Monday, March 20, 2017

Causality and Quantum Mechanics: a Cosmological Kalamity (Part 2 of 2)

This is the second in a two-part series of posts about the Kalam Cosmological Argument for the existence of God.  If you haven't read the first part you should probably do that first, notwithstanding that I'm going to start with a quick review.

To recap: the KCA is based on the central premise that "whatever begins to exist has a cause."  But quantum mechanics provides us with at least two examples of things that begin to exist without causes: radioactive decay results in the decay products beginning to exist, and vacuum fluctuations result in the virtual particles beginning to exist.  In the latter case, the particles are created literally from nothing, but that's just a detail, a little icing on the cosmological cake.  The KCA premise isn't about whether or not things that begin to exist are fashioned from previously existing materials.  It only speaks of causes.  And quantum events don't have causes — at least not local causes — as shown by Bell's theorem.  Bell's theorem actually does more than rule out local causes, it rules out all local hidden state models, not just causal ones.  So there are only two possibilities: either quantum events are not (locally) caused, or quantum mechanics is wrong.

But Bell's theorem does not rule out non-local hidden state, and so it does not rule out non-local causes.  Indeed, what Bell's theorem shows us is that quantum states are in general non-local: an entangled system is a system with a single quantum state spread out over multiple locations.  So could this be the source of quantum causality?

No, it couldn't.  Non-local causality is ruled out both by relativity and by the no-communication theorem.  For a non-local state to be causal, the causal effect would have to propagate faster than the speed of light, otherwise it would just be an ordinary run-of-the-mill everywhere-local chain of causation.  Some popular accounts of entanglement would have you believe that this (faster-than-light causality) does happen, but it doesn't.  Measuring one member of an entangled pair does not change the state of its partner.  So non-local quantum states cannot be causal.

There is one last possibility: maybe there is some other kind of state in the universe, some non-local non-quantum state.  As I noted at the end of part 1 we can never rule out this possibility on the basis of any experiment.  Indeed, we can even demonstrate a hypothetical non-local state that would account for all possible observational data: a cosmic Turing machine computing the digits of pi from wherever it happens to be that they correspond exactly with the outcomes of all experiments that have ever been done or will ever be done.  Assuming pi is normal, this will always be possible.

This is the fundamental problem with hidden state: it's hidden.  Our universe could be run by a cosmic Turing machine, or it could be a simulation built by intelligent aliens.  We can't eliminate either possibility, nor a myriad others, on the basis of experiment.

When I have pointed this out to Christians their response has been: what difference does it make if we're in a simulation?  The aliens were still created by God.  But in fact this possibility is devastating not just to the KCA, but to all theological arguments.  If the universe is a simulation, then I can accept all of the claims of theologians at face value, and still not get to God.  I can accept that Jesus was a real historical figure, that he really did perform miracles, that he really was crucified and rose from the dead, that he really did claim to be God, that the scriptures are the literal truth, that the Flood really happened, that the earth is 6000 years old.  I can accept all of that and still not believe in God because all of that could have just been built in to our simulation by the aliens who designed it.

I can even accept the cosmological argument and still not believe in any particular god.  I only have to accept the uncaused cause in the abstract.  I cannot possibly know anything about God's true nature because all of the information I have at my disposal is filtered through the intelligent aliens who built this simulated universe that I live in.  The information that I have access to may or may not reflect the actual metaphysical truth.  In fact, the aliens that built our universe may themselves not know the metaphysical truth because they themselves could be living in a simulated universe built by meta-aliens.

There could be an arbitrary number of layers of simulation between us and the uncaused cause.  For us to have accurate information about God, that information would have to somehow percolate down through all of those layers without being altered.  It would be like a cosmic game of Chinese whispers.  The odds of the truth emerging unscathed down here at the very bottom of the hierarchy are indistinguishable from zero.

It is worth noting that we may not be at the bottom of the hierarchy for long.  We are on the verge of being able to create simulated universes of our own.  When that happens, will the artificially intelligent inhabitants of that universe have souls?  Unless we are 100% certain that the answer to that question is yes, how can we be sure that we have souls?

In sum, the KCA is completely untenable.  Its central premise is refuted empirically by quantum mechanics.  Even if this were not the case, the KCA only gets you to some unknown uncaused cause.  The nature of the uncaused cause cannot be determined by any experiment, since no experiment can rule out the cosmic Turing machine.

Furthermore, the possibility of simulated worlds is devastating not just to the cosmological argument but to all religious arguments.  Even if you accept all religious claims at face value, you still have to either show that information about God necessarily propagates reliably into a simulation, or somehow prove that our universe is not a simulation, that we are living in the One True Universe, and that any simulations we create will be the first level down.  Otherwise, even in the face of miracles and revelations we cannot know if they are the work of God or the aliens who programmed our simulation.  Or, what is most likely of course, of our own ancestors' imaginations.

9 comments:

Publius said...

It's Turtles All The Way Down

@Ron
>This is the fundamental problem with hidden state: it's hidden. Our universe could be run by a cosmic Turing machine, or it could be a simulation built by intelligent aliens. We can't eliminate either possibility, nor a myriad others, on the basis of experiment.

At this point, you start to veer from the philosophical (even if that philosophy is a particular interpretation of quantum mechanics) to experimental proof.

One can't run a physics experiment to discover God.

The nature of God and the heavens is more like the The Fly of Despair.

Yet you always default to physics, which is queen of the hard sciences. What about the other sciences? Could archaeology prove the existence of God? How about sociology? Psychology? Biochemistry? Geology? Linguistics?

> If the universe is a simulation, then I can accept all of the claims of theologians at face value, and still not get to God.. . . I can accept all of that and still not believe in God because all of that could have just been built in to our simulation by the aliens who designed it.

>I can even accept the cosmological argument and still not believe in any particular god. I only have to accept the uncaused cause in the abstract. I cannot possibly know anything about God's true nature because all of the information I have at my disposal is filtered through the intelligent aliens who built this simulated universe that I live in. The information that I have access to may or may not reflect the actual metaphysical truth. In fact, the aliens that built our universe may themselves not know the metaphysical truth because they themselves could be living in a simulated universe built by meta-aliens.

It's Turtles all the way down.

Yet, once again, we observer that everything we need to know can be found in Star Trek.

Odo: Has it ever occurred to you that you believe the Founders are gods because that's what they want you to believe? That they built that into your genetic code?

Weyoun 6: Of course they did. That's what gods do. After all, why be a god if there's no one to worship you?

From Star Trek Deep Space Nine: Treachery, Faith and the Great River.

>Furthermore, the possibility of simulated worlds is devastating not just to the cosmological argument but to all religious arguments. Even if you accept all religious claims at face value, you still have to either show that information about God necessarily propagates reliably into a simulation, or somehow prove that our universe is not a simulation,

Really? One has to prove that the universe isn't a simulation? I don't see it as a serious hypothesis; it's science fiction. If you believe it, though, watch out for Roko's basilisk.

>Otherwise, even in the face of miracles and revelations we cannot know if they are the work of God or the aliens who programmed our simulation. Or, what is most likely of course, of our own ancestors' imaginations.

It's such a better story to believe that all of the mass and energy of the universe was compressed into a single particle the size of a quark, which spontaneously exploded, thereby creating the universe.

Ron said...

> The nature of God and the heavens is more like the The Fly of Despair.

I don't know if that link was a mistake or not, but if not, then things like that make it very hard for me to take you seriously.

> If some "thing" comes from sampling a random process, can't we say that "thing" is caused by the random process?

You can say anything that you want. You can say that furious green ideas sleep furiously. Watch: furious green ideas sleep furiously. Whether what you say is true (or even meaningful is another matter.

Saying that an event is caused by "the random process" or even "a random process" is the *same thing* as saying that the event has no cause. There is no local state that correlates with the event. That is the *definition* of not having a cause.

> One can't run a physics experiment to discover God.

Oh? Then how does one distinguish God from things that don't exist? Because in science, not being able to run an experiment to demonstrate the existence of something is the *definition* of not existing.

(Maybe you should re-read 31 flavors of ontology.)

> What about the other sciences? Could archaeology prove the existence of God? How about sociology? Psychology? Biochemistry? Geology? Linguistics?

All of these things are subservient to physics because they study the behavior o things that are made of atoms, and atoms behave according to physics.

> It's such a better story to believe that all of the mass and energy of the universe was compressed into a single particle the size of a quark, which spontaneously exploded, thereby creating the universe.

Better compared to what? That the universe was created by a jealous deity who is so insecure that he will condemn sentient beings to eternal suffering if they don't worship him? And that this sad state of affairs has come about because one of our ancestors was snookered by a talking snake into eating a piece of fruit?

Damn straight the big bang is a better story than *that*.

Publius said...

Rogue Random

@Ron:
>Saying that an event is caused by "the random process" or even "a random process" is the *same thing* as saying that the event has no cause. There is no local state that correlates with the event. That is the *definition* of not having a cause.

This seems curiously ill-defined. Given the above, the two examples you give - virtual particles and radioactive decay - have causes. The time between virutal particle creation/destruction or radioactive decay events may be unpredictable - random - but once it's happened, we have models for the cause.

Yet staying with your model for a moment, would these phenomena also have no cause?
1) Rogue waves? If you object to ocean waves, then how about Peregine solitons?
2) Winning lottery numbers?

Random Numbers

Consider that, for any physical phenomena, we could take measurements from it and use those measurements to generate sequences of random numbers.

What makes a set of numbers "random"?
1. The numbers are unpredictable; there is no fixed rule governing their selection.
2. The numbers are independent, or uncorrelated.
3. They are unbiased, or uniformly distributed.

Does the black box have a causal process?

Say I present you with two boxes, a black one and a red one.
A. The red box produces a continuing sequence of random numbers, which are based on measurements from radioactive decay.
B. The black box also produces a continuing sequence of random numbers.

After any length of examination, the sequences from the red box and the black box pass all the tests of numerical randomness.

Can you then conclude that the process inside the black box is from a physical process with "no cause", like radioactive decay?

>Oh? Then how does one distinguish God from things that don't exist? Because in science, not being able to run an experiment to demonstrate the existence of something is the *definition* of not existing.

Well, then you will have quite a problem with cognitive dissonance!

Does the Universe not exist? You can experiment in the observable universe, but you cannot know anything by direct experimentation of the volume of the universe beyond that.

You also can't run an experiment to determine if I was (or wasn't) thinking of elephants last week.

Wait - I'm thinking of a number. Hah, you can't guess it with certainty! Yet it exists! It's between 0 and 4. Hah, you still can't do it!

>> What about the other sciences? Could archaeology prove the existence of God? How about sociology? Psychology? Biochemistry? Geology? Linguistics?

>All of these things are subservient to physics because they study the behavior o things that are made of atoms, and atoms behave according to physics.

Full reductionism then?

I look forward to your physics description of traffic waves (see also here), Charles Bonnet Syndrome, and the use of stone tools.

>That the universe was created by a jealous deity who is so insecure that he will condemn sentient beings to eternal suffering if they don't worship him? And that this sad state of affairs has come about because one of our ancestors was snookered by a talking snake into eating a piece of fruit?

Still creating unskilled religions.

Yet the story of the big bang requires the inclusion of inflation, which can't be falsified. What would Karl Popper say?

Ron said...

@Publius:

(Sorry for the long delay in responding. I've been on the road.)

> once it's happened, we have models for the cause.

Really? What is it? (Note that a demonstrably correct answer to that question will win you a Nobel prize in physics.)

> would these phenomena also have no cause?

No. All classical phenomena have causes.

Quantum physics is fundamentally different from classical physics. It all hinges on Bell's theorem, which only applies to quantum systems. If you don't understand Bell's theorem you cannot possibly understand my argument.

> You also can't run an experiment to determine if I was (or wasn't) thinking of elephants last week.

That's not true. For example, I can ask you: were you thinking of elephants last week? That experiment may not produce reliable results, but then again it might. There's nothing in the laws of physics that *prevents* that experiment from producing reliable results.

By way of contrast, the laws of physics *prohibit* any experiment that allows you to predict when a particular radioactive decay will occur. (See Bell's theorem.)

> inflation, which can't be falsified

Why do you think inflation can't be falsified? Of course it can. Large-scale anisotropy in the cosmic background radiation would falsify it.

Publius said...

Theory of Anything.

Ron said...

@Peter:

> > Mass/energy is conserved

> Not globally in a curved spacetime.

I debated with myself when I wrote that whether to say "momenergy is conserved" rather than mass/energy, but decided that would be too pedantic. It's hard to tell how much physics a commenter knows, and my blog is targeted towards a general audience.

Yes, you're right. Mass/energy is not conserved, momenergy is the conserved quantity. But these details don't matter. What matters is that there is some conserved quantity in this universe, and that, plus the second law, puts a limit on how much computation you can do.

> It costs kTln2 energy to compute one bit of information.

No, it costs *at least* that much. The Landauer limit is a lower bound. There is no guarantee that you can actually *do* a computation for that cost.

The kTln2 Landauer limit is a simple thermodynamic limit: in order to compute you need to be able to discharge heat somewhere, and the colder your cold reservoir is the more efficient you can be. This is no different from the classical calculation of the efficiency of a heat engine. But to do useful work you not only need a cold reservoir to discharge heat into, you also need a hot reservoir from which to extract energy. You need both the air conditioner *and* the data center. If the entire universe is the same temperature you can't compute no matter how cold it is.

> So I think the essence of the above claim is still true, even if we have to tweak somewhat the exact physics statements.

Well, I'm glad we can agree about that!

@Publius:

> Consider alpha decay. When we observe an alpha particle, we know that it tunneled through the coulomb barrier of its host nucleus. Is this not a description of the "cause" of that alpha particle?

It begs the question: what caused the alpha particle to tunnel?

Go back to the case of a light bulb turning on: the bulb beginning to emit light was caused by electric current beginning to flow through it. That in turn was caused by the switch closing. That in turn was caused by my hand exerting a force on the switch. That in turn was caused by my brain sending electric impulses to my muscles. That in turn was caused by some computational process in my brain that we don't yet fully understand, but if we understood it we could trace the causal chain back to some input into my brain through my sensory systems, and back out into the world. In a purely classical world we could trace that causal chain back to the beginning of time.

In the quantum world, the causal chain stops immediately before the decay process begins. This is not mere speculation or an expression of ignorance or technological limitations. In QM the causal chain of a quantum event stops at that event. That's why radioactive decay is used as the initiating event in the Schroedinger's cat thought experiment.

> That would be prediction, not causation.

Causation is a pre-requisite for prediction. If you can reliably predict, then there must be a cause which serves as the basis for prediction. The absence of the ability to predict does not necessarily imply the absence of causation. It could be a technological limitation. It is often hard to know whether the inability to predict is a technological limitation or an indication of the absence of a cause. It might be the case that with powerful enough measuring devices and computers you *could* predict the powerball outcomes. You actually *can* predict e.g. Roulette:

https://phys.org/news/2012-10-chaos-theory-outcome-roulette-table.html

For a long time it was controversial whether the inability to predict radioactive decay was due to the absence of a cause or some other factor. But thanks to Bell's theorem we know that it is the former. I keep telling you this same thing again and again, and you keep ignoring it.

Publius said...

Not Getting It


@Ron
>For a long time it was controversial whether the inability to predict radioactive decay was due to the absence of a cause or some other factor. But thanks to Bell's theorem we know that it is the former. I keep telling you this same thing again and again, and you keep ignoring it.

>In the quantum world, the causal chain stops immediately before the decay process begins. This is not mere speculation or an expression of ignorance or technological limitations. In QM the causal chain of a quantum event stops at that event. That's why radioactive decay is used as the initiating event in the Schroedinger's cat thought experiment.

From the main post (part 2):
> But quantum mechanics provides us with at least two examples of things that begin to exist without causes: radioactive decay results in the decay products beginning to exist, and vacuum fluctuations result in the virtual particles beginning to exist. In the latter case, the particles are created literally from nothing, but that's just a detail, a little icing on the cosmological cake. The KCA premise isn't about whether or not things that begin to exist are fashioned from previously existing materials. It only speaks of causes. And quantum events don't have causes — at least not local causes — as shown by Bell's theorem.

I'm not getting it.
I've copied above where you've asserted 3 times that quantum events don't have a cause.

For each example - radioactive decay and virtual particles - it appears to me that physicists have come up with models that do provide a cause. Alpha decay has models with the nuclear force, electromagnetic forces, the coloumb barrier, etc., that appear to me to provide the cause.

You seem to key in on the random occurence in time -- such as why did the decay happen at time t and not time t+1, and in fact, if we record the times of decays, tn, we see a random distribution.

Yet time isn't the event. Time is the marker of the event - the value by which we order the events.

In addition, if one creates statistical models, with particles as random variables, then it should not be surprising that one gets randomness out of the model. To quote Werner Heisenberg: "The incomplete knowledge of a system must be an essential part of every formulation in quantum theory. Quantum theoretical laws must be of a statistical kind. To give an example: we know that the radium atom emits alpha-radiation. Quantum theory can give us an indication of the probability that the alpha-particle will leave the nucleus in unit time, but it cannot predict at what precise point in time the emission will occur, for this is uncertain in principle."

Finally, there are other formulations of quantum mechanics - such as de Broglie Bohm theory (pilot waves), which are deterministic. See Quantum mechanics, randomness, and deterministic reality. Pilot wave theory also has a sensible resolution to the two-slit experiment and tunelling. [note]

Ron said...

> You seem to key in on the random occurence in time -- such as why did the decay happen at time t and not time t+1, and in fact, if we record the times of decays, tn, we see a random distribution.

Yes, that is exactly right.

> Yet time isn't the event. Time is the marker of the event - the value by which we order the events.

Yes, that is also right. So?

> Quantum theoretical laws must be of a statistical kind.

Yes. That is exactly the same thing as saying that individual quantum events do not have causes. (Note BTW that when Heisenberg said this it was a controversial statement. Einstein, for example, didn't believe it to be true, insisting that this was an indication of QM being an incomplete theory. The experimental vindication of Bell's theorem shows that Einstein was wrong and Heisenberg was right.)

> Finally, there are other formulations of quantum mechanics - such as de Broglie Bohm theory (pilot waves), which are deterministic.

Yes, but they are non-local. Non-local theories only get you to the cosmic TM, not to the uncaused cause.

Ron said...

Oh, one more thing:

> Quantum theoretical laws must be of a statistical kind.

The operative word there is "must". There are many things that *can* be modeled statistically (weather, the stock market) but nonetheless (almost certainly) have causes. Our inability to make exact predictions of weather and the stock market are not fundamental physical limitations, but rather a consequence of our limited ability to collect enough data and do the math.

That is not the case in QM. Our inability to predict individual quantum events really is a fundamental limitation of physics. No amount of mathematical cleverness or technological advance can ever get around it.