Physics

Standard temperature and pressure Conventional reference conditions for reporting and comparing physical measurements, especially gas properties. Multiple definitions exist; commonly used values and their uses are…

Standing wave (stationary wave) Standing wave A standing wave is a stationary pattern produced by interference of waves traveling in opposite directions; this article explains nodes, antinodes, boundary conditions, harmonics,…

Static electricity: causes, behavior, history, and practical effects Static electricity Static electricity is the buildup of electric charge on surfaces. This article explains how it forms, common examples, historical study, risks (like ESD and ignition), and methods…

Statistical mechanics: connecting microscopic states to macroscopic behavior Statistical mechanics Branch of physics that uses probability to relate microscopic particle behavior to macroscopic thermodynamic properties, explaining entropy, temperature, and phase behavior from at…

Statistical Physics: Principles, Methods, and Applications Statistical physics An accessible overview of statistical physics: core concepts, mathematical framework, methods, history, and applications across physics, chemistry, biology and social sciences.

Stefan–Boltzmann law Physical law stating that an ideal blackbody emits energy per unit area proportional to the fourth power of its absolute temperature: R = σT^4. Important in thermodynamics, astroph…

Sterile neutrino A hypothetical neutrino that does not interact via Standard Model forces; proposed to explain neutrino masses, cosmological phenomena, and experimental anomalies.

Stevens' power law Psychophysical law stating perceived intensity is a power function of stimulus magnitude; proposed by S. S. Stevens, it is used in sensory scaling and debated versus logarithmic mo…

Stone (unit of mass) Stone (unit) Traditional British unit of mass equal to 14 pounds (≈6.35029 kg), still used informally for body weight and in some trade contexts; historically varied by place and commodity.

Stopping power (firearms and ammunition) Stopping power Stopping power describes a projectile's ability to quickly incapacitate a target. The concept blends physics, terminal ballistics, shot placement, and practical considerations for…

Strange matter A theoretical form of dense quark matter containing up, down and strange quarks; considered in astrophysics for neutron-star cores and as a candidate ground state of dense matter.

Strange quark: properties, history and role in particle physics Strange quark A light quark flavor with electric charge −1/3 and a negative strangeness quantum number. Found in kaons and hyperons, it shaped the development of the quark model and weak-interac…

Stress (mechanics): definition, types, measurement, and engineering use Stress (mechanics) Mechanical stress is the internal force per unit area within materials. This article explains definitions, stress types, measurement, common formulas, continuum assumptions, and en…

String (theoretical physics) String (physics) One-dimensional vibrating objects postulated by string theory to replace point particles; their modes and interactions aim to unify quantum mechanics and gravity but remain experim…

String theory and its role in modern physics String theory String theory is a theoretical framework proposing one-dimensional strings as the basic constituents of matter and forces, aiming to reconcile quantum mechanics and gravity and to…

Strong interaction (strong nuclear force) Strong interaction The strong interaction is the fundamental force that binds quarks into hadrons and holds atomic nuclei together. It is described by quantum chromodynamics and features confinement…

Subatomic particle: definition, classification, history, and significance Subatomic particle An overview of subatomic particles: what they are, how they are classified, key discoveries, how scientists study them, and why they matter in physics and technology.

Sunlight: Nature, Effects, and Importance Sunlight Overview of sunlight as solar electromagnetic radiation: its composition, how the atmosphere alters it, biological and climatic effects, practical uses, and key distinctions.

Superconductor A superconductor is a material that, below a critical temperature, exhibits zero electrical resistance and expels magnetic fields. This article explains properties, types, history,…

Superfluidity: frictionless flow and quantum fluids Superfluidity Superfluidity is a quantum phase in which a liquid or fluid flows without viscosity, showing effects such as persistent currents, quantized vortices, and unusual heat transport; fo…

Superposition Principle The superposition principle: in linear systems, the total response equals the sum of individual responses. Applies broadly to waves, circuits, and electrostatics; limited or altere…

Supersonic (speeds faster than the speed of sound) Supersonic Supersonic describes motion faster than the local speed of sound (Mach > 1). Covers physics of shock waves, history, aircraft design, examples, and distinctions with transonic and…

Supersymmetry: theory, motivations, and experimental status Supersymmetry Supersymmetry (SUSY) is a proposed symmetry between bosons and fermions that predicts partner particles, offers solutions to theoretical problems, and remains unconfirmed by curren…

Surface Tension: Causes, Effects, Measurement, and Applications Surface tension Surface tension is the tendency of a liquid surface to resist external force, arising from molecular attraction. It controls droplets, capillarity, wetting, and many engineering an…

Surface wave (physics and applications) Surface wave Wave localized near an interface between different media; includes water and seismic surface waves, electromagnetic surface modes, and radio ground waves with applications in ocean…

Synchrotron (circular particle accelerator) Synchrotron A synchrotron is a circular particle accelerator that synchronizes magnetic and electric fields to keep particles on a fixed orbit while increasing their energy; used in research a…

Tachyon: Hypothetical Faster‑Than‑Light Particle Tachyon A tachyon is a theoretical particle that would always travel faster than light, associated with imaginary rest mass and causality challenges; it appears in thought experiments, fie…

Tau lepton (tauon): the heavy third‑generation charged lepton Tau lepton Overview of the tau lepton: properties, production and decay, discovery and role in particle physics, distinguishing features and common decay channels.

Tau neutrino The tau neutrino is the neutral lepton partner of the tau, a third-generation neutrino that interacts via the weak force and appears in oscillation phenomena and high-energy astrop…

Teleportation Teleportation: the idea of relocating matter or information without traversing intervening space; contrasts between fictional instant transfer and real-world quantum state teleport…

Temperature Temperature is a physical quantity that indicates how hot or cold a system is, tied to the motion of particles and measured with various scales and instruments.

Tension (mechanics): definition, properties, and applications Tension (mechanics) Tension is the axial pulling force transmitted through a flexible connector such as a string, rope, cable or rod. This article explains its physics, measurement, examples, and prac…

Terajoule (TJ) — unit of energy Terajoule The terajoule (TJ) equals 10^12 joules, commonly used to express large energy quantities. This article explains its scale, common conversions, practical examples (Hiroshima, ISS, h…

Terminal velocity (falling objects and fluids) Terminal velocity Terminal velocity is the steady speed a falling object reaches when drag balances weight. It depends on mass, shape, cross‑section, fluid density and flow regime; important in engi…

Tesla (unit) The tesla (T) is the SI derived unit of magnetic flux density (magnetic field B). This article explains its definition, SI relationships, typical magnitudes, measurement methods, h…

Tevatron: Fermilab’s Circular Proton–Antiproton Collider Tevatron The Tevatron was a superconducting circular particle collider at Fermilab (Batavia, Illinois) that accelerated protons and antiprotons to about 1 TeV and produced major discoveries…

The Force (Star Wars): concept, abilities, and cultural role The Force A concise encyclopedia entry on the Force from the Star Wars universe: what it is, how it is depicted, major abilities, organizations that use it, and its cultural impact.

Theoretical particle A theoretical particle is a hypothesized constituent of matter or force predicted by physical theories but not yet confirmed experimentally; they guide research and shape models of…

Unified physical theories: approaches to combining general relativity and quantum mechanics Theory of everything Overview of attempts to reconcile general relativity and quantum mechanics, surveying string theory and other quantum gravity approaches, key conceptual challenges, and prospects f…

Theory of Relativity Foundational physical theories by Albert Einstein—special and general relativity—recasting space, time, motion and gravitation, explaining high-speed effects and gravity as geometr…

Thermal conductivity: how materials transfer heat Thermal conductivity Thermal conductivity measures a material’s ability to conduct heat. This article explains the concept, mechanisms, typical materials, measurement, applications, and practical examp…

Thermal expansion: causes, coefficients, materials, and engineering implications Thermal expansion Thermal expansion is the change in size or volume of matter with temperature. This article explains causes, linear and volumetric coefficients, special cases, measurement, and comm…

Thermal physics: an introduction to heat, entropy, and statistical behavior Thermal physics Study of heat, work, temperature, and the microscopic origins of thermodynamic behavior; unites thermodynamics, statistical mechanics, and kinetic theory with practical application…

Thermal radiation: emission of heat as electromagnetic waves Thermal radiation Thermal radiation is electromagnetic energy emitted and absorbed by matter due to temperature. This article explains its physical basis, spectrum, laws, examples, and practical sig…

Thermal resistance Thermal resistance quantifies how strongly a material or assembly opposes heat flow. It relates to geometry and material properties and is used in electronics, building insulation,…

Thermodynamic cycle: principles, types, and applications Thermodynamic cycle A thermodynamic cycle is a sequence of processes that returns a system to its initial state. It underlies engines, refrigerators, and power plants and is constrained by the laws of…

Thermodynamic Entropy: Definition, Meaning, and Applications Thermodynamic entropy A comprehensive overview of thermodynamic entropy: what it measures, how it is quantified, its microscopic basis, role in the laws of thermodynamics, and practical examples and dis…

Thermodynamic equilibrium State of a thermodynamic system in which macroscopic flows vanish and intensive variables are uniform; described by extremal thermodynamic potentials and corresponding equilibrium…