مقاله سال ۲۰۱۶

Over the last 70 years, a remarkably simple model of our universe has evolved in which everything in it is made up from a handful of fundamental particles governed by four fundamental forces. Our best understanding of how these particles and forces interact is encapsulated in a theory now called the Standard Model of particle physics. Developed in the 1970s it successfully explains a wide variety of phenomena. We now know that all matter consists of building blocks of two basic types called quarks and leptons. There are three “generations” each containing 2 quarks and 2 leptons. The lightest and most stable particles form the first generation and make up the matter in our universe today. The other two generations are heavier and less stable. They can be made in our particle accelerators but do not occur naturally.

There are four fundamental forces through which matter interacts, the strong, weak, electromagnetic and gravitational force. The Standard Model tells us that the weak and electromagnetic forces are two manifestations of the same thing, but there is no place for the oldest known force, gravity. Three of the forces result from the exchange of forcecarrying particles called bosons, the strong force is carried by the gluon, the electromagnetic force by the photon and the weak force by the W and Z bosons discovered at CERN in 1984. The Standard Model has recently been completed by the highly acclaimed discovery of the Higgs boson at CERN in 2012 for which the surviving two theoretical physicists of the three who predicted its existence in the 1960s received the Nobel Prize in 2013.

The discovery of most of these elementary particles has only been made possible by building more and more powerful particle accelerators. They work by colliding particles (usually protons or electrons) at very high energy. Since Einstein told us that mass and energy are equivalent, this energy can be converted into mass, giving a fleeting glimpse of the unstable particles of the Standard Model. The heavier the particle, the higher the energy required to produce it. It was only possible to produce the Higgs boson with the world’s most powerful machine, the Large Hadron Collider.