Barycentric Dynamical Time
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Barycentric Dynamical Time (TDB) is a specialized timescale used in astronomy to describe the motion of celestial bodies. It is a dynamical timescale, meaning it's based on the gravitational forces that govern the movement of objects in space. TDB is defined in relation to the solar system's barycenter, which is its center of mass.12
The International Astronomical Union (IAU) defined TDB as the independent variable in the equations of motion for celestial bodies, including relativistic terms. This allows for precise calculations of the positions of planets and other bodies relative to the solar system's center. TDB differs from Terrestrial Time (TT) by periodic terms related to Earth's orbit, but it is applied within a reference system at rest with the solar system's barycenter.123
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