Astrophysics (Index) | About |

**General relativity** is a description of gravity in terms
of spacetime geometry, characterizing acceleration due to
gravitational force as constant motion within a curved spacetime.
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 (and since I'm standing still
on Earth, I'm moving "upward" relative to that space, and in fact,
accelerating).

*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 that "common" behavior.
It is encapsulated in
**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 spacetime,
i.e., *R*_{μν}, *g*_{μν}
and *T*_{μν} each indicate a relationship
between the four individual scalar values (a tensor, e.g., a 4×4 matrix).

*R*_{μν}- Ricci curvature tensor.*R*- scalar curvature.*g*_{μν}- metric tensor.- Λ - cosmological constant.
*G*- gravitational constant.- c - speed of light in a vacuum.
*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 term to make the equation to match observed reality, hypothesizing dark energy to explain it.

https://en.wikipedia.org/wiki/General_relativity

https://preposterousuniverse.com/wp-content/uploads/2015/08/grtinypdf.pdf

https://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/general_relativity/

https://www.space.com/17661-theory-general-relativity.html

alternative cosmologies

anti-de Sitter space (AdS)

areal coordinate system

black-hole information paradox

black hole model

Big Bang

Birkhoff's theorem

black hole (BH)

Chern-Simons gravity

CMBFAST

core collapse supernova (CCSN)

cosmological constant (Λ)

cosmology

critical density (ρ

curvature

dark energy

dark matter

Doppler shift

effective field theory (EFT)

Einstein-de Sitter model

ephemeris

f(R) gravity

Friedmann model

geodesic

GR1D

gravitational constant (G)

gravitational field

graviton

gravity

gravitational wave (GW)

GW detection (GW)

Hawking radiation

Hubble time (t

innermost stable circular orbit (ISCO)

Johannsen-Psaltis metric (JP metric)

Kerr black hole

law of cosmic censorship

Legendre polynomials

light cone

Lovelock gravity

Mach's principle

mathematical field

metric

no-hair theorem

numerical relativity (NR)

post-Newtonian formalism (PN formalism)

parameterized post-Newtonian formalism (PPN formalism)

Hulse-Taylor Binary (PSR B1913+16)

relativity

scalar-tensor gravity

Schwarzschild radius (R

Shapiro delay

gravitational singularity

SpEC

special relativity (SR)

strong-field gravity

supergravity (SUGRA)

supersymmetry (SUSY)

theoretical modified GR metrics

time dilation

Theory of Everything (TOE)

Tolman-Oppenheimer-Volkoff limit (TOV)

wide binaries (WB)

worldline

wormhole

ZAMO frame