Word origin · etymology
Standardized English name.
Terrestrial comes from Latin terra, earth. TT abbreviates Terrestrial Time, the Earth-associated theoretical time scale.
How we know · epistemology
Astronomical time scale
TT supplies the time argument for uniform astronomical models. It is not the time shown on an ordinary birth record, and the correct conversion matters when comparing ephemerides.
Connected concepts
Terms used in this explanation
Mentioned in 3 other entries
These links connect subjects and terminology. They do not establish a shared historical origin.
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.