Definition that contains orbital motion
- tt (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
- perturb cause a celestial body to deviate from a theoretically regular orbital motion, especially as a result of interposed or extraordinary gravitational pull
- ephemeris time (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
- tdt (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
- terrestrial dynamical time (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions
- terrestrial time (astronomy) a measure of time defined by Earth's orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth's motions