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In physics, energy (from Ancient Greek ἐνέργεια (enérgeia) 'activity') is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat and light. Energy is a conserved quantity—the law of conservation of energy states that energy can be converted in form, but not created or destroyed. The unit of measurement for energy in the International System of Units (SI) is the joule (J).
Common forms of energy include the kinetic energy of a moving object, the potential energy stored by an object (for instance due to its position in a field), the elastic energy stored in a solid object, chemical energy associated with chemical reactions, the radiant energy carried by electromagnetic radiation, and the internal energy contained within a thermodynamic system. All living organisms constantly take in and release energy.
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, 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.
Human civilization requires energy to function, which it gets from energy resources such as fossil fuels, nuclear fuel, or renewable energy. The Earth's climate and ecosystems processes are driven by the energy the planet receives from the Sun (although a small amount is also contributed by geothermal energy). (Full article...)
The remaining worldwide energy resources are large, with the remaining fossil fuels totaling an estimated 0.4 YJ (1 YJ = 1024 J) and the available nuclear fuel such as uranium exceeding 2.5 YJ (1 YJ = 1024 J). Mostly thanks to the Sun, the world also has a renewable usable energy flux that exceeds 120 PW (8,000 times 2004 total energy usage), or 3.8 YJ/yr, dwarfing all non-renewable resources.
Despite the abundance of fossil fuels there are a number of pressures that may move the world’s energy consumption to alternative energy sources. These include political considerations over energy security and potential pressure from energy superpowers, environmental concerns related to global warming and sustainability, and economic pressure resulting from energy price rises, carbon emissions trading and green taxation.
This move is already starting to happen in some countries, notably as a result of the Kyoto Protocol, and further steps in this direction are proposed. For example, the European Commission has proposed that the energy policy of the European Union should set a binding target of increasing the maximum level of renewable energy in the EU’s overall mix from less than 7% today to 20% by 2020.
Photo credit: Senior Airman Joshua Strang, United States Air Force
An aurora, caused by the release of energy as charged particles collide with atoms in the Earth's upper atmosphere.
Born in Texas, Hubbert studied geology, mathematics, and physics at the University of Chicago. He pursued his Ph.D. while working for the Amerada Petroleum Company, then worked for the Shell Oil Company from 1943 until 1964. On leaving Shell he became a senior research geophysicist for the United States Geological Survey until retiring in 1976. Hubbert was also a professor at Stanford University and at UC Berkeley.
Hubbert is most well-known for his studies on the capacities of oil fields and natural gas reserves. He predicted that, for any given geographical area, the rate of petroleum production over time would resemble a bell curve. At the 1956 meeting of the American Petroleum Institute, Hubbert predicted that United States petroleum production would peak in the late 1960s or early 1970s. He became famous when his prediction came true in 1970.
In 1974, Hubbert projected that global oil production would peak in 1995 "if current trends continue". Various subsequent predictions have been made by others as trends have fluctuated in the intervening years. Hubbert's theory, and its implications for the world economy, remain controversial.
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