During the 19th and 20th centuries, physicists began to probe deep into the nature of matter and energy. In so doing, they quickly realized that the rules which govern them become increasingly blurry the deeper one goes. Whereas the predominant theory used to be that all matter was made up of indivisible atoms, scientists began to realize that atoms are themselves composed of even smaller particles. From these investigations, the Standard Model of Particle Physics was born. According to this model, all matter in the Universe is composed of two kinds of particles: hadrons – from which Large Hadron Collider (LHC) gets its name – and leptons. Where hadrons are composed of other elementary particles (quarks, anti-quarks, etc), leptons are elementary particles that exist on their own.
What are Leptons?
