<P> Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature . </P> <P> Mass and energy are closely related . Due to mass--energy equivalence, any object that has mass when stationary (called rest mass) also has an equivalent amount of energy whose form is called rest energy (in that frame of reference), and any additional energy (of any form) acquired by the object above that rest energy will increase the object's total mass just as it increases its total energy . For example, after heating an object, its increase in energy could be measured as an increase in mass, with a sensitive enough scale . </P> <P> Living organisms require available energy to stay alive, such as the energy humans get from food . Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy . The processes of Earth's climate and ecosystem are driven by the radiant energy Earth receives from the sun and the geothermal energy contained within the earth . </P> <Table> <Tr> <Td> </Td> <Td> This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (September 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table>

Where does the energy for most external processes on the earth come from