Physics terms starting with G

Galaxy Astrophysics, Cosmology & Relativity Solar Masses (M_☉) and Kiloparsecs (kpc) A massive, gravitationally bound system consisting of stars, stellar remnants, interstellar gas, dust, and dark matter. M_galaxy = v² r / G (includes Dark Matter)

Galaxy Cluster Astrophysics, Cosmology & Relativity Megaparsecs (Mpc) & M_☉ A gravitationally bound structure containing hundreds to thousands of individual galaxies bound together by gravity. M_total ~ 10¹⁴–10¹⁵ M_☉ (80% Dark Matter, 15% Intracluster Gas, 5% Stars)

Gamma Decay Nuclear & Particle Physics MeV or keV (Photon Energy) A radioactive decay process where an excited atomic nucleus transitions to a lower energy state by emitting a high-energy gamma-ray photon. ᴬ_Z X* → ᴬ_Z X + γ (High-energy photon emission)

Gauss's Law for Electricity Electromagnetism & Electronics N·m²/C (or V·m) Maxwell's first equation stating that the net electric flux through any closed Gaussian surface equals the total enclosed charge divided by vacuum permittivity. Φ_E = ∮ E · dA = Q_enclosed / ε₀, ∇ · E = ρ / ε₀

Gauss's Law for Magnetism Electromagnetism & Electronics Wb (Webers) Maxwell's second equation stating that the total magnetic flux passing through any closed surface is always identically zero. Φ_B = ∮ B · dA = 0, ∇ · B = 0

Gay-Lussac's Law Thermodynamics & Statistical Physics Pa/K An ideal gas law stating that gas pressure is directly proportional to absolute thermodynamic temperature at constant volume. P1 / T1 = P2 / T2 (at constant V)

Geiger-Müller Counter Nuclear & Particle Physics Counts per Minute (CPM) or μSv/h A gas-filled radiation detection instrument that measures ionizing radiation by detecting current pulses produced by Townsend avalanches in a high-voltage tube. Townsend Avalanche ionization in high electric fields

General Relativity Astrophysics, Cosmology & Relativity Geometric Field Theory Albert Einstein's 1915 geometric theory of gravitation describing gravity not as an attractive force, but as the curvature of 4D spacetime produced by mass and energy. G_μν + Λ g_μν = (8 π G / c⁴) T_μν

Genetic Algorithms Mathematical & Computational Physics Stochastic Heuristic Optimization A search heuristic optimization method inspired by natural biological evolution that iteratively evolves candidate solutions toward optimal physics configurations. Evolutionary Operators: Selection, Crossover, Mutation

Geodesic Astrophysics, Cosmology & Relativity Spacetime Path Trajectory The path of shortest (or extreme) spacetime interval between two points in curved spacetime, representing the free-fall trajectory of particles under gravity. (d²x^μ / dτ²) + Γ^μ_αβ (dx^α / dτ) (dx^β / dτ) = 0

Geoid Geophysics & Environmental Physics Meters (Geoid Undulation Height) The hypothetical shape of Earth's surface defined by an equipotential surface of Earth's gravity field matching mean ocean sea level in the absence of tides and winds. Equipotential Surface V_gravity = Constant

Geomagnetic Reversal Geophysics & Environmental Physics Geologic Time Interval A major planetary event during which Earth's magnetic field undergoes a complete polarity flip, swapping magnetic North and South poles. Reversal Interval ~ 200,000 to 300,000 years

Geomagnetic Storm Geophysics & Environmental Physics nT (Nanoteslas, Dst / Kp Index) A major temporary disturbance of Earth's magnetosphere caused by solar wind shockwaves or Coronal Mass Ejections (CMEs). Dst Index < -50 nT (Distortion of Equatorial Ring Current)

Geomagnetism Geophysics & Environmental Physics μT (Microteslas, ~30–60 μT at surface) The scientific study of Earth's magnetic field, its internal origin in the liquid outer core, spatial variations, and temporal fluctuations. B_geo = ∇ × A (Geodynamo Induction: ∂B/∂t = ∇ × (v × B) + η ∇²B)

Geostrophic Wind Geophysics & Environmental Physics m/s (Wind Velocity) A theoretical atmospheric wind resulting from a exact balance between the horizontal Pressure Gradient Force and the Coriolis acceleration force. v_g = (1 / (2 ρ Ω sin φ)) (dP / dn) = (1 / f ρ) ∇P

Geothermal Gradient Geophysics & Environmental Physics °C/km or K/km The rate at which Earth's interior temperature increases with increasing depth below the surface. q = -k (dT / dz) (Heat Flux = Conductivity × Gradient)

Giant Magnetoresistance (GMR) Condensed Matter & Materials Physics % (Resistance Change Ratio) A quantum spintronic phenomenon where electrical resistance drops dramatically when adjacent ferromagnetic layers align magnetically parallel in an external field. GMR = (R_AP - R_P) / R_P × 100%

Gibbs Free Energy Thermodynamics & Statistical Physics J A thermodynamic potential measuring maximum reversible work obtainable from a system at constant temperature and pressure. G = H - T S, ΔG = ΔH - T ΔS

Glaciology Geophysics & Environmental Physics m/year (Glacier Flow Velocity) The scientific study of glaciers, ice sheets, snow, and all natural ice phenomena in the cryosphere. Glen's Flow Law: ε̇ = A τ^n (Non-linear ice creep)

Gluons Nuclear & Particle Physics Gauge Boson Class Massless elementary gauge bosons that mediate the strong nuclear force between quarks in quantum chromodynamics (QCD). Spin = 1, Mass = 0, 8 Color-Anticolor Combinations

Goldman-Hodgkin-Katz Equation Biophysics & Medical Physics mV (Membrane Potential) An equation calculating resting membrane potential considering relative membrane permeabilities (P_Na, P_K, P_Cl) and concentrations of multiple key ion species. V_m = (R T / F) ln((P_Na[Na]_out + P_K[K]_out + P_Cl[Cl]_in) / (P_Na[Na]_in + P_K[K]_in + P_Cl[Cl]_out))

Graded-index Fiber Optics N/A An optical fiber whose core refractive index decreases continuously from the central axis outward toward the cladding. n(r) = n0 √(1 - 2 Δ (r/a)^g)

Gradient Mathematical & Computational Physics [Scalar Field Unit] / m A vector operator that points in the direction of the greatest rate of increase of a scalar field, with magnitude equal to that maximum rate of change. ∇f = (∂f/∂x) î + (∂f/∂y) ĵ + (∂f/∂z) k̂

Gradient Descent Mathematical & Computational Physics Iterative Optimization Method An iterative first-order optimization algorithm for finding local minima of a differentiable scalar objective function by taking steps proportional to the negative gradient. x_(k+1) = x_k - α ∇f(x_k)

Terms starting with G