Geoscience Reference
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life and is also a central concern, given the heavy impact of energy consumption on
the environment, especially in the last two centuries. Material underpinnings to
economic success are not to be underrated, in their opinion. 1
1.2 Denitions and Concepts
1.2.1 An Economic De
nition
In daily life we have direct contact with matter, but not with energy. Matter can be
touched, its form described and it is to be found underfoot as well as around us.
With energy it is different. Its indirect effects are only perceived deriving from
changes either in the structure, that is the molecular or atomic composition of
matter, or in its location in space, such as in the case of a stream of water or wind,
whose potential energy we can exploit. In both cases effects such as movement, heat
or light reveal the presence of what we call energy from about 200 years.
In physics energy is de
ned as the ability of bodies to perform work. 2 Since
work is the result of force by distance, then energy includes any movement of some
material body in space together with the potential energy deriving from its position.
Heat as well is the result of the movement of the components of matter. When
dealing with the economy and then with the interrelationship between humans and
the environment, our de
ne energy in
economic terms as the capacity of performing work, useful for human beings,
thanks to changes introduced with some cost or effort in the structure of the matter
or its location in space. Solar heat is of primary importance for the existence of life.
The de
nition must be a little different. We could de
nition of energy in physics includes it. Since it is a free source of energy, it
is not included in our economic de
nition; whereas the capture of solar rays by
means of some mechanism in order to heat water or produce electric power is
included. In the
rst case solar heat is not an economic resource, while it is in the
second. The formation of biomass in a forest is a transformation of the Sun
'
s energy
by the plants through photosynthesis and is not included in this de
nition either. On
the other hand,
rewood is included, which is a part of forest biomass used by
human beings for heating, cooking and melting metals. Food is a source of energy
in economic terms, since its consumption enables the performance of useful work
and its production implies some cost. Food for animals is only exploitable, and then
it is an economic resource, when metabolised by those animals utilized by humans
for agricultural work. It is their fuel, and, since the power of the working animals is
exploited by the people, its calories have to be divided among the consumers (such
as the fuel of our cars today is divided among the population and is part of their per
capita consumption). When consumed by wild animals in a forest, however, these
1 On these topics see the rst two chapters of Kander et al. ( 2013 ) chaps. 1 and 2.
2 Useful the discussion of the de nitions of energy in Kostic ( 2004 , 527 - 538) ( 2007 ).
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