History of subatomic physics

The historical development of theories, experiments, and technologies for investigating matter and interactions at subatomic scales.

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Cathode ray: A stream of electrons emitted from a cathode in a vacuum tube. Cathode-ray experiments revealed the electron as a constituent of atoms.
Wave-particle duality: The principle that quantum objects exhibit both wave-like and particle-like properties. It captures a central challenge in interpreting electron and photon experiments.
Electron: A stable, negatively charged elementary particle in the lepton family. Its discovery began the experimental case that atoms have internal structure.
Cloud chamber: A particle detector that reveals charged-particle tracks through droplets condensed along their paths. It made tracks from cosmic rays and radioactive decays visible for early particle studies.
Discovery of the electron: The identification of the electron as a particle smaller than the atom, established through cathode-ray research. It ended the presumption that atoms were indivisible constituents of matter.
J. J. Thomson: English physicist who discovered the electron and proposed an early model of atomic structure. His measurements established that atoms contain smaller charged particles.
Schrödinger equation: The equation governing how a quantum system's wave function changes over time. Its use turned quantum theory into a tool for predicting atomic behavior.
Proton: A positively charged baryon made of two up quarks and one down quark. Identifying the proton clarified the positive charge concentrated in atomic nuclei.
Cosmic ray: A high-energy particle arriving at Earth from space, usually a proton or atomic nucleus. Cosmic rays supplied energetic collisions before accelerators could reach comparable energies.
Discovery of the neutron: The 1932 identification of a neutral particle in the atomic nucleus by James Chadwick. It explained missing nuclear mass and reshaped models of the nucleus.