Re: [asa] Results of Cameron's Survey

From: George Murphy <>
Date: Tue Jun 30 2009 - 08:53:37 EDT

Moorad -

Your definition of "virtual particle" is of course correct but your closing
statement about photons seems odd. Whether or not all pgotons are in the
process of being absorbed (as required, e.g., by the old Feynman-Wheeler
theory) is debatable. But even if that's correct, why aren't transverse
photons travelling through a vacuum "real" between emission & absorption?
Of course to detect them you have to absorb them but the same is true for
electrons &c.


----- Original Message -----
From: "Alexanian, Moorad" <>
To: "wjp" <>; "David Clounch" <>
Cc: "George Murphy" <>; "Iain Strachan"
<>; <>
Sent: Tuesday, June 30, 2009 7:47 AM
Subject: RE: [asa] Results of Cameron's Survey

Technically, virtual particles are particles that are not on the mass shell,
that is, E^2 is not equal to p^2+ m^2, where I have set the speed of light
in vacumm =1. E=energy, p= momentum and m=mass. Free particles are the
only particles that are on the mass shell. For instance, photons, with m=0,
are always virtual since they are always in the process of being absorbed
and so actually are never free.

From: [] On Behalf Of
wjp []
Sent: Tuesday, June 30, 2009 1:33 AM
To: David Clounch
Cc: George Murphy; Iain Strachan;
Subject: Re: [asa] Results of Cameron's Survey


Methodological Naturalism (MN) is an agnostic position.
As such, it bears some resemblance to Bohr's attitude toward
QM and the entire unobservable, abstract physics of
atomic physics.

His attitude would have been to assign reality to the
commonsensical world of our experience, but say nothing of
the reality of this unobservable world.

As such, it seems that he would have assigned no reality to
entities such as virtual particles, and who knows what else.
I presume he would have assigned reality to electrons and
protons, but perhaps have said little of their properties.

Instead, the physics of this world is more to be treated as
a formal procedure by which observables are predicted.
In some sense, it appears to be a throw back to Ptolomeic
science. Not even, so much, an instrumentalism, for that
is committed to seeing scientific theory as only a tool.
That may be saying too much for Bohr.

Bohr apparently believed that this fantastic invisible
world was beyond the ken of the human mind. We should
therefore not attempt to say much about it, for it would
generally be misleading or just plain wrong. But that
did not mean that a predictive theory could not be devised
and empirically tested.

What similarity does this bear to MN? The motivation for
MN appears to be different. As Duhem argued, the purpose
of something like MN was to prohibit science from adopting
a particular metaphysics. It was intended to be
metaphysically neutral so that all could participate.
Whether this was possible was discussed by Plantinga and
found lacking. MN was suppose to be a big tent, housing
realists and anti-realists of all stripes.

The supposed wall of separation between discovery and
theory assessment permitted the theories of science to
exist in a kind of platonic bubble, untouched by
human hands. Discovery, on the other hand, is a
dirty business for it relies upon metaphysics,
attitudes, goals, and the price of beef.

MN is adopted for the sake of the scientific community.
Whereas Bohr's view of QM was adopted for epistemological
reasons. MN, one might say, was adopted because of the limits
of human community, whereas Bohr's view (complementarity) was
adopted because of the limits of human understanding.

Is there any value in the comparison?


On Mon, 29 Jun 2009 11:33:09 -0500, David Clounch <>
> George wrote:
> "but is a statement that position-momentum pairs that violate it don't
> exist. "
> Q1.
> George, my question is (because I don't know the rules) is this true for
> virtual particles as well?
> The reason I ask is it seems to me virtual particles exist ontologically
> but not in a way we could ever observe.
> [an aside]
> My son was telling me about muon decay and how it produces a number of
> virtual particles, and there are always a neutrino/anti-neutrino virtual
> pair produced, but these almost always destroy each other. But about
> every
> millionth time they don't and the neutrino exits. And these neutrinos are
> always left-handed. He was trying to tell me about the fact that all
> neutrinos are left handed but there is no law or rule of nature as to why
> it
> should be that way - that nobody knows why. My point is there are at
> least
> 10^6 virtual pairs for every real neutrino.
> [end aside]
> Obviously scientists believe in virtual particles. But, if we can never
> observe them, are they really there? Aren't they beyond the edge of MN?
> aren't they just something we pretend are there so we can get a logical
> reason for things we are able to see (the observed products).
> I agree with your statement as applied to real particles. Its not just
> about
> limits of knowledge, but is a real statement about existence. I'm just
> wondering if the same QM rules apply to virtual particles.
> Q2.
> If virtual particles are just a game and don't have ontological
> existence,
> then under the rules of MN aren't they really in the same category as
> other beyond the (playground) edge topics (like ID is alleged to be)? If
> the answer is yes, then are teachers allowed to discuss these areas where
> God plays dice?
> On Mon, Jun 29, 2009 at 11:10 AM, George Murphy
> <>wrote:
>> Iain -
>> This gets into the murky area of the interface between classical chaos
>> theory & quantum mechanics, where I claim no great expertise. Since
> quantum
>> mechanics is linear there's no "quantum chaos" in a straightforward
> sense.
>> But in specifying the initial conditions more & more precisely for a
>> classical system, as you suggest below, you'll eventually get to the
> limit
>> specified by the uncertainty principle, & below that point you can't go.
>> With a strong interpretation of QM even God can't because the
> uncertainty
>> principle is not just about limits on what we can measure but is a
> statement
>> that position-momentum pairs that violate it don't exist.
>> Shalom
>> George
>> ----- Original Message -----
>> *From:* Iain Strachan <>
>> *To:* George Murphy <>
>> *Cc:*
>> *Sent:* Monday, June 29, 2009 11:13 AM
>> *Subject:* Re: [asa] Results of Cameron's Survey
>> On Mon, Jun 29, 2009 at 3:52 PM, George Murphy<>
>> wrote:
>> > You can put me down with Terry's #4. (Or, if only the 3 answers given
>> > originally are allowed, as is usually the case with standardized
> tests,
>> I'll
>> > take #3 "under protest.")
>> >
>> > I would not absolutely rule out the idea of front-loading of design
> (#2)
>> but
>> > it seems to me that hardwiring the detailed outcome of any physical
>> process
>> > into its initial conditions billions of years in advance is just the
> sort
>> of
>> > thing that chaos theory - which is more precisely "sensitivity to
> initial
>> > conditions" - rules out for systems of any complexity (i.e.,
>> nonlinearity).
>> George:
>> Just a quick query here. Is it not the case that it's not ruled out so
>> much as non-computable
>> For example if I try to integrate the third order non-linear
> differential
>> equations for the Lorenz
> Attractor<>then I experience
> that if a slight change is made to the initial values of
>> the state variables, then after a certain time, two runs that are
> otherwise
>> the same diverge and bear no resemblance to each other. But the smaller
> the
>> initial delta, the longer it will take to diverge. However, divergences
> can
>> be observed even at the machine precision level, for example if I change
> X0
>> to X0*(1+eps) where eps is the smallest constant so that in the machine
>> 1+eps > eps. (In standard double precision arithmetic eps has the
> value
>> 2.2204e-016).
>> But if one had a machine with billions of bits of precision for the
>> arithmetic, instead of 53 (double precision arithmetic has 53 bits for
> the
>> mantissa, 10 for the exponent and 1 for the sign, making 64 in total),
> then
>> it's clear that macroscopic changes in the outcome will only appear
> after an
>> immensely long time because the corresponding value of eps is so much
>> smaller.
>> So I wouldn't have said it was ruled out unless God only uses 64 bit
>> arithmetic!
>> Iain

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Received on Tue Jun 30 08:54:33 2009

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