Astronomers use mathematical models of the solar system to translate between barycentric time, geocentric time, and terrestrial time, which are all different re

Astronomers use mathematical models of the solar system to translate between barycentric time, geocentric time, and terrestrial time, which are all different relativistic frames of reference. Only TT has actual clocks: TAI ticks at the same rate as TT, tho for historical reasons there is a fixed offset. That isn’t counting the clocks derided from observing the orbits of the moons and planets…