The Large Hadron Collider is a particle accelerator and is the largest of its type in the world. It is used for conducting experiments in theoretical physics and was built with a focus on determining whether the Higgs boson particle exists.
The Collider is housed underground and consists of a circular tunnel lined with concrete that is 17 miles in circumference. There are two adjacent beam pipes that each contain a proton beam. The beams travel in opposite directions around the ring at close to the speed of light, with a primary goal of trying to create proton-proton and proton-ion collisions that can be measured and studied. The beams are guided by a magnetic field maintained by a complex series of electromagnets. For the electromagnets to operate in a superconductive state they must be kept at a temperature colder than outer space using a liquid helium cooling system.
The Large Hadron Collider began operation in September of 2008 with a successful test run. Later in the month, however, an accident involving magnets caused further operations to be pushed back to November 2009. The Collider then operated successfully from 2009 to 2013 but was shut down temporarily for an upgrade to beam energy. As of 2014, it is expected to resume operations in early 2015.