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Re: the energy



On 19-Oct-04 Paolo Cavallo wrote:

What should be added at this point is: mass is also an abstraction.

Mass is a physical concept, matter a philosophical one.
Both are abstractions, but of quite a different kind.
Also, the questions:
a. what is mass?
b. what is matter?
are very different. I don't think we, as physicists, are entitled to
answer to b. We take matter as a fact of life, and go on to study how
it behaves in different condition, e. g. at very high velocities.
Maybe I am wrong on this, but I am pretty sure that you cannot speak
correctly on this matter if you identify matter and mass.

One can make an operational definition of the mass of an
isolated system. Based on this definition one can make a
device to measure the mass of a system.

One cannot make an operational definition of the energy.
No device capable of measuring "energy content" exists,
and I doubt that one is capable of existence.

This difference is important. It is related to my
operational definition of reality.

Leigh