Re: Entropy vs energy
- From: "Edward Green" <spamspamspam3@xxxxxxxxxxx>
- Date: 20 Aug 2006 08:01:49 -0700
Mike wrote:
Could you folks check me out on something. Is the following statement
true? The earth does not actually gain energy from the sun since earth
radiates away as much energy as it gets from the sun. Rather the earth
gets ``low entropy" from the sun by receiving a relatively fewer number
of high frequency photons and then radiating away the same energy
equivalent in the form a greater number of low frequency photons.
You may be able to understand it that way, but I would simply say that
processes on the Earth, suspended between a source at a high
temperature and a sink at a low temperature (space) is running your
friend and mine, a heat engine.
I assume something similar is going on when I feel hungry and need
replenishment. Is it energy I seek, or ``low entropy", or both?
The Fathers of Thermodynamics coined a term just to answer such
questions: what you seek is _free_ energy, which is, roughly, the
ability to do work. The ability to do work is, roughly, the ability to
create some entropy, so you could say we seek low-entropy, or, as I
just learned from following a link provided by a crank/troll -- which
shows that few people have absolute zero utility -- what Shrodinger
called "negentropy".
As to whether "the Earth receives energy from the sun", that's
partially semantics. Energy is certainly flowing from Sun to Earth,
even if reradiated into space. During times when biomass is
accumulating, there may be a trivial retention.
.
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