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[Phys-L] Re: Fields etc

Jack, I don't know if I'm walking into a mine field here, but I think
we got circularity here.

I think the charge is defined (measured) by the force, not the other way
around.

bc, worried.

Jack Uretsky wrote:

Go back to basics, in this case the definition of "field". Charged
objects, in a certain region, experience forces that are proportional to
the charges, and for each object there is a unique force vector at each
point of the region. Divide the force vector by the associated charge on
the object. The resulting set of vectors is called the "vector field in
the region". Is it real? Depends upon your definition of reality. The
force vectors were measurable; does that fact make them "real"? This is,
an example that is appropriate to an electrostatic of gravitational field.

A vector field is, simply stated, a process that assigns a unique vector
to each point of a space - where I use "space" in a generalized sense that
includes ordinary 3-d space as a special case.

Regards,
Jack

On Fri, 25 Mar 2005, Hugh Haskell wrote:

At 21:47 -0700 3/24/05, Daniel Crowe wrote:

Does "real" necessarily imply a tangible object? Can intangible
properties be real? I don't know that anyone is arguing that fields and
energy are tangible objects. Can anyone explain what it means to say that
an intangible property is real? Or is it impossible for an intangible
property to be real? Is the color blue real, or is it just a convenient
fiction? Are quarks and leptons real, or are they just convenient
physical models of reality? Are they just shadows in Plato's cave? Is
reality limited to Plato's forms?

What seems to me to be real is the action at a distance between
tangible bodies. The there is some interaction among them seems
undeniable to me. Fields provide a relativistically consistent way to
explain that action at a distance, so in that sense, one could call
them "real." However, at the quantum level, we replace fields with
"exchange particles," also apparently intangible, but certainly a
more concrete concept than a field. Does that make exchange particles
more real than fields? I dunno. Energy, fields and exchange particles
are all constructs that have been invented to account for what we
observe. Does that make them imaginary? Again, I dunno. There is
always the possibility that in one or more of these ideas, we have
hit upon the "real" solution to the problem, but since all three are
intangible, I don't see how we can ever know if that is true.

After all, we treat electrons as tangible things, but we have never
seen one, just lots of evidence that they were where we looked a some
time shortly before we looked there, and of course, chemistry is
certainly well-explained by the existence and imputed properties of
electrons, but are they any more real that fields, energy or exchange
particles?

At what point can we stop asking these questions and simply say this
is real and that isn't? I think this is one of the central questions
of epistemology, and I suspect that no one has ever some up with a
final answer to the question. I certainly can't conceive of my feeble
mind inventing the two computers that sit on my desk in front of me,
or even of the chair that supports my rear end. But I can't prove
otherwise, either.

It's fun to talk about it, though.

Hugh
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