Juan R. González-Álvarez 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.


Either you are not reading or just lying.

Neither. You did not read what I wrote carefully enough.

It is well-known that textbooks and papers *often* invoke *causality* to
select the retarded potentials:
http://adsabs.harvard.edu/abs/1992AmJPh..60..465A
(\blockquote
The use of retarded potentials in solving the wave equation is usually
justified on physical grounds or else by an appeal to *causality*.
) Emphasis mine.

Sure. But there is a GREAT BIG PUN involved, and the word "causality"
here does NOT mean the same thing as when I used it IN VAN FLANDERN'S SENSE.


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.


** quantum field theory most definitely has what you call "creation
ex nihlo" and "demise ad nihil".
Surely it does not, Tom.
Particle pairs pop in and out of existence spontaneously. The quantum
vacuum clearly does what he calls "creation ex nihlo" and "demise ad
nihil".

But you are making a beginner mistake because a quantum vacuum is not
empty and Tom van Flandern's "creation ex nihlo" refers to creation out
from nothing, or like Tom van Flandern would probably say: "empty space".

I was discussing VAN FLANDERN'S statements, not QFT. I merely pointed
out that QFT violates his statements. Yes, there are subtleties, but
they, like the above, involve PUNS on the words used. Your statements
here do not use the words in the same way Van Flandern uses them.

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
"caused" them to "pop out". This _IS_ what VAN FLANDERN means by
"creation ex nihlo" -- even though the vacuum is not "empty", his phrase
applies.


A small problem is you have not the exclusive of the definition of
science, even if you believe you have one.
Making up "principles" like Van Flandern does has not been part of ANY
definition of science, since the middle ages.

That is your belief Tom, just that. Like or not like it, science is that
is published in textbooks, journals and discussed at conferences.

Nowhere is science related to making claims about the world and then
expecting Nature to obey those claims. That is what Van Flandern is
trying to do, and that simply is not science. shrug


Tom Roberts