↑ Science
The word "particle" entered English in the late 14th century (around 1350-1400) with the meaning "a bit or fragment, small part or division of a whole, minute portion of matter." Scientists simply kept the same word when they started talking about atoms, molecules, electrons, and subatomic bits in the 19th and 20th centuries. The specific term "particle physics" (for the study of subatomic particles) emerged gradually during the 60s as the field truly took off as its own discipline.
Definition
There are 2 definitions for a particle:
- Classical Physics
-
A classical particle is a solid, distinct, and predictable "point mass" with a known location and path. Distinct: a particle is a particle; a wave is a wave.
- Modern Physics
-
Particles are excitations (quanta) of underlying quantum fields. They are not tiny solid balls — they are fundamentally fuzzy and can behave as both particles and waves (wave-particle duality). There are two big families:
-
Matter particles (fermions): electrons, quarks, neutrinos, etc.
-
Force-carrying particles (bosons): photons (light), gluons, W/Z bosons, Higgs boson, etc.
-
Classical vs Quantum Particles
| Aspect | Classical Particle | Quantum Particle |
|---|---|---|
Nature |
Tiny, solid, point-like object with definite size zero |
Localized excitation of a quantum field; not a solid ball |
Position & Momentum |
Exact values at every moment (Newton’s laws) |
Cannot be known exactly simultaneously (Heisenberg uncertainty principle) |
Behavior |
Deterministic: predictable trajectory |
Probabilistic: described by a wave function Ψ(x,t) |
Wave Properties |
None (purely particle-like) |
Wave-particle duality: behaves as both wave and particle |
Energy & States |
Continuous energy possible |
Quantized (discrete allowed values) |
Identical Particles |
Can be distinguished (label them) |
Indistinguishable; swapping two identical particles changes nothing |
Creation / Destruction |
Cannot be created or destroyed (conserved) |
Can be created or annihilated (e.g., electron + positron → photons) |
Spin |
Not a concept (classical objects rotate, but no intrinsic spin) |
Intrinsic angular momentum (½, 1, etc.); fermions vs. bosons |
Obeys |
Newton’s laws, Maxwell’s equations (classical) |
Schrödinger / Dirac / quantum field equations |
Examples |
Billiard ball, planet, dust grain (approximated) |
Electron, photon, quark, Higgs boson |
Sources
-
Etymology: Oxford English Dictionary, entry "particle, n." Earliest English senses recorded from the late 14th century.
-
Richard P. Feynman, Robert B. Leighton, Matthew Sands, The Feynman Lectures on Physics, Vol. III: Quantum Mechanics (Addison-Wesley, 1965). Free online: https://www.feynmanlectures.caltech.edu. Chapters 1-3 are the cleanest setup of the classical-vs-quantum particle question ever written.
-
David J. Griffiths, Introduction to Quantum Mechanics, 3rd ed. (Cambridge University Press, 2018). Standard undergraduate textbook for the full mathematical treatment.
-
Mark Srednicki, Quantum Field Theory (Cambridge, 2007). For the modern definition — "particles are excitations of fields." Free draft posted by the author: https://web.physics.ucsb.edu/~mark/qft.html.
-
A. Zee, Quantum Field Theory in a Nutshell, 2nd ed. (Princeton, 2010). More readable QFT introduction than Srednicki; good second source.
-
Heisenberg uncertainty principle: W. Heisenberg, "Über den anschaulichen Inhalt der quantentheoretischen Kinematik und Mechanik," Zeitschrift für Physik 43, 172 (1927). Translated into English as "The Physical Content of Quantum Kinematics and Mechanics."
-
Wave-particle duality: Louis de Broglie, "Recherches sur la théorie des quanta," doctoral thesis (Paris, 1924). C. Davisson and L.H. Germer, "Diffraction of Electrons by a Crystal of Nickel," Physical Review 30, 705 (1927) — the first experimental confirmation that electrons behave as waves.
-
Indistinguishability and spin-statistics: W. Pauli, "The Connection Between Spin and Statistics," Physical Review 58, 716 (1940). Why fermions and bosons behave so differently.
-
CERN, "The Standard Model," https://home.cern/science/physics/standard-model. Up-to-date popular explainer of the modern particle catalog.
