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**General relativity** is a description of gravity in terms
of space-time geometry, characterizing acceleration due to
gravitational force as constant motion within a curved space-time.
In other words, what I feel as the Earth's gravitational force
is an artifact of the space I'm occupying moving in that
direction relative to the Earth.

*General relativity* consists of the mathematical equations
that provide such a characterization consistent with
Newton's laws and special relativity. It relegates gravitational
force to be an artifact, like centrifugal force or Coriolis force.
It was developed by Einstein in 1916 following his
earlier development of special relativity. General relativity
remains the current favored model of gravity, based on its unique
ability to explain the common, intuitive behavior of gravity as
well as observed extreme cases that defy the common behavior.

The formula is known as
**Einstein's field equation** or **Einstein's equation**:

1 8πGR_{μν}- ——g_{μν}R+g_{μν}Λ = ————T_{μν}2 c^{4}

μ and ν each indicate the four dimensions of space-time,
i.e., *R*, *g* and *T* each indicate a relationship
between the four individual scalar values.

*R*_{μν}- Ricci curvature tensor.*R*- scalar curvature.*g*_{μν}- metric tensor.- Λ - cosmological constant.
*G*- gravitational constant.- c - speed of light.
*T*_{μν}- stress energy tensor.

Of interest is Λ, the cosmological constant, which Einstein included to compensate for the formula's implication that the universe would otherwise be expanding or contracting. Upon Edwin Hubble's later discovery of the visible expansion of the universe, Einstein no longer saw reason to include it. More recent observations showing expansion not following general relativity's predictions has induced physicists to revive the "constant", as a rug under which they can sweep the unexplained visible phenomena, also known as dark energy.

http://preposterousuniverse.com/grnotes/grtinypdf.pdf

Big Bang

Birkhoff's theorem

black hole (BH)

core collapse supernova

cosmological constant (Λ)

critical density (ρ

curvature

dark energy

dark matter

Doppler shift

Einstein-de Sitter model

ephemeris

geodesic

GR1D

gravity

gravitational wave (GW)

GW detection (GW)

law of cosmic censorship

Legendre polynomials

light cone

metric

numerical relativity (NR)

Hulse-Taylor Binary (PSR B1913+16)

relativity

Schwarzschild radius

SpEC

strong-field gravity

time dilation

Theory of Everything (TOE)

worldline

wormhole