I'm not arguing for determinism, although I'm biased in that direction. I'm arguing that its undecided.
posted by Bort at 7:30 AM on December 4, 2005


Could you guys do the rest of us a favor? I dont'e keep up with the IRL names of you mouthy guys, so can we keep with screen names? "keith"? "alex"?who?
posted by notsnot at 7:37 AM on December 4, 2005


"...it's still awfully rich of you to feign that much indignation at being called on it."

Well, Gyan emailed me about this, too. I'd love to admit that I was wrong and you guys are right, but I honestly didn't write my comment for the purporse of trolling Rothko. I just wrote it—it was impulsive because I'm very irritated with Rothko about this subject.

Anyway, I apologize for it, and I apologize to Rothko, it was petty of me.
posted by Ethereal Bligh at 7:44 AM on December 4, 2005


provolot's answer should be expanded..

Does God play dice?

Nay, God is the dice.
--
Interesting thread though, perhaps a response is worthwhile, but certainly not till after coffer.
posted by wah at 7:51 AM on December 4, 2005


And God rolls a 42!
posted by kozad at 7:53 AM on December 4, 2005


I apologize to Rothko, it was petty of me.

It was petty of you, Keith. Apology accepted.

I just wrote it—it was impulsive because I'm very irritated with Rothko about this subject.

Go get laid. The universe will tick along just fine regardless of our opinions about it.
posted by Rothko at 8:36 AM on December 4, 2005


And Keith: If the universe is not deterministic, it would not otherwise be chugging along to its inevitable heat death.

Our inability to predict the future does not mean the universe we live in isn't deterministic, it just means there are limits to our predictive abilities and knowledge.
posted by Rothko at 8:50 AM on December 4, 2005


i'm beginning to think that at least one person and possibly two need a time out
posted by pyramid termite at 8:56 AM on December 4, 2005


The human intuition is that of a universe that is deterministic with the exception of human consciousness - Ethereal Bligh

Most people - especially the intuitive type - also seem to be happy talking about effects caused by various Gods and Goddesses, luck, karma, the spirits of places and trees, and various other (potentially) conscious entities. (Sylphs from the fifth dimension, even, in some cases, but that's another thread.)

So the general human intuition is of a universe which includes effects caused by human and non-human consciousness.

We also intuitively talk about "What if..." scenarios, suggesting the idea of a near-infinite number of parallel universes in the past, present, and future, as postulated in some interpretations of QM.

I also like flabdablet's handwaving worldview. It ties in well with a crackpot psychology theory I've held for some time ... that is, that our brains are constantly thinking all possible thoughts, only a tiny minority of which achieve sufficient coherence and longevity for us to notice and remember (become aware) of them.

Given the human brain's astounding capacity for predicting the universe's local behavior, it would be unsurprising if the two systems had similar underlying design principles; and even less surprising if, more weakly, our brains could only conceive of the universe as something which functions in the same way as themselves.

What the Universe actually is, is almost certainly beyond the capacity of our brains to understand. But at least we should be able to describe (and hopefully enjoy) the best model we can possibly intuit.

So, balls on the chopping board, my model looks like this: Lots of conscious entities roll lots of dice. For every roll, multiple Universes are created, one for each possible result. Each resulting Universe includes, naturally, copies of all the consciousnesses from the pre-branch Universe, differentiated from each other only by the effects of the most recent event. The consciousness I currently inhabit is thus simply the one in which these particular results have been obtained.

Each conscious entity in the Multiverse can thus be completely specified as the list of probabilistic choice-universes it has inhabited through history on its route from the Origin (the point where the first quantum branch occurred, and the first consciousness divided into two possible consciousnesses).

In fact, the terms "consciousness", "universe", and "choice" are, in this model, completely interchangeable. Which is kind of cute. Also, each consciousness is directly descended from the original consciousness, and we differ from our siblings only as a result of chance.

As you may have gathered, IANA physicist. :-))
posted by cleardawn at 9:07 AM on December 4, 2005


I am a physicist and would be glad to answer some questions about Quantum Mechanics. Also, I would like to state that determinism means different things to different people. Personally I see the Universe as determinstic in the sense that for every effect there is a cause.
posted by ozomatli at 9:26 AM on December 4, 2005


A physics grad student has some strong views on some of the things discussed here.
posted by Gyan at 9:50 AM on December 4, 2005


ozomatli:

Do you subscribe to a particular interpretation of QM?

I remember when I first started reading about QM the thing that bothered me the most was randomness. I felt that a truly random event implied that a "decision" was being made and that information was entering the system from nowhere.
posted by justkevin at 10:09 AM on December 4, 2005


Who knew that MetaChat was more of an exclusive club than MetaFilter (does this have something to do with the cabal?)...

Anyway, since I can't post this summary to the thread Gyan meantioned over there, I will just post it here...

By my recollection (and my participation) the recent debate has run through the following threads:
  1. Nov 7 question by jswanson19: Quantum Physics, active until Nov 14, with a few posts later.
  2. Nov 24 thread by y2karl: Is God An Accident?, active until Nov 28.
  3. Dec 2 question by Rothko: The end of time, active until Dec 3.
  4. Dec 3 thread by Gyan: The physics of reality (aka Does God Play Dice?), currently active, I guess.
posted by Chuckles at 11:38 AM on December 4, 2005


I think we should be clear on what determinist means. It can mean a variety of things in casual conversation. But in the context of the philosophical implications of physics, it has a specific meaning. I wrote this elsewhere, but I'll repeat it here:
My expertise is in the philosophy and history of science, which is, in fact, the context for the argument about "determinism", really. As the physicist ozmatli says [here], "Also, I would like to state that determinism means different things to different people.", which is obviously true; but the thing is that in the context of the larger philosophical debate in the history of western science "determinism" has a specific meaning. That meaning specifically is that classical mechanics completely describes the universe and, as such, every event in the universe, large or small, is completely determined by the universe's history back to its origin. This is clearly not true in the context of QM.
Rothko writes:
"Our inability to predict the future does not mean the universe we live in isn't deterministic, it just means there are limits to our predictive abilities and knowledge."
...which is necessarily true as a literal statement. However, this isn't the claim I, or anyone, was making. My claim is that our "inability to predict the future" is a result of the nature of the universe itself, that no one, within this universe could, even theoretically, "predict the future [of the universe in all its detail]" because of the implications of QM. Rothko's assertion clearly implies a deterministic universe that exists but is outside our intellectual grasp; QM itself, as it stands, describes a universe where that determinism doesn't exist, even hypothetically. Yes, there are/were physicists, Einstein chief among them, who want/wanted a physics beyond QM that described the deterministic universe that classical mechanics showed us. There are various ways in which such a conception could be—one of them is Everett's "many-worlds interpretation" which describes a "mutiverse" where the waveform doesn't collapse and thus is deterministic and it is only our consciousness[es], making its way along a specific-to-a-universe path through this multiverse which is indeterminate. Another is simply asserting what Einstein asserted: that there is a physics we haven't yet discovered which "corrects" this flaw in QM. And others. I don't think String Theory is determinist; but it remains opaque to me, as it is to pretty much everyone. :)

Nevertheless, the dominant view among particle theorists is that QM is essentially correct and the universe is not deterministic in the classical mechanics sense.

Rothko also says:
"If the universe is not deterministic, it would not otherwise be chugging along to its inevitable heat death."
Well, no, in a variety of ways. One is best described by quoting "Sam", of MetaChat, the aforementioned physicist Gyan pointed us to. This was in an email to me, but I'll take a risk and assume he won't mind me quoting him:
"the fact that the universe is headed inexorably toward a known, given state, and the fact that it currently exists in some given state DO NOT together constitute proof that it is a deterministic system. the classic proof by contradiction is the coffee cup full of hot coffee: we know when i pour it that it's at 212F. and we know it ends up at room temperature. but it's a chaotic system in-between -- it's much easier for us to say what temperature the cup will be at in ten hours than in ten seconds. the small fluctuations that occur in the interim have huge effects on subsequent evolution, and although there is an attractor in the phase space, the coffee can take a weird path to get there."
Another is pointing out that, until very recently, this inevitable heat death Rothko speaks of wasn't inevitable: it wasn't known if the universe, in terms of GR, was closed or open and thus whether it was headed to a heat death or a "big crunch". (We only recently—within the last ten years—know that the universe is either perfectly flat or slightly open.)

And of course another is to point out that Rothko's statement is essentially a non sequitor—one quality of a thing among many being "determined" does not wholly "deterministic" make.
posted by Ethereal Bligh at 2:43 PM on December 4, 2005


Non-linear (chaotic) systems are not examples of non-determinism. Our inability to calculate the precise state of particles in a cup of coffee doesn't preclude our ability to find an attractor for their phase space, which is to say it does not preclude the inevitability of the cup of coffee going cold. I'll refer you to this text for a good introduction to non-linear dynamics, if you're genuinely interested.
posted by Rothko at 3:08 PM on December 4, 2005


Things fall apart and things fall together. Our local environment is akin to a super saturated solution. All that 'is' starts as a seed. The more interesting and attractive the seed the more complex and intriguing the result. Then it falls apart and becomes part of the solution again.

Long winded hand waving academics make me want to puke.
posted by Mr T at 3:17 PM on December 4, 2005


This, being tautological, is clearly true.
I have a new weapon in my rhetorical arsenal. Thanks for that flabdablet.
posted by Popular Ethics at 4:02 PM on December 4, 2005


Rothko: Non-linear (chaotic) systems are not examples of non-determinism.

Personally, I don't think the coffee cup is a good example, too complicated, lets take a double pendulum instead...

Like the coffee cup we know that it will eventually come to rest at a local minimum energy equilibrium, but if the energy contained in the system is above a certain threshold the path to that equilibrium will be completely unpredictable. This is true no matter how precisely it is built, and no matter how precisely we know the initial conditions. Furthermore, it is true of the mathematical model as well as the experimental apparatus - It is easy to say that the model isn't a good representation of reality, but try to build one that is predictable and you'll see that there is a problem...

You may find it easy to cling to the fact that the final resting position is known, but that doesn't have to be so. It would be easy enough to build an apparatus that allowed only a finite number of rotations about the middle joint in either direction, after which it would freeze up (think of it being a nut on a small piece of threaded rod, enough rotations in one direction and the lower link falls off). That would create a whole family of local minima in the phase space, and you wouldn't be able to predict which one the apparatus would land on for any particular run of the experiment. That is a final outcome that is non-deterministic.
posted by Chuckles at 5:16 PM on December 4, 2005


I'll start with a quote from the recent comment by ozomatli:
“I am a physicist and would be glad to answer some questions about Quantum Mechanics. Also, I would like to state that determinism means different things to different people. Personally I see the Universe as determinstic in the sense that for every effect there is a cause.”ozomatli, this thread
As I said before, determinism in this context has a specific meaning. It is, in my own words:
Determinisn asserts that every event in the universe, large or small, is completely determined by the universe's history back to its origin. It is like an immense and intricate clockwork, ticking away.
Quantum Mechanics denies this view. That this is the case is why there are countless pages written on this topic and why Einstein said:
“Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. Quantum theory says a lot, but does not really bring us any closer to the secret of the Old One. I, at any rate, am convinced that He (God) does not throw dice.”—Albert Einstein, A letter to Max Born, December 12, 1926 cited in Einstein: The Life and Times, p. 414
The previously referenced Stanford Encyclopedia of Philosophy, in its entry on causal determinism, provides a "loose and (nearly) all-encompassing definition as follows":
Determinism: The world is governed by (or is under the sway of) determinism if and only if, given a specified way things are at a time t, the way things go thereafter is fixed as a matter of natural law.”—Hoefer, Carl, "Causal Determinism", The Stanford Encyclopedia of Philosophy (Summer 2005 Edition), Edward N. Zalta (ed.)
...about which it clarifies:
“The roots of the notion of determinism surely lie in a very common philosophical idea: the idea that everything can, in principle, be explained, or that everything that is, has a sufficient reason for being and being as it is, and not otherwise. In other words, the roots of determinism lie in what Leibniz named the Principle of Sufficient Reason. But since precise physical theories began to be formulated with apparently deterministic character, the notion has become separable from these roots. Philosophers of science are frequently interested in the determinism or indeterminism of various theories, without necessarily starting from a view about Leibniz’ Principle.”
Implicit is the historical context, but I think I should be more explicit.

These competing views of the universe—random/chaotic (in the common language use of the word) and the universe as a scripted story, every event already determined—are found throughout history in most human cultures. In our tradition in the West, at its beginning with the Greeks, we find this argument. (Somehow I expect the sophists to have taken the indeterminate position, but I don't recall this from Plato's dialogs.) It's probably accurate to say that these competing ideologies roughly correspond to the competing ideologies of the "heart" and "mind", being the case that intellectualism is associated with logic, particularly deductive logic, where everthing is predetermined. And of course the matter is central to the idea of free will, also much discussed througout history.

However, in western culture, the successes of the Enlightenment, particularly the physics of Newton, saw the notion of determinism become dominant. In physics, determinism is closely related to the reductionism of Newton's mechanics and the later Dalton's atomism. (Note that the Greeks had their atomists, too, in Democritus. See Lucretius's On the Nature of Things for a cosmology that seems surprisingly modern.) This determinism and reductionism characterizes a worldview that reached its apogee in the late nineteenth century but was challenged on several fronts, the emerging physics of subatomic particles playing a strong role.

It should be noted that the Stanford Encyclopedia's page on determinism makes the case, presumably with great influence from John Earman, that even in classical mechanics there can be truly indeterminist systems.

But the Stanford Encyclopedia characterizes the QM argument against determinism like this:
“...according to QM the fullest description possible of a radium atom (or a chunk of radium, for that matter), does not suffice to determine when a given atom will decay, nor how many atoms in the chunk will have decayed at any given time. The theory gives only the probabilities for a decay (or a number of decays) to happen within a given span of time. Einstein and others perhaps thought that this was a defect of the theory that should eventually be removed, by a supplemental hidden variable theory that restores determinism; but subsequent work showed that no such hidden variables account could exist.”
The entry goes on to attempt to repudiate this, arguing in favor of Bohmian Mechanics, a theory that, as mentioned in the other thread, is interesting but certainly not orthodox. A more credible source for a defense of Bohmian Mechanics is found in "What is Bohmian Mechanics?", V. Allori and N. Zanghi, quant-ph/0112008. The standard objections to this theory are covered in that paper, as well as in the Stanford encyclopedia. But, again, this is nevertheless an unorthodox theory. Orthodox quantum mechanics is decidedly indeterministic.

The page linked in this post contains a few casual interesting thoughts on the completeness of QM, including smoe other "hidden variable" related physical hypothesis by which physics can again be determinist.

Finally, as discussed earlier, this indeterminism is closely philosophically related to Heisenberg Uncertainty if you interpret HU as epistemological rather than mechanistic which is, I believe the correct and dominant interpretation.

The Stanford encyclopedia deals with chaotic systems such as "Sam" describes and agrees with Rothko, correctly, that a chaotic system is not necessarily indeterministic. But see Chuckles's recent comment for another argument defending indeterminism.

Throughout this debate, in the back of my mind was a recognition of the context that, I think, best explains Rothko's assertion of determinism. Rothko is a math and biology major (a combination that seems suited for computational biology, a hot field right now—why is he working as an IT admin?) and during the period that physics has become radically less determinist the other sciences, particularly biology, have become much more determinist. This determinism is closely related—as it long has been—the reductionism of much of science. Biology has done nothing if not become more and more reductionist and it is in this sense, I think, that an argument that "the scientific view has become more determinist" can be made.

That that Stanford site—a philosophy archive—deals with QM and such indicates how much physics has interacted with philosophy and shaped our contemporary Western worldview. Really, Nietchze was right that science has in a real sense made philosophy superfluous. Nevertheless, in my opinion there are still many things related to this discussion that are worth investigating in philosophy and, anyway, I think that both the arguments about free will and determinism continue to be fruitfully discussed purely in the philosophical realm without support from the (presumed) authority of physics.
posted by Ethereal Bligh at 6:08 PM on December 4, 2005 [1 favorite]


Going back to the original article, I've read Paul Davies section and am not sure I understand his thesis. If I read it correctly, he is predicting that the elusive "collapse" occurs when a quantum system reaches a certain complexity with 10^120 possible states-- the maximum number of bits of information the Universe could have processed since the Big Bang.

My first question is, what was his logic in choosing this number?

My second question is, since the Universe processes more information as time goes by, that seems to imply the quantum/classical boundry moves toward progressively more complex systems over time. Is he predicting that eventually macroscopic systems would appear to exhibit entanglement? Would this also predict that the early universe had "less" quantum effects?
posted by justkevin at 7:16 PM on December 4, 2005


BTW, while I'm skeptical about Mr. Davies theory, I appreciate that he's actually put forward a falsifiable thesis about where the quantum/classical boundary occurs.
posted by justkevin at 7:21 PM on December 4, 2005


"BTW, while I'm skeptical about Mr. Davies theory, I appreciate that he's actually put forward a falsifiable thesis about where the quantum/classical boundary occurs."

Yeah, me too. I agree that there's some big problems with his idea as is, but I think it's a good step in the right direction in an attempt to both qualify and quantify "complexity".
posted by Ethereal Bligh at 7:50 PM on December 4, 2005


I said this earlier, which is completely wrong in at least one sense:
Now that I have looked into it a bit more I think I understand the problem. I think information in the quantum mechanical sense isn't actually information at all, more like complexity. I think the entire discussion about the burned paper is a completely false analogy. I wonder where the notion originated, and I kind of doubt that it comes from a physicist at all.
The notion of the burned paper is definitely brought up by the physicists discussing the theory (sometimes the notion is throwing an encyclopedia into a black hole)... I'm not convinced it is meant literally though, as the wikipedia entry on physical information makes obvious, the word 'information' can mean a lot of different things.
posted by Chuckles at 11:18 PM on December 4, 2005


Ethereal Bligh : "'determinism' has a specific meaning. That meaning specifically is that classical mechanics completely describes the universe"

I don't see why determinism needs to be tied to classical mechanics. That may be a historical vestige.

My claim is that our "inability to predict the future" is a result of the nature of the universe itself, that no one, within this universe could, even theoretically, "predict the future [of the universe in all its detail]" because of the implications of QM.

This doesn't preclude determinism. 'Nature of the universe' may be interpreted two ways:

1)True randomness as fundamental
2)Information inaccessibility as fundamental

How would you prove the former?
posted by Gyan at 12:03 AM on December 5, 2005


"I don't see why determinism needs to be tied to classical mechanics. That may be a historical vestige."

Determinism in this context is tied to classical mechanics because it is. It's what determinism is in this context. The word can mean a lot of different things and if you want to make up a meaning based upon common language but applied to this context you're going to run into the problem that the word in this context already has a specific meaning.

"This doesn't preclude determinism."

To begin with, "information inaccessibility as fundamental" is a much stronger assertion than anyone here is making as part of their assertion of their notion of "determinism". Rothko clearly sees this information as theoretically possible either through a revision of theory or an abundance of resources (both data and computational).

"1)True randomness as fundamental
2)Information inaccessibility as fundamental"


I think the burden of proof is on one who asserts the latter, not the former. The second proposition is not falsifiable. This assertion of determinism is strikingly similar to the theist assertion that God exists but cannot be proven to exist and/or conversely challenging atheism by asking for a disproof. If you're, um, determined to see the universe as deterministic you can always wave your hands and say that things have been, are, and will be exactly so and if one were God one would see the truth of this assertion. You just need to be omniscient. Which is certainly what the second proposition demands for it to be a defense of determinism.

If you're going to push "determinism" so far as to find yourself deep in philosophical territory—as I think your two propositions do—then you're going to have to deal with a rigorous analytical philosophic analysis which, I think, will find that your definition of "determinism" either has no meaning or doesn't at all mean what you claim it means. This is why the correct context for this discussion is the history of physics and the advent of QM.

Additionally, putting that aside, there is the glaring, blinding, screamingly loud fact that this discussion is occuring in the context of Einstein's quote which certainly is QM versus classical mechanics.
posted by Ethereal Bligh at 2:00 AM on December 5, 2005


Ethereal Bligh : "I think the burden of proof is on one who asserts the latter, not the former."

I think the burden of proof is on anyone asserting either of the two, as you do.
posted by Gyan at 2:43 AM on December 5, 2005


Thank God this great link finally got down to decent conversation after the bullshit upthread by the gape-mouthed.
posted by klangklangston at 7:45 AM on December 5, 2005


When respectable physicists are reduced to desperate handwaving and speculation about how things actually work, it's clearly time for the real crackpots to come out of the woodwork and contribute.

I think this bears repeating at this point in the conversation.
posted by carsonb at 8:17 AM on December 5, 2005


It bears repeating at every point in the conversation!
posted by Chuckles at 9:53 AM on December 5, 2005


Thank God for KlangKlangston's wonderful contribution to this thread! I'm a great fan of his work. Meanwhile...

An intuitively satisfying middle way between the extreme claims of determinism and randomness is the notion that the Multiverse (set of all co-existing parallel Universes) is completely deterministic. Which single Universe a given observer happens to inhabit, on the other hand, is entirely governed by the laws of probability.

Thus, as someone mentioned above, God does throw dice, but rolls all possible outcomes at once. To put it another way, when I choose to roll a die, I have no way of knowing which of the six future observers will happen to be the one I experience as me.
posted by cleardawn at 11:15 AM on December 5, 2005


Not only does God roll dice, the mofo owes me money roughly equal to the age of the universe divided by the amount of time we played.

(There is no God, and Dirac is his Prophet)
posted by Smedleyman at 11:52 AM on December 5, 2005


wow, i love same the physicist, Probably because I agree with everything he says. I was just wondering where the Humeans where.

"(in the thread Gyan linked) Rothko:
"
So do you agree the universe is causal, that one event follows as a consequence of another?
"

me: no. but i'm aware that i have a very extreme point of view on this, which holds that (non-mathematical) induction is completely fallacious and bullshit and usually works but doesn't mean anything except so far we've had a long string of coincidences. mathematical induction, on the other hand, i hold to be essentially uninteresting because i do not have a platonist type view of the universe -- i don't think that the inverse square law actually has anything to do with me falling back to earth when i jump.

the point being that so called natural law has nothing to do with what goes on around us.

i submit that this is a very strange perspective and not one that is very convincing. but it is incredibly liberating to refute causality.

it's also fun considering everyone in my professional circle grew up on asimov and star trek.
posted by sam 04 December | 12:04 "
posted by afu at 3:13 AM on December 6, 2005 [1 favorite]


More handwaving...

ISTM that QM is not necessarily incompatible with determinism as defined by EB; it's just that as a provider of probabilities rather than specific predictions, it's not a complete modelling procedure - just a bloody useful one.

What its success does tell us, though, is that everything really is entangled, to some degree, with everything else - and that any model that was reliably capable, in principle, of predicting exactly where any given electron was going to end up would need to take, as inputs, exact descriptions of every single particle in the Universe.

I think the reason Davies picked the 10^120 number is that it puts a reasonably conservative upper bound on the amount of computing power actually available to formulate and solve such models.

ISTM that to talk about things that are theoretically or in-principle possible without taking account of that kind of upper bound is to speak in useless contradictions. Is it reasonable to assert that the Universe is modellable in principle, given that any such model must, in principle, require more compute capacity than can, even in principle, exist? Not without crossing the line into theology, thinks I.
posted by flabdablet at 7:10 AM on December 10, 2005


what keeps a physicist from crossing that line?
posted by carsonb at 9:10 AM on December 10, 2005


" Is it reasonable to assert that the Universe is modellable in principle, given that any such model must, in principle, require more compute capacity than can, even in principle, exist? Not without crossing the line into theology, thinks I."

That's a very good point and is something I've been puzzling over one way or another for 15 years. I'm strongly inclined to say that you can't assert such a thing. But one time a friend of mine, an astrophysicist, and I were talking about black holes and we had an interesting argument. I was inclined to say that there's nothing that can reasonably be said about anything past the event horizon, looking at it from this very abstract information theoretic point of view. Her response was very interesting and stopped me dead in my tracks. She asked why does it make sense to not assume that the basic physics of the universe as we know aren't the same inside the event horizon?

I puzzle over these two points of view all the time.
posted by Ethereal Bligh at 10:21 AM on December 10, 2005


Ethereal Bligh : "She asked why does it make sense to not assume that the basic physics of the universe as we know aren't the same inside the event horizon?"

Basic psychology: there has to be an element of recognisability. We don't assume that a cat behaves like a dog (never mind that we have empirical access to both).
posted by Gyan at 10:40 AM on December 10, 2005


what is the general attitude in the physics community about David Bohm? As a student of philosophy with a strong interest in cosmological questions, I find his work appealing, and intuitively in keeping with a general Aristotelian metaphysics, but I am not well grounded enough in the math to know if I'm missing something.

From a layperson perspective, it almost seems that quantum mechanics has run into the same hurdle as David Hume did, approaching nature as actually being the immediate fragmented data we take in, rather than being a unified whole necessarily experienced in pieces, so to speak. But if Bohm is respectable, (as he seems to be) then why are his conceptions of QM so often ignored?
posted by mdn at 10:40 AM on December 10, 2005


mdn, I haven't looked into Ethereal Bligh's link on Bohmian mechanics, but I did read the link you posted when the subject came up in the Is God an Accident post. Basically, I don't think Bohmian mechanics claims what some want it to. For determinism to be proved you have to have deterministic initial conditions as well as a deterministic system... Well, that statement is harder to get my head around than I thought it would be...

Bohmian mechanics addresses a certain contradiction (to some) with the double slit experiment, from the stanford article:
The most puzzling aspect of the two-slit experiment is perhaps the following: If, by any means whatsoever, one is able to determine through which slit the particle passes, the interference pattern will be destroyed. This dramatic effect of observation is, in fact, a simple consequence of Bohmian mechanics. To see this one need only carefully consider what determining the slit through which the particle passes should mean. In particular, one must recognize that this must involve interaction with another system that must also be included in the Bohmian mechanical analysis. This destruction of interference is related, naturally enough, to the Bohmian mechanical analysis of quantum measurement (Bohm 1952), and it occurs via the mechanism that leads, in Bohmian mechanics, to the "collapse of the wave function."
But it seems to me that this doesn't even attempt to address the source of the deterministic/probabilistic disagreement, the uncertainty principal. I quoted from the stanford article in the other thread (here):
For any quantum experiment we merely take as the relevant Bohmian system the combined system that includes the system upon which the experiment is performed as well as all the measuring instruments and other devices used in performing the experiment (together with all other systems with which these have significant interaction over the course of the experiment). The "hidden variables" model is then obtained by regarding the initial configuration of this big system as random in the usual quantum mechanical way, with distribution given by |ψ|2. The initial configuration is then transformed, via the guiding equation for the big system, into the final configuration at the conclusion of the experiment. It then follows that this final configuration of the big system, including in particular the orientation of instrument pointers, will also be distributed in the quantum mechanical way, so that this deterministic Bohmian model yields the usual quantum predictions for the results of the experiment.
So the uncertainty principal still guides particles going into the Bohmian mechanical system and Bohmian mechanics doesn't claim to be able to do anything that the uncertainty principal says you can't do. Of course I could be completely full of shit, that is usually the case.
posted by Chuckles at 11:37 AM on December 10, 2005


Ethereal Bligh: The Stanford encyclopedia deals with chaotic systems such as "Sam" describes and agrees with Rothko, correctly, that a chaotic system is not necessarily indeterministic. But see Chuckles's recent comment for another argument defending indeterminism.

Well, I think my argument there is a little problematic... There are non-linear differential equations that do not have unique solutions, which is what I was trying to get at when I said "this is true of the mathematical model". Trying to connect that math with real systems is causing me some trouble though, I guess this wouldn't be an interesting question otherwise...

Throughout this debate, in the back of my mind was a recognition of the context that, I think, best explains Rothko's assertion of determinism. Rothko is a math and biology major (a combination that seems suited for computational biology, a hot field right now—why is he working as an IT admin?) and during the period that physics has become radically less determinist the other sciences, particularly biology, have become much more determinist. This determinism is closely related—as it long has been—the reductionism of much of science. Biology has done nothing if not become more and more reductionist and it is in this sense, I think, that an argument that "the scientific view has become more determinist" can be made.

I've made a similar observation about Computer and Electrical Engineers... People who spend a lot of time around in an analogue world tend to accept non-determinism a lot easier than people spending a lot of time coding.
posted by Chuckles at 12:59 PM on December 10, 2005


wow, I somehow totally missed that EB had posted a link on Bohm above... I guess because I wasn't thinking of it as a defense of strict determinism and maybe sorta scrolled past some of the post because it was focused on that issue. I guess the standard interpretation of QM bothers me because it seems to deny the principle of non-contradiction, but I don't really consider myself a determinist, philosophically.

However, it's possible that's sort of an issue of semantics - I don't think "free will is an illusion" but I don't really have a problem with the idea that free will is the name we give the feeling of being a collection of various material causes aware of themselves enough to consider consequences and experiences etc etc. In other words, What Is, Is - but it would not be the same if 'you' weren't there to make the choice - your being conscious is absolutely part of the equation, but it is a materialistic equation.
posted by mdn at 1:54 PM on December 10, 2005


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