Relative dating
Relative dating is a set of geological and archaeological methods for placing rocks, fossils, and artifacts in chronological order without assigning numerical ages in years.
Relative density
Relative density, or specific gravity, is the ratio of a substance's density to that of a reference substance, usually water; it is a dimensionless number independent of units.
Relative equilibrium
A relative equilibrium is a solution of the Newtonian N-body problem in which bodies keep fixed mutual distances while rotating rigidly at constant angular velocity.
Relative humidity
Relative humidity is the ratio, expressed as a percent, of water vapor in the air to the amount that would saturate it at the same temperature.
Relative intensity noise
Relative intensity noise (RIN) is a measure of the random fluctuations in a laser's optical power, normalized to its average power and usually specified in dBc/Hz.
Relative lability and selective cleavage of silyl ethers
Silyl ethers are alcohol protecting groups whose lability depends on steric bulk, from acid-sensitive TMS to robust TBDPS, enabling selective protection of primary alcohols and stepwise removal with acid, fluoride, or TBAF.
Relative molecular mass
Relative molecular mass (Mr), formerly called molecular weight, is the dimensionless ratio of a molecule's average mass to one twelfth of a carbon-12 atom's mass.
Relative permittivity
Relative permittivity, also called the dielectric constant, is the ratio of a material's permittivity to that of vacuum; filling a capacitor with a dielectric multiplies its capacitance.
Relative sensitivity factor
The relative sensitivity factor (RSF) is a calibration coefficient in secondary ion mass spectrometry that converts measured ion intensity ratios into atomic concentrations, chiefly for trace elements below 1%.
Relativistic angular momentum
Relativistic angular momentum is the generalization of angular momentum to special relativity, where it becomes an antisymmetric tensor with six components: three generate spatial rotations and three generate Lorentz boosts.
Relativistic beaming
Relativistic beaming, also called Doppler boosting or the headlight effect, is the concentration of radiation from a near-light-speed source into a narrow forward cone, brightening approaching jets.
Relativistic center of mass
The relativistic center of mass is the collective position variable of a system in relativity theory; unlike the Newtonian one, it is not a single unambiguous point.
Relativistic collision kinematics
Relativistic collision kinematics is the study of two-body collisions using conservation of total energy and momentum in special relativity, governing the energy available to create new particles.
Relativistic collisionless shocks
A relativistic collisionless shock is a shock wave moving at nearly the speed of light through tenuous plasma, mediated by collective electromagnetic fields rather than particle collisions.
Relativistic corrections in satellite navigation
Relativistic corrections in satellite navigation account for the difference between ground and orbital atomic clocks by compensating for gravitational and kinematic shifts, preventing massive location errors.
Relativistic Doppler effect
The relativistic Doppler effect, also called the relativistic Doppler shift, is the change in frequency and wavelength of light from a moving source, calculated consistently with special relativity.
Relativistic electromagnetism
Relativistic electromagnetism treats electric and magnetic fields as one entity whose components depend on the observer's frame, with what one observer calls an electric field another sees as a mixture.
Relativistic ephemerides
A relativistic ephemeris is a numerically integrated table of Solar-System body positions and velocities whose equations of motion include general-relativistic corrections, as in JPL's DE series.
Relativistic Euler equations
The relativistic Euler equations are the equations of motion of a perfect (non-viscous) fluid in a form consistent with special or general relativity, governing fluids at speeds where relativistic effects matter.
Relativistic force
In special relativity, force is redefined as the four-force, the rate of change of a particle's four-momentum with respect to proper time, reducing to Newton's second law at low speeds.
Relativistic Hamiltonian
The relativistic Hamiltonian generates time evolution consistently with special relativity; for a free particle of mass m it is H = sqrt(p²c² + m²c⁴), the energy as a function of momentum.
Relativistic hydrodynamics in numerical relativity
Relativistic hydrodynamics in numerical relativity is the set of formulations and numerical methods used to evolve relativistic fluids coupled to dynamical spacetime governed by Einstein's equations.
Relativistic jet
A relativistic jet is a collimated outflow of particles moving near light speed, launched from the poles of an accreting black hole or neutron star, seen in quasars and X-ray binaries.
Relativistic jet kinematics
Relativistic jet kinematics is the study of the speeds, directions, and apparent motions of plasma jets launched near black holes and neutron stars at nearly the speed of light.
Relativistic jet shock interactions
Relativistic jet shock interactions are collisions inside and at the boundaries of relativistic jets from active galactic nuclei and gamma-ray bursts, converting kinetic energy into radiation.
Relativistic kinetic energy
Relativistic kinetic energy is the kinetic energy of a moving body in special relativity, K = (γ − 1)mc², which grows without bound as speed approaches light speed.
Relativistic kinetic theory
Relativistic kinetic theory is the extension of kinetic theory to particles whose speeds approach the speed of light, using a relativistic Boltzmann equation to describe gases and plasmas.
Relativistic Lagrangian
Relativistic Lagrangian is a Lagrangian whose action is invariant under Lorentz transformations and whose equations yield the relativistic equations of motion, originating with Henri Poincaré in 1905.
Relativistic Lagrangian mechanics
Relativistic Lagrangian mechanics is the formulation of particle dynamics using an action and Lagrangian consistent with special relativity, built from Lorentz-invariant quantities such as proper time.
Relativistic magnetohydrodynamics
Relativistic magnetohydrodynamics (RMHD) extends magnetohydrodynamics, the fluid description of conducting media coupled to magnetic fields, to flows approaching the speed of light in a Lorentz-invariant form.