We can view the flow of energy from sun to earth and back to outer space as constituting a great natural open system. In the broadest sense, an open system is any organized configuration of matter open to the inflow or outflow of energy or matter, or both. The life layer, man's environment on earth, can be regarded as an open system with arbitrary boundaries-one in the atmosphere above and another lying at the base of a shallow layer of soil or water. It is through the upper boundary that the open system of the life layer has its input and output of energy.
Within the life layer energy moves in many complex pathways. These movements of energy require the presence of matter, both to transport energy from place to place and to store it temporarily. Air and water, as highly mobile fluids, are the principal transporters of energy. Solid earth materials, such as soil, rock, and organic compounds along with air and water, provide for storage of energy within the open system. Placing energy in storage requires that it be transformed. Thus incoming solar energy in the radiant form goes into storage as sensible heat. In this form the energy may be transported by moving air or water, or it may be further transformed into latent energy.
An essential principle in the operation of open systems is that they tend to attain a dynamic equilibrium or steady state, in which rate of input of energy and matter equals rate of output, while the quantity of stored energy and matter within the system remains constant. In the case of the total global system of atmosphere, hydrosphere, and lithosphere only energy enters and leaves the system. Matter remains within the system boundary where it is forced to run repeatedly through flow cycles. Matter is thus recycled within the system. We can conclude that with respect to matter only, the global system is closed, rather than open. Energy, on the other hand, is cycled within the system and also enters and leaves the system.
"The world is a book, and those who do not travel read only a page", St. Augustine said. Here at www.travel-university.org we believe that every page must be read and explored. Travel is an avenue of learning that no text or classroom can teach. The world is a living classroom and you the student. We invite you to the www.travel-university.org library where you can read general interest and detail oriented articles.
