Revision of Time Scales
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). Difficulties were recognized, which led to these being in turn superseded in the 1990s by time scales Terrestrial Time (TT), Geocentric Coordinate Time GCT(TCG) and Barycentric Coordinate Time BCT(TCB).
Read more about this topic: Ephemeris Time
Famous quotes containing the words time and/or scales:
“You need an infinite stretch of time ahead of you to start to think, infinite energy to make the smallest decision. The world is getting denser. The immense number of useless projects is bewildering. Too many things have to be put in to balance up an uncertain scale. You can’t disappear anymore. You die in a state of total indecision.”
—Jean Baudrillard (b. 1929)
“Love once
Tipped the scales but now is shadowed, invisible,
Though mysteriously present, around somewhere.”
—John Ashbery (b. 1927)