GENEVA (AP) -- A European laboratory that was the birthplace of the World Wide Web and home of Nobel prize-winning developments in the quest to understand the makeup of matter wished itself a happy 50th birthday Tuesday.

Representatives of the 20 member nations attended ceremonies commemorating the founding of the European Organization for Nuclear Research, which goes by its original French initials, CERN.

"When the 12 founding member states ratified the CERN convention Sept. 29, 1954, they gave the new organization a mission to provide first class facilities, to coordinate fundamental research -- in particle physics -- and to help reunite the countries of Europe after two world wars," said CERN's Director-General Robert Aymar.

King Juan Carlos of Spain, who attended the birthday ceremony, noted that CERN was intended to stop the brain drain from postwar Europe to the United States and helped Europe regain the position it had held earlier in the 20th century.

"CERN is certainly the leading particle physics laboratory in the world, a center of excellence that attracts world experts in the field," the king said.

French President Jacques Chirac also attended the event.

After the U.S. Congress pulled the plug on the construction in Texas of the proposed Superconducting Super Collider in 1993, CERN became the focus of much of the world's research into matter and into understanding the origins of the universe.

Among the highlights of CERN's history was the awarding of the 1984 Nobel physics prize to Carlo Rubbia and Simon van der Meer for the discovery of two particles _ the W boson and Z boson -- the previous year.

In 1992 Georges Charpak of CERN was awarded the Nobel physics prize for his invention of the "multiwire proportional chamber," which revolutionized the tracking of particles and is used in many medical applications.

In 1990, British scientist Tim Berners-Lee was working at CERN when he proposed a way to help researchers by linking related pieces of information across the Internet in what became the World Wide Web.

The 50th-anniversary observance came at a time of reduced research at CERN because the largest collider is being replaced in the 27-kilometer (17-mile) circular tunnel under the Swiss-French border.

The previous equipment -- the Large Electron-Positron collider -- has been pulled out of the tunnel big enough for a subway train. It is being replaced by the US$1.8 billion Large Hadron Collider.

That massive machine, with underground detectors the size of cathedrals, is to be finished and switched on in 2007.

"Experiments at the LHC will allow physicists to complete a journey that started with Newton's description of gravity," a CERN statement says. "Gravity acts on mass, but so far science is unable to explain why the fundamental particles have the masses they have.

"Experiments at the LHC may provide the answer. LHC experiments will also probe the mysterious missing mass and 'dark' energy of the universe -- visible matter seems to account for just 5 percent of what must exist.

"They will investigate the reason for nature's preference for matter over antimatter, and they will probe matter as it existed at the very beginning of time."

The CERN member states are Austria, Belgium, Britain, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden and Switzerland.

Many scientists from the United States, which still has major rival laboratories, are among the hundreds of physicists who take turns conducting experiments with the particle accelerators.

Other observer nations whose physicists work at CERN include India, Israel, Japan, Russia and Turkey.

Richard Webb, a 25-year-old British scientist at CERN, told The Associated Press, "The scale of the experiments we perform is so huge that no one institute or even country can conduct them alone."

"CERN is a mixing place of different nationalities and that's good because it helps everyone to learn from each other," Webb said. "That's what science is about, and when we work together we can achieve much more."