The LHC or Large Hadron Collider is the world's largest and highest-energy particle collider. It is the largest machine in the world. It was built by CERN (the European Organization for Nuclear Research) between 1998 and 2008. This was done in collaboration with over 10,000 scientists. There were hundreds of universities and laboratories involved. There were over 100 countries involved as well.
The LHC lies in a tunnel 17 miles or 27 kilometers in circumference. It is as deep as 574 feet or 175 meters. It lies beneath the France-Switzerland border. This is near Geneva, Switzerland.
The first collisions occurred in 2010. This was the energy of 3.5 TeV per beam. This is about 4 times the previous world record. After upgrades, the LHC reached 6.5 TeV per beam. The total collision energy here would be 13 TeV, the current world record. At the end of 2018, it entered a 2-year shut down period for further upgrades.
The collider has 4 crossing points and 7 detectors. Each of these is designated for a specific kind of research.
The LHC primarily collides proton beams. It can also use beams of heavy ions. One month per year, typically, lead-lead and proton-lead collisions are done. The primary aim of the LHC is to test certain theories of particle physics. This includes measuring the properties of the Higgs boson. It also includes the search for supersymmetric particles or sparticles.
What even is a hadron? A hadron is a composite particle composed of several quarks, held together by gluons, which are described by Quantum chromodynamics, the theory of the strong nuclear force. The best known hadrons are the baryons, the proton and neutron, which are composed of 3 quarks. A proton is 2 up quarks and 1 down quark while a neutron is 2 down quarks and 1 up quark. There are also mesons, such as the pion and the kaon. These particles were discovered in the late 1940s and early 1950s.
What is a collider then? A collider is a type of particle accelerator. There are 2 directed beams of particles. Colliders are used as research tools in particle physics. Particles are accelerated to very high kinetic energies. They are then allowed to impact other particles. Analysis of the byproduct of these collisions, gives scientists good evidence for the nature of the subatomic world and the laws that govern it. Many of these by-products are produced only by high energy collisions. They also may only decay after a very short period of time. This makes them very difficult to study in other ways.
Many physicists hope that the LHC may answer some of the deepest problems in particle physics. This includes the deep structure of spacetime, as well as the relationship between general relativity and quantum mechanics.