GENEVA — Questions and answers about the Large Hadron Collider:

Q: What is the Large Hadron Collider?

A: It is the world's most powerful particle accelerator. It is buried inside a 17-mile tunnel and surrounded by massive detectors.

Q: What does "hadron" refer to?

A: It is a particle, such as a proton or neutron, found in the nucleus of an atom.

Q: How long did it take to build the collider, who is involved, and how much did it cost?

A: The project was conceived in 1984 by scientists at the European Organization for Nuclear Research, or CERN. The organization's 20 member nations along with observer countries such as the United States and Japan have contributed $10 billion.

Q: How does the collider work?

A: The collider fires protons around the tunnel at near the speed of light — more than 186,000 miles per second. Supercooled magnets guide the protons in opposite directions around a near-vacuum until they collide at four points inside the tunnel.

Q: What do the detectors do?

A: As protons collide, the detectors will search for evidence of extra dimensions — apart from the three dimensions of space and one dimension of time.

They will also look for the "dark matter" believed to make up most of the universe, antimatter that mirrors all known matter, and the elusive Higgs-boson particle — sometimes called the "God particle," because it is believed to give mass to all other particles. All of these have previously only been theorized, but not confirmed.

One of the detectors will smash together lead ions to simulate conditions shortly after the "big bang"— the event believed to have created the universe 13.7 billion years ago. Scientists hope to learn from this how matter was formed.

Q: Is the experiment safe?

A: Some people fear the collider could create black holes or release massive amounts of energy that would destroy Earth. CERN and leading particle physicists insist there is no danger. Other scientists have calculated the odds of this happening as too minute to worry about. This hasn't stopped bookmakers from taking bets from people willing to wager that the end of the world is near.

Q: What else do scientists hope to learn from the experiment?

A: If the collider proves the existence of new particles, it could test the dominant physics hypothesis of "string theory," which seeks to reconcile quantum mechanics and gravity in an all-encompassing formula that has eluded all scientists since Albert Einstein.

Q: Will the collider prove the existence of God?

A: The experiment will examine what happened shortly after the universe was created. It does not seek to confirm or deny the existence of any supernatural being.