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Re: [Phys-L] Sources of all of Earth's energy



Beware that the word "energy" has multiple inconsistent meanings.
Even within the present seemingly-narrow context there are two
wildly different meanings.
-- There is the physics /energy/. It is conserved. It cannot
be created or destroyed.
-- There is the DoE "energy". It is not conserved. People will
pay you money to "create" this kind of "energy".

Ideas are more important than terminology. Terminology is important
only insofar as it helps us formulate and communicate the ideas.
Alas, in this case, the terminology is *not* helping.

In terms of physics energy, people don't pay you to make energy;
to a first approximation they pay you to make energy /flow/ in
useful ways. As a negative example, consider the rest-energy
of a lump of stone. There is an enormous amount of energy there,
but it's not worth much, because it does not flow in any useful
way.

To address the question that was asked: In terms of physics
energy, the sun explains most of the large-scale energy /flows/
that we see on earth. The main exception is radioactivity.
Geothermal energy-flow is a subcategory of radioactivity, since
it is mainly a manifestation of radioactivity within the earth.

People try to quantify the DoE energy using the same units as
physics energy, but this by-and-large misses the point. They
ought to be measuring the /usefulness/ of the energy-flow.
That's important, but the topic belongs more to economics than
to physics.

=============

BTW similar words apply to electricity. Electric charge is
conserved. It cannot be created or destroyed. People don't
pay you to create electric charge; they pay you to make
electric charge /flow/ in useful ways.