The Large Hadron Collider (LHC) near Geneva, Switzerland is the world's most powerful particle accelerator, producing energy levels seven times higher than the former record-holder, the Fermi National Accelerator Laboratory outside Chicago, IL.

Higher energy levels allow scientists to detect a wider variety of particles, thanks to Einstein's famous equation, E=mc2. What it says is that matter and energy are different forms of the same thing; so the higher the energy, the more matter—and the more kinds of matter—can be produced. At the LHC, conversions happen both ways. A tightly focused stream of protons is blasted around the 27-km beam pipe; another stream is propelled in the opposite direction. The two beams are steered into collisions at one of the LHC detectors. The ensuing smash-up of heavy particles at nearly the speed of light produces an enormous amount of energy. That total energy then congeals back into particles of matter and light in dozens of different combinations. Typically, the collision energy creates extremely short-lived exotic particles that then "decay," as physicists say, into a shower of yet other particles, which themselves decay until eventually a stable roster is reached. The detectors track the collision by-products, allowing physicists to identify the particle type and energy content, and thus to recreate the initial event. That is how new particles, the smallest components of physical reality, are discovered.

Scientists have never detected some of the most important particles that are known to exist, notably the elusive "dark matter" particles that form titanic haloes around galaxies (with a mass four times the visible galaxy itself!), but interact so weakly with ordinary matter that they cannot be seen with conventional instruments. In addition, theory predicts a host of peculiar "supersymmetric" particles, as well as the existence of a particle that confers the property of mass on other particles: the "Higgs boson."

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