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Re: [Phys-L] Perpetual Motion Machine, Earth as



Why, then would the solar system, for example, be any less of a "machine"
than any human construct?

On Thu, Mar 26, 2015 at 10:45 AM, John Denker <jsd@av8n.com> wrote:

On 03/26/2015 07:28 AM, Bill Norwood wrote:
Might as well open this one up for critique:


Earth is a better perpetual motion machine than anything on it could ever
be, say, relative to a human lifetime.

The critique is this: That's just word games.

The term "perpetual motion" in this context is
an /idiomatic expression/. That is to say, you
cannot infer its meaning based on the separate
words "motion" and "perpetual". Just because
something is in motion, perpetually, does not
make it a perpetual motion machine.

As another example in the word-games category,
consider an oxygen atom, or perhaps one of the
electrons in an oxygen atom. It is perpetually
in motion, and will outlive even the earth.

==========

If we want to do physics, as opposed to word
games:

A perpetual motion machine of the first kind
violates the first law of thermodynamics i.e.
local conservation of energy.

A perpetual motion machine of the second kind
violates the second law of thermodynamics i.e.
local paraconservation of entropy.

The earth is not either of these things.

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