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Foundations of Physics

Gravitational Constant

The empirical physical constant relating the gravitational force between two masses to their product and inverse-square separation.

G = 6.67430 × 10⁻¹¹ N·m²/kg² N·m²/kg² Astrophysics, Cosmology & Relativity

Gravitational Lensing

The bending of light rays from a background astronomical source around a massive foreground object acting as a gravitational lens.

θ_deflection = (4 G M) / (c² b) Arcseconds (Angular Deflection) Foundations of Physics

Gravitational Mass

A measure of the strength of the gravitational force exerted or experienced by an object in a gravitational field.

m = F_g / g kg Astrophysics, Cosmology & Relativity

Gravitational Time Dilation

The phenomenon where time passes measurably slower in regions of lower gravitational potential (stronger gravity).

t_0 = t_f √(1 - 2 G M / (r c²)) Seconds (Relativistic Time Difference) Astrophysics, Cosmology & Relativity

Gravitational Waves

Ripples in the curvature of spacetime that propagate outward as transverse waves at the speed of light, generated by accelerating…

h_ij = (2 G / (c⁴ r)) (d²I_ij / dt²), Strain h = ΔL / L ~ 10⁻²¹ Dimensionless Strain h (10⁻²¹) Classical Mechanics

Gravity

The universal attractive force between masses, causing mutual acceleration proportional to mass and inversely proportional to squared…

Fg = G m1 m2 / r² N Astrophysics, Cosmology & Relativity

Great Attractor

A massive gravitational anomaly in intergalactic space at the center of the Laniakea Supercluster pulling galaxies across hundreds of…

v_peculiar ~ 600 km/s towards Laniakea Supercluster center M_☉ (Gravitational Anomaly Mass) Mathematical & Computational Physics

Green's Function

An impulse response function used to solve inhomogeneous linear differential equations subject to specified boundary conditions.

L G(x, x') = δ(x - x'), y(x) = ∫ G(x, x') f(x') dx' Impulse Response Function Mathematical & Computational Physics

Green's Theorem

A 2D vector calculus theorem relating a line integral around a simple closed curve C to a double area integral over the enclosed plane…

∮_C (L dx + M dy) = ∬_D ((∂M/∂x) - (∂L/∂y)) dx dy 2D Vector Integral Theorem Geophysics & Environmental Physics

Greenhouse Effect

The thermodynamic warming process by which atmospheric greenhouse gases absorb outgoing infrared terrestrial radiation and re-emit it in…

T_surface = T_effective (1 + ¾ τ_IR)^(1/4) (Radiative Equilibrium) °C or Kelvin (Warming Effect) Mathematical & Computational Physics

Group Theory

The mathematical study of groups and algebraic symmetry structures.

Group Axioms: Closure, Associativity, Identity, Inverse Symmetry Groups (SO(3), SU(2), SU(3)) Waves, Oscillations & Acoustics

Group Velocity

The velocity at which the overall envelope shape of a wave packet travels through space, representing energy transport speed.

v_g = dω / dk m/s Geophysics & Environmental Physics

Gutenberg Discontinuity

The major geophysical boundary located at a depth of ~2,890 km marking the sharp transition between Earth's solid mantle and liquid outer…

Depth z ≈ 2890 km (Core-Mantle Boundary D'' Layer) km (Boundary Depth) Plasma Physics

Gyroradius & Cyclotron Frequency

The helical orbital radius (Larmor radius r_L) and angular frequency (cyclotron frequency ω_c) of a charged particle orbiting a magnetic…

r_L = (m v_⊥) / (|q| B), ω_c = (|q| B) / m m (Larmor Radius) & rad/s (Cyclotron Frequency) Plasma Physics

H-mode Confinement

High-confinement operating regime in tokamaks characterized by a steep edge pressure barrier (pedestal) and doubled energy confinement time.

Energy Confinement Time τ_E(H-mode) ≈ 2 × τ_E(L-mode) s (Energy Confinement Time τ_E) Nuclear & Particle Physics

Hadrons

Subatomic composite particles made of quarks and gluons held together by the strong nuclear force.

Strongly interacting composite particles (Baryons & Mesons) Composite Particle Class Nuclear & Particle Physics

Half-Life

The time required for half the radioactive nuclei in a given sample to undergo spontaneous radioactive decay.

t_½ = ln(2) / λ ≈ 0.693 / λ, N(t) = N₀ (½)^(t / t_½) Seconds, Hours, or Years Electromagnetism & Electronics

Hall Effect

The production of a transverse electric potential difference (Hall voltage) across a current-carrying conductor in an orthogonal magnetic…

V_H = (I B) / (n q t), R_H = 1 / (n q) V (Hall Voltage), m³/C (Hall Coefficient) Plasma Physics

Hall Effect Thruster

A electric space propulsion plasma engine that accelerates ions across an electrostatic potential drop using trapped electrons in an…

F_thrust = ṁ v_exhaust, v_ex = √(2 e V_acc / m_ion) N or mN (Thrust) & s (Specific Impulse ~1500–3000 s) Mathematical & Computational Physics

Hamiltonian Formalism

A formulation of classical mechanics describing system dynamics in 2N-dimensional phase space using position q_i and canonical momentum p_i.

H(q, p, t) = ∑ p_i q̇_i - L, q̇_i = ∂H / ∂p_i, ṗ_i = -∂H / ∂q_i Joules (Energy) Condensed Matter & Materials Physics

Hardness

A material's resistance to localized plastic surface deformation induced by mechanical scratching, abrasion, or indentation.

H = Load / Indentation Surface Area (Mohs, Vickers, Rockwell) MPa or GPa (Mohs scale 1 to 10) Waves, Oscillations & Acoustics

Harmonics

Resonant frequencies of a system that are integer multiples of its fundamental frequency.

f_n = n f1 (where n = 1, 2, 3, ...) Hz Astrophysics, Cosmology & Relativity

Hawking Radiation

Thermal blackbody radiation predicted to be emitted by black holes due to quantum field fluctuations near the event horizon.

T_H = ℏ c³ / (8 π G M k_B), P = ℏ c⁶ / (15360 π G² M²) Kelvin (Blackbody Temperature T_H) Thermodynamics & Statistical Physics

Heat Engine

A physical device that converts thermal energy absorbed from a high-temperature heat source into mechanical work, discharging waste heat to…

W = Q_hot - Q_cold, η = W / Q_hot W (J/s)