Terran Pace

How it works. One Terran Cell is 15° of longitude wide, one time zone, and the Sun crosses one cell every hour. A cell is narrower away from the equator, so the Sun’s ground speed is 1,669.8 km/h × cos(latitude): about 1,670 km/h at the equator, 1,181 km/h at 45°, 835 km/h at 60°. Your solar ratio ρ is your east–west speed divided by that. It equals the number of cells you cross per hour, east positive, and your local solar day lasts 24 ÷ (1 + ρ) hours. At ρ = 0 you stand still against the ground. At ρ = −1 you travel west with the Sun’s own pace and your solar time stands still. Beyond −1 you overtake the Sun and local solar time runs backward. North–south motion changes your row, one cell per degree of latitude, which is 111.32 km. One Tick of the decimal Solar Clock is 0.864 s, so the Sun’s equatorial pace is 401 m per Tick.

Limits. This is arithmetic on the definitions of Document XXIII, not new physics. It assumes a spherical grid at constant latitude, ignores the altitude of the traveller, and uses the 24-hour solar day. For interstellar speeds, where the clocks themselves diverge, use the Terran Interval (Document XXII).