Science Fair Project Encyclopedia
2003 North America blackout
A massive power outage produced a blackout in parts of the northeastern United States and eastern Canada on August 14, 2003. Although not affecting as many people as the later 2003 Italy blackout , but larger than the 2004 Luxembourg blackout , it was the largest blackout in North American history. It affected an estimated 10 million people in Ontario, Canada (about one-third of the population of Canada) and 40 million people in eight U.S. states (about one-seventh of the population of the U.S.). Estimated financial losses related to the outage were put at $6 billion.
According to system logs, a massive power fluctuation affected the transmission grid at 4:10:48 p.m. EDT. Between 4:12 and 4:15 p.m. EDT, outages were initially reported in Cleveland, Toledo, New York City, Albany, Detroit, and parts of New Jersey. This was followed by other areas initially unaffected, including all 5 boroughs of New York City and parts of Long Island, Westchester County, Rockland County, New Jersey, Vermont, Connecticut, and most of Southern and Northeastern Ontario, including Toronto, Ottawa, Kingston, Sudbury and London. It was estimated that the blackout covered an area of roughly 9,300 square miles (24,000 square kilometers). Eventually a large area bounded by Lansing, Michigan, Sault Ste. Marie, the shore of James Bay, Ottawa, New York and Toledo was left without power. 100 power plants, 22 of which were nuclear power plants, shut down during the outage.
Over 200,000 people in the Niagara Peninsula of Ontario, Canada, and the portion of New York State north and west of Albany continued to have power while the entire surrounding area dropped off the power grid. This was due to the action of transmission circuit protective devices at Sir Adam Beck Generating Station in Niagara Falls, at a switching station in Cornwall, and in central New York State, that arrested the collapse of this portion of the grid. Power remained in Niagara Falls, half of Welland, a quarter of St. Catharines, Grimsby (near Hamilton) and most of Fort Erie until rolling blackouts began the next day in an effort to provide power to areas that hadn't had it for nearly 24 hours.
Some essential services remained in operation in most of these areas, although backup generation in some cities was not up to the task. The phone systems remained operational in most areas, however the increased demand by people phoning home left many circuits overloaded. Water systems in several cities lost pressure forcing boil water advisories. Cellular telephones experienced significant service disruptions as cellular transmission towers depleted their reserves of backup power. Television and radio stations mostly remained on the air with the help of backup generators, or by relaying their broadcasts through the Grimsby transmission towers , which were online throughout the blackout.
Most interstate rail transportation in the United States was shut down, and the power outage's impact on international air transportation and financial markets was widespread. Meanwhile, the reliability and vulnerability of all electrical power grids was called into question.
In areas where power remained off until nightfall, the Milky Way and orbiting artificial satellites became visible to the naked eye in metropolitan areas where they cannot ordinarily be seen due to the effects of light pollution.
Media coverage and official reports
In the United States and Canada, the regional blackout dominated news broadcasts and news headlines beginning August 15. American broadcast media pre-empted normal programming in favour of full-time, commercial-free coverage of the unfolding story, as did Canadian broadcast media. Once terrorism had been conclusively ruled out as a cause, many stations switched back to normal programming following an 8:30 p.m. EDT address by President George W. Bush. National news stations, such as CBC Newsworld and CNN, continued to cover the story by inviting politicians and electrical experts to discuss the situation and ways to prevent blackouts. Internationally, coverage of the story focused on the development of the situation in New York City.
More than two days later, the cause of the blackout was officially still under investigation, but the possibility of a terrorist attack was uniformly dismissed only 20 minutes into the blackout.
Statements made in the aftermath
During the first two hours of the event, various officials offered speculative explanations as to its root cause:
- Official reports from the office of Canadian Prime Minister Jean Chrétien stated that lightning had struck a power plant in northern New York, resulting in a cascading failure of the surrounding power grid and wide-area electric power transmission grid. However, power officials in the State of New York responded by stating that the problem did not originate in the United States, that there was no rain storm in the area where the lightning strike was supposed to have taken place (though lightning can occur without storm clouds), and that the power plant in question remained in operation throughout the blackout.
- Canadian Defence Minister John McCallum blamed an outage at a nuclear plant in Pennsylvania, but that state's authorities reported that all the plants were functioning normally. McCallum later stated that his sources had given him incorrect information.
- CNN cited unnamed officials as saying that the Niagara-Mohawk power grid, which provides power for New York and parts of Canada, was overloaded. Between 4:10 and 4:13 p.m. EDT, 21 power stations throughout that grid shut down.
- New Mexico governor Bill Richardson, who formerly headed the Department of Energy, in a live television interview 2 hours into the blackout characterized the United States as "a superpower with a third-world electricity grid". In Europe this statement was published accompanied with comparisons highlighting the tighter, safer and better interconnected European electricity network.
- In the ensuing days, various critics have focused on the role of electricity market deregulation for the inadequate state of the electric power transmission grid, claiming that deregulation laws and electricity market mechanisms have failed to provide market participants with sufficient incentives to construct new transmission lines and maintain system security.
- Later that night, claims surfaced that the blackout may have started in Ohio up to one hour before the network shut down, a claim denied by Ohio's FirstEnergy utility.
- The president of the North American Electric Reliability Council (NERC) said that the problem originated in Ohio. 
- As of Saturday morning, investigators believed that the problem began with a sudden shift in the direction of power flow on the northern portion of the Lake Erie Transmission Loop , a system of transmission lines that circles Lake Erie on both U.S. and Canadian soil.
Electricity cannot easily be stored over extended periods of time, and is generally consumed within hundreds of milliseconds of being produced. The demand load on any power grid must be matched by supply to it and its ability to transmit that power. Any great overload of a power line or underload or overload of a generator can cause hard-to-repair and costly damage, so the power grid is disconnected if a serious imbalance is detected. Power lines normally grow longer and sag between their towers when they get hotter as they carry more power, reaching a designed lowest height above the ground at a specified power level. To prevent the sagging lines from coming too close to trees and causing a short circuit the trees are pruned, often on a five year cycle. If the lines touch the trees the lines are disconnected by systems which detect the sudden change in power flow from the short circuit.
These power changes from a line going out of service can sometimes cause cascade failures in the areas around them as other parts of the system see the fluctuations. These are normally controlled by delays built into the shutdown processes and by robust power networks with many alternative paths for power to take, which have the effect of reducing the size of the ripples. The borders of the blacked out areas on August 14th were where the blackout areas encountered the systems with more spare capacity.
The operators of the power system control center are responsible for ensuring that they balance the supply of power, the loads (customers) demanding that power and the transmission line capacity, so that their system was in a state where no single fault can cause it to fail. After a failure affecting their system, operators are required, within thirty minutes, to obtain more power from generators or other regions, or to shed load (meaning cut power to some areas) until they can be sure that the worst remaining possible failure anywhere in the system won't cause an unplanned system collapse. In an emergency they are expected to immediately shed load as required to bring things into balance.
To assist the operators there are computer systems, with backups, which issue alarms when there are faults on the transmission or generation system. They also have power flow modeling tools which let them analyze what is currently happening on their network, predict whether any parts of it may be overloaded and predict what the worst possible failure left is so that they can change the power generation, load or transmission to prevent a failure if that accident happens. If the computer systems and their backups fail they are required to scan themselves instead of relying on the computer alerts. If they can't analyze and understand what they are seeing on their system they are supposed to switch to a more assuredly safe operating pattern. If there is a failure they also notify adjacent areas which may be affected, so they can predict the effect on their own systems.
Backing up the local operators are regional coordinating centers which bring together information from adjacent areas and perform further checks on the system, looking for possible failures and alerting operators in different systems to them.
A joint federal task force was formed by the governments of Canada and the US to oversee the investigation and report directly to Ottawa and Washington. The task force was led by then-Canadian Natural Resource Minister Herb Dhaliwal and US Energy Secretary Spencer Abraham.
In addition to determining the initial cause of the cascading failure, the investigation of the incident also included an examination of why safeguards designed to prevent a repetition of the Northeast Blackout of 1965 failed. Issues of failure to maintain the electrical infrastructure, failure of upgrading to so-called "smart cables", failure of shunting and rerouting mechanisms, AC vs DC intersystem ties, and substitution of electricity market forces for central planning were expected to arise. The North American Electric Reliability Council, a joint Canada-US council, is responsible for dealing with these issues.
Despite the absence of any indication of terrorism or sabotage, and days before terrorist claims were made, the United States Department of Homeland Security immediately started a separate investigation of its own.
On November 19, 2003, the U.S.-Canada Power System Outage Task Force released an interim report placing the cause of the blackout on FirstEnergy Corporation's failure to trim trees in part of its Ohio service area. The report said that a generating plant in the Cleveland, Ohio area went off-line amid high electrical demand and strained high-voltage power lines later went out of service when they came in contact with "overgrown trees". It also found that FirstEnergy did not warn other control centers until it was too late because of a bug in the UNIX based General Electric Energy's XA/21 system  and inadequate staff. The cascading effect that resulted ultimately forced the shutdown of more than 100 power plants. 
Sequence of events
Blackout sequence of events, August 14, 2003 
- 1:58 p.m. The Eastlake, Ohio, generating plant shuts down. The plant is owned by First Energy, a company that had experienced extensive recent maintenance problems, including a major nuclear-plant incident.
- 3:06 p.m. A First Energy 345-kV transmission line fails south of Cleveland, Ohio.
- 3:17 p.m. Voltage dips temporarily on the Ohio portion of the grid. Controllers take no action, but power shifted by the first failure onto another power line causes it to sag into a tree at 3:32 p.m., bringing it offline as well. While Mid West ISO and First Energy controllers try to understand the failures, they fail to inform system controllers in nearby states.
- 3:41 and 3:46 p.m. Two breakers connecting First Energy’s grid with American Electric Power are tripped.
- 4:05 p.m. A sustained power surge on some Ohio lines signals more trouble building.
- 4:09:02 p.m. Voltage sags deeply as Ohio draws 2 GW of power from Michigan.
- 4:10:34 p.m. Many transmission lines trip out, first in Michigan and then in Ohio, blocking the eastward flow of power. Generators go down, creating a huge power deficit. In seconds, power surges out of the East, tripping East coast generators to protect them, and the blackout is on.
|City||Number of people affected|
|New York City and Surrounding Areas||21,100,000|
|Ottawa||780,000 of 1,120,000*|
- Ottawa-Hull is a special case in that it is divided by a provincial boundary and the Ontario and Québec grids are not interconnected in any way. Gatineau had power.
With the power fluctuations on the grid, power plants automatically went into "safe mode" to prevent damage in the case of an overload. This put much of the nuclear power normally available offline until those plants could be slowly taken out of "safe mode". In the meantime, the coal and oil fired plants were brought online, bringing some electrical power availability to the area by the morning of the 15th. Homes and businesses both in the affected area and in nearby areas were requested to limit power usage until the grid was back to full power.
Some areas lost water pressure because pumps did not have power. This loss of pressure caused potential contamination of the water supply. 4 million customers of the Detroit water system in 8 counties were under a boil water advisory until August 18. One county, Macomb, ordered all 2300 restaurants closed until they were decontaminated after the advisory was lifted. 20 people living on the St. Clair River claim to have been sickened after bathing in the river during the blackout. The accidental release of 140 kg (310 lb) of vinyl chloride from a Sarnia, Canada chemical plant was not revealed until 5 days later. Cleveland also lost water pressure and instituted a boil water advisory. Cleveland and New York had sewage spills into waterways requiring beach closures. Kingston lost power to sewage pumps, causing raw waste to be dumped into the Cataraqui River at the base of the Rideau Canal.
Amtrak's Northeastern corridor railroad service was stopped north of Philadelphia, Pennsylvania, and all trains running into and out of New York City were shut down, including the Long Island Rail Road and the Metro-North Railroad. Canada's VIA Rail, which services New York City, suffered service delays, but most routes were still running, and normal service was resumed on most VIA routes by the next morning.
Passenger screenings at affected airports ceased. Regional airports were shut down for this reason. In New York, flights were cancelled even after power had been restored to the airports because of difficulties accessing "electronic-ticket" information. Air Canada flights remained grounded on the morning of the 15th due to reliable power not having been restored to its Mississauga, Ontario control centre. It expected to resume operations by mid-day. This problem affected all Air Canada service and cancelled the most heavily travelled flights to Halifax and Vancouver.
Many gas stations were unable to pump fuel due to lack of electricity. In North Bay, Ontario, for instance, a long line of transport trucks was held up, unable to go further west to Manitoba without refuelling. In some cities, traffic problems were compounded by motorists who simply drove until their cars ran out of gas on the highway. Gas stations operating in pockets of Burlington, Ontario that had power were reported to be charging prices up to 99.9 cents/litre when the going rate prior the blackout was under 70 cents/litre. Customers still lined up for hours to pay prices most people considered unjustified by any additional difficulties imposed by the blackout. Although part of the price hike was arguably due to price gouging, station operators could also claim that they had a limited supply of gasoline and did not know when their tanks would be refilled, prompting the drastic price increases.
Many oil refineries on the East Coast of the United States shut down as a result of the blackout, and were slow to resume gasoline production. As a result, gasoline prices were expected to rise approximately 10 cents/gallon (3 c/L) in the United States. In Canada, gasoline rationing was also considered by the authorities.
Many people were very surprised to find that (unlike wired telephones) cellular communication devices were disrupted. Wired telephones continued to work although some systems were overwhelmed by the volume of traffic. Many people who in prior blackouts would have relied on transistor radios for news discovered to some dismay that they no longer had one, having long since replaced them with portable CD players and other such devices. Most New York and many Ontario radio stations were momentarily knocked off the air but were able to return with back-up power.
Cable television systems were disabled and areas that had power restored (and had power to their television sets proper) could not receive information until power had also been restored to the cable provider. Those who relied on the Internet were similarly disconnected from their news source for the duration of the blackout, with the exception of dialup access from laptop computers, which was widely reported to work until the battery would run out of charge.
Large numbers of factories were closed in the affected area and others outside the area were forced to close or slow work because of supply problems and the need to conserve energy while the grid was stabilized. At one point a 7-hour wait developed for trucks crossing the Ambassador Bridge between Detroit and Windsor due to the lack of electronic border check systems. Freeway congestion in affected areas affected the "just-in-time" supply system. Some industry including the auto industry did not return to full production until Aug. 22.
Incidents of looting were reported in Ottawa (notably in the suburb of Orleans where it appeared to be systematic) and Brooklyn. However, these were isolated incidents in specific areas. All of New York City suffered only four burglaries as of noon August 15 -- in fact, crime rates for the night of August 14 were actually down from statistical averages.
Unlike the New York City blackout of 1977 looting was minimal. In general, the public was orderly; public officials attributing this to increased public awareness and emergency preparedness plans put in place since the terrorist attacks of September 11, 2001.
New York, USA
In New York State, all prisons were blacked out and switched to generator power. The two Indian Point nuclear reactors on the Hudson River near Peekskill, New York, the two reactors at Nine Mile Point nuclear plant and the FitzPatrick reactor near Oswego, New York, and several Long Island nuclear reactors all shut down as had two in Ohio, for a total of nine reactor shutdowns. The governor of New York State, George Pataki, declared a state of emergency.
Manhattan, including Wall Street and the United Nations, was completely shut down, as were all area airports, and all New York area rail transportation including the subway, the PATH lines between Manhattan and New Jersey, Metro North Railroad and the Long Island Rail Road. Hundreds of people were trapped in elevators; by late evening the New York City Fire Department had reportedly confirmed that all stalled elevators in approximately 800 Manhattan high-rise office and apartment buildings had been cleared. Over 600 subway and commuter rail cars were trapped between stations; the NY State Metropolitan Transportation Authority and the Port Authority of New York and New Jersey -- which operates the PATH lines -- reported that all passengers were evacuated without serious injury.
Without traffic lights, a gridlock was reported as persons in lower and midtown Manhattan fled their offices on foot; for hours into the evening the streets, highways, bridges and tunnels were jammed with traffic and pedestrians leaving Manhattan. Mayor Michael Bloomberg advised residents to open their windows, drink plenty of liquids to avoid heat stroke in the heat, and not to forget their pets. Temperatures were 92°F (33°C), with high humidity as New York had just experienced a record-breaking rain spell that had started at the end of July. With cell phone operation mostly stalled by circuit overloads, New Yorkers were lining up 10 deep or more at pay phones as ordinary telephone service remained largely unaffected.
While some commuters were able to find alternate sleeping arrangements, many were left stranded in New York and slept in parks and on the steps of public buildings. While practically all businesses and retail establishments closed down, many bars and pubs reported a brisk business as some New Yorkers took the opportunity to spend the evening "enjoying" the blackout.
40,000 police and the entire fire department were called in to maintain order. At least two fatalities were linked to the use of flames to provide light, and many non-fatal fires also resulted from the use of candles.
New Jersey, USA
Affected areas included most of Essex, Union, Passaic and Bergen Counties, including the major cities of Newark and Paterson. Power was returned first to the urban areas because of concerns of safety and unrest.
The day following the blackout, August 15, the New Jersey Turnpike stopped collecting tolls until 9:00 am.
Parts of New London County, Fairfield County, from Greenwich to Danbury and Bridgeport, was affected, although most of the rest of the state had power. Metro North trains stopped, and remained on the tracks for hours until they could be towed to the nearest station.
A local controversy ensued in the days after the blackout, when the Federal government ordered an electrical 345 kV cable between Norwalk and Long Island turned on. This cable had been installed, but had not been activated due to environmental and fisheries concerns. The Attorney General of Connecticut, Richard Blumenthal, and the Governor of New York, George Pataki, traded insults over the cable. Most Connecticut politicians expressed their outrage that the cable was being turned on, since it did not help anyone in Connecticut, as the cable would transport power from Connecticut to Long Island.
A small area of extreme western Massachusetts was affected. Worcester endured power dips sufficient to reboot some computers, but was otherwise unaffected.
About 2.3 million households and businesses in the cities of Detroit, Lansing, Ann Arbor and surrounding communities in southeast Michigan were affected. TV stations were temporarily knocked off the air and water supplies were disrupted in Detroit due to the failure of electric pumps. Because of the loss of water pressure all water was required to be boiled before use until August 18. Several schools which had planned to begin the school year August 18 were closed until clean water was available. A Marathon Oil refinery in Melvindale near Detroit suffered a small explosion from gas buildup, necessitating an evacuation within one mile around the plant and the closure of Interstate 75. Officials feared the release of toxic gases. Heavy rains on Friday coupled with the lack of sewage pumps closed other expressways and prompted urban flood warnings. Untreated sewage flowed into local rivers in Lansing and Metropolitan Detroit as contingency solutions at some sewage treatment plants failed.
Over 540,000 homes and businesses were without power. In Cleveland, water service stopped because the city is supplied by electric pumps and backup electricity was available only on a very limited basis. Portions of the cities of Mansfield, Marion and Ashland were without power. Cleveland declared a curfew on all persons under the age of 18.
Traffic lights, the subway and streetcars, the Toronto Stock Exchange, the CBC's Toronto studios, and Pearson International Airport were shut down in Toronto (CBC Television and Newsworld switched to its backup studios in Calgary for coverage because newsgathering in Toronto was extremely difficult due to limited power in the Toronto Broadcast Centre. CBC.ca remained online during the blackout as it was protected by UPS systems). Many passengers had to be evacuated from subway trains by walking through the tunnels. Major Toronto hospitals reported that they had switched to generators and hadn't experienced problems. The 9-1-1 system was operational. Highway 407, the world's first all-electronic toll highway, was gridlocked with passengers hoping to get a free ride. Parliament Hill was evacuated in Ottawa.
Toronto officials were asking residents to curtail unnecessary use of water, as the pumps were not working and there was only a 24-hour supply.
Traffic lights, having no backup power, were all knocked out. Coupled with the beginning of the evening rush hour, this caused traffic chaos. In many major and minor intersections in both large and small cities, such as Toronto and Burlington respectively, ordinary citizens began directing traffic until police or others relieved them.
Fierce disruptions of truck traffic in northeastern Ontario were reported due to the unavailability of fuel, including the backlog near North Bay. The tunnel between Windsor and Detroit was also closed.
About 140 miners were marooned underground in the Falconbridge mine in Sudbury when the power went out. Mine officials said that they were safe and could be evacuated if necessary, but were not being evacuated due to the risks of doing so with no power. They were safely evacuated by the morning. In Sarnia, a refinery scrubber lost power and released above-normal levels of pollution; residents were asked to close their windows.
In the evening of August 14, Ontario premier Ernie Eves declared a state of emergency, advising non-essential personnel not to go to work on August 15 (a Friday). Residents were asked not to use televisions, washing machines, or air conditioners if possible, and warned that some restored power might go off again. Although the full state of emergency was lifted the next day (a Saturday), residents were warned that the normal amount of power would not be available for days, and were still asked to reduce power consumption.
The Toronto Transit Commission operated its streetcars on the Friday, but not on the weekend, and did not reactivate the subway and RT until Monday, August 18, after assurances were received that they would be exempted from any rotating blackouts that might be needed. Major events such as concerts were canceled for several days, and the opening of the Canadian National Exhibition, scheduled for the 15th, was postponed to Tuesday, August 19.
For two days of this recovery period, diversion of water from the Niagara River for hydroelectric generation was increased to the maximum level, normally used only at night and in winter in order to maintain the scenic appearance of Niagara Falls. The resultant drop in the river level below the falls meant that the Maid of the Mist tour boats could not dock safely, and their operation had to be suspended.
The blackout contributed to at least eight fatalities,
- In Ottawa, two fatalities were reported. 
- In Connecticut, one fatality was reported.
- In New York City, five fatalities were reported. Two were deaths from carbon monoxide, two were deaths from fire, and the fifth was a fall from a roof while breaking into a shoestore.
Long Term Effects
The Ontario government fell in a provincial election held in October, 2003; power had long been a major issue. The government may have been hurt by the success of Quebec and Manitoba in avoiding calamity while Ontario was shut down. The extra publicity given to Ontario's need to import electricity from the United States, mostly due to a decision of the government not to expand the province's power generating capabilities, may also have adversely affected the Conservative government. Premier Ernie Eves' handling of the crisis was also criticized; he was not heard from until long after Mayor Bloomberg and Governor Pataki had spoken out. However, due to the regular announcements he gave in the days following the blackout, Eves enjoyed a moderate increase in the polls that his party took as a sign of an opportunity to call an election they could win. However that did not prove to be the case.
In the United States, the effects may be even more profound, as the George W. Bush administration has emphasized the need for changes to the US national energy policy, Critical Infrastructure Protection , and Homeland Security. During the blackout, most systems that would detect unauthorized border crossings, port landings, or detect unauthorized access to many vulnerable sites, failed. There was considerable fear that future blackouts would be exploited for terrorism. In addition, the failure highlights the ease with which the power grid can now be taken down.
see also: power outage
Restoration of service
By evening of August 14, power had been restored to:
- Parts of south-western Ontario, particularly areas near the Bruce Nuclear Power Plant, only lost power for a few hours;
- parts of London, Ontario;
- western Ottawa and Kanata;
- a portion of downtown Toronto;
- three-quarters of the million customers who had lost power in New Jersey;
- parts of Pennsylvania and Ohio.
- parts of Long Island
- New London County, Connecticut
By early evening, two New York airports and Cleveland airport were back in service.
Half of the affected part of Ontario had power by the morning of August 15, though even in areas where it had come back online, some services were still disrupted or running at lower levels. The last areas to regain power were usually suffering from trouble at local electrical substations that was not directly related to the blackout itself.
By August 16, power was fully restored in New York and Toronto, although the Toronto subway was closed till the 18th. Power has been mostly restored in Ottawa, though authorities warned of possible additional disruptions and advised conservation as power continued to be restored to other areas. Ontarians were asked to reduce their electricity use by 50% until all generating stations can be brought back on line. Four remained out of service on the 19th. Illuminated billboards were largely dormant for the week following the blackout, and many stores had only a portion of their lights on. Those who did not engage in electricity conservation were treated with derision and scorn from fellow citizens. Among these were the news television stations that had many lights, TV screens, and sets fully working, the CHUM Network to note.
Preparations against the possible disruptions threatened by the Year 2000 problem have been credited for the installation of new electrical equipment and systems which allowed for a relatively rapid restoration of power in some areas.
See the article Power outage for other blackouts.
- CBC News (indepth feature)
- NPR News (special feature)
- Ronda Hauben: Why Was the Blackout So Widespread? (August 19, 2003)
- Dar Al Hayat: Al Qaeda claims responsibility (August 18, 2003)
- San Francisco Chronicle: Chaos theories calculate the vulnerability of megasystems (August 15, 2003)
- BBC: Blackouts cause North America chaos (August 15, 2003)
- CBC: Eastern blackout slowly lifting (August 15, 2003)
- CNN: Major power outage hits New York, other large cities (August 14, 2003)
- CBC: Blackout report blames Ohio utility (November 19, 2003)
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details