The Large Hadron Collider (LHC), the world's largest and highest-energy particle accelerator, could generate astonishing new insights into the Big Bang, the building blocks of the universe, the mysterious properties of dark matter and perhaps even extra dimensions in the universe.
Located at the CERN laboratory outside Geneva, the immense collider, which measures more than 16 miles in circumference, is expected to usher in a new era of particle physics research, enabling scientists to replicate conditions immediately after the Big Bang.
To that end, on March 19, the collider fired beams of protons in both directions, clockwise and counter-clockwise, at a new world-record energy: 3.5 trillion (or tera) electron volts. The LHC will soon collide these proton beams against each other, allowing physicists to analyze the particles produced in the collisions. CERN eventually plans to collide proton beams at a blistering 7 tera-electron-volts in both directions. Robert Cousins, a UCLA professor of physics who has served as a leader of the Compact Muon Solenoid (CMS) experiment at CERN — one of the LHC's four main experiments — is hopeful the collider will lead to extraordinary discoveries about the nature of the universe.
"We're going to study the Big Bang as far back as we can take it," said Cousins, whose research group is supported by the U.S. Department of Energy and who is principal investigator on a CMS grant funded by the National Science Foundation.
"The fundamental questions," he said, "were asked by the ancient Greeks: Where did we come from, what are we made of? How did the universe evolve and what are the forces of the universe?
"We think there are undiscovered forces. The history of physics is one of unification of ideas. Isaac Newton discovered that the same force that makes apples fall also holds the Earth to the sun and holds the moon to the Earth. When I teach Newton's universal law of gravity, the key word is 'universal.' One law of gravity accounts for apples falling and the relationship between the moon and the Earth. Historically, optics, electricity and magnetism were three different fields; now there is one theory of electromagnetism.
"Nature likely contains extra forces that we have not found yet," Cousins said. "Any successful attempt to unify the known forces of nature will almost certainly unify some unknown forces of nature at the same time. The job of experimental physicists is to go find those forces. I am most excited about finding new forces that shed light on unification. If you're going to paint the complete picture, you need to know what the other forces are."
The LHC is one of the most complex scientific instruments ever built. Funding for it comes from many sources, including the U.S. Department of Energy's Office of Science and the NSF. Ten thousand people from 60 countries helped design and build the collider and its experiments, including more than 1,700 scientists, engineers, technicians and students from more than 90 U.S. universities and laboratories supported by the DOE's Office of Science and the NSF. Participating U.S. universities include strong research groups from UCLA and seven other UC campuses.
Physicists may make dark matter at the LHC by colliding protons at high energy, which will make new types of unknown particles that decay down to the particles that make up dark matter, Cousins said.
The LHC will recreate conditions that existed less than one-billionth of a second after the Big Bang, and will do so repeatedly in a controlled way. Collisions of protons at energies as high as existed just after the Big Bang will be recorded by giant digital cameras. Eventually, there will be nearly 1 billion collisions per second.
Historically, high-energy particle physics has addressed the smallest pieces of matter and the forces between those objects.
"In the last few decades, an enormous amount of progress has been made in cosmology, which addresses very large questions, such as how the universe evolved from the Big Bang," Cousins said. "If you run the equations of general relativity for cosmology back to the Big Bang, you also need to know what the smallest objects in nature are and what the forces are between them in order to get close to the Big Bang.