86 The Poetry of Physics and The Physics of Poetry
the form of potential energy by virtue of its position. Once the body
begins to fall this potential energy is converted into kinetic energy.
Summing up our discussion of work, we see that work can generate the
different forms of energy we have so far encountered namely heat,
motion (or kinetic energy) and potential energy, and that these different
forms of energy are interchangeable.
In addition to the forms of energy that we have so far discussed, there
are other forms, which also deserve mention. For example, there is
chemical energy, the energy that is released by chemical reactions. It is
the source of energy that generates the heat within our bodies and the
work and motion we are able to generate with our bodies. There is also
light energy, the energy of electromagnetic radiation, which is the form
of energy by which the Sun transmits its energy to Earth. Sound is
another form of energy, which in fact is the kinetic energy of the air
molecules, the oscillations of which create sound.
There is also nuclear energy, the energy generated by the nuclear
processes of fission, the splitting of a heavy nucleus of an atom into
smaller nuclei and neutrons, and nuclear fusion, where smaller nuclei
combine to form a larger nucleus. In both fission and fusion mass is
destroyed and converted in energy according to Einstein’s famous
formula E = mc^2. This energy is popularly referred to as atomic energy,
when in fact it is nuclear energy. It refers to the energy released both
peacefully by atomic reactors and violently by A-bombs and H-bombs. It
is also the source of the tremendous amount of energy generated by the
Sun. Energy takes many forms. The processes of nature may be
considered as the conversion of energy from one form to another.
The Sun is the original source for the different forms of energy we
find on Earth with the exception of geothermal energy due to radio-
activity. The energy we derive from our food whether animal or
vegetable originates with the vegetation of the Earth. The energy stored
in plants is a result of the process of photosynthesis whereby plants
transform the energy of sunlight into chemical energy and store that
energy in the form of hydrocarbons. The energy generated in the Sun by
nuclear fusion is converted into heat or internal motion of atoms of the
Sun. The internal motion of the atoms causes them to radiate light, which
propagates to the Earth and through photosynthesis is converted into
chemical energy or food. This chemical energy or food is then converted
through oxidation into body heat and motion. The energy of our bodies,
therefore, had its genesis in the Sun and has assumed many different