It all begins with a collection of theories known as the “standard model.” The standard model answers two important and fundamental questions: What is matter made of? And why does it behave the way it does?
As to the first question, the standard model says that all matter is made of 12 particles with zany names such as the “charm quark” and the “muon-neutrino.”
The answer to the second question comes down to the four forces observed in the universe. Ordinary people are familiar with gravity and electromagnetism, but there are also the strong and weak forces, which operate on the subatomic level. Under the standard model, bosons transmit forces between particles of matter.
One of the most cherished goals of physics is a “unified field theory,” which would explain the relationships among these forces. For the most part, this theory has been elusive. However, in the 1960s, scientists came up with an idea that would unify at least two of the forces: electromagnetism and the weak force. (They called it the electroweak force, which is rather disappointing for a field that has such a knack for colorful monikers.) But there was a problem with the theory: In order for it to be true, the particles that carry the electroweak force would have to be without mass, and such particles have never been observed.
Enter English physicist Peter Higgs, who came up with a way to save the electroweak force. Higgs theorized that, in the moments after the big bang, mass didn’t exist. However, as things cooled down, a field settled over the universe. When certain particles interact with that field, they gain mass. Physicists don’t know how to observe the Higgs field, but the theory is that when the field acts on a particle, a boson particle is left behind.
This is not easy to conceptualize. Indeed, very little is easy to conceptualize in this field, but one physicist suggests thinking of it as a kind of condensation: The Higgs boson is to the Higgs field as a water droplet is to the water vapor from which it emerges. Higgs’s theory goes a long way toward explaining an enduring problem of physics: why mass exists at all.
Higgs’s theory set off a race to find the Higgs boson, which would help prove the theory. Theoretical physicists worked out a range for the particle’s mass, and experimental scientists got to work smashing things together and hunting for particles within that mass range. At the end of last year, scientists at the Large Hadron Collider at the European Organization for Nuclear Research (CERN) laboratory observed traces of a particle in the range, but the evidence wasn’t definitive. Now they’ve turned the machine, a particle accelerator, back on after a winter slumber, and this is a make-or-break year for the Higgs.