Expert reviewed • 22 November 2024 • 6 minute read
The Standard Model of Matter represents our most comprehensive theory of the universe's fundamental building blocks. It describes how elementary particles interact through fundamental forces to create everything we observe in the universe.
The Standard Model classifies all matter into three primary categories:
Quarks are fundamental particles that combine to form larger particles called hadrons. They exist in six "flavors" organized into three generations:
Each quark carries a fractional electric charge:
Scientists confirmed the existence of quarks through Deep Inelastic Scattering experiments. By firing high-energy electrons at protons in particle accelerators, they observed that protons contained smaller constituents - providing evidence that protons weren't fundamental particles.
Hadrons are particles composed of quarks, existing in two types:
Leptons are fundamental particles that exist independently, organized into three generations:
J.J. Thomson discovered the electron through cathode ray experiments, marking the first identification of a fundamental particle.
Discovered by Anderson and Neddermeyer while studying cosmic radiation, muons are approximately 200 times heavier than electrons but share the same charge. Initially mistaken for mesons, they were later correctly classified as leptons due to their non-interaction with the strong nuclear force.
The existence of neutrinos was first proposed by Wolfgang Pauli to explain the apparent violation of energy conservation in beta decay. In beta decay, the energy spectrum of emitted electrons was continuous rather than discrete, suggesting missing energy. This led to the theoretical prediction and later experimental confirmation of the electron neutrino.
The Standard Model describes three of the four fundamental forces:
*Note: Gravity, theoretically mediated by gravitons, is not currently included in the Standard Model.