Tom Roberts wrote on Mon, 05 May 2008 09:35:50 -0500:
Juan R. González-Ãlvarez wrote:
Tom Roberts wrote on Sun, 04 May 2008 10:10:36 -0500:
The choice of
retarded vs advanced potentials is boundary conditions, not
"causality",
Note the quotation marks -- I was using the word "causality" in VAN
FLANDERN'S SENSE.
Tom van Flandern did a remark about causality, Every effect has an
*antecedent* cause.
That is the meaning taken in textbooks when selecting the retarded
potentials. It is believed that effects precede the cause for advanced
potential.
Moreover, in some sense, it is wrong to speak about "boundary
conditions" for that case.
Not really. It is boundary conditions applied to the Green's function.
This _IS_ how we use the language.
Speaking about boundary conditions in the four dimensional space is
really wrong thing to do. Dynamical questions, causality, and other
issues are better solved in the 3+1 formalism.
I was discussing VAN FLANDERN'S statements, not QFT. I merely pointed
out that QFT violates his statements.
You did a beginner mistake when said that quantum field theory has
"creation ex nihilo" and "demise ad nihil".
In particular, those virtual pairs DO NOT EXIST in the vacuum BEFORE
they "popped out of the vacuum", and no other contents of the vacuum
From the section on virtual particles in the link i provided before
http://en.wikipedia.org/wiki/Vacuum_state
(\blockquote
These virtual particles are included in the definition of the vacuum.
)
Maybe you would also take a look to
http://www.ts.infn.it/physics/experi...s/quantum.html
for a 'picture'. Tom van Flandern 'empty space' is also pictured.
Nowhere is science related to making claims about the world and then
expecting Nature to obey those claims.
Science is a dialog with Nature.
--
http://canonicalscience.org/en/misce...guidelines.txt