Particle
A particle is a separate part of a larger system.
In the physical sciences, a particle (or corpuscle in older texts) is a separate part of a larger system. Depending on the system, particles vary greatly in size or quantity, from subatomic particles like the electron, to microscopic particles like atoms and molecules, to macroscopic particles like powders and other granular materials. Particles can also be used to create scientific models of large objects within very large systems, such as humans moving in a crowd, celestial bodies in orbit, or galaxies in the expansion of the universe.
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- Physical sciences
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- Fundamental concept used across physics, chemistry, atmospheric science, soil science, and astrophysics
Lore & Background
The term particle is rather general in meaning and is refined as needed by various scientific fields. Anything composed of particles may be referred to as being particulate, though the noun particulate is most frequently used to refer to pollutants in Earth's atmosphere. In physics, particles can be used to make simplifying assumptions when modeling nature, such as idealizing a baseball as a rigid smooth sphere to calculate its trajectory. Particles are usually applied to three classes of sizes: macroscopic particles (much larger than atoms, often abstracted as point-like), microscopic particles (ranging from atoms to molecules), and subatomic particles (smaller than atoms, including protons, neutrons, and electrons).
Reader's Guide
The concept of a particle is foundational across many scientific disciplines. In particle physics, particles may be elementary (not made of other particles, such as leptons, quarks, and gluons) or composite (composed of other particles, such as protons made of quarks). Massive particles have non-zero rest mass and must move slower than light, while massless particles (like the photon and gluon) must move at the speed of light. Rest mass is not conserved in particle interactions, and particles can decay from high-energy to lower-energy states. In statistical mechanics, vast numbers of interacting particles are analyzed using statistical approaches to predict average quantities, providing a theoretical basis for thermodynamics and the ideal gas laws. In astrophysics, particles are used to model galaxy formation, and in computational physics, N-body simulations model dynamical systems of particles under conditions like gravity. The term also applies in atmospheric science to pollutants and in soil science to discrete solid particles that transmit force through points of contact.
Did You Know?
- A massive particle can decay into massless particles, and massless particles can combine to produce massive particles.
- Colloidal particles have a diameter between approximately 5 and 200 nanometers.
- In computational physics, N-body simulations are common in cosmology and computational fluid dynamics.
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