finite sources of energy, such as petrochemicals derived from fossil fuels, can be seen as a nest egg, something to be preserved for emergencies, then used sparingly—in certain medical situations, for example. For the majority of our simple energy needs, humans could be accruing a great deal of current solar income, of which there is plenty: thousands of times the amount of energy needed to fuel human activities hits the surface of the planet every day in the form of sunlight.
