In physics, the Standard Model is the name given to a theory that explains the behavior of certain subatomic particles. The Standard Model includes three of the four known forces in the universe: strong nuclear force, weak nuclear force, and electromagnetism. It also explains how these forces work together.
The Standard Model was developed in the 1970s. At that time, physicists had observed six types of quarks (the building blocks of protons and neutrons), but they could not explain why there were only six. The Standard Model predicted that there should be another type of quark, called the top quark. This prediction was confirmed by experiments conducted at Fermilab in 1995.
The Standard Model also predicts that there are two types of leptons (particles that do not interact with nuclei): electrons and neutrinos. Electrons are well-understood, but neutrinos were not observed directly until 1998. Since then, experiments have shown that there are three types of neutrinos: electron neutrinos, muon neutrinos, and tau neutrinos.
The Standard Model has been incredibly successful in explaining a wide variety of phenomena related to subatomic particles. However, it is not a complete theory; it does not include gravity or dark matter/energy, which make up most of the universe. Nonetheless, the success of the Standard Model has led many physicists to believe that it may be possible to develop a “theory of everything” that would incorporate all known physical laws into one framework.