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Introduction
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...)
Selected article
The Brazilian government provided three important initial drivers for the ethanol industry: guaranteed purchases by the state-owned oil company Petrobras, low-interest loans for agro-industrial ethanol firms, and fixed gasoline and ethanol prices where hydrous ethanol sold for 59% of the government-set gasoline price at the pump. These pump-primers have made ethanol production competitive yet unsubsidized.
In recent years, the Brazilian untaxed retail price of hydrous ethanol has been lower than that of gasoline per gallon. Approximately US$50 million has recently been allocated for research and projects focused on advancing the obtention of ethanol from sugarcane in São Paulo.
Selected image
Photo credit: NASA/TRACE
Plasma being channeled by the magnetic field loops of a sunspot.
Did you know?
- The Stuart Shale Oil Plant (pictured) in Australia was in operation only five years?
- Atlantic LNG Company of Trinidad and Tobago operates the world's largest LNG train?
- Despite projections of producing four times as much power as it used in heating, the Riggatron fusion reactor was never built due to a lack of funding?
- In the late 1980s, as many as 50 percent of Argentina's thermal power plants had to be shut down due to lack of maintenance, causing a supply crisis?
- Kashiwazaki-Kariwa Nuclear Power Plant in Japan, the largest nuclear power plant in the world, was shut down after being hit by the Chūetsu offshore earthquake in July 2007?
- The world's largest surface oil shale pyrolysis reactor is Petrosix, operated by the Brazilian oil company Petrobras?
- Russia plans to build several floating nuclear power stations?
- Shale gas, a form of natural gas extracted from shale, may also refer to oil shale gas?
Selected biography
Edison invented the first commercially practical electric light bulb which, by 1879 would burn for hundreds of hours. He was able to sell the concept to homes and businesses by mass-producing them and creating a complete system for the generation and distribution of electricity.
Edison patented an electric distribution system in 1880, and in January 1882 he switched on the first steam generating power station at Holborn Viaduct in London, UK. The direct current (DC) supply system provided electricity supplies to street lamps and a number of private dwellings within a short distance of the station. The first investor-owned electric utility, Pearl Street Station, New York City, started generating on September 4, 1882, providing 110 volts direct current to 59 customers in lower Manhattan.
Life magazine (USA), in a special double issue, placed Edison first in the list of the "100 Most Important People in the Last 1000 Years," noting that the light bulb he promoted "lit up the world." He was ranked thirty-fifth on Michael H. Hart's list of the most influential figures in history.
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Quotations
- "My administration is committed to a leadership role on the issue of climate change. We recognize our responsibility and will meet it - at home, in our hemisphere, and in the world." – George W. Bush, 2001
- "While the Kyoto Protocol is a crucial step forward, that step is far too small. And as we consider how to go further still, there remains a frightening lack of leadership." – Kofi Annan, 2006
- "It is going to be very difficult to keep temperature increases down to between 2 and 3 degrees centigrade [3.6 - 5.4°F]. We should work very hard to do that." – Nicholas Stern, 2006
- "Halting global warming requires urgent, unprecedented international cooperation, but the needed actions are feasible and have additional benefits for human health, agriculture and the environment." – James E. Hansen, 2004
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