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According to the second law of thermodynamics, closed systems ultimately reach the state of maximum entropy. The apparent high degree of orderliness of ecological systems and the persistence of this orderliness through time indicates that there is a continuous external input of order (information) into ecological systems. The source of this information is the solar energy, the primary source of energy for life on Earth. Both solar radiation and thermal radiation of Earth consist of particles - photons. Mean energy of one photon is proportional to absolute temperature measured in degrees kelvin. Absolute temperature of Sun is about T$ = 6000 K. Absolute global mean surface temperature of Earth is about TE = 288 K (i.e., about 15 °C). Mean energy of one solar photon is about Ts/ Te = 6000/288 ~ 20 times larger than the mean energy of one thermal photon of Earth. According to the law of energy conservation, the cumulative energy of all solar photons coming to Earth is equal to the cumulative energy ofthermal photons emitted by the Earth into space. It means that the number of thermal photons emitted by Earth into space is about 20 times larger than the number of solar photons reaching Earth's surface. Consequently, one solar photon decays on average into 20 thermal photons. Decay of solar photons gives rise to all ordered, information-rich processes on Earth, of which life is most powerful (Table 1).

Information capacity of a system is characterized by the available number N of memory cells. If a cell's memory can be characterized by only two possible values of a certain variable, the total number of possible combinations of these values in all memory cells is 2N. The system possesses the maximum possible amount of information equal to N bits when the values of the measured variable are defined in all N memory cells. If states of N1 cells remain unknown, the amount of information reduces to N — N1. If the measured variable remains undefined in all memory cells, the information becomes zero while the entropy of the system reaches its maximum.

Solar photons interact with molecules of vegetation covering the Earth's surface. These molecules can be viewed as elementary memory cells of the ecosystem. Solar photons can excite molecules, that is, impart a certain amount of energy to molecules and increase their energy above the average thermal level. A good approximation is to assume that molecular memory cells are characterized by two states - excited (a definite state) and nonexcited (indefinite state) compared to the average chaotic thermal level. During the process of decay, solar photons are able to excite molecules until their own energy becomes equal to the average energy of thermal photons of the Earth's surface. Each solar photon possesses an amount of energy equal to that of about 20 thermal photons of Earth. Consequently, one solar photon can excite about 20 molecules, that is,. impart information to

Table 1 Solar power and some routes of its dissipation on Earth

Power

Power source/sink 1012 W Relative to the solar power

Table 1 Solar power and some routes of its dissipation on Earth

Power source/sink 1012 W Relative to the solar power

Total solar power coming from Sun to Earth

1.7 x 105

1.0

Physical processes

2 x 103

2

Wind power

10-

3

Oceanic waves

103

6x

10-

Natural biota

Transpiration

3 x 103

2x

10-

2

Photosynthesis

102

6x

10-

4

Modern civilization

Energy consumption

10

6x

10-

5

Consumption of the net primary production of the biosphere

9

6x

10-

5

about 20 molecular memory cells. Such consideration makes it possible to estimate the amount of information (in bit s— ) coming from Sun to Earth per unit time. It is roughly equal to the number of thermal photons emitted from the Earth to space, because each thermal photon is emitted from an excited molecule, which represents a memory cell containing one bit of information. The number of Earth's thermal photons emitted to space in a unit of time is equal to the power Q (Q« 2 x 1017W) of solar radiation reaching the Earth divided by the energy e of one thermal photon, which is determined by the Earth's temperature TE, e = kBTE, where TE « 288 K, kB is Boltzmann constant, which is proportional to the reverse Avogadro number (kB = 1.4 x 10— J K— molecule- ). As far as one molecule represents a memory cell with two possible states, dimension molecule-1 in Boltzmann constant corresponds to bit-1. The information flux F coming from Sun to Earth is F = Q/(kBTE) « 1038bits-1.

If one solar photon possesses energy equal to that of Ts/Te « 20 thermal photons, the maximum number of molecules it can excite is Ts/Te — 1 « 19, because after 19 acts of excitation its energy becomes equal to that of one thermal photon. After that it cannot impart any additional energy to molecules, and, therefore, cannot excite them. So, only (TS/TE — 1)/(TS/TE) x 100% = (TS — Te)/Ts x 100% « 95% of Earth's thermal photons come from excited molecules and characterize information flux coming from Sun to Earth. The ratio (TS — TE)/ Ts describes the well-known Carnot efficiency of the solar radiation on Earth. If the Sun's temperature were equal to that of Earth, solar photons would have the same energy as thermal photons of Earth and could not excite any molecules on the Earth's surface. In such a case the information flux from Sun to Earth would be equal to zero.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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