Re: the energy

[Paolo Cavallo <ton0621@IPERBOLE.BOLOGNA.IT>]

----- Original Message -----
From: "Leigh Palmer" <palmer@SFU.CA>
To: <PHYS-L@LISTS.NAU.EDU>
Sent: Friday, October 22, 2004 10:28 PM
Subject: Re: the energy


> On 19-Oct-04 Paolo Cavallo wrote:
>
> > What should be added at this point is: mass is also an abstraction.
> >
> > ...
>
> One can make an operational definition of the mass of an
> isolated system...
>
> One cannot make an operational definition of the energy.
> ...
>
> This difference is important. It is related to my
> operational definition of reality.

I agree that the difference is important, but I cannot find
it relevant here.
"Abstraction" is not the same as "fictional". *Any* concept
in physics is an abstraction, not a "thing". It is (as in
the much quoted Einstein) a human construct. But it
describes reality as we experience it.

"Reality" and "matter" are philosophical concepts, "mass"
and "energy" physical ones. In physics we cannot say a thing
about issues like "What is matter?" or "Is the world real?".
We take the reality of the world for granted.

(I wish I could tell it better, but my English is not as
good as I would need.)

(And, yes, I would like to know your operational definition
of reality, too. I'm sure it's interesting.)

============================================================
Paolo Cavallo                 " I am a teacher at heart, and
                          there are moments in the classroom
                           when I can hardly hold the joy. "
                                        P. J. Palmer, 1998
paolo.cavallo@iperbole.bologna.it
http://paolo.cavallo.free.fr
============================================================