What is the Standard Model?

Posted on Wednesday 12th August 2015 at 7:36

The Standard Model in particle physics definitely does not suggest that the answer to life, the universe and everything is 42. However, it does give physicists a profound understanding of what life, the universe and everything is made up of. It describes the fundamental particles that essentially make up all matter and the forces that act upon them. CERN (the European Organisation for Nuclear Research) states that, "how these particles and three of the forces are related to each other is encapsulated in the Standard Model of particle physics."

Elementary Particles

Even though the development of the Standard Model was a cumulative effort of scientists around the world for many years, the term itself was coined in the 1970s. They categorised the basic elementary particles, quarks and leptons into six groups, which were then paired and called 'generations' based on their weight and stability. The lightest and most stable particles were called the first generation and they make up all stable matter in the universe. The Standard Model has been used to not only identify different types of particles but also to predict their existence. Over the years its reliability at predicting the existence of particles has been proven time and time again as these particles have subsequently been discovered.

Fundamental Forces

There are four Fundamental Forces that are exerted on these elementary particles and they are the strong force, the weak force, the electromagnetic force and the gravitational force. Interestingly, the Standard Model includes all of these forces except gravity. Being the best known force to the average person, it seems odd that this force is not included but it does not fit comfortably into the Standard Model and this is partly due to the fact that gravitational force is so weak when exerted on particles that its effect is negligible. Each of the other forces works by matter particles exchanging force-carrier particles called 'bosons'. Different forces have different bosons. The strong force has one called 'gluons', while the weak force is carried by the 'W and Z bosons'. Electromagnetic force is carried by 'photons' but, although it is thought that gravity should have a force-carrying particle called a 'graviton', it has never been discovered. This is an example of how the Standard Model is "still incomplete" as CERN states. It cannot explain dark matter and CERN suggests that it is "part of a bigger picture that includes new physics hidden deep in the subatomic world or in the dark recesses of the universe". Experiments are done continuously to test theories within and beyond the Standard Model such as the attempts to discover the Higgs boson particle in the Large Hadron Collider at CERN. However, many other such experiments are taking place all over the world using vacuum conditions to isolate particles.

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