After a two year hiatus, “season two” of the world’s largest particle accelerator at CERN began on April 5, 2015, and scientists from all over the world are hoping for this to be the biggest smashing success yet.
The Large Hadron Collider (LHC) at CERN is often described as a big tube that physicists use to accelerate subatomic particles to incredible speeds in opposite directions, with the intention of crashing them into each other to discover “what lies inside.” The idea is really pretty simple…smash two seemingly fundamental particles such as protons together to discover that they are in fact made of even more elementary particles themselves. The physics behind these phenomena is incredibly sophisticated, and the LHC is a beautiful example of theoretical physicists and experimentalists working together (i.e. the people who derivate models and theories with math, and the people who seek to prove these ideas in reality).
The LHC residues in a 27 kilometer (17 mile) tunnel near Geneva, Switzerland, and was constructed between 1998 and 2008. During its “first season” of use, the LHC’s most publicized success was the discovery of the Higgs boson whose existence had been predicted for decades, but was finally discovered in 2012. By the end of this run, the particle beams reached energies of 6.5 TeV (teraelectronvolts), but are expected to reach the unprecedented level of 13 TeV by this summer (“tera-” is the prefix for one trillion).
While CERN scientists were looking for specific evidence to either confirm or deny their theories about the Higgs during their first run of the accelerator, the goals this time are somewhat more open-ended. Researchers hope to uncover further secrets about the Higgs boson that were left unanswered during the first run, and hope that the higher energies will shine some light on myriad of mysteries about dark matter.
One goal of CERN has been to further validate, or invalidate what is known as “The Standard Model.” This is the nearly, but not-quite, all-encompassing theory that seeks to unify all known physical forces in the universe. Electromagnetic, weak, and strong nuclear interactions are all adequately described by the Standard Model, and many accurate predictions have been made with the framework. Dark energy and gravity have proven more difficult however.
The theory of gravitation is described by the theory of general relativity for which Albert Einstein is famous, but it is not fully compatible with the physics of the Standard Model. Likewise, the Standard Model fails to explain why the universe is expanding at a continually accelerating rate. One suggestion for this is the existence of “dark energy,” which is an as-yet unknown form of energy that can help account for observations such as the expanding universe. This is not to be confused with “dark matter,” which is an as-yet unknown form of matter that has thus far eluded detection, but whose effects can be detected with gravity.
Dark matter and dark energy are heavy things that are not readily understandable or explainable with our classical notion of physics. And just because they have evaded discovery so far does not mean that they will forever remain a mystery. The improvements made to the LHC over the past two years have led to the development of proton beams with nearly twice the energy as before, and both experimental and theoretical physicists alike hope that these high-power collisions will generate new data with unanticipated possibilities to discover experimental evidence for physical forces that can help correct the Standard Model.
It may be another couple of years (or more) yet before data can roll in and be analyzed to get more exciting news stories such as the discovery of the Higgs Boson, but for more information about the LHC at CERN, and other projects, check out their website for a plethora of great background information and news updates.