Re: [asa] Brain and Determinism (fwd)

From: Bill Powers <wjp@swcp.com>
Date: Thu Oct 01 2009 - 19:46:24 EDT

David:

It may be new to me, which is why I want to understand it. JP&NB
apparently, by using macrophysics, want to persuade us that the
randomness in QM is really already present in our "observable" or
comprehensible world.

bill

On Thu, 1 Oct 2009, David Clounch wrote:

> Just briefly because I am on the run today, JP&NB seem to be making an
> argument based on classical physics, not QM. They indicate classical
> physics shows some things are non-deterministic.
>
> Where is this going and why should we care? Minds, being based on brains,
> brains being based on hypercomplex analog processes, exhibit
> non-deterministic characteristics. This is new to me, having never thought
> about it before.
>
>
>
> Thanks,
> Dave C
>
>
> On Thu, Oct 1, 2009 at 4:03 PM, Bill Powers <wjp@swcp.com> wrote:
>
>> Forwarded to ASA on behalf of Merv:
>>
>>
>> I will happily reply here as best I can, exposing my own ignorance when it
>> comes
>> to Planck lengths or quantum uncertainties -- and hoping that then some of
>> the
>> real physicists can step in and clarify for both of us. Here goes...
>>
>> Regarding ontological vs. epistemological uncertainties first: I think I
>> understand your confusion on this since it is the same confusion I am
>> emerging
>> from. I used to think that the Heisenberg uncertainty principle was no
>> more
>> than a statement of a limitation on what we could find out about a small
>> particle. I.e. Any instrument will affect what it is measuring -- a
>> thermometer slightly changes the temperature of a liquid, a volt-meter will
>> slightly alter the circuit in which it is connected to get its voltage
>> reading,
>> etc. So that's easy! (I used to think.) The electron can still be in a
>> precise
>> place, have its simultaneously precise velocity and all, and we just aren't
>> able
>> to measure those things since any instrument would massively affect the
>> particle. So I was able to preserve my notion of ontological determinism
>> by
>> thinking "*In principle* the electron does have a precise location and
>> velocity
>> --even if we can never know both with infinite precision." (and come to
>> think
>> of it, we could never know anything with infinite precision anyway.) But
>> our
>> lack of knowledge doesn't make it not so any more than my lack of knowledge
>> about where you are right now would make your location be indeterminate.
>> But
>> physicists come along and tell me "not so fast!" Actually, the uncertainty
>> principle runs deeper and informs us that the electron's simultaneous
>> position
>> and velocity are indeterminate *even in reality*. I.e. there are no
>> simultaneously precise values to known *even in principle*! Not even by
>> God.
>> This is what apparently defeats the notion of ontological determinism even
>> though I can't wrap my mind around it. It is philosophically a much
>> different
>> and more bizarre ball game than merely saying "we can't know it."
>>
>>
>> Regarding Planck lengths, I too would love to know more about this. But
>> from
>> what I've gathered it represents a "smallest possible" increment in space
>> that
>> would be astronomically smaller than a proton. (Probably having to do with
>> how
>> far light could travel in a Planck instant). It is apparently the smallest
>> "unit?" of length anything could actually have. To my already fried
>> imagination, this has the effect of "digitizing" space. Just as we can
>> recognize the digitized and pixelated graphics of an object "moving" across
>> a
>> computer screen, now I imagine a pixelated space where things "lurch along"
>> from
>> one Planck length to the next without being able to exist in between. How
>> this
>> fits with classical Newtonian notions of momentum or inertia I would love
>> for
>> somebody else to explain to me. A digitized motion where something is
>> pausing
>> at a new quantized location on your screen for 1/30 of a second before it
>> is
>> instantaneously relocated to the next position is not at all the same as
>> "continuous" motion where inertia is preserved. But if Planck lengths and
>> times
>> are ontologically accurate descriptions of reality, maybe there is no such
>> thing
>> as "continuous" motion? George, ... somebody? ..... help!
>>
>> --Merv
>>
>>
>>
>> Quoting Bill Powers <wjp@swcp.com>:
>>
>> Merv & David:
>>>
>>> A few comments.
>>>
>>> First, I don't understand the seemingly discontinuous comment about the
>>> Planck length.
>>>
>>> Second, I don't follow the argument. It seems to me that from beginning
>>> to end they are discussing epistemological uncertainty and not
>>> ontological uncertainty. In fact, it seems to me that the Heisenberg
>>> uncertainty can be similarly interpreted.
>>>
>>> Since I don't consider the Heisenberg uncertainty to really get at the
>>> matter (it can be viewed as merely the result of not attempting to
>>> measure an eigenvalue), consider instead something like the decay of a
>>> radioactive nucleus.
>>>
>>> We are told that if one were to ask why this particular nucleus decayed
>>> at this instance that the "appropriate" answer is that there is no
>>> reason. Yet, we are also told that the statistical decay of a host of
>>> such atoms has such a small variance that we can make extremely accurate
>>> atomic clocks from them.
>>>
>>> The situation is analogous to tossing an honest penny. If one were to
>>> try to predict whether this penny on this toss would be a head or a
>>> tail, our knowledge would be completely uncertain. All we could say is
>>> that it will be either a head or a tail. And this is why we in Bayesian
>>> fashion say that the result is 50-50, a measure of complete ignorance.
>>> Yet, were we to toss 10^23 such coins we could predict with
>>> extraordinary accuracy the fraction of coins that are heads and the
>>> fraction that are tails.
>>>
>>> In this analogical story would we say that there was no reason that the
>>> flip of a single coin came up heads? I don't think so. Such a story
>>> was well known long befor QM came along, and no one was led to argue
>>> that we live in a random universe. Well, maybe not no one. It was
>>> probably a common belief prior to the advent of modern science.
>>>
>>> I know that what I'm suggesting seems to lead to hidden variables. I've
>>> just never quite understood the claim that we live in a random universe,
>>> which appears to imply what?
>>>
>>> Is a random universe that is unpredictable? That's epistemological.
>>> Ontologically, it must mean something like events occur for no reason
>>> whatsoever, and yet they are statistically deterministic. This appears
>>> to me, at least, to be a paradox. Does ontological randomness entail
>>> that events occur without any antecedent conditions, not just
>>> unobservable, but none whatsoever. Even with the pennies there are
>>> antecedent condtions: the penny must be tossed.
>>>
>>> In summary, I don't get Polkinghorne's argument. Please, explain.
>>>
>>> thanks,
>>>
>>> bill
>>>
>>> On Thu,
>>> 1 Oct 2009,
>>> mrb22667@kansas.net wrote:
>>>
>>> My comments injected below...
>>>>
>>>> Quoting David Clounch <david.clounch@gmail.com>:
>>>>
>>>>
>>>>> Polkinghorne and Beale write about determinism and the
>>>>> brain1<#sdfootnote1sym>
>>>>>
>>>>>
>>>>> Consider a single nitrogen molecule in the air you are now breathing.
>>>>> On
>>>>> average it is traveling 450 m/s and bounces off about 7 billion other
>>>>> air
>>>>> molecules every second, thus 7,000 every microsecond. Suppose you knew
>>>>>
>>>> the
>>>
>>>> exact position and momentum of every one of these particles (even though
>>>>> this is impossible by Heisenberg's uncertainty principle), then perhaps
>>>>>
>>>> you
>>>
>>>> could, at least in principle, predict exactly where that nitrogen
>>>>>
>>>> molecule
>>>
>>>> would be one microsecond later. Of course there are all kinds of
>>>>> complications, such as electrostatic forces, angular momentum, and so
>>>>> on,
>>>>> but lets make it simple and pretend that these were all perfect spheres
>>>>>
>>>> and
>>>
>>>> Newton's laws exactly applied – the kind of eighteenth-century
>>>>>
>>>> worldview
>>>
>>>> that shaped the Enlightenment and still influences much of our thinking.
>>>>>
>>>> But
>>>
>>>> suppose a tiny error is introduced in the angle at which this air
>>>>>
>>>> molecule
>>>
>>>> is traveling, for any reason at all. A little bit of uncertainty about
>>>>>
>>>> the
>>>
>>>> position of an electron, say. Call this error (epsilon). After one
>>>>> collision, the error is 2 ; after two collisions 4 , and so forth.
>>>>> Each
>>>>> microsecond this error will increase by 2^7000, or roughly 10^2100. The
>>>>> situation is clearly hopeless even if the initial error corresponds to a
>>>>> Planck length (1.6 x 10 ^ -35 m – the smallest possible length, at
>>>>>
>>>> which
>>>
>>>> conventional physics breaks down) per meter, after just 97 collisions the
>>>>> uncertainty will be enough for the position of the molecule to be out by
>>>>> more than the diameter of a nitrogen molecule (6.2 x 10^-10m), which
>>>>>
>>>> means
>>>
>>>> it will miss the 98th target. This will happen in less than a 70th of a
>>>>> microsecond. And making the error one Planck length in the size of the
>>>>> observable universe (about 3 x 10 ^23 m) just means it will miss the
>>>>> 176thmolecule. So even with the unrealistic assumptions of a perfect
>>>>> Newtonian
>>>>> world elsewhere, exact determinism is dead.
>>>>>
>>>>
>>>> It isn't the error amplification (chaos theory) that kills determinism.
>>>>
>>> Because
>>>
>>>> the original 18th century thought assumed up front that such knowledge
>>>> was
>>>> impossible anyway, they had already premised their speculation as being
>>>> so
>>>>
>>> *in
>>>
>>>> principle* since they knew nobody could know all this. And that caveat
>>>>
>>> allows
>>>
>>>> them (and us now even with Chaos theory) to reduce the initial state
>>>> error
>>>>
>>> *in
>>>
>>>> principle* to zero (infinitely smaller than a Planck length). So it is
>>>>
>>> only the
>>>
>>>> Heisenberg uncertainty as mentioned below that actually drives the real
>>>>
>>> stake
>>>
>>>> into the heart of determinism. Yet for all this, it doesn't prevent some
>>>>
>>> from
>>>
>>>> still thinking deterministically about the universe as a strictly causal
>>>>
>>> domain.
>>>
>>>> Since my mind can't fully fathom the nature of our ontological
>>>> uncertainty,
>>>>
>>> I
>>>
>>>> find myself in this deterministically minded camp at least every other
>>>>
>>> Thursday.
>>>
>>>> Maybe the atoms in my brain will happen to bounce that way today.
>>>>
>>>> --Merv
>>>>
>>>> In fact, of course, we use
>>>>> statistical mechanics to describe the behavior of gases and liquids and
>>>>>
>>>> do
>>>
>>>> not try to predict the behavior of individual small molecules. But many
>>>>> people think of the indeterminacy in statistical mechanics as simply a
>>>>> limitation on our knowledge rather than a reflection of real
>>>>>
>>>> indeterminacy
>>>
>>>> as in the quantum world. This kind of argument strongly suggests, to our
>>>>> satisfaction at least, that in cases like the movement of molecules in
>>>>>
>>>> air
>>>
>>>> the indeterminacy is real.
>>>>>
>>>>>
>>>>> They go on to describe calcium ions in te synapses in the brain, and
>>>>> use
>>>>>
>>>> a
>>>
>>>> similar analysis. They conclude:
>>>>>
>>>>>
>>>>> We will see later that this entirely destroys the idea that the brain
>>>>> is
>>>>>
>>>> a
>>>
>>>> fully deterministic system.
>>>>>
>>>>>
>>>>>
>>>>> 1 <#sdfootnote1anc>Questions of Truth, pp. 126-127
>>>>>
>>>>>
>>>>
>>>>
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>>>>
>>>>
>>
>

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Received on Thu Oct 1 19:47:19 2009

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