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How big is the Large Hadron Collider?

8.49 kilometers!

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Large Hadron Collider

The Large Hadron Collider, or LHC, is a particle accelerator: a machine that speeds up tiny particles and smashes them together. Its main ring is 26.7 kilometers (16.6 miles) around and about 8.5 kilometers (5.3 miles) across. It lies in a tunnel underground near Geneva, crossing the border between France and Switzerland.

Size

CERN, the European Organization for Nuclear Research, runs the LHC and gives the ring's circumference, the distance around it, as 26,659 meters. The ring is not a perfect circle. It is made of eight curved arcs joined by eight straight sections. Its width of about 8.5 kilometers comes from dividing the circumference by pi (about 3.14), so it is a close approximation.

The tunnel itself is much narrower. In the curved sections it measures 3.7 meters (12 feet) across on the inside. It lies between 45 and 170 meters (150 and 560 feet) below the surface, on a plane that slopes gently toward Lake Geneva.

Most of the ring is filled with magnets. Its 1,232 main bending magnets are each 15 meters long, so together they take up about 18.5 kilometers, or 69 percent, of the ring.

Size comparisons

  • The ring is almost as wide as Mount Everest is tall: about 8.5 kilometers across, against Everest's 8,849 meters (29,032 feet) above sea level.
  • A runner covering a marathon, 42.195 kilometers (26.2 miles), would go about 1.6 times around the ring.
  • About 240 American football fields, each 120 yards (110 meters) long including the end zones, would fit end to end around it.
  • The tunnel is a little more than twice as wide as a person 1.7 meters (5 feet 7 inches) tall, yet the ring it forms is about 2,300 times as wide as the tunnel.

What happens inside

Two beams of particles, usually protons, travel around the ring in opposite directions inside separate pipes. Each beam makes 11,245 laps of the ring every second. That is about 300,000 kilometers each second, very close to the speed of light.

Superconducting magnets, which carry electricity without losing energy, steer the beams around the curves. To work, they are cooled to −271.3 °C, colder than outer space. The beams are made to collide at four points around the ring, where large detectors record the particles that fly out.

As of 2026, CERN describes the LHC as the world's largest and most powerful particle accelerator. In July 2012, scientists there announced the discovery of the Higgs boson. The discovery confirmed an idea first proposed in 1964 to explain how fundamental particles get their mass.

A tunnel built for an earlier machine

The tunnel was dug between 1984 and 1989 for an earlier collider, the Large Electron-Positron Collider, known as LEP. LEP closed in 2000 to free the tunnel for the LHC. Reusing it saved the cost of digging a new one.

The CERN Council approved the LHC in December 1994. It was built between 1996 and 2008 and first started up on September 10, 2008.

Sources

Scale of the Universe > Large Hadron Collider
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