Newton defined energy as a force which is is capable of moving things. Since then
the concept of energy has often changed. At the beginning of the century Einstein
introduced the equation e = mc˛. Apart from this equation there is another very well
known scientific law - the first law of thermodynamics i.e. energy can neither be created
nor destroyed - only transformed. Although energy doesn’t change its form does.
For example gravity is a form of energy. In a plant powered by water, water through
the force of gravity flows over large turbine wheels and produces electricity i.e. gravity
was transformed in electricity. Electricity is transformed into light, light penetrates our eye
and sets off a nerveimpulse. Here we are dealing with changes of forms of energy.