The instant that the gravitational correction started to be applied serves as the epoch for Barycentric Coordinate Time ( TCB ), Geocentric Coordinate Time ( TCG ), and Terrestrial Time ( TT ).

Difficulties were recognized, which led to these being in turn superseded in the 1990s by time scales Terrestrial Time ( TT ), Geocentric Coordinate Time GCT ( TCG ) and Barycentric Coordinate Time BCT ( TCB ).

* Barycentric Coordinate Time

For the calculation of ephemerides, TDB was officially recommended to replace ET, but deficiencies were found in the definition of TDB ( though not affecting T < sub > eph </ sub >), and these led to the IAU defining and recommending further time scales, Barycentric Coordinate Time ( TCB ) for use in the solar system as a whole, and Geocentric Coordinate Time ( TCG ) for use in the vicinity of the Earth.

Barycentric Coordinate Time is a coordinate time scale at the center of mass of the solar system, which is called the barycenter.

* Barycentric Coordinate Time ( TCB ) is a coordinate time having its spatial origin at the solar system barycenter.

Practical examples include the International Atomic Time standard and its relationship with the Barycentric Coordinate Time standard used for interplanetary objects.

TDB is now ( since 2006 ) defined as a linear scaling of Barycentric Coordinate Time ( TCB ), and a feature that distinguishes TDB from TCB is that TDB, when observed from the Earth's surface, has a difference from Terrestrial Time ( TT ) that is about as small as can be practically arranged with consistent definition: the differences are mainly periodic, and overall will remain at less than 2 milliseconds for several millennia.

) After the difficulties were appreciated, in 1991 the IAU refined the official definitions of timescales by creating additional new time scales: Barycentric Coordinate Time ( TCB ) and Geocentric Coordinate Time ( TCG ).

Barycentric Coordinate Time ( TCB, from the French Temps-coordonnée barycentrique ) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to orbits of planets, asteroids, comets, and interplanetary spacecraft in the Solar system.

* Barycentric Coordinate Time ( from the French temps-coordonnée barycentrique ), a coordinate time standard in the Solar system

In 1976 the IAU resolved that the theoretical basis for its current ( 1952 ) standard of Ephemeris Time was non-relativistic, and that therefore, beginning in 1984, Ephemeris Time would be replaced by two relativistic timescales intended to constitute dynamical timescales: Terrestrial Dynamical Time ( TDT ) and Barycentric Dynamical Time ( TDB ).

For practical purposes the length of the ephemeris second can be taken as equal to the length of the second of Barycentric Dynamical Time ( TDB ) or Terrestrial Time ( TT ) or its predecessor TDT.

It was the counterpart to Barycentric Dynamical Time ( TDB ), which was a time standard for Solar system ephemerides, to be based on a dynamical time scale.

* Barycentric Dynamical Time ( TDB ) is similar to TDT but includes relativistic corrections that move the origin to the barycenter.

Barycentric Dynamical Time is a dynamical time at the barycenter.

Barycentric Dynamical Time ( TDB ), a form of atomic time, is now used in the construction of the ephemerides of the planets and other solar system objects, for two main reasons.

The day was also redefined to be exactly 86400 SI seconds when measured at mean sea level on the Earth: in practice, it is measured in Barycentric Dynamical Time ( TDB ).

Barycentric Dynamical Time ( TDB ) is a relativistic coordinate time scale, intended for astronomical use as a time standard to take account of time dilation when calculating orbits and astronomical ephemerides of planets, asteroids, comets and interplanetary spacecraft in the Solar System.

Barycentric subdivision is an important tool in simplicial homology theory, where it is used as a means of obtaining finer simplicial complexes ( containing the original ones, i. e. with more simplices ).

Barycentric subdivision is a convenient way to convert that " user-friendly " model into a " computer-friendly " one.

* Barycentric coordinates ( mathematics ) as used for Ternary plot

Barycentric coordinates for the incenter are given by

The new time scale to supersede ET for planetary ephemerides was to be Barycentric Dynamical Time ( TDB ).

It was intended as one of the replacements for the ill-defined Barycentric Dynamical Time ( TDB ).

It was intended as one of the replacements for the ill-defined Barycentric Dynamical Time ( TDB ).

Barycentric coordinates are not unique: for any b not equal to zero, () are also barycentric coordinates of p.

Motion of Barycentric coordinates ( astronomy ) | barycenter of solar system relative to the Sun.

* Barycentric coordinate system

A simulated example of a binary star, where two bodies with similar mass orbit around a common Barycentric coordinates ( astronomy ) | barycenter in elliptic orbit s

Two bodies of different mass orbiting a common Barycentric coordinates ( astronomy ) | barycenter.

Two bodies with similar mass orbiting around a common Barycentric coordinates ( astronomy ) | barycenter with elliptic orbits.

Two bodies with a slight difference in mass orbiting around a common Barycentric coordinates ( astronomy ) | barycenter.

Barycentric coordinates are a form of homogeneous coordinates.

Barycentric coordinates on an equilateral triangle and on a right triangle.

Barycentric or areal coordinates are extremely useful in engineering applications involving triangular subdomains.

If a point lies in the interior of the triangle, all of the Barycentric coordinates lie in the open interval.

TT was formally defined in terms of Geocentric Coordinate Time ( TCG ), defined by the IAU on the same occasion.

TT differs from Geocentric Coordinate Time ( TCG ) by a constant rate.

where TT and TCG are linear counts of SI seconds in Terrestrial Time and Geocentric Coordinate Time respectively, L < sub > G </ sub > is the constant difference in the rates of the two time scales, and E is a constant to resolve the epochs ( see below ).

The present definition of TT is a linear scaling of Geocentric Coordinate Time ( TCG ), which is the proper time of a notional observer who is infinitely far away ( so not affected by gravitational time dilation ) and at rest relative to the Earth.

* Geocentric Coordinate Time

Geocentric Coordinate Time is a coordinate time scale at Earth's center.