Encyclopedia Britannica Illustrated Science Library 2009 14 – Energy and Movement

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Encyclopedia Britannica Illustrated
Science Library 2009 14 – Energy and Movement
Edition 2009
pages 56


Encyclopedia Britannica Illustrated
Science Library 2009 14 – Energy and Movement

.We use the word “energy” daily to refer
to different things. We are told, for instance, that certain food does not
provide sufficient energy; we are told about the exploitation of energy
resources; or we are warned by the politicians about the energy
crises. When we are tired, we have “no energy.” We also hear about
alternative sources of energy and the mention, by some religions and
pseudosciences, of spiritual energy and so on. But what is
energy? In general, and in the sense used in this book, energy
is “the potential to produce change,” the capacity to act,
transform, or set in motion. Other accepted meanings that we
will use refer to energy as a natural resource and as the technology
associated with exploiting and using the resource, both
industrially and economically. The development of steam engines during
the Industrial Revolution generated the need for engineers to develop formulas
and concepts to describe the thermal and mechanical efficiencies
of the systems they were developing. Thus, they began speaking
about “energy.” Energy is an abstract physical quantity. This means
that it cannot be measured in a pure state but that only variations of
energy in material systems can be observed. These variations are
equivalent to the work required to change one system from
its initial state to a subsequent one. Energy cannot be created
or destroyed; it can only be transformed from one form to another.
Obviously there are forms of energy that can be transformed
or used more easily than others and, in the end, all forms
of energy will become heat energy, one of the most disordered
forms of energy. This loss of energy in the form of heat results
in machines and human-developed processes working with less
than the 100 percent efficiency one would expect if one were
to apply the principle of the conservation of energy literally.
However, as already mentioned, there is also another
definition of the word “energy” that refers to the natural
resources necessary to produce energy as engineers and
physicists understand it. This understanding of energy is
very important and affects us all. Its role in the global
economy is essential, and it could be said that most recent
wars have had as one of their goals the control of energy
resources both renewable and nonrenewable. I n this book, we
present some of the most important sources of energy used by
humanity. We show how human ingenuity has been able to
put the different forms of energy at its service by developing
machines of all kinds, and we describe some of the most
important manifestations of energy in the natural world. We
also dedicate a chapter to describe the uses of clean, renewable
sources of energy, including solar, wind, water, and geothermal
sources. Finally, we list some of the inventions that people
throughout history have developed to satisfy their instinct to
explore. These are inventions that made people move faster
and travel farther with less and less energy. The progression
from animal driven transportation to steam engines and
internal-combustion engines is a key to understanding
. modern civilization