ABSTRACT
Explanation. In the 1992 presidential campaign, candidate Bill Clinton kept saying to his staff, “It's the economy, stupid,” to remind them that the state of the U.S. economy was the main issue at that time. In the future it may well be “It's energy, stupid!” If you were asked to pick out a single common denominator for life on earth, that is, something absolutely essential and involved in every action, large or small, the answer would have to be energy. We use the word “energy” for the ability or capacity to do work, with work defined in the broadest sense of to do or perform something. While you are working at your job or hobby or relaxing, or even sleeping, your body is performing thousands of vital functions that require energy of a specific amount and kind. The fantastic variety of organisms and functions involved in keeping our air, water, soil, and food life-support systems operating requires a great deal of energy.
