The Large Hadron Collider and the Frontier of Physics

A tunnel at CERN
The LHC tunnel, part of the CERN LHC experiment on September 2, 2014 in Geneva, Switzerland. Getty Images

The science of particle physics looks at the very building blocks of matter — the atoms and particles that make up much of the material in the cosmos. It's a complex science that requires painstaking measurements of particles moving at high speeds. This science got a huge boost when the Large Hadron Collider (LHC) began operations in September 2008. Its name sounds very "science-fictiony" but the word "collider" actually explains exactly what it does: send two high-energy particle beams at nearly the speed of light around a 27-kilometer long underground ring.

At the right time, the beams are forced to "collide". Protons in the beams then smash together and, if all goes well, smaller bits and pieces — called subatomic particles — are created for brief moments in time. Their actions and existence are recorded. From that activity, physicists learn more about the very fundamental constituents of matter.

LHC and Particle Physics

The LHC was built to answer some incredibly important questions in physics, delving into where mass comes from, why the cosmos is made of matter instead of its opposite "stuff" called antimatter, and what the mysterious "stuff" known as dark matter could possibly be. It could also provide important new clues about conditions in the very early universe when gravity and electromagnetic forces were all combined with the weak and strong forces into one all-encompassing force. That only happened for a short time in the early universe, and physicists want to know why and how it changed.


The science of particle physics is essentially the search for the very basic building blocks of matter. We know about the atoms and molecules that make up everything we see and feel. The atoms themselves are made up of smaller components: the nucleus and electrons. The nucleus is itself made up of protons and neutrons.

That's not the end of the line, however. The neutrons are made up of subatomic particles called quarks.

Are there smaller particles? That's what particle accelerators are designed to find out. The way they do this is to create conditions similar to what it was like just after the Big Bang — the event that began the universe. At that point, some 13.7 billion years ago, the universe was made only of particles. They were scattered freely through the infant cosmos and roamed constantly. These include mesons, pions, baryons, and hadrons (for which the accelerator is named).

Particle physicists (the people who study these particles) suspect that matter is made up of at least twelve kinds of fundamental particles. They are divided into quarks (mentioned above) and leptons. There are six of each type. That only accounts for some of the fundamental particles in nature. The rest are created in super-energetic collisions (either in the Big Bang or in accelerators such as the LHC). Inside those collisions, particle physicists get a very fast glimpse at what conditions were like in the Big Bang, when the fundamental particles were first created.

What is the LHC?

The LHC is the largest particle accelerator in the world, a big sister to Fermilab in Illinois and other smaller accelerators.

LHC is located near Geneva, Switzerland, built and operated by the European Organization for Nuclear Research, and used by more than 10,000 scientists from around the world. Along its ring, physicists and technicians have installed extremely strong supercooled magnets that guide and shape the beams of particles through a beam pipe). Once the beams are moving fast enough, specialized magnets guide them to the correct positions where the collisions take place. Specialized detectors record the collisions, the particles, the temperatures and other conditions at the time of the collision, and the particle actions in the billionths of a second during which the smash-ups take place.

What Has the LHC Discovered?

When particle physicists planned and built the LHC, one thing they hoped to find evidence for is the Higgs Boson.

It's a particle named after Peter Higgs, who predicted its existence. In 2012, the LHC consortium announced that experiments had revealed the existence of a boson that matched the expected criteria for the Higgs Boson. In addition to the continued search for the Higgs, scientists using the LHC have created what's called a "quark-gluon plasma", which is the densest matter thought to exist outside of a black hole. Other particle experiments are helping physicists understand supersymmetry, which is a spacetime symmetry that involves two related types of particles: bosons and fermions. Each group of particles is thought to have an associated superpartner particle in the other. Understanding such supersymmetry would give scientists further insight into what's called the "standard model". It's a theory that explains what the world is, what holds its matter together, and the forces and particles involved.

The Future of the LHC

Operations at the LHC have included two major "observing" runs. In between each one, the system is refurbished and upgraded to improve its instrumentation and detectors. The next updates (slated for 2018 and beyond) will include an increase in collisional velocities, and a chance to increase the luminosity of the machine. What that means is that LHC will be able to see ever more rare and fast-occurring processes of particle acceleration and collision. The faster the collisions can occur, the more energy will be released as ever-smaller and harder-to-detect particles are involved.

This will give particle physicists an even better look at the very building blocks of matter that make up the stars, galaxies, planets, and life.