Earth system
A circa 2010 Carnot cycle model (thermodynamic system) view of the surface section of the earth.
In science, the Earth is the third planet rotating about the sun, intermediate between the orbits of Venus and Mars. [1] The solar flux of energy received by the earth at its surface is 1370 watts per meters squared.

The Earth, according to the science of environmental physics, is defined as a thermodynamic entity: [2]

“At the macroscopic level the Earth is a thermodynamic entity. Life is sustained on it because of the temperature gradient maintained by the net energy balance between the energy that comes from the Sun and the energy that leaves the Earth. At the microscopic level, i.e. the level of the individual person or animal, living organisms are also thermodynamic structures exhibiting energy exchanges between themselves and the environment.”

A surface section of earth is defined as an earth-bound thermodynamic system.

Solar chemistry
In human chemistry, the earth is defined as an “earth molecule”, i.e. a large 92-element molecule. [3] In this view, animate atomic structures, such as "human molecules", are attached to the surface of the earth; in same manner as "bacteria molecules" are attached to the surface of humans; in the same manner that lipopolysaccharides, i.e. large endotoxin-type molecules, are attached to the outer surface of gram-negative bacteria.

Thermodynamic system models
See main: System, Thermodynamic system, Biological system, Social system, Economic system, etc.
There are a number of various ways to study the earth from the perspective of thermodynamic analysis, some more intuitive, others less so, depending upon where the boundary is drawn and what time periods or cycles (heat inputs, heat outputs) are studied. A few of these diagrammatic attempts are shown below:

Photon mill (1982)
The original 1982 schematic of the earth or earth surface section acting as a photon mill, by German physical evolutionists Werner Ebeling and Rainer Feistel, depicting the estimation of the terrestrial entropy export, about which the earth is described as existing at mean surface temperature of about 300 K, located amid a radiative thermal gradient of 6000 K (the hot sun) and 3 K (the cold cosmic background), through which the flow of photons (similar to the flow of water in a water mill), operate, as they describe in 2011, as such: “entropy production necessarily accompanies the multiple self-organization phenomena and sustained dissipative structures observed in our natural environment.” [7]

Scott sun earth model (1985)
The 1985 sun-earth model by American physical organic chemist George Scott. [6]

earth sun system Roland
A 1992 thermodynamic view of the earth diagram made by Canadian biophysicist Marek Roland-Mieszkowski used to explain life in relation to entropy and energy. [4]

Photon mill (Peter Strazewski)
A circa 1999 rendition of a photon mill from Peter Strazewski’s talk “A Pleading for Chemistry”, based on the 1994 version by Werner Ebeling and Rainer Feistel, which describes a photon mill as being the main driving force for the self-organization and evolution on planets. [9]

A 2004 online German animated gif version of a "Photonenmühle", described as such: “the mill supplies the earth with photons or physical negative entropy and provides information for life processes”, or something along these lines. [10]

Earth sun system (Schneider)
A modified 2005 version of Roland's sun earth system diagram Hawking temperature of outer space by American ecologist Eric Schneider and science writer Dorion Sagan. [5]

Earth sun system
A 2005-2008 temperature difference view of the earth made by American chemical engineer Libb Thims, based on Schneider-Sagan version, with the "hot photon" and "cold photon" labels removed, as these were found to be objectionable terminologies by many. [3]

Earth (heat engine view)
A 2007 Carnot cycle depiction of a given earth surface section, from American electrochemical engineer Libb Thims's Human Chemistry; an upgrade, so to speak, to the 1982 photon mill concept, taking into account (a) the rotative nature of the earth, and (b) the volume expansion and volume contraction aspects of each surface-attached system. [8]

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1. Daintith, John. (2005). Dictionary of Science. Oxford University Press.
2. Mason, Nigel, Hughes, Peter, and McMullan, Randall. (2001). Introduction to Environmental Physics (ch. 2: The Human Environment, pgs. 17-55). Taylor and Francis.
3. (a) Thims, Libb. (2008). The Human Molecule (ch. 8: Modern Views, section: “Planetary-sized molecules”, pgs. 57-59) (preview). Morrisville, NC: LuLu.
(b) Thims, Libb. (2007). Human Chemistry (Volume One) (pgs. 20-21, 44, 53) (preview), (Google books). Morrisville, NC: LuLu.
(c) Solar-gradient.jpg - Wikipedia.
4. Roland-Mieszkowski, Marek. (c.1992). “Life on Earth - Flow of Energy and Entropy.” (PDF), Digital Recordings.
5. Schneider, Eric D. and Sagan, Dorion. (2005). Into the Cool - Energy Flow, Thermodynamics, and Life (pg. 164). Chicago: The University of Chicago Press.
6. Scott, George P. (1985). Atoms of the Living Flame: an Odyssey into Ethics and the Physical Chemistry of Free Will (pg. 175). University Press of America.
7. Ebeling, Werner and Feistel, Rainer. (2011). Physics of Self-Organization and Evolution (§3.1: The Photon Mill, pgs. 88-). John Wiley & Co.
8. Thims, Libb. (2007). Human Chemistry (Volume One) (pg. 53). Morrisville, NC: LuLu.
9. Photon mill – Paul Reisberg, Chemistry Department, Wellesley College.
10. Photon Mill (German → English) –

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