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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; matter and energy may also be converted to one another. 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
Iceland's location on the Mid-Atlantic Ridge makes it one of the most tectonically active places in the world, with over 200 volcanoes and over 20 high-temperature steam fields. Geothermal energy for heating was first used in 1907 when a farmer piped steam from a hot spring into his house. In 1930, the first pipeline was constructed in Reykjavík, heating two schools, 60 homes, and the main hospital. In 1943, the first geothermal district heating company started. Geothermal power now heats 89% of the nation's houses, provides around 19% of electricity generation and over 54% of primary energy. The first hydroelectric plant was built in 1904 and produced 9 kW of power. Hydropower now provides 81% of Iceland's electricity supply.
Imported oil provides most of Iceland's remaining energy. Replacing this with hydrogen was first suggested after the 1970s energy crisis, but the idea was not adopted until 1998. Iceland's small size makes it ideal for testing the viability of hydrogen as a fuel source for the future, while the plentiful renewable energy sources can be harnessed for its production. Iceland participates in international hydrogen fuel research and development programs, and many countries are following the nation's progress.
As a result of its transition to renewable energy, Iceland is ranked 53rd in the list of countries by carbon dioxide emissions per capita in 2003, emitting 62% less than the United States despite using more primary energy per capita.
Selected image
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/79/Operation_Upshot-Knothole_-_Badger_001.jpg/340px-Operation_Upshot-Knothole_-_Badger_001.jpg)
Photo credit: United States Department of Energy
The fireball created as energy is released in a nuclear explosion.
Did you know?
![A compact fluorescent lamp](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c3/Compact-Fluorescent-Bulb.jpg/85px-Compact-Fluorescent-Bulb.jpg)
- Buildings constructed to the German Passivhaus standard use 75% to 95% less energy for space heating and cooling than current new buildings in the United States?
- Crossing 4,000 km (2,500 miles), the Druzhba pipeline is the world's longest oil pipeline?
- Coal is ground to a powder before being burnt in fossil fuel power plants?
- Compact fluorescent lamps (pictured) use about 1/4 of the energy of normal incandescent light bulbs, and pay for themselves after about 500 hours of use?
- Nuclear power in France produces 78% of all the country's electricity - more than in any other nation?
- Positive lightning bolts are typically six to ten times more powerful than normal lightning — and aircraft are not designed to withstand them?
- Dark energy is a hypothetical form of energy which permeates all of space?
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.
In the news
- 16 June 2024 – Russo-Ukrainian war
- Norway announces that it will give Ukraine 1.1 billion kroner (US$103 million) to help repair its energy infrastructure and secure the country's electricity supply before the winter. (Le Monde)
- 15 June 2024 – Russian invasion of Ukraine
- The United States announces a $1.5 billion aid package to Ukraine, focused primarily on the country's energy industry and humanitarian assistance. (Politico)
- 1 June 2024 – Russian invasion of Ukraine
- Russia launches missile and drone strikes across Ukraine, injuring at least four people and damaging critical infrastructure, including energy facilities. Ukraine says that it shot down 35 of 53 missiles and 46 of 47 drones. (Reuters)
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Quotations
- "Without radical international measures to reduce carbon emissions within the next 10 to 15 years, there is compelling evidence to suggest we might lose the chance to control temperature rises. Failure to act will make an increase of between 2 and 5 degrees [3.6 - 9°F] in average temperatures almost inevitable." – Tony Blair, 2006
- "The question is not whether climate change is happening or not, but whether, in the face of this emergency, we ourselves can change fast enough." – Kofi Annan, 2006
- "I promise you a day will come when our children and grandchildren will look back and they will ask one of two questions. Either they will ask, 'What in God's name were they doing? Didn't they see the evidence?' Or, they may look back and say 'How did they find the uncommon moral courage to rise above politics and redeem the promise of American democracy?'" – Al Gore, 2007, on global warming.
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