Energy is a set of physics measures. Popularly the term is most often used in the context of energy as a technology: energy resources, their consumption, development, depletion, and conservation. Biologically, bodies rely on food for energy in the same sense as industry relies on fuels to continue functioning. Since economic activities such as manufacturing and transportation can be energy intensive, energy efficiency, energy dependence, energy security and price are key concerns. Increased awareness of the effects of global warming has led to global debate and action for the reduction of greenhouse gases emissions; like many previous energy use patterns, it is changing not due to depletion or supply constraints but due to problems with waste, extraction, or geopolitical scenarios.
In the context of natural science, energy can take several different forms: thermal, chemical, electrical, radiant, nuclear, etc. These are often grouped as being either kinetic energy or potential energy. Many of these forms can be readily transformed into another with the help of a device - from chemical energy to electrical energy using a battery, for example. Most energy available for human use ultimately comes from the sun, which generates it with nuclear fusion. The enormous potential for fusion and other basic nuclear reactions is expressed by the famous equation E = mc2.
The concepts of energy and its transformations are useful in explaining natural processes on larger scales: Meteorological phenomena like wind, rain, lightning and tornadoes all result from energy transformations brought about by solar energy on the planet. Life itself is critically dependent on biological energy transformations; organic chemical bonds are constantly broken and made to make the exchange and transformation of energy possible. Read more...